Have had major tune up with multiple fuel injection cleanings, engine code states engine misfire. What is the average cost for a valve job?
by Visitor in Tomball, TX on May 06, 2011
If you have a misfire and can verify that all external parts are ok you should then have a compression test done. If a cylinder or more is low, a leak down test must be done to determine if a valve is a problem. Only then would I consider going down the "valve job" path, as you may have alternatives, such as replacement heads, etc. But it's all guesswork until you test it.
Thank You Dave!!! My husband travels and isn't here to help with what we should be asking or looking for. You've been VERY helpful and now we know where to start. We'll keep you posted. Again, many, many thanks!!!
Glad to help!
Please start only by rechecking the "major tune up" to make sure all components that could be needed were replaced before being concerned with the compression test and thinking of engine issues.
I actually gave the shop, owned by a family friend, the receipts and detail of what Kwik Kar had already done and their diagnosis.
They replaced the plugs 1 coil, but, will there be a different code if it's a coil vs. misfire??? And could you please give me the values of what the test should show if nothing is wrong so I'll know what to look for and what to ask?
Leak Down Test
You've really saved the day Dave! My daughter and I are at the mercy of repair shops since my husband was transferred to Shanghai. I cannot thank you enough for taking the time to answer my questions.
When was the coil replaced? Coils are very much causes of misfires and misfire codes.
If your code was a P0301 or P0300 or P0316 - or all of those - then your #1 coil may fix the problem.
If after coil(s) or plug(s) are replaced you still have a rough running engine, then you could proceed with the compression test. It would be unnecessary though, if things are better now.
A compression test will show cylinders with a pressure of above 100 psi, unless there is a problem. All 6 cylinders will be very close in pressures to each other - any more than 25% off from the others would constitute a problem. Your compression pressures will probably be more like 140-170, but will be all the same.
A leak down test is only done if the compression test is a failure. If you get this far, advise and I can help explain further. Good luck!
Yes, the #1 coil pack was replaced and the problem still exist. The puzzle seems to be that the code is for a "random misfire", the first shop seems to think there is a carbon build up. They say they did a compression test, but have no documentation and no values... this makes me wonder how much was really done.
I took all this information to the repair shop and they really haven't gotten into it yet. I'll keep you posted.
Many, many thanks Dave.
A "Random Misfire" code alone (P0300, P0316 possibly) can be due to engine software issues too. A processor update may be in order. If your shop doesn't have the capabilities to check software level and impact on engine performance - you may need to take it to a shop that has what is needed. Just a thought.
That was me, by the way...forgot to sign in first.
Todays developments: The shop called and said they couldn't replicate the problem. They said to drive it till the check engine light came back on. So I picked it up and drove it home, but a mile from our house at a red light I put it in neutral and revved the engine to about 18000 RPM's, so the AC compressor would stay engaged and blow cool, and very suddenly the RPM's dropped and it started idling so rough I thought it was gonna die.
I made it through the light, but it was running so rough I didn't think I would make it home. Twice it seemed to just bog down like it wasn't getting any fuel, or maybe too much.
After talking with my daughter, this is exactly how it happened with her, but after it cooled down it seemed to run okay. At one point the check engine light even went off. Now it's just flashing. I'm afraid it wont even make it back to the shop.
Does this shed any light on the situation? Thanks Dave, your time and help is truly and deeply appreciated .
A flashing check engine light is a clear indication of a misfire that is either related to plugs and coils OR fuel injectors. Most likely plugs and coils. Why it happens when it does - I don't entirely know; things like this do happen erratically and intermittently. Have you had rain lately - like today when you drove it? Sometimes rain causes ignition problems to become more apparent.
The thing I'm getting most concerned about is the fact that a flashing check engine light indicates that continued operation of the engine will damage the catalytic converters, because of all the excess unburnt fuel going into the exhaust due to the misfiring. This could make an already troubling problem worse.
If you go to take it back to the shop and the light is flashing and the running is poor - you may want to just tow it back in to prevent a very expensive repair.
So sorry to hear of your continued issues. Keep us posted...
I agree, I'm afraid to drive it with the light flashing, We're planning on hauling it back to the shop on our trailer Monday.
Could any of this be a factor in ther AC not working unless the RPM's are up? Vice Versa, the flashing light comes when she's in Neutral or park and revving the engine for the AC?
This is just so frustrating Dave. Your advice is the best we've gotten and I'm confident we have the information now for the problem to be identified. I will keep you posted. Goodmorning, and thanks again Dave.
PS: Do you own a shop? Freelance. Dealer? How close to Texas are you?
The AC not working -- AC works best at about 2000 RPM; if the idle is low and poor, you won't get as much immediate cold air, although overall the system should still work. Your AC concern may be a stand alone issue that requires checking out.
You basically need a technician that will follow this through start to finish and get your diagnosis complete without more unnecessary drama.
I am located in California. I am the Service Director of a multi-line dealership group. Sorry I can't help first hand!
We're taking it back to the shop Monday. Your step by step instructions have truly made the difference. My daughter and I cannot thank you enough for your time and patience. You have given us the information to make an informed and educated decision and to not be taken advantage of, for this, I wish I could do more than just say Thank You.
Computer codes now read Misfire on Cylnders 1,3 and 6. Waiting to hear more. What should be the things that are checked and in what order???
I have a 2006 Liberty. Same issues stated above. There has been a service bulletin released some time ago stating this all as known issues having to do with excess carbon build up and the valves going bad.
Mine is in the shop right now with a repair bill or $2890 to replace the valves and heads.
Yup. My daughter traded me her 2006 Liberty because it was becoming problematic and I needed a "Doggie mobile". I slowly fixed everything and even had to replace the brain for $400 bucks to get the door locks to work by remote ????. All went away but the mis-fire while idling. After replacing plugs and one coil the problem was still there so I did a leak down test and found a bad valve. When I took it apart the heads were totally carboned up. It cost about $450 in parts and head work. Runs like a champ now. It had 110K miles and I hope to put another 50K or more on it without problems.