weird idle (not another bs "i didnt search!" post =P)

[SunshineAcid]

history: had a rusted out 91 (guy drove to michigan all the time =\)while doing maint. on 91 i put 3 fingers *through* the frame. so...bought a blown 89 for 150 bucks (great body, hole the size of a pancake in the block itself)swapped the de into the e chassis91's engine ran fine before swap (was auto, 89 is 5 speed)did not mess with sensors, or change idle setup in any way/shape/formfirst started the de with no problems, im very confident about the wiring, we traced *everything* and even the diagnostic plug works, nothing was left unchecked/unhooked/cut)heres the question: when i start the car, it revs up and holds about 1k to 1.1k rpm and is a bit sporratic (sp?). it will stay like this until i turn teh car off, no matter how hard/soft i drive it, or ambient temperature. the reason i dont change it, is because after i drive the car and let it fully warm up, and turn it off, then start it up again (like going to a gas station) it idles perfectly. bout 775 rpm (i set it a bit high intentionally, as i think it sounds better and doesnt vibrate nearly as much)ive read up and and i think ive narrowed it down to the idle control sensor, the water temp sensor and the o2 sensor.i dont think its the o2 sensor, as my last tank, i got bout 18 mpg in the city (and i do have a bit of a lead foot)i dont smell the richness that a lot of nissans put off.but if it were the water temp sensor, wouldnt my readings in the cockpit be off too? i mean on the instrument panel, if my temp sensor was faulty, wouldnt my needle show it? unless that is on a different temp sensor (i know there are at least two of them =P)just trying to troubleshoot, if anybody has any .02 let me know pleasethanks in advance

[DjPantsSpecR]

no sorry, the coolant temp sensor and the sensor that sends the temp to your gauge are different. Look on your intake manifold near the bleed hole. The red plug is the coolant temp sensor and the black one is the gauge's sensor. I'm sure someone will now note how inaccurate the temp gauge is...

Recently i relocated the battery and made a much shorter intake on the passenger side of the car. The car idled like crap because the large tube coming off the intake that goes to the aaiv valve was recieving a bunch of unmetered air. I plugged that bad boy with a spark plug and now its idle is rock solid. just something i would try to trace other problems

[Arrow]

Did you by any chance swap out the instrument cluster from the DE to the E? I don't know if that could cause any differences or not.. I'd think that if it did it would only be differences in your reading and not how the engine runs... But yeah, like said before the coolant temp sensor is a 2 part deal and could be an issue. You might also want to check your O2 sensor especially if it is still the factory one b/c it would be 15 years old or so... I would also think that you shoulr get slightly better mpg if you drive it as easy as you say. I would say that I'm moderate on the gas and I get right around 20 mpg (although I do have an "E")... Just my 2 cents. hope it helps and GOOD LUCK!

[SunshineAcid]

well i tried replacing both sensors, one at a time, then both at the same time and still got the same thing.i guess next on the list is the o2, as i really dont want to go down to the dealer and get a new idle valve. they will ream me =\anyhow thanks for the input guys

ps: DJ which hose exactly are you referring to? the large one coming off the intake?