BAD VALVE????? I think...

[lorenambrose]

Well I have been having trouble with this truck for awhile now. I went out today and did some real troubleshooting and thinking and think it may be a bad valve.

Here is what I have now:

1. Engine runs rough at idle, but ok at highway speeds.
2. After a 15 minute warmup at idle the forward O2 sensor on bank #2 steadily climbs to about .775v and does not fluctuate, indicating a steady RICH condition.
3. During the same time the #2 bank long and short term fuel trims go steadily lean.
4. If you hold an index card over the exhaust pipe it will get sucked down to the pipe intermittently.
5. Cyl 5, which is on bank #2 has slightly lower compression than the rest of the cylinders.
6. Engine idle drifts up and down through a range of about 50 RPM's.


To me this is screaming "BAD VALVE".

What do you guys think????? Could it be anything else?

 

[Quartermile]

If you know this much you should know what the problem is

 

[lorenambrose]

If you know this much you should know what the problem is

I think that is what I said. However, I have been battling this rough idle for 8 months and the dealer has three times told me there was nothing wrong and it was supposed to run like that.

So I was trying to get some opinions from some knowlegable people to see if I am heading in the right direction. I see you have a wealth of constructive input on my thread. What point are you trying to make? Are you just trying to be a wise guy?

Anyway, thanks for the thoughtful insight....

 

[Rearanger]

5. Cyl 5, which is on bank #2 has slightly lower compression than the rest of the cylinders.

How much "slightly"?

 

[Big Jim M]

Nope! You don't have a bad valve! What you have is a normally running engine that you are worried about. NEVER pull heads that aren't really needing it. Every time the heads are R&R'd the shape of the block can be changed from the retorqueing of the head bolts..
I think I'd be trusting the real mechanics that stood to gain from telling you there was something wrong with your engine.
Big JIm

 

[Ranger44]

I've had a "slight miss" at idle for a while now too. It's a 3L. I think it's just common.

 

[lorenambrose]

im with everyone else on the valve, my dad bought the 02 brand new, and it never had a silk smoothe idle, always seems to miss slightly and fluctuate a bit at idle from day 1. i have 150000 on it now and it runs great. i would try to test the fuel pressure and see if it is correct, too high will wake it run rich. i had a bank one system too lean and a bank two system too rich at the same time. the problem wound up being the o2 sensors getting lazy at the end of their lives, replaced them and cleaned the mafs, problem solved

I changed both O2 sensors and the MAF. I know that bank 2 should not be going steady rich. Something is causing this. I do not believe this is a 3.0l thing. It can get pretty bad sometimes, to the point of shaking the whole truck.

It also has a slight pinging under load that can not be gotton rid of.

 

[Ranger44]

Now, the truck shaking and the pinging is a problem. Any other symptoms?

 

[lorenambrose]

Now, the truck shaking and the pinging is a problem. Any other symptoms?

Well the truck is at another dealership, and they seem to think there is a issue causing this. They feel that there is something wrong internally.

 

[family builders co]

I had the same problem with #6 cylinder, cranking compression was about 140lbs, within limits. We then did a running compression check, was around 40lbs, should have been around 70lbs at the lowest. It was my valve seat. This is the second time within 30,000 miles that this has happened on this engine. After 1,000 miles on the second valve job, the engine seized, and is now back at the mechanics shop, for a rebuilt engine from Ford. My mechanic should be able to retire after hes done with my truck $$$$$$.

 

[lorenambrose]

Nope! You don't have a bad valve! What you have is a normally running engine that you are worried about. NEVER pull heads that aren't really needing it. Every time the heads are R&R'd the shape of the block can be changed from the retorqueing of the head bolts..
I think I'd be trusting the real mechanics that stood to gain from telling you there was something wrong with your engine.
Big JIm

Got it back from the dealer today. They had it for 4 days of troubleshooting. They have said it was definatly rings/cylinder walls or valves. I am not sure where you get your info from, but whatever.They were on the phone with the Ford engineers for 2 of those days. So it is definatly NOT a normal running engine and IS a valve or rings. I have an appointment to have more work done. I had to pick it up cause I could not afford the rental car any longer. Hopefully all will be taken care of under the warranty.

 

[BRUTUS_T_HOG]

Got it back from the dealer today. They had it for 4 days of troubleshooting. They have said it was definatly rings/cylinder walls or valves. I am not sure where you get your info from, but whatever.They were on the phone with the Ford engineers for 2 of those days. So it is definatly NOT a normal running engine and IS a valve or rings. I have an appointment to have more work done. I had to pick it up cause I could not afford the rental car any longer. Hopefully all will be taken care of under the warranty.

if they did a cylinders leak down test they would be able to tell you EXACTLY what the problem is.

you can do this same test by rigging some stuff up from a compression tester and an air compressor.

anyways... when you say the fuel trims are going lean... you are saying its adding positive numbers right? not negative numbers?

have you checked for vacuum leaks or leaking fuel components?

 

[Big Jim M]

??

Got it back from the dealer today. They had it for 4 days of troubleshooting. They have said it was definatly rings/cylinder walls or valves. I am not sure where you get your info from, but whatever.They were on the phone with the Ford engineers for 2 of those days. So it is definatly NOT a normal running engine and IS a valve or rings. I have an appointment to have more work done. I had to pick it up cause I could not afford the rental car any longer. Hopefully all will be taken care of under the warranty.

We get our information from the original poster...in this case it was you. So far you haven't described a bad valve. Even after bringing it back from the dealer.
Big JIm

 

[Rearanger]

They have said it was definatly rings/cylinder walls or valves. Hopefully all will be taken care of under the warranty.

"Definately" is not very accurate when they include "rings/cylinder walls/valves". They could have said definately the engine. I hope it's under warranty but unless you purchased extended warranty it'll be up to you to pay. A leakdown test may tell you better where the problem is but that involves listening to where the air is leaking from - not an exact science. I don't know if a smoke machine can be used to give a better indication. I think you're into a least pulling the heads to get a better idea if it's a valve. I guess you're not getting any codes?

 

[lorenambrose]

"Definately" is not very accurate when they include "rings/cylinder walls/valves". They could have said definately the engine. I hope it's under warranty but unless you purchased extended warranty it'll be up to you to pay. A leakdown test may tell you better where the problem is but that involves listening to where the air is leaking from - not an exact science. I don't know if a smoke machine can be used to give a better indication. I think you're into a least pulling the heads to get a better idea if it's a valve. I guess you're not getting any codes?

No CEL codes, but the mode 6 data shows a code for a random misfire. Unfortunatly mode 6 data does not illuminate the check engine light. The next step according to the engineers is a cylinder leak down test. I do have an extended warranty through 2012.