idle problems

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Senior Member
well, i bought a '92 cx hatch about a week ago.. d15b8, sweet ass 70hp motor. anyways, the guy i bought it from has it mod'd a little (god knows why). one of the things he added was a skunk2 cam gear.

here's the problem.. it doesnt idle worth a shit. if i just start it and let it sit in the driveway it will idle all day long. but once i start driving around, when i come to a stop the idle gets real rough and unless i keep giving it gas it will die. i let a few service techs at the isuzu dealership i work at take a look at it, and i got different opinions.

one of them seems to think the cam gear is too far advanced. but would that affect the idle? i thought the cam gear changed valve timing, not ignition timing?

the other guy told me he thinks its probably the iac valve. he recommended i start by changing the o-ring and see if that solves the problem, so that is what im going to do. makes sense, i guess.

i just wanted to hear some other opinions! also, oddly enough, i guess, when the ac is on it idles fine stop light to stop light.. well, for the 10mins or so i was driving around with the ac on at least.
i advanced my cam timing to like 4 on the intake cam once by mistake and it caused a crazy idle surge/failure type thing much like you describe.
If you are running different pistons in the engine (higher compression) the engine will load up with fuel after driving and coming back to idle. The fix is replacing the cam with one that will work correctly with the pistons. I have the same problem with my car. I have 11:1 on a stock cam. New cam is on the shopping list. This is on a z6.

It is also possible that the throttle cable is too tight. Try loosening it a little. (probably not it but it's much cheaper)

A third possibility is that the fuel return at the end of the fuel rail isn't working correctly.
tonight we replaced the cam gear with the stock one, replaced iac valve o-ring, adjusted valves, replaced cam seal, and what not. the car runs perfect now. it was either the cam gear or the iac.. pretty sure it was the cam gear.

on a sad note, now that i do have the stock cam gear i can feel a nice bit of oomph is gone. oh well.. :p

but check this out.. went to take the cam gear off, and there was NO BOLT TO TAKE OFF. the bolt had apparently been broke off in the cam, by the previous owner. the only thing holding my skunk2 cam gear on was the woodruff key. hEH. fortunately, the broke bolt was pretty loose in the cam and we were able to turn it out with a screwdriver.. luckily we found a bolt laying around that fit.