2003 chevy venture p0304
- Thread starter Trievel
- Start date
NHBandit
Well-known member
You don't even need to back off the rockers if you make sure the engine is in position where both valves on the cylinder you're checking are closed. On my compression tester it is a 2 piece hose with a quick disconnect in the middle. I made an adaptor using the proper combination of male & female air hose fittings so I can plug my air hose directly onto the compression tester hose that screws into the sparkplug hole. This allows you to hear whether that cylinder holds pressure or leaks into the intake or the exhaust and will narrow down the source of the problem. Doing it with the plugs out of the adjoining cylinders will show if there is a head gasket blown between cylinders. It dosn't sound like that though from the numbers you got. There are specialty tools for doing a leak test as well but this is the poor mans way and does work.
B&H
Well-known member
It's hard to believe that you can have 160 psi on a dynamic compression check. Did you have the valve out of the compression tester hose? I prefer a static compression test before a dynamic one.
Does the engine miss all of the time, as in a "dead hole"?
If indeed there is a compression problem in cylinder #4, I recommend removing the valve cover (easy on the front) to not only back the valves off for a leak down test, but to inspect the cam action, rocker arms, valve springs, etc. This is just basic testing.
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SpiderGearsMan
Banned
#1 bank is in the rear
SpiderGearsMan
Banned
2001 we had a valve spring recall
BillK
Well-known member
But you can afford to waste all of the money you have wasted on parts that havent fixed anything ????????
How about find a decent shop that knows how to use a scope and pay them for an hours labor, probably around $100 depending on your area, and they should at least be able to get you close with a diagnosis. Then you can either have them fix it or fix it yourself, but geeeeze, stop wasting your money throwing parts at it
Just my opinion,
B&H
Well-known member
The check valve is installed in the end of the hose that threads into the cylinder head, similar to a Schrader valve.
You are frustrated and may not be seeing things correctly. Check to make sure there is a check valve (does the gauge hold pressure w/o the engine tuning)? Disconnect the wiring connectors on the driver's side of the coil pack/module to keep the engine from starting, install compression tester on cyl 4 and crank the engine for 15 seconds. What does the gauge read?
But you can afford to waste all of the money you have wasted on parts that havent fixed anything ????????
How about find a decent shop that knows how to use a scope and pay them for an hours labor, probably around $100 depending on your area, and they should at least be able to get you close with a diagnosis. Then you can either have them fix it or fix it yourself, but geeeeze, stop wasting your money throwing parts at it
Just my opinion,
i've only spent $45 on the o2 sensor,$18 on the wires, & $28 on plugs...all items it needed regardless. i haven't wasted anything
mrbreezeet1
Banned
Do you happen to have a vacuum gauge?
When I worked at the tune up shops in the 80's , usually a mechanical problem on a cylinder would make the vacuum gauge jump around at idle.
When I worked at the tune up shops in the 80's , usually a mechanical problem on a cylinder would make the vacuum gauge jump around at idle.
mrbreezeet1
Banned
that *****, where are you located? maybe someone here could help you?
mrbreezeet1
Banned
OK then yeah, there is a check valve in there.
Usually screwed in the spark plug end like stated above.
Drew_flux
Well-known member
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Just to confirm, you have disabled the fuel supply whilst doing your comp testing? if not you may have fuel washed the cylinders. The way you disscribe your comp testing sounds incorrect. Not having all plugs out can slow the cranking speed. It's time to get plugs out,even if the UIM has to come off. As much as I am for diy,
At this time, it may be cheaper to off load to a shop for diagnosis.
mrbreezeet1
Banned
Yeah, maybe time to start over and do the compression test from the beginning. All plugs out, Fuel pump disabled, throttle plate wide open.
B&H
Well-known member
No need to remove all plugs or block throttle open. We are looking for a BIG problem, not whether a cylinder has 150 vs 152 lbs of compression.
Disconnect crank sensor wiring connector @ ignition module, as I outlined before. This kills both spark and fuel delivery. Starting w/ cylinder 2, remove only that plug and crank the engine long enough to get a peak compression reading. Reinstall the spark plug, and repeat procedure for cylinders 4 and 6. Post findings. Don't give up yet!
Disconnect crank sensor wiring connector @ ignition module, as I outlined before. This kills both spark and fuel delivery. Starting w/ cylinder 2, remove only that plug and crank the engine long enough to get a peak compression reading. Reinstall the spark plug, and repeat procedure for cylinders 4 and 6. Post findings. Don't give up yet!
