Bt-Ryoku said:

I have a 1G non turbo, have had it for almost 5 years. Hand me down from my brother. Have literally replaced everything in the car besides the shell itself. Low mileage motor that ran perfect when i put it in. Completely stock besides an upgraded suspension, muffler for the sound, and a K&N stock air filter upgrade. Lately I've been having problems with my idle(idling around 700). Seems like i have a misfire ONLY at idle, but when i get up and running the car runs smooth. Back down to idling and it seems like the car is running on 3 cylinders(more like 3 1/2). Since it started, I've replaced the o2 sensor, plugs, wires and none fixed the problem. Even throwing in fuel additives didn't help. Had someone check out compression and vacuum leaks, all checked out fine. Said i should replace the ignition coils and power module near it but both had no success. Got to the point to pull out all the injectors and found 2 cracked. Thought, Hey! there's my problem. Only had enough money for one so i replaced the more damaged one. Still no success. Now I'm completely stumped. Only thing's i haven't replaced are the MAF and EGR. Also pulled out wires from motor and it seems like cylinder 4 doesn't have as much effect on misfire like the first 3 do. It also seems like I'm going through gas quicker than I go through an order of french fries. Any help?

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What kind of spark plugs and wires did you use and what gap on the plugs?

When the car started acting up i threw in the original NGK's and BWD wires. All the good stuff. The car started acting up a few weeks after i decided to clean up my motor with engine degreaser. But i made sure everything open was covered before doing so. And the gap is what's shown on the hood.

i seafoamed my engine and it was fine for a few days and then all of a sudden it started doing exactly what your is, all i did was change the plugs and its been fine ever since.

I had the same problem with my Z. It turned out to be an injector. try pulling the wire off of one at a time and see if the miss changes or get worse. If it stays the same you found your bad injector. The same could go for the coil packs. Good luck at least you done have to pull the plenum to replace these injectors.

Jeff90Z99GST2G said:

I had the same problem with my Z. It turned out to be an injector. try pulling the wire off of one at a time and see if the miss changes or get worse. If it stays the same you found your bad injector. The same could go for the coil packs. Good luck at least you done have to pull the plenum to replace these injectors.

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Yeah I had a similar problem, turns out it was the injectors.

A friend had a problem with misfiring as well, although his problem was that he had a 3" exhaust, once he put 2.5 back on it fixed the problem.

But for sure look into the injectors! good luck man!

Well I've already done the plugs. Car wouldn't have much change when I pulled out cylinder 4 wire, so thinking it was the injector I replaced it. Still no luck. Even went out and replaced my coil pack and power module near it. Still nothing. Took it to a neaby shop to get another opinion. Checked compression, all passed with flying colors. After pulling out all the plugs they seemed a little white and he told me I was running lean. So thinking my fuel filter was plugged, I replaced it. Nothing. Since there's nowhere to check my fuel pressure I've started thinking of replacing my fuel pump considering I have an old, but good fuel pump sitting in my garage. Any other suggestions?

if the car runs good off idle then you could have a vacuum leak could be the intake gasket . try spraying carb cleaner around the intake to see if it smooths out.

Well I sprayed around the intake with some carb cleaner. When I got around to the bottom it started sucking some in and raised the rpm's a bit, but didn't exactly smooth it out. Couldn't really see if anything was cracked or came loose. Looks like I'm gonna have something to do this weekend, pull off my intake manifold.... Will post up with results. Wish me luck.

So reading up on what I posted here years ago, I gave up on my car and have been running is as is since then. I'm finally now trying to get it running back to normal with no idle issues, but still no luck. Honestly the car is just a commuter to work about 10 minutes away so it doesn't get many miles on it. Here's a list of what I've done to it since : replaced my intake hose since it corroded away and had a big hole with an aftermarket setup from my local autoparts store, had the intake manifold gasket replaced the other day since it was sucking in unwanted air, a basic tuneup consisting of plugs and wires, and the car still has an idle issue. Again it runs fine when up and going but has a horrible idle. At cold startup it revs like crazy like it's an idle air control valve issue, but once it warms up its as if it's running on 3 1/2 cylinders. Not 3 cause when I disconnect a spark plug wire, any wire, you really feel the 3 cylinders. And when it warms up the high/low revving goes away. The shop I took it to thinks I may have a throttle body issue with it. On that note, I did a little research but could only find info on a turbo version throttle body rebuild, which was basically the shafts seals and clean out the internals. Has anyone ever had a similar issue with the same motor? Again all info I find is regarding the turbo version of my motor and the vacuum leaks that version would have, but nothing concrete on a non turbo engine. Any help or tips would be greatly appreciated.

I may have missed it, but is your motor a 4g37 or 4g63? I vote for a nasty tb or iac, need to clean both, maybe rebuild the tb. Since under load/@ throttle it seems fine, id say it's a vacuum issue or fuel related at idle.

check your injectors resistance (make sure they are similar) to atleast check the electronic component of them.

Could be anything that is fuel/air/timing related.