R32 gtr misfire at idle

[-BNR32-]

Just bought a 92 R32 GTR, and the previous owner said it just needed new injectors.. Its running on 3 cylinders atm. I've put in new injectors, plugs, coilpacks w/harness, battery, igniter, head and turbo gaskets. Cleaned out the mafs, and did a timing adjustment and compression. 165 across all 6. Misfires at idle, and sits at about 1500 rpm. Runs perfect as soon as you give it gas, but if you let it idle, it starts popping.

Don't know what else to try.. Intake gasket? Vacuum leak?

Would really like to drive my new car.. Please help!!

[Armanio]

R32 gtr misfire at idle

Checked tps, idle air control valve? Does it misfire in the higher end also? Were the harness and coils/ignitor brand new that you swapped in?

Check for vac leaks. The most common issue is the ignitor/coils/ harness.
What plugs and gap are you running?


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[-BNR32-]

I will check tps and idle air control valve tonight. Harness coilpacks and igniter are brand new. NGK Iridium plugs, also brand new, pre gapped but double checked for 0.08. Plugged up one vacuum leak, might be more though.. Only misfires at idle (1500rpm..) Anything higher is mint, no problems at all.
Going to also try spraying some carb cleaner tonight, see if I can find any spots it might be getting in.

[Owen18]

Why do you have the idle set to 1500? Should be at around 900

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[Armanio]

I bet you still have a vac. Leak somewhere...


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[-BNR32-]

Ya Armanio, we sprayed some carb cleaner, and found a leak on the intake manifold. I've got a full set of gaskets, but that's a lot of work to pop that puppy off...

[Skym]

Usually it's the o2 sensors picking up on an intake airleak. If you unplug o2 sensors the engine can idle glass smooth with no missfiring.

What's happening is the o2 sensors are making the engine run too lean, thus a lean missfire.

Usually means the ECU needs to retuned, where this problem can be fixed by the tuner.

It's noticeable after fitting a mod like exhaust that requires the ECU to be retuned.

But sometimes it can be the oil is too thick at certain oil temps and engine struggles to idle. Stock oil is 7.5w30, but only 5w30 or 10w30 oil can be bought off the shelf. Ideally you would run a w40 for mild street use, up to 120 degrees C oil temps and w50 for above 120 degrees C (racetrack, etc).

Intake airleak can be spotted by rpm rising, falling (due to o2 sensors) and can be seen via rpm on dash. Rpm should be fairly solid, fluctuate mildly when there's no intake airleaks.