# High IDLE RPM after Head gasket replacement !!! Confused and Frustrated!!!



## Godzy mini (Jan 17, 2020)

Hello guys after a lot of work i am back here to ask for some help.. here is the story i own a 1994 nissan sunny/pulsar hatchback ga16dne with 1gen EFI 5 month ago i blew my head gasket and from then i start the rebuilding project but I am really frustrated and confused with the remaining HIGH IDLE problem the last thing i done is IACV replacement, please spend a minute to read. The work done is :
1-) Resurfaced the head , porting and polishing, valve lapping, valve guides replacement , valve stem replacement , head bolts gaskets , fuel rail
2-) New Spark plugs , ignition module ( CAS sensor for Nissan) , distibutor cap and rotor fuel injectors , Coolant Temp Sensor, EGR Solenoid , PCV valve and hoses, IAC valve and all the hoses and vacuum lines with new one, fuel hoses, radiator hoses throttle body gaskets , new oil and coolant
3-) MAF sensor cleaned , butterfly valve cleaned , egr cleaned , battery terminals cleaned and lubed with dielectric grease
4-) Mechanical timing is OK, ignition timing is Ok, TPS checked and voltages are ok, fuel pump ok , maf sensor ok unless i took wrong measurments i dont think so but again...the only thing i dont took measurement is EGR valve solenoid. Smoke test done no vacuum leaks, starter fluid test no vacuum leak. Idle adjusting screw closed (no extra air can go in to the engine)
But yesterday before i replace the IAC valve i find coolant leak at coolant drain plug my coolant level was low i did not refuel the radiator with coolant and replaced IAC valve then i start the car and i noticed little change at idling it was little bit lower as temperature keep rising i noticed infinitesimal rpm dropping i dont let the car to get the operating temperature i saw whitish smoke coming out of my exhaust and shut it down. So my question is can low coolant level affect idling so much i think i have lean condition. Is CT sensor doesnt has the correct readings cause of low coolant level ? Do i need fast idle recheck and adjustment? i ordered nissan consult Diagnostic tool but i really dont know what to check again and solve this problem . I cant understand what is going on really . I really appreciate any suggestion, guide or help . THANKS in advance.


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## VStar650CL (Nov 12, 2020)

Lean without any vacuum leaks should make the idle crappy and stall-prone, not high like a vacuum leak. Vacuum leaks cause a high idle because it's unmetered air, lean burn is a byproduct. And no, coolant level won't cause a high idle. Coolant could cause a white cloud, though. What did the cloud smell like? Not sure on a '94, but later Nissan IACV's all need to be programmed to the ECM as part of IAVL, that could be a problem too.


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## Godzy mini (Jan 17, 2020)

VStar650CL said:


> Lean without any vacuum leaks should make the idle crappy and stall-prone, not high like a vacuum leak. Vacuum leaks cause a high idle because it's unmetered air, lean burn is a byproduct. And no, coolant level won't cause a high idle. Coolant could cause a white cloud, though. What did the cloud smell like? Not sure on a '94, but later Nissan IACV's all need to be programmed to the ECM as part of IAVL, that could be a problem too.


Yes its sound crazy but i can assure you that i dont have vacuum leaks..i think maybe coolant level can cause high rpm because of nissan wax type thermal element ..but i never heard them fail...never...i dont know man i am really out of solutions and ideas...i am waiting for my order tommorow i brougth a nissan consult diagnostic ..


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## VStar650CL (Nov 12, 2020)

Just a thought, but is your PCV maybe stuck open? That will act like a _big_ vacuum leak but will come back out the inlet on a smoke test and might not be noticed, and you'll certainly get an oil-cloud on startup.


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## Godzy mini (Jan 17, 2020)

VStar650CL said:


> Just a thought, but is your PCV maybe stuck open? That will act like a _big_ vacuum leak but will come back out the inlet on a smoke test and might not be noticed, and you'll certainly get an oil-cloud on startup.


I will check it again today ...so i fill it with coolant let it warm up with high idle and take it for a ride and now i think i have bigger problem with flactuating idle !!


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## smj999smj (Jan 1, 2006)

I have seen some incidents where there are two engine harness connectors that are the same and in the same area and the person working on it had those connectors swapped. I saw someone do it on a old Quest and I did it myself on an old Honda Accord.


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## Godzy mini (Jan 17, 2020)

smj999smj said:


> I have seen some incidents where there are two engine harness connectors that are the same and in the same area and the person working on it had those connectors swapped. I saw someone do it on a old Quest and I did it myself on an old Honda Accord.


Soo after some experiment with the only thing that i didnt mess up everything seems fine..i just needed fast idle cam adjustment all these days


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