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94 d21 high idle PLEASE HELP ME!!!!

28190 Views 9 Replies 4 Participants Last post by  dylandames123
I have a 94 nissan D21 with 2.4L with which seems to start and run great until it is warmed up. The motor Idles between 1000 to 1100 which is fine but Once the motor is warmed up the idle increases to about 1700rpm.

If you continue to drive the truck the idle will eventually settle down to 1000 but will usually increase all on its own back to 1700rpm without touching the gas pedel.

I have READ LOTS OF POSTS and have a great mechanical knowledge but cant seem to fix this isseue.

- I have cleaned the TB with cleaner
- Cleaned / Oiled throttle linkages (Nothing sticking)
- Did remove and clean old IAC valve
- Ended up replacing IAC valve with new one
- Bent the indicator for the wax kit, very hard to explain but I have removed the cold start linkage so that it CANNOt open the throttle body
- Replaced the cooling temp sensor
- Replaced the O2 Sensor
- Replaced air filter, Fuel filter

I give up!!!! I keep replacing part after part but no luck. I have tried to feel and inspect ALL vacuum lines and cannot find anything that is broken or cracked etc.

I know that someone has posted to try and ground a couple wires from some harness and that may solve my problem but I have NO IDEA what wire or wire colours I need to try and ground.

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I AM still LOST!!!

My truck still Idles way to high.

Recently I have removed the air cleaner assembly and completly sprayed the hole engine with a thick soapy leak detector solution including the intake manfold gasket to try and TEMPORY seal any vacuum leak if any and during the hole procedure the truck sat there at idle of 1700rpm..


Should I open up all electrical wire harness looking for a bad splice?????

I tempory turned the idle screw counterclockwise 1 FULL turn and the IDLE DID COME DOWN :waving:

But I really think this will end up causing the truck to idle too low now or stall.

:balls: what do I do
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Ok I am gonna test the tps sensor with a ohm meter and will post my readings. Gonna tighened the intake manfold but I am sure it is not a leak because I have sprayed the intake manfold gasket and all vacuum lines aND NO CHANGE.
I have checked my throttle position sensor and found the readings to be 1500 with throttle closed and 9980 ohms at 7/8 throttle. At full throttle the ohm reading was open.

I have adjusted the tps so at WOT the reading is 9980 ohms and at idle the reading is about 800 ohms.

The truck still idles high at 1600rpm and does settle down to about 900rpm.

ANY OHER IDEAS ??? how do I check the mass air flow sensor??
WELL I have removed the mass air flow and cleaned it with carb cleaner with a cotton swab.

Also remove all tape from main wiring harness and I FOUND the 3 ground wires (black with green stripe) splice and a couple of other factory splices within the harness. Everything looked good but I DID re strip the wires and used a marett and taped everything back up.

The Truck has been great!!!!

Problem was believed to be bad ground wire in harness
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