Idle slightly rough after T-belt change?

[nogirlsatgt]

I had my timing belt, water pump, and associated accessory belts and gaskets changed last Friday by a local independent mechanic who has a good reputation.

After picking the car up I drove to the post office (~ 1 mile away) and noticed while sitting at a red light it seemed a little rougher than before. The needle dose not jump around, there is no unusual noise . . . it just seems to "buck" a little harder every couple seconds when sitting still ad idle. There is no hesitation when dipping into the throttle, and the car feels otherwise the same as before when driving around.

I stopped back by the shop, the mechanic took a quick peek around for loose vacuum lines or sensors but couldn't find any. He recommended driving it a bit over the weekend as I normally would to allow the computer to go through it's readjustment process (the battery was disconnected during the repair) to see if it went away.

Welp, I went through about half a tank of gas this weekend and still think it idles a bit rougher than before. I can't tell if it was there before and I never noticed it, but I'm usually very observant about things like that.

What could cause something like this that may have come up during a timing belt installation? What if the timing belt was installed one tooth off?

 

[cbrcrx]

My did that after the t belt change, but was idling a little low too. It was a tooth off on the timing belt.

 

[bucksatan]

+1, sounds like it is a tooth off. I'd have a shop check into that. If it isn't that it could be any one of the usual suspects, loose ground connection, loose battery, EGR etc. But since you just had the timing belt done I would check that first.

 

[nogirlsatgt]

Noticed it's only doing this once warmed up, if that makes a difference. After sitting all night and starting up this morning, it idled fine before it got up to temp and dropping down to ~800 RPM.

Guess I'll clean out the EGR tonight and take it back in if that fails to solve the problem.

 

[cbrcrx]

It could still be the timing belt a tooth off. When it is cold, it idles higher and it doesn't feel rough until the rpm drop. Mine felt fine at any rpm until warm idle.

 

[Qcpro5]

Just had my T-belt done and same thing is going on with my idle. It does not really bother me but could it be a source of further problems? I don't really want to go back in and get to the timing belt again, that was one heck of a process...

 

[bucksatan]

If the shop put the belt one tooth off, they should be fixing it for free. They probably won't want to do this as it will take most of a day, but they should be fixing their errors.

 

[TheMAN]

why should anyone pay for someone's **** up?

 

[sephiroth]

I remember doing the T-belt on my FP.. it's very easy to miss a tooth.

 

[i12drivemyMP5]

why should anyone pay for someone's **** up?

That's a good question for those that do insufficient work & expect to be paid again when you bring it back because it has issues. The correct answer of course is nobody should, the fucker uppers should be paying or spending more of their time to complete what they started. They should also pay you for the extra time of yours they are now wasting from not doing the job correct the first time. But of course that'll never happen.

 

[slavrenz]

That's a good question for those that do insufficient work & expect to be paid again when you bring it back because it has issues. The correct answer of course is nobody should, the fucker uppers should be paying or spending more of their time to complete what they started. They should also pay you for the extra time of yours they are now wasting from not doing the job correct the first time. But of course that'll never happen.

Is it fucker uppers, **** uppers, or fucker ups? lol, seriously tho, I agree completely.

 

[P-Funk!]

+3 for the timing belt tooth. Return and they can check.

 

[RABID_MP5]

yeah this is a bit trickier than on a single cam engine where a tooth off is precisely that. On the P5 you're synching up 2 camshafts, either or both could be off vs. the crankshaft. I'm thinking you just need to pull the top timing belt cover and verify vs. the crankshaft timing wheel. Or maybe put a screwdriver in a spark plug hole to find TDC that would correspond? i.e. I'm thinking what's the easiest way to verify without much teardown?

 

[TheMAN]

no way to do it unless you pull some cover off

you think this is bad, try doing a timing belt on a 929

 

[kudakev615]

Or the miller cycle s/c millenia