B&H
Well-known member
You need to find out where the compression is going. What I do is remove the "elusive" check valve in the end of the compression tester hose, remove the front valve cover, back off the rocker arms and apply shop air into the offending cylinder through the compression tester hose. You will need an air compressor and an adaptor to adapt your air compressor hose to the compression tester hose. The leakage will be out the tailpipe, throttle body or into the base.. Also (again), check the action of the valves on that cylinder while cranking the engine over (before removing the rocker arms) and check the valve springs carefully.
I don't want to hear it's too cold out - hike up your skirt and get to it!
Reality Sucks
Well-known member
- Joined
- Dec 16, 2010
- Messages
- 276
leak down test as stated above. These things are a complete nightmare. ive work on several. with this issue. Mis-fire when cold due to the cylinder filling up with coolant. Headgaskets on these are a nightmare. Do leak down test as stated by B&H. remove the rad cap as well and check for bubbles. These things were problem engine from the factory, and putting them in a van only added insult to unjury,imo. You do not need to remove the vc to do this, just make sure you have a breaker bar on the crank bolt to turn/hold engine. 1 to keep the valves closed and 2 so that when you apply shop air the engine doesnt try to turn over. Good luck, let us know what you find.
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B&H
Well-known member
I admire the effort you put forth! FWIW, this doesn't sound like a head gasket issue. I've only seen head gaskets blow on cylinder #1 on these, and you would have other symptoms. Removing the heads or replacing the engine is labor intensive, but not hard. How many miles are on the van?
Yeah,i kinda think it's a valvletrain issue, i doubt the HG,as it Never even gets hot,no oil coolant loss or burning. Guess it could be a piston ring,but i'm thinkin sticky valves or bad lifter,maybe a rod issue if someone else did the intake mani's,but the look like theyve been there for a while. Oh,and the van has 98,600 miles
Copytech
Well-known member
how hard is to pull the valve cover? Since it is on the front it shouldn't be that bad.
Edit It appears the intake has to come off.
Edit It appears the intake has to come off.
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mrbreezeet1
Banned
Oh good deal, were you still gonna pull the valve cover to have a look, and back off the rockers for the cylinder leakage test?
mrbreezeet1
Banned
Who knows about that motor? Does it have separate nuts torqued down he can just back off to close the valve's?
Or are they bolts, of adjustable like a old small block chevy.
In any case, as stated above, I would say pull the valve cover and look at the valve action compared to the others when it is running or cranking, and also look at the valve spring real good.
If you get lucky and it is a valve spring, you could probably hold the valve up with air and replace the valve spring that way.
Or are they bolts, of adjustable like a old small block chevy.
In any case, as stated above, I would say pull the valve cover and look at the valve action compared to the others when it is running or cranking, and also look at the valve spring real good.
If you get lucky and it is a valve spring, you could probably hold the valve up with air and replace the valve spring that way.
mrbreezeet1
Banned
Yeah, you can do the leakage test 1st. Just have to position (rotate crank) the motor so both # 4 cylinder valves are closed.
I am not sure what the crank position is though.
I am not sure what the crank position is though.
well,got bored waiting for the air compressor,and got an idea. since it's raining/snowing,i can't pull the valve cover today. so,i pulled the oil cap,grabbed a mini-lite & a micro-mirror. the cyl. 4 rocker arm isn't even moving. so i guess next nice day,valve cover's comin off...so,place your bets,broken rocker bolt,valve spring,pushrod,or camshaft problem?
I know I'm late to the party, but those engines are notorious for pulling the rocker studs from the block. If you have ruled out the obvious, then its a good place to look.
Edit just saw your last post, my money is on the exhaust rocker stud pulled from the head for #4. If it was the intake stud the compresion would be off.
The good news is I have"repaired" several of those with heli-coils when the customer couldnt afford a proper repair. I ve never had issues with helicoils although its not an ideal solution.
Ok just saw the results above, its the intake rocker. I really should read tge thread before posting
Edit just saw your last post, my money is on the exhaust rocker stud pulled from the head for #4. If it was the intake stud the compresion would be off.
The good news is I have"repaired" several of those with heli-coils when the customer couldnt afford a proper repair. I ve never had issues with helicoils although its not an ideal solution.
Ok just saw the results above, its the intake rocker. I really should read tge thread before posting
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