Low idle after GS911 throttle body sync

[Tourmaster]

Just completed my first throttle sync on my 2012 R1200RT , used a GS911 to lock out the actuators and a manometer to balance the throttle bodies. All went well, I adjusted the right side only (checked for slack in the cables first, there was some). The manometer showed the right side pulling over 12" (2 stroke oil) when I started, got them balanced to within less than 1" from 3000 to 4000 RPM. Seemed strange to me that I had to "unscrew" the adjuster (RHS) to correct the imbalance. I would have thought the cable was already too tight if the right side was pulling more vacuum.

Now after a throttle opening, the engine idles momentarily at around 850 RPM (about 2.5 seconds) then jumps back up to 1147 on the GS911. I did an actuator re-calibration, no difference. I guessing I'm going to have to re-do the sync., just wondering if anyone (DR) has any pearls of wisdom?

I will be away for until Sunday evening.

 

Thanks in advance, Rick

[dirtrider]

Just completed my first throttle sync on my 2012 R1200RT , used a GS911 to lock out the actuators and a manometer to balance the throttle bodies. All went well, I adjusted the right side only (checked for slack in the cables first, there was some). The manometer showed the right side pulling over 12" (2 stroke oil) when I started, got them balanced to within less than 1" from 3000 to 4000 RPM. Seemed strange to me that I had to "unscrew" the adjuster (RHS) to correct the imbalance. I would have thought the cable was already too tight if the right side was pulling more vacuum.Now after a throttle opening, the engine idles momentarily at around 850 RPM (about 2.5 seconds) then jumps back up to 1147 on the GS911. I did an actuator re-calibration, no difference. I guessing I'm going to have to re-do the sync., just wondering if anyone (DR) has any pearls of wisdom?

I will be away for until Sunday evening.

 

Afternoon Rick

 

The side that has the HIGHEST vacuum would have the most closed throttle plate (remember vacuum is highest at closed throttle & goes down as the throttle plate is opened & lets atmospheric pressure in)

 

As far as your balance goes you really need to re-check it.

 

Personally I would recommend that you ride the bike a few miles to allow some idle quality re-learn. THEN, while still hot do a balance check at about 2500-3000.

 

I would also recommend that you do not use the GS-911, or actuator re-calibration, & DON'T lock the steppers during the balance check. (just ride the bike to warm it up, then hook your U tube up & run the engine long enough to go into closed loop, then check & adjust the balance @ 2500-3000)

 

Basically you ride the bike down the road without the steppers being locked so why would you want the steppers locked for a TB balance?

[Tourmaster]

Hi DR,

 

Thanks for the response. I guess my mindset was the right side throttle plate was open more, therefore pulling more vacuum. I figured the vacuum source tubes were on the atmospheric side of the throttle plates, not downstream of them.

I had ridden the bike about 45 minutes after the sync attempt, most of it was highway, probably about 15 stops in that time. I seem to recall reading somewhere there is no adjustment for the idle RPM, that the control module sets it.

 

just ride the bike to warm it up, then hook your U tube up & run the engine long enough to go into closed loop

Please explain 'closed loop'.

 

It will be a couple of days before I can do a re-sync.

Regards,

Rick

[dirtrider]

Hi DR,

 

Thanks for the response. I guess my mindset was the right side throttle plate was open more, therefore pulling more vacuum. I figured the vacuum source tubes were on the atmospheric side of the throttle plates, not downstream of them.

I had ridden the bike about 45 minutes after the sync attempt, most of it was highway, probably about 15 stops in that time. I seem to recall reading somewhere there is no adjustment for the idle RPM, that the control module sets it.

 

just ride the bike to warm it up, then hook your U tube up & run the engine long enough to go into closed loop

Please explain 'closed loop'.

 

It will be a couple of days before I can do a re-sync.

 

Morning Rick

 

The idle RPM is controlled by the fueling computer so there is no rider adjustment. Low battery voltage can/will raise the idle RPM until the voltage increases.

 

Closed Loop is when the o2 sensors come on line (get warm enough) to start controlling the engine fueling.

 

If in doubt then just idle a somewhat warm engine for about 3 minutes & it should be in closed loop by then.

