Hi, I have a 98 Isuzu Amigo with a 2.2 engine. While I was driving the other day I noticed a slight knocking noise so I drove home and the minute I parked it, the car started running really rough. So I had a friend check it out and the timing belt was missing a couple teeth in 3 or 4 places. So I replaced that, but when I start it up it runs really rough until it gets warmed up then it seems to run smoother, however it still has knocking noise on acceleration only. If I idle it or have it at low RPM's its barely noticeable, but given gas its still there. Its not a hard slamming noise like I've heard rod knocks do. So we thought it might be a collapsed lifter and took it apart. But that doesn't look like the problem. Any idea what it may be. Also the car had oil in it when this took place. Any info will be highly appreciated. dimndi48
I found a service bulletin on timing belts that suggests that at a timing belt change that if the engine is running rough that a valve adjustment should be performed. I listed part of the bulletin from the Alldata automotive information website below.
1998-2000 VehiCROSS (VX) / Trooper
(UX) / Rodeo (UE) / Amigo (UA) V6 models
with "direct-attack" valvetrain.
For the above affected vehicles, periodic 60,000 mile valve clearance inspections are not required. Adjust if valve noise is evident or a rough idle condition exists.
NOTE :When checking valve clearance, adjustment is required only when the clearance (lash) is out of specification. Be sure to retorque the camshaft bearing cap bolts before checking and adjusting the valve clearance.
As of the knock; Check the compression of each cylinder. When a timing belt slips a few teeth on some engines there is no valve clearance so that few teeth missing puts the valve timing off and the valves hit the piston and sometimes bends the valve causing an engine miss, rough running engine or no start.
Do the compression test first then if that is ok then check the valve lash (clearance) to see if any valves may be too tight.
Try these few suggestions and get back to me with your results, we can diagnosis the problem further from there.
It acts like the plugs not firing because of the unburned fuel smell. We looked at the lifters and they don't seem to be collapsed. Is there a way to tell if one may be collapsed other then pushing down on them, which the book says is one way to tell. Why would the miss make such a clacking noise? The car was still in time when this happened when the belt was damaged. Any suggestions. Also my car is a 4 cylinder not a six, and I gathered from your response you may have thought the car had slipped time which it did not.
Did you check the oil pressure?
Check the oil pressure with a mechanical pressure gauge and not rely on the oil pressure gauge on the dash or the oil light.
The oil pressure should be checked with the engine at normal operating temperature and it should be about 21 PSI at idle.
There was a service bulletin that states that the oil pressure galley in the head could become blocked causing no oil pressure to the cam bearings. This could be caused by anything that is big enough to block the hole.
Check the pressure and get back to with the results we can go on from there.
Thanks for your response. I will try that and get back to you.