1997 tahoe valves sticking

[tstokes71]

If you really want to know if it is a valve train issue, you must try the vacuum gauge. It will tell you if the valve train is bad or not. It will be the best $15-$20 you'll ever spend on a engine diag tool. It's old school and is a very simple tool. Good compression is a plus. That means it's valve train(but not a burnt valve), fuel, or ignition problem. The more I think about the 305 obdII error, I keep thinking ignition system. I saw something similar in a 95 tahoe and after the guy spent a lot of $ on the trans, he found a bad distributor. You said you did replace the #5 spark plug, #5 spark plug wire, cap and rotor, right? I had a 302 error (which was a misfire cyl#2) on a Ford F150 and it was the spark plug wire. The vaccum gauge is still goingto tell you the deal. I will be glad to help you diag the vaccum gauge reading, if needed. I will just need a good desciption of what the readings are and what the needle is doing while the engine is idling. Is it steady, bouncing, moving back and forth slowly. Does the SES light go out by it's self or do you have to reset it? These test shouldn't cost you much if anything. Let me know if I can help.

[tkdieter]

Had the same problem with my 97 tahoe so I replaced the wires and plugs but kept doing it. Ended up being the non gm cap that I had put on 10,000 miles before the problem.

[DJ JEFF]

Wish this guy would of finished out this post so that we all would know what the fix ended up being.

[aero246]

I suggest having your injectors cleaned before you do the head if all else fails. Do everything here that is listed from other users and if no satisfaction even after the mystery oil then do you injectors. You can take them out yourself, send them off to be thoroughly cleaned and flow tested. This should cost anywhere from $12 per injector to $25. Search the net and you can find good deal. Just make sure you mark which injector goes with which cylinder so when you re-install there is no problem. Good luck and let us know. I just realized, you may not have actual injectors, you may have a throttle body injection to which my advice would be incorrect.

[gurrzt]

If it is a sticky valve, try GM's "Sea Foam" top engine cleaner. You will have to change your oil after the proceedure.

[ChevyBobby]

Originally Posted by GMMerlin

Valves sticking in the guides of these engines is not an uncommon occurance. Especially # 3 or #5 cylinders.
Usually I can duplicate the complaint by revving the engine in Park and watch the missfire counters on the Tech2 as the engine comes back down to an idle.
It is also important to perform tests on the fuel injection and secondary ignition to eliminate those systems and then to perform a static and dynamic compression test to eliminate burnt valves,broken springs on any other internal engine concern

The fix is to remove the heads and have the valve guides replaced.

Depending on the dealers relationship with GM (which is the result of many factors), the dealer may or may not be able to offer you some assistance after the 3/36 warranty period.
Also "Goodwill" extensions to warranty include your relationship with the dealer also.
At 72k I can tell you that you have a less than 1% chance of getting assistance from GM

How do you perform a DYNAMIC an STATIC compression test?
What what does each do?

[GMMerlin]

Originally Posted by ChevyBobby

How do you perform a DYNAMIC an STATIC compression test?
What what does each do?

A Static compression test is done with all the plugs out and cranking the engine.
A Dynamic compression test is done with 1 plug removed (compression gage installed)and the engine running...

Static compression readings should be in the 140-180 range (depends on engine) and the dynamic test results should be at least 50% of the static.
If the static test fails (1 cylinder less than 70% of the highest) then a cylinder leak down test should be performed.
If the static test passes, then run the dynamic test.

Old school test was to use a compression gage and observe the vacum with the engine running, if it dips then you could have a valve concern.
personally I like the compression test better (more consistant results), but I do use a vacum gage quite often.

[ChevyBobby]

Originally Posted by GMMerlin

A Static compression test is done with all the plugs out and cranking the engine.
A Dynamic compression test is done with 1 plug removed (compression gage installed)and the engine running...

Static compression readings should be in the 140-180 range (depends on engine) and the dynamic test results should be at least 50% of the static.
If the static test fails (1 cylinder less than 70% of the highest) then a cylinder leak down test should be performed.
If the static test passes, then run the dynamic test.

Old school test was to use a compression gage and observe the vacum with the engine running, if it dips then you could have a valve concern.
personally I like the compression test better (more consistant results), but I do use a vacum gage quite often.

OK, I did that today and all cylinders showed 170 Static and 75 Dynamic.
Thats less than 50% of static.