[Tourmaster]

Thanks DR,

 

You mentioned 2500 - 3000 rpm for the sync, the bike runs at about 3300 on the highway, a little more when going through the gears. Is there a reason to do it at a lower rpm? Would there be any benefit to having the rear wheel driven, and possibly a slight amount of rear brake to simulate some engine loading, therefore more throttle opening for a given rpm...or am I just overthinking things.

 

R.

[dirtrider]

Afternoon Rick

 

 

The throttle plates are at a much different opening sitting still than while under road load so doing it a 3300 RPM static really doesn't equate to any on road throttle opening.

 

In most cases you want to do the balance above idle but at about the highest vacuum possible. 2500-3000 is a good place but 3300 shouldn't show enough difference to mean anything.

 

Don't try to do any setting by dragging the rear brake as that is not needed & will probably add more problems than help.

 

 

 

 

[Don_Eilenberger]

Just a FWIW - watching the O2 sensors with a GS-911 in plotting mode - they go closed loop within about 30-60 seconds after startup - no ride down the road needed. They are heated sensors and they are close to the exhaust outlets.

 

FWIW - the factory procedure to balance the TB's is slightly different, and is the reason to have the ability to lock the steppers.

 

The factory process is:

1. Zero the steppers

2. Lock the steppers so they're "in-sync" - open the same amount.

3. Measure the vacuum offset in mm/hg at idle on a warm engine.

4. Adjust so that offset remains throughout the throttle range. Same mm/hg offset from "balance"..

 

The thinking is that if the valves aren't exactly the same - or for some other reason your engine isn't drawing the same amount of air through both cylinders - there will be a slight offset and if the TB's are set to open the exact same amount - that offset will remain.

 

Dunno if that process is better or not - I haven't tried it. The process the vast majority of owners use "compensates" for any difference in the engine condition that might cause it to draw more air through one cylinder.

 

Both seem to work. Just differently.

[dirtrider]

Just a FWIW - watching the O2 sensors with a GS-911 in plotting mode - they go closed loop within about 30-60 seconds after startup - no ride down the road needed. They are heated sensors and they are close to the exhaust outlets.

 

FWIW - the factory procedure to balance the TB's is slightly different, and is the reason to have the ability to lock the steppers.

 

The factory process is:

1. Zero the steppers

2. Lock the steppers so they're "in-sync" - open the same amount.

3. Measure the vacuum offset in mm/hg at idle on a warm engine.

4. Adjust so that offset remains throughout the throttle range. Same mm/hg offset from "balance"..

 

The thinking is that if the valves aren't exactly the same - or for some other reason your engine isn't drawing the same amount of air through both cylinders - there will be a slight offset and if the TB's are set to open the exact same amount - that offset will remain.

 

Dunno if that process is better or not - I haven't tried it. The process the vast majority of owners use "compensates" for any difference in the engine condition that might cause it to draw more air through one cylinder.

 

Both seem to work. Just differently.

 

Afternoon Don

 

The problem with the BMW method is you just don't know the basis for the idle vacuum offset. If a little coaking in the stepper bores or some coking on the stepper pintles you are basically bringing up an unnatural idle offset into the riding range.

 

 

That factory manual way has been debated for years & is a pretty sloppy way of getting a decent mid range balance.

 

The factory manual gives you a little over 10" of H2o delta at idle before it says to address the problem. It gives about 6" of H2o delta above idle.

 

I guess we haven't ever been able to figure out why BMW would have an idle delta brought up into the riding range.

 

The steppers self zero every time the engine is started so that seems like a useless step using a GS-911.

 

If there is a vacuum difference of over few inches at hot curb idle my (personal) suggestion is to find & repair the reason for the vacuum delta at idle rather than bring that delta up into the riding range.

 

Over the last few years (since the GS-911 is heavily in riders hands) I have had to re-do or help un-do a number or 1200 TB balance screw ups caused by the rider trying to zero or lock the steppers during a TB balance. I haven't had to address a single one that the rider just warmed the engine up until closed loop the put the U tube on & did a simple above idle balance.

 

 

 

 

[Don_Eilenberger]

Afternoon Don

 

The problem with the BMW method is you just don't know the basis for the idle vacuum offset. If a little coaking in the stepper bores or some coking on the stepper pintles you are basically bringing up an unnatural idle offset into the riding range.

 

No argument there.. I was just pointing out that BMW calls for it to be done "differently".. (and last I checked they didn't use a manometer - they used discrete vacuum gauges - big ones - but discrete.)

