Bent Valves? Or something else?

valves

#1

The check engine light in my 2003 Acura CL 6 speed manual transmission (under extended warranty) began coming on about three months ago. I felt a loss of power from the V6; it felt like I was running on fewer than 6 cylinders.



The first time I brought it into the dealership, they told me that it was an “ignition coil,” and replaced it under warranty. The car seemed fine for another 2 1/2 months, before the light came on again. I again felt a loss of power.



This time, they told me that it was the fuel injectors, and they replaced them. They reset the light once more, I drove the car home and it felt fine. The next morning, the check engine light was on again, and again I noticed a loss of power.



I brought it back to the dealership and after several days of them not being able to diagnose the problem, the service advisor called me and told me that the engine was losing compression and they suspected bent valves, which are not covered under warranty. The advisor essentially accused me of “over-revving” the engine, and that was the reason the problem was not covered.



The advisor then promptly quoted me a price of between $2500-$3000 to replace the bent valves, but was sure to tell me that they couldn’t be sure that this was the problem without “dismantling the engine and sending it to a machine shop.”



The dealership did perform a compression (but NOT a leakdown) test with the following results:



Cylinders 1, 3, 6 at “normal pressure” of 185 psi.

Cylinder 2 at 80 psi, cylinder 4 at 60 psi, and cylinder 5 at 100 psi.



n.b. I do not race or otherwise abuse my engine, and although I do downshift, I never remember downshifting to such a degree as to cause the cause the car to buck or the tach to go into the red, even slightly, not to mention, “burying the needle.”



With this as background, I have two questions:



1. A mechanic friend tells me that the black box in Acuras should be able to report if, when, and for how long the engine was ever over revved. If this is so, the dealership should be able to point to specific instances of “owner-caused” damage.



In other words, diagnosing this problem as bent valves caused by the operator is a guess by them, and based on speculation, not hard data from the computer. Is this information available from the computer in this model?



2. My mechanic friend also said that typically, bent valves caused by over revving affects ALL valves, or at least all valves on ONE SIDE. He seemed to think that a loss of compression in cylinders 2, 4, and 5, but not 1, 3, and 6 sounded like something other than bent valves as a result of the operator.


#2

P.S.: based on the fact that the dealership first thought it was an ignition coil, then fuel injectors, and lastly valves, it sounded to my mechanic friend that the dealership was just “throwing parts” at the car to see what would work. When they couldn’t figure it out, and rather than have the warranty company deny payment for misdiagnosis, they put it on me to roll over and just pay the cost to do the repairs, even though this may not be the real problem.

Thoughts? Advice???


#3

I would see if my mechanic friend can have a reasonable conversation with the Acura mechanic and/or service advisor, first. He could rebut any of the technical statements, which you cannot.

I would also see if the warranty company would entertain a second opinion from another shop.

My next step would be dependent on the outcomes of these two actions.

Was this a used car purchase? How long have you owned it? I can see a possibility of owner-caused damage done before you purchased it, depending on when you purchased this car.


#4

Do not pay much attention to what service writers tell you. They are not mechanics and the vast majority have little or no mechanical aptitude.

As to bent valves the engine cannot be overrevved. The engine computer will prevent this and besides, overrevving an engine will not bend valves. At the very worst the valves would do what is called “float” and this will not bend them.

My feeling is that what is happening is that the valve lash adjustment is not correct.
Did no one there consider the possibility of tight valve lash?
When the valve lash is tight the adjuster prevents the valve from fully closing and this will easily lower compression readings.

I constantly harp on this board about valve lash inspection being performed every 30k miles (in spite of idiotic factory recommendations otherwise) and odds are great this is the problem.
They should check the stinking valve lash, adjust as necessary, and recheck the compression while praying that overly tight exhaust valves have not burned.

Hope that helps and good luck.


#5

You do need a leak down test to confirm the valve diagnosis. Did it have a timing belt replaced?


#6

Thanks for the response!

I bought the car over 2 years ago, and never had a problem until about three months ago. My mechanic friend tells me that had the valves been bent when I bought it, I would have known soon after I bought it, not almost two years. So I think it was either caused by me, or it’s something else.

As far as the second opinion, I’ve spoken with the warranty company, and they told me that just to diagnose the problem, the engine may need to be sent to a machine shop, which will run close to $1000. If it winds up being the valves, and they are not covered, I’m on the hook for everything, including the diagnostic. Because it is an Acura warranty, I have to go to an Acura dealership. And I’m told that if the valves are truly the problem, I should not be driving the car anywhere, which means considerable towing/diagnosis expenses.

