93 trooper intermittent rattle/knocking sound

[humanbreathing]

Hi Guys,

My 3.2 DOHC trooper has intermittently been making a noise for the past 50K miles... When the noise is present, it sounds very much like a diesel engine.... (a rattling/knocking sound)

The noise will appear, sometimes lasting for days, and then mysteriously disappear for weeks on end. There doesnt seem to be any pattern to the appearance of the noise... i.e. temp, climate, how long the engine has been running, etc. gas, oil treatments. There is also no real change in the noise between idling, acceleration, highway speed, slowing down. (other than the noise speeds up or slows down according to engine RPM.s)

Numerous mechanics say that it DOES NOT sound like valves. They are also quite stumped as to what it might be.

It also does not appear to be a pinging from pre-detonation as when the noise appears, it is consistent whether idling, driving normal, or under acceleration...

The best theory was the sound was coming from the timing belt tensioner... However, I have replaced the belt and oil-filled pressurized tensioner TWICE! This has not ended the noise... it still comes and goes when it pleases.

Most recently the noise has been accompanied by a periodic lack of power.. which is most obvious when depressing the accelerator pedal as the engine sounds like it is bogging down (and slows) This happened last on a two hour trip... about half of the trip I was unable to accelerate above 45 mph as I could only depress the acc pedal 1/3 way (or the engine would bog and slow WAY down)

The check engine light normally accompanies the "sound"

Most recently the check engine light threw codes 43 and 44.

Based on Code 44, my mechanic diagnosed the "periodic lack of power" problem as defective fuel pump.... the pump has since been replaced, but the problem still occurs.

My mechanic did not have an explanation for Code 43.

I just took it to my the dealer, but by the time the mechanic got around to looking at it.. the "noise" had stopped, and he could find "nothing wrong"! He said the engine checked out normally... and drove normally. So he could find no reason for the Codes.

Any ideas or suggestions would be helpful and appreciated

[Slanter]

this seems to be a common thing among 93's... mine started making that noise around 190,000 miles, and at about 230,000 miles I was driving it home, the engine lurched and I lost a good 3/4's of my horsepower. I limped home and had it checked out, and it turns out that the engine needs to be overhauled because it threw a rod... I don't know if they were related, but as soon as that knocking noise started I started gradually losing little bits of horsepower until finally the engine blew out. By the way, anybody know a good place to get rebuild kits for a 93 isuzu trooper or a new engine to drop in?

[IsuzuRS]

next oil change go to using synthetic, or atleast use additive like "sea foam". That would let you know if it is your lifters. I dunno about a rod.....thats would suck majorly!!

[JGBOFFROAD]

okay, i had a similar sound after a two plus hour road trip back from seattle... slight tick, that turned more into a knock... but then to a tick again, pulled the top end thinking to find bad lifters, but everything looked good, put it back together and it was still there... last week did a oil change with MOBIL 1 10-30 synthetic and after about twenty miles or so it went away, after about 2 hrs of high rev muddin still not there..... sooooo my thought is that the oil passages on the lifters are so darn small, that the synthetic with its high detergent profile are able to penetrate the passages on the valve train allowing the lifters to fill up... so i would try the synthetic step up... good luck!