That factory manual way has been debated for years & is a pretty sloppy way of getting a decent mid range balance.

 

The factory manual gives you a little over 10" of H2o delta at idle before it says to address the problem. It gives about 6" of H2o delta above idle.

 

I guess we haven't ever been able to figure out why BMW would have an idle delta brought up into the riding range.

 

The steppers self zero every time the engine is started so that seems like a useless step using a GS-911.

Indeed they do, I pointed this out around 2007 on the GS-911 forum. People debated it until I suggested they listen to the steppers. Rule is - let the instruments do their dance and when it's done start the engine.

If there is a vacuum difference of over few inches at hot curb idle my (personal) suggestion is to find & repair the reason for the vacuum delta at idle rather than bring that delta up into the riding range.

I would agree - and I suspect if there was a significant difference in vacuum BMW would agree too..

Over the last few years (since the GS-911 is heavily in riders hands) I have had to re-do or help un-do a number or 1200 TB balance screw ups caused by the rider trying to zero or lock the steppers during a TB balance. I haven't had to address a single one that the rider just warmed the engine up until closed loop the put the U tube on & did a simple above idle balance.

 

Dunno if you've observed what the steppers seem to do. On my bikes it appears that they go into sync (same number of steps on the GS-911) at any RPM significantly above idle, so locking them in a set position really isn't a lot different. Have you observed otherwise?

 

As a final word on TB sync on R1200's - my general advice - unless there is a real reason to - LEAVE THEM ALONE.

 

My first R1200R passed 100k miles without ever really needing to be sync'd (I checked it - it never changed.) The "new" R1200R is at about 13,000 miles and hasn't been touched. The trick is simply to get the rest of the engine set correctly. Unlike the R1150xx engines, these don't seem to drift out of sync. At least mine haven't.

 

BTW - the "risk" of how we do it - is people may (and I've had to sort some of these out) tend to use the balance to compensate for poorly adjusted valves on these engines. The other big rule IMHO is - ADJUST THE VALVES FIRST (or check them on a camhead, chances are they won't need adjusting) THEN do the TB balance check. Chances are excellent nothing will need to be done.

[Tourmaster]

BTW - the "risk" of how we do it - is people may (and I've had to sort some of these out) tend to use the balance to compensate for poorly adjusted valves on these engines. The other big rule IMHO is - ADJUST THE VALVES FIRST (or check them on a camhead, chances are they won't need adjusting) THEN do the TB balance check. Chances are excellent nothing will need to be done.

 

Hi Don,

 

I checked the valves a month ago, all were well within spec. The u tube was showing a 12" difference R/L (and still climbing, I was running out of tube).

 

Rick

 

 

[dirtrider]

 

Afternoon Rick

 

The valves would have to be WAY out to cause a 12" H2o delta.

 

On the hexhead or camhead when you find something like 12" H2o side to side difference that should put up a large red flag as those models almost never get that far out of adjustment by themselves. I have seen most hexhead/camhead hold pretty darn close unless something is amiss in the cables or TB's.

 

If the air filter was replaced or checked make darn sure the throttle cable running to that side is properly routed around the air box inlet (it's ever so easy to get that out of place or pulled tight).

 

Then verify that the short cables are pushed all the way into the cable splitter box (if a cable was pulled on it can be out of the box just slightly & that can cause an erratic idle & strange balance issues.

 

Then look right at the TB's themselves for signs that one of the throttle cable adjusters is broken (I have seen a few). You can usually tell this by lightly pulling up on the cables.

 

Then get some help & have someone slowly open the twist grip (just a few degrees) as you feel/look to verify that the TB cams lift off the idle stops screws at the EXACT SAME TIME. If one is lifting slightly before the other that should put up another large red flag.

 

If a 1200 hexhead or camhead is healthy & not buggered up by an inept technician then you should seldom have to move a cable adjuster more than one nut flat.

 

A little trick that I do on my personal 1200 bikes is to run vacuum hose to each TB nipple then run those up to the crossbar under the seat. Then re-route the purge hose to also terminate in that area. Then plug off one hose with a golf tee or screw & hook the other one to the purge hose (same side as stock).

 

This allows a quick check of the TB balance after a long ride with the engine very hot & the steppers running at road load position.

