Engine Vibration after Timingbelt and Waterpump change

[AZ-3,1498cc,UK]

Just had Timing belt and waterpump changed on DOHC japanese version. Since the change the engine vibrates a lot more at idle when engine has warmed up. The vibration is felt strongly in cabin at idle. The back box has also developed a judder. The car idles between 650-750 when warm with rpm needle not quite as steady as before. I have reset ECU to no avail any ideas?

[perhapsadingo8yerbaby]

Educated guess on my part here but not too much of one I think. If the car was running fine before, and I assume it was, take it back and insist the work be inspected and timing belt reinstalled if needed. Sounds as though the mechanic allowed a camshaft pulley(s) to slip from its/their correct position when putting on the new belt. This is easy to happen but no excuse for a qualified mechanic to let it go back to the customer that way. After all, that's why you took it to a professional right? I'll wager whoever worked on it may have had some idea that the car was running worse than before you brought it to them, and their post-repair testing for this kind of job should have included running the engine to operating temp.

The same thing happened to me once on my 2.0L DOHC 626. The shop initially resisted (bAAAD idea on their part...) but after arguing with the manager that I KNEW what was wrong w/the job they did, could've done the work myself, had done it on other DOHC's & knew how to do it right, and with an interference type engine-did they really want to further risk bent valves?... they relented. Sure enough, one of the cam pulleys was slightly "off" position.

[AZ-3,1498cc,UK]

Took car back to garage their opinion being the Timing belt could be a little tighter than before that is why it is causing vibration at idle. The mechanic suggested adjusting the ignition timing to compensate. The mechanic decided to check the ignition timing instead of being 10 degrees it was 8 so he adjusted it to 10. This has not resolved the problem. The mechanic reackons to leave it a few days to see if belt adjusts. The mechanic also refitted the alternator belt and the fan belt saying they might be be too tight. He will adjust those first in a few days if problem does not improve.

[perhapsadingo8yerbaby]

Ok. What your mechanic is saying doesn't make sense to me but the important thing is that you not take possession of the car until it is running correctly. (assuming this "rock & roll" malfunction was not a performance issue before you brought it to them) Generally speaking, timing belts do not "adjust". They are made with extremely strong non-stretching cordage-not like a new alternator belt that may stretch a bit as it breaks in.

I picture your engine rocking & rolling because of uneven cylinder compression. i.e Combustion is occurring when the cylinders aren't sealed properly with the valves in a closed position-that is, the intake/exhaust valves are slightly "off" their desired position. Now before you had the work done, this was not the case. These valves are driven up/down-open/closed by the camshafts which are rotating as driven by each camshaft pulley-both pulleys are driven by the timing belt. However, installing a new timing belt with a camshaft pulley slightly "off" its correct position causes the problem you have described. Maybe an over-simplified explanation but hopefully it makes sense.

BTW before, when I sounded so high & mighty in my last post , I should add that I once made this cam pulley-position mistake myself when replacing a T-belt so have experienced identical symptoms twice- once for my mistake and again from a sloppy mechanic who made the same error. (different engines but both DOHC-principle is the same though). Dunno if that helps but keep us posted...

<small>[ June 22, 2004, 02:41 PM: Message edited by: perhapsadingo8yerbaby ]</small>

[AZ-3,1498cc,UK]

Got problem sorted now. Power steering belt and alternator belt were slackened. No vibration at idle although revs not quite as steady and slightly higher then before job was previously done. When warm idles between 825rpm and 875rpm.
Mechanic said covers were taken off to check and timing belt was not a tooth out.