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not datsun but still need help

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have an 89 trooper, 2.6, 5spd, and am having trouble getting it to idle correctly. any way i can check the throttle positioning sensor? was told it might also be the maf sensor too. is this possible? i'm also running a cone style k&n air filter that is in need of cleaning also. any ideas would be helpful.


also, engine is a 91, i just replaced the head gasket about 250 miles ago. i replaced the egr about 2 years ago and the idling problem was there beforee i did the head gasket.


i've replaced both maf and tps, maf was used out of a running vehicle. tps was new. this is a fuel injected multi? port engine. any ideas? i've also replaced the airfilter.

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The TPS is tested with a multimeter- you just check each terminal and ensure it makes contact at different spots (usually they're just a multiposition switch, though some systems had switched to a potentiometer so it would only have a couple terminals and have a ohm range. But I don't think Isuzus used that type).


Normally, poor idle (and no other obvious symptoms) on those is simply a case of air hoses that are cracked/ leaking or not sealed well. Essentially, ALL air has to go through the MAF, so you're looking for a leak between the MAF and the throttle body. A leak causes the system to go lean, but at higher air flow (off idle) it doesn't show up.

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91 is OBD 1, you should be able to check the codes on the ECU without a code reader. Nissan has a flashy light, I'm not sure about your trooper. You FSM should have something about it.


Is it a ruff idle or just low? You should have an idle air control valve, on the valve there will be a adjustment screw, if you idle is just low you can bump it up there. You should also have 8" or more inches in-between the k&n/maf and your throttle body, if it is less it will get a bad reading.


I would check the ECU for codes first, if it says everything is A OK I would check for vacuum leaks. When was the last time it had a tune up? I always do a full tune up before diagnosing any EFI problem.

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