 

After I get home from a ride & without turning the engine off I use my spare key to remove the seat, then use a couple of hemostats (or vacuum clamps) to COMPLETELY clamp off those 2 vacuum hoses under the seat. Then, with both hoses clamped off I unhook the purge hose & unplug the other hose & hook up my U tube. The simply unclamp the hoses & do an idle vacuum delta test as well as 1500 RPM test & 2500RPM test as well as a just off idle to about 3k throttle sweep vacuum delta test.

 

 

[Tourmaster]

I had a fellow '12 RT owner assisting me when I did the sync, he had never done one before either, sort of a courage in numbers, blind leading the blind thing. He borrowed the U tube and did his the day after mine, same result with the wonkey idle. He found this on the hexcode site:

 

http://forum.hexcode.co.za/forum/index.php?topic=150.0

 

I performed a "Reset All Adaptation Values" with the GS911 and did a gear shift relearn, presto runs like a top! (today it would not idle at a cold start)

 

I will do as you suggest DR... re-sync the throttle bodies once again after checking the entire throttle actuation system, I didn't see anything amiss on the weekend but I will take a closer look, just in case.

As mentioned this is the first sync I have performed, I purchased the RT new and it was dealer maintained up until now (warranty expired), presently it has 30,500 kms, last previous service was at 20 k.

FWIW the cable adjustment was about 1/2 of a turn in total.

Getting on it this spring the bike felt like it had a little more highway speed vibration than I remembered, possibly last year I was just accustomed to it. It is noticeably smoother since the sync. I'm going to commute to work with it tomorrow before tearing the Tupperware off one more time, will report back after the re-sync. Thanks for all the input.

 

Rick

[dirtrider]

Morning Rick

 

You can (or should be able to anyhow) re-check the TB sync without removing the Tupperware.

 

You will need a pair of long bent-tip needle nose pliers or a medium length bent tip hemostat.

 

With the correct tool (I use a hemostat) you can reach in & remove the evap hose on one side & vacuum plug on the other then use the same tool to hook up the U tube hoses.

 

You won't be able to make any adjustments but you can re-check the balance.

[Tourmaster]

Hi DR,

 

I will just pull the plastic off, getting pretty good at (3 times this spring...yea I forgot to put the Bowden box cover back on at the sync), that way I can check ALL the cable connections / routing and then ride confident that all is well.

 

R.

[Tourmaster]

OK, so I tore it apart this afternoon. Before starting it I removed the air intake tube, checked the Bowden box and cables, I couldn't see anything out of position. I checked the throttle opening off the stops, the right side was slightly ahead of the left. Started the bike and warmed it up, when I pulled gently on the short cables from the Bowden box, the left side made the engine accelerate (as expected) however pulling the right side caused the engine to run a little rougher and actually drop a few RPM. When I attached the U tube, the left side was pulling significantly more vacuum than the right, about 10 inches. I did another balance around 2700RPM, let it cool off some and checked it again. Some more adjusting, let it cool and some more adjusting...I seemed to be chasing it. Checked the throttle opening off the stops again, they were simultaneous.

 

Is it doing some relearning along the way?

 

With the previous stepper lock out and then the Reset All Adaption Values having been done, is there any resetting to do now with the new sync settings? Is it a matter of riding it a bit, recheck, readjust...ride, recheck, readjust?

 

Thanks, Rick

[Tourmaster]

As a side note, the right side had pulled more vacuum at the first sync attempt, I had checked it about 5-6 weeks earlier (spring check over) and it was pulling more vacuum then as well.

[dirtrider]

Morning Rick

 

I checked the throttle opening off the stops, the right side was slightly ahead of the left.---That should make the above idle vacuum higher on the L/H side.

 

As a side note, the right side had pulled more vacuum at the first sync attempt, I had checked it about 5-6 weeks earlier (spring check over) and it was pulling more vacuum then as well.---It sounds that on you last TB adjustment that you got the R/H side adjusted ahead of the L/H side.

 

Started the bike and warmed it up, when I pulled gently on the short cables from the Bowden box, the left side made the engine accelerate (as expected) however pulling the right side caused the engine to run a little rougher and actually drop a few RPM. ---This is perfectly normal as the L/H side has the TPS sensor so it adds fuel as you open that side. The R/H side has no TPS sensor so it doesn't add any fuel as you open that side throttle plate.