They don’t want to even confirm that the valves are truly the problem because then maybe they will be left to pay for the diagnosis and/or work.

I think I’m getting the shaft! (pun intended)


#7

It sounds like the dealer’s people are trying to get you to pre-agree that the repair work will be paid by you because the manufacturer knows that the mechanics have no idea what they are doing. I’ll bet that there has been trouble getting warranty work paid for. The only options they have are getting you to pay or getting you to go somewhere else to get the car fixed. Option two is highly recommended.


#8

No timing belt replacement. Each time the check engine light has come on, the computer reported the following codes:

OCT '08: P0304 (Cylinder 4 misfire)-ignition coil replaced.

JAN 8, 09: P0301 (Cylinder 1 misfire) and P0303 (Cylinder 3 misfire)-fuel injectors replaced.

JAN 16, 09: check engine light on again, no code reported-dealership thinks bent valves.

The leakdown is my next step…but unfortunately I have to do it at an Acura dealership. I’m going to have to have the car towed there, because I’m told that if the valves are the problem, driving the car is a big NO-NO.

Any opinion on only three of the cylinders losing compression (and non-sequential ones at that), or do you need to know the results of the leakdown?


#9

This is exactly what I’m hearing from multiple people.


#10

I will have them look into the possibility of a tight lash valve as well…thanks for the advice!


#11

Er, tight valve lash.


#12

Will a leak down test be able to tell me for sure that it is the valves? If it does turn out to be the valves, is there any way to confirm that I was the one that caused the damage, or could it be manufacturer’s defect?


#13

I’m going to back up a step and retract the valve lash statement. I was thinking of the smaller displacement engine and you have the 3.2 which uses hydraulic valve adjusters; all the more reason why overrevving would not cause this problem.

Since they had compression readings that varied wildly on non-sequential cylinders the next step should be performing a “wet” compression test. Very easy to do and if the readings go up this means a piston ring problem and any cylinder head work is not going to repair that. (Overheated engine by the prior owner could be responsible for that)

Now the reason for the misfires (coil, etc.) could be due to low compression. Low compression means a plug will start misfiring and this in turn will knock out other things along the line; coils, etc.
Also, diagnosing fuel injectors is not a guessing game and replacing all of them means wild guessing.


#14

"JAN 16, 09: check engine light on again, no code reported-dealership thinks bent valves."
If the check engine light is on, then there are code(s) to be read. I think you need a better dealer to go to.


#15

Thanks for all the great responses…PLEASE keep them coming!!!


#16

After some additional thought, a more plausible explanation has come to me.
The 3 questionable cylinders are 2, 4, and 5.
The firing order on this car is 142536. Notice the 3 bad cylinders are one after the other?

Here’s a theory. It’s possible that before you purchased the car the prior owner could have suffered a timing belt failure. At highway speeds it is quite likely when the belt breaks all of the intake valves in the heads will bend due to piston contact.

Maybe the belt broke at idle or upon startup with the latter causing the most strain on the belt. In this situation momentum may not have been enough to bend every intake valve in the head and it was simply 4,2,5 valve/piston collision which tapered off in a nano-second. In other words, the rotation would have damaged 425 in order and stopped instantly before proceeding to the next cylinders in order; 3,6, 1.

If the valves were not bent too badly it’s possible that compression could have been good enough for this problem to go unnoticed for a few years. Of course, during this some valve leakage would occur and eventually compression drops off enough that misfires begin. Misfires then destroy spark plugs, coils, etc.

It’s also possible that the prior owner may have had knowledge of this problem, decided to unload the car, and the next owner would be stuck with the headache.

My opinion is that a “wet” comrpession test should be done (should HAVE been done actually) and if the problem appears to be cylinder heads only then they are repairable.
Bottom line is that overrevving did not do this and as I stated, engine computers will not allow the engine to overrev along with the additional fact that even if one could overrev the engine this will not bend the valves but “float” them instead.

With the cylinder heads removed the tops of the pistons could be inspected. If the piston tops are nicked up this means the engine suffered a timing belt failure in the past.
Hope some of that helps and good luck with the warranty business. My opinion is that they should cover this as I don’t consider it a vehicle abuse problem by you.
As to whether the computer stores data and is retreivable, I do not know. You might contact the regional offices for Acura and check with them about it.


#17

Bent valves…HOW???

Did the timing belt break?? If not I don’t see how the valves could be broken.