2,5 tdi AKE running rough when warm.

[ametlib]

Hi,
This car is running great, except for one annoying issue.
I have a suspicion about what's wrong, but the suspect is rather expensive, so if one of you guys have a cheaper
solution I'll appreciate it.
Works like this:
When starting from cold the engine runs soo smooth. Then the enginetemp. rises, and "bang" At exactly 78.1 degree watertemp,
the engine sound changes from nice petrol Toyota to old Russian tractor.
When getting fully warmed up, it gets a bit better, but above 78.1 degrees the "bark" is always there.
However, this is only present at low load/ light throttle.
If this change happens at high speed/ load, it's not notisable. If happens at low speed in a quiet neighborhood, early sunday morning, well..
No codes, no smoke and lots of power.
Anyone experienced this or have an idea?

[adamss24]

Have a scan done, i believe the timing is either too advanced or the needle lift injector is faulty. You need to pull the codes and- if VCDS is available - check the timing plotted on the graph.

[ametlib]

Hi,
Thanks for answering.
No, I guess it's not that simple. Some more info,
I'we only owned this car for a short time. After I bought it I have had both heads off, replaced exhaust valves ( and guides) , camshafts, rockers and lifters.
Also replaced MAF, turbo, egr valve and injectors ( incl. needlelift) + all of the belts and rollers.
Cam timing is checked twice after I changed the cams. I.P. timing is spot on.
Funny thing is , according to my VCDS (lite) everything seem to work fine and all readings make sence, Advance solenoid, boost system,egr, temp sensors, MAF , and so on.
No fault codes. I might end up selling this to a deaf man . Any ideas?

[adamss24]

Faulty advance solenoid on the injector pump ? You could check for fault codes and injector imbalances with vcds...If no faults then it might need rebuilding anyway as the fault might be mechanical ! You used locking tools when timed the cambelt , yes ? Also what size head gaskets were fitted and i take it you replaced it with the same or thicker gaskets ?

[ametlib]

Yes , used pins and plates. Checked it again the following day, as I suspect the timing was a tooth out ( due to the barking)
Head gaskets, Elring, 2 holes in the left,3 in the right, same as the old ones.
Advance solenoid is interesting. When starting from cold, it lays around 25 ( giving a timing of approx. 12 degrees btdc)
During engine warm up, the number rises slowly( decreasing the timing) until 78.1 degrees watertemp, then the advance solenoid readings takes a jump,
and decreases the timing with approx 4 degrees from one second to another ( and the engine starts to bark)

This barking is not the usual (bag of marbels-too advanced timing knock) its more of a " lazy" bark. ( timing too retarded ? )

Questions: If the cam timing was a tiny bit out, would it really make this fault?
The I. P. is my candidate too, but if there is a mechanical failure ( advance piston) would'nt the ECU pick that up from
the needlelift and throw a code?

Keep the good answers coming, very appreciated.

[ametlib]

Well, this was helpful.
Even though I am 90 % sure this is an injection pump issue, I will still try to rule out the last 10 %.
Could the ECU , MAP sensor or some fault in the wireing make the engine run rough, but only when
warm and at low load, without giving a fault code ?
Anyone ?

[adamss24]

Why would you have different thicknesses head gaskets ? This is a new one for me ?!

[ametlib]

Why would you have different thicknesses head gaskets ? This is a new one for me ?!

Sorry, having language problems. Is your question : Why did I choose to fit two different head gaskets, or why did I find two different headgaskets
when I took the heads off ? Did all of theese engines leave the factory with two similar thick head gaskets ?

[adamss24]

Yes mate, every one i worked on had 2 identical head gaskets, you should not have one thinner or thicker unless you skim the head- which is not recommended on a diesel anyway !

[ametlib]

Thanks, I didn't know. Have replaced a couple of heads/ gaskets before, but not both sides at the same time.
Today I checked injectors imbalance, measuring blocks 13 & 14. Engine temp 91 degrees.

And , bingo, the right bank seems to be out, readings -2,75, -2,81 and - 2.86.
Left bank, both around 0. Have checked this earlier ( at least 10 times) and only once had readings slightly outside spec.
All the other readings (right bank) have been within spec. ( usually around -1 ) but all readings where negativ. Left bank always around 0.

What could cause this? ( Remember, I've checked cam timing twice since I put the new cams in, plates and cranshaft pin, went right in )
Also wonder, is a negativ reading more or less fuel ?
Any ideas?