 

(you should NEVER pull on individual cables just before or during a TB balances as that can change the cable tracking therefore make the TB balance slightly change during the balance procedure)

 

When I attached the U tube, the left side was pulling significantly more vacuum than the right, about 10 inches. I did another balance around 2700RPM, let it cool off some and checked it again. Some more adjusting, let it cool and some more adjusting...I seemed to be chasing it. Checked the throttle opening off the stops again, they were simultaneous--- It sounds like you are getting it close to being right. Probably that individual cable pulling is part of your variance. You will probably chase it a little until you ride the bike a bit to allow the cables to return to normal tracking. As long as you are under 6" of h2o delta then you are within BMW specs.

 

Is it doing some relearning along the way? --Yes, but most of the learning is in the fueling control & that shouldn't effect the vacuum. At 2700 the steppers should be automatically linking together to the same counts so any stepper learning should not be a factor at 2700 RPMs.

 

With the previous stepper lock out and then the Reset All Adaption Values having been done, is there any resetting to do now with the new sync settings? Is it a matter of riding it a bit, recheck, readjust...ride, recheck, readjust?---With all you have done & adjusted if the vacuum delta is under 4" h2o or so now then personally I would ride it for a few days then re-check it. (if you have hemostats or long bent nose needle nose pliers then you can re-check the balance without removing the plastic--you can't adjust it but you can check it. -- Or add lengths of vacuum hose to the TB nipples & run them & the purge hose up under the seat to make after ride checking VERY EASY.

 

One more thing-- if you stop thinking of one side PULLING more vacuum & think of it more as one side having higher or lower vacuum it will be less confusing. When a person talks of PULLING more vacuum they automatically equate that to that side having a more open throttle plate & that is directionally incorrect. (vacuum goes DOWN as the throttle plate is opened)

[Tourmaster]

Good Afternoon D.R.

 

I went for a ride yesterday (150 km) mostly highway, and did the commute thing today (30 km X 2), again mostly highway. I checked the balance without removing the plastic, its a pain but doable. (I have the BMW formed aluminum valve cover protectors so I lose a bit of space with them)

I seem to be back where I started (almost), the right is higher vacuum, 12" delta @ 2700 RPM but the balance is within 1" at idle.

As soon as the throttle begins to crack open (no noticeable increase in RPM) the right side starts climbing.

 

I know the idle is not really what we are concerned with, however, before I made the first adjustment (a week ago) the balance was off at least 12" at idle AND at about 3000 RPM (right side higher vacuum).

I am going to, as you suggested, pick up some vacuum tube and install a couple of short lines to give me access under the seat.

 

Maybe it needs a wash?

 

Regards,

Rick

[dirtrider]

As soon as the throttle begins to crack open (no noticeable increase in RPM) the right side starts climbing.

 

Evening Rick

 

That means the L/H side is opening before the R/H side.

[Tourmaster]

That means the L/H side is opening before the R/H side.

 

Hi D.R.

 

When I balanced it on Saturday, the throttle plates were lifting off their stops at the same time, as far as I could tell by touch...index fingers on each tb, the wife gently rolling the throttle grip.

Any adjustment of the right throttle cable at the 2700 RPM balance will affect the throttle plate off idle stop (L / R throttle timing), correct?

Do I ignore the idle and focus on a balance at 2700 or do the plates HAVE to lift off the stops simultaneously?

 

Thanks,

Rick

 

[dirtrider]

Morning Rick

 

Any adjustment of the right throttle cable at the 2700 RPM balance will affect the throttle plate off idle stop (L / R throttle timing), correct?--- Correct

 

Do I ignore the idle and focus on a balance at 2700 or do the plates HAVE to lift off the stops simultaneously?--- You basically need both.

 

I'm not sure what you have going on there but the BMW 1200 is usually very easy to balance correctly. Any chance that you are using a fluid in your U tube that is a little too thick so is clinging to the tube walls & impeding the balance response? (personally I just water with a bit of color in it)

 

 

[Tourmaster]

Hi D.R.

 

I'm using 2 stroke oil, (dark blue) in the U tube, being a little lighter than water I assume it would show a slightly wider delta spread. It takes about 4 seconds to go from being equal at idle to stabilizing at 12" delta @ 2700, and about the same back down. I could thin it with gas but I don't think this is the issue. I think I'll try a 6" delta, higher vacuum on the right, and see what happens.

 

Thanks,

Rick

 

 

[Tourmaster]

I took another stab at it last night. Pulled off the Tupperware and checked the balance, idle was within a 1/2", 2700 rpm was 6" higher vacuum on the right (previously 12")...NO ADJUSTMENT between readings.

The checking process will be easier now with the vacuum extension hoses installed (under the seat).

The only variables I can come up with are:

1) ambient temperature, was 24 deg C yesterday, about 10-12 deg C on previous 2 attempts.

2) center stand vs side stand

3) plastic off vs plastic installed

 

Any Ideas D.R.?

[Tourmaster]

I adjusted the balance to about 2" higher vacuum on the left at idle and 3" higher on the right at 2700. So I have run 3 checks since (the hoses make it a breeze, thanks DR). The first 2 checks remained 2" high left idle, 3 " high right at 2700. Today I did one, 3" high left idle , about 1" high right at 2700. The temp was 25 deg C today, about 15 deg C each of the previous 2 checks.

Is the day to day variation normal or is there something else going on? Next time the plastic is off I'll check the TB simultaneous opening, I'm guessing its a bit off at this point.

[Tourmaster]

Another check today, 31 deg C, 4 " higher left at idle, 1" higher LEFT @ 2700 rpm.

[roger 04 rt]

If you have a GS-911, it would be useful to know the state of the tank vent solenoid during your measurements.

[dirtrider]

If you have a GS-911, it would be useful to know the state of the tank vent solenoid during your measurements.

 

Morning Roger

 

I'm not sure the tank vent solenoid has much bearing on the MEASURED idle or off-idle vacuum delta as the vent hose (between the vent solenoid & throttle body) is disconnected during the vacuum measurement so the vent solenoid position should have no effect on the vacuum readings

[Tourmaster]

If you have a GS-911, it would be useful to know the state of the tank vent solenoid during your measurements.

 

Morning Roger

 

I'm not sure the tank vent solenoid has much bearing on the MEASURED idle or off-idle vacuum delta as the vent hose (between the vent solenoid & throttle body) is disconnected during the vacuum measurement so the vent solenoid position should have no effect on the vacuum readings

 

Hi DR,

 

No vent hose on mine, just 2 rubber caps. Am I missing something?

 

R.

[dirtrider]

If you have a GS-911, it would be useful to know the state of the tank vent solenoid during your measurements.

 

Morning Roger

 

I'm not sure the tank vent solenoid has much bearing on the MEASURED idle or off-idle vacuum delta as the vent hose (between the vent solenoid & throttle body) is disconnected during the vacuum measurement so the vent solenoid position should have no effect on the vacuum readings

 

Hi DR,

No vent hose on mine, just 2 rubber caps. Am I missing something?

 

 

Yes, the emission evap system. I wonder if the Canadian bikes even got the emission evap system back then?

[Tourmaster]

I checked the balance again last evening, about 24 deg C and its back to 3" higher left idle, 1" higher on the right side at 2700.

Would temperature have that much bearing on the balance?

[dirtrider]

I checked the balance again last evening, about 24 deg C and its back to 3" higher left idle, 1" higher on the right side at 2700.

Would temperature have that much bearing on the balance?

 

Evening Tourmaster

 

The idle balance kind of floats so a slight difference each time that you measure it is normal (if the steppers weren't allowed to float a little the engine would surge like crazy at idle due to trying to precisely control the idle RPM)

 

On the 2700 RPM variance, that 1" variance is WELL within BMW specs & could be due to the different lengths of the short lower cables (the right cable is slightly longer so could stretch slightly more as the engine heats up therefore skewing the delta slightly.

[Bernie]

1" higher on the right side at 2700.

 

Good evening, I think you are checking your balance at to low of a RPM, I always check between 3,500-4,000 rpm. I did this on the R1100RT and the same on the R1200RT. I have never spend much of anytime riding around at 2,700 rpm. I would always down shift, I try to keep the rpm's up.

You maybe trying to be a little to accurate or one of your head gaskets/intake tube is leaking, messing up your balance. You may try to spray some W-40 or starting fluid on the intake tube, to see if the idle picks up, or something like that.

Or maybe you need to a leak down test or a compression test, to see if you have a bad intake valve or leaking head gasket.

Best of luck.