Idle probs

neverfastenough

Registered User
Well heres the story my idle is about 1000 at idle in park and goes back and forth from 800 to 1000 while idling rough.then if you put it in drive or reverse it drops to 600-700 and has pulsing idle rough for 3 seconds smooth for 1 and then twice as bad in drive and a/c. Plus when you start it jumps to 2500 and veryslowly comes back to 1000-900. It has new IAC, TPS, coil pack, Throttle body gasket, PCv valve, MAPP sensor and plugs and wires changed at 70000 it has 103000 now
 
Have you noticed the vac. gauge reading less than normal? It should read around 20 in park and about 15 or so in gear.

You may have a vac. leak some where...
 
I just a similar kind of problem and it turned out to be the plugs. It is always a pain to trace an idle problem. And somtimes expensive. What kind of plugs did you put in when you changed them?
 
Did you try disconnecting the battery for a while, and then drive the car around to let the computer re-learn? Just a thought for you.

Mike
 
Did you check for any CEL codes stored in the EEC. It sounds too erratic to me for a vacuum leak. Definitely check for codes and then do the 're-learn' by disconnecting the battery. It could be as simple as a cracked insulator on one of the plugs - which is very easy to do on these cars, especially if you used a large ratchet handle to tighten them. I learned my lesson the hard way and now always use a palm ratchet. Otherwise it could be your cam sensor going bad - but