I have a 2001 jag stype v8 with 180k miles. I bought the timing kit and aligned the camshafts correctly but it still idling rough and sounding like a diesel truck. Anyone have any ideas as to what still maybe the problem?
Have you done a compression test?
Have you put a vacuum gage on it?
The “diesel truck” sound suggests a valve problem.
Yea I did the compression was 130-135 on all 8 cylinders
Is the exhaust system in good shape from the exhaust manifold to the tail pipe? Leaks in the exhaust system can cause both symptoms.
Thsoe compression numbers are low. I would suggest that the test be done again using the wet version; meaning a small squirt of oil in each cylinder before it’s retested.
If the numbers jump up by a fair amount there’s a piston ring/cylinder wall issue. If they stay about the same then it’s a cylinder head valve issue.
That’s all assuming cam timing is dead on, etc.
That may or may not be the cause of the rough idle as a number of things could be responsible for that. Vacuum leak, weak valve spring, ignition miss, fuel injector, etc, etc, etc.
The noise could possibly be excessive valve lash which could also cause a rough idle if loose enough or it could be related to the timing chain tensioner which is allowing the chain to rattle. It’s impossible for me to know if the noise is up top or down low.
Assuming compression ratio is 8-9:1 I’d expect 160-180 psi.
I bought the timing kit and aligned the camshafts correctly but it still idling rough and sounding like a diesel truck.
Did it have these symptoms before the new timing kit?
Yea it was doing it before the timing kit… I did a vacuum test and it was reading a shaky 16.5-16 in.Hg… I havent checked the valve lash but thats my next step… I also made to a video of engine running and the vacuum test
If the vacuum was unstable, you either have a vacuum leak or a valve problem. My money is on the valve problem.
So, has it ever idled smoothly and quietly while in your possession? What I’m getting at is do you have any idea what (if any) changes occurred coincident with the onset of symptoms. If you bought it like this, sounds like you bought a trashed engine that’s probably gonna have to come apart.
No it I bought it with a rough idle but it was quiet. I bought knowing it was gonna need some work, I was hoping for it to be not as bad as I thought. I think it might be the intale valves on thr driver side. I checked all the valve lashes on the exhaust and intake valves and they all are within spec except the driver intake valves. They were all inconsistent
I bought it with a rough idle but it was quiet.
So the noise started with the timing kit, right?
It started jus right before I bought the kit but after I bought the car
I checked all the valve lashes on the exhaust and intake valves and they all are within spec except the driver intake valves. They were all inconsistent
Please list those “inconsistent” valve clearances (along with the specs).
If the valve clearances on the driver side intake valves are out of spec, what makes you think the symptom isn’t caused by that? Are they just slightly out of spec then?
.28mm on all 8
.24mm on all 8
.27mm on all 8
The intake valves are supposed to be .18mm to .22mm clearance
The exhaust valves are supposed to be .23mm to .27mm clearance
A hundredth of a millimeter out of spec is meaningless and there’s nothing there to worry about.
Is it still possible to have a bent valve with those clearance values?
When a valve stem gets bent the lash increases and usually by quite a bit. It often comes across as a loud metallic and comparatively tinny knocking sound.
Based on those specs I don’t see an issue with it.
It does make a loud metal ticking noise. On the first page I posted 2 vids, one of a vacuum test and the other of just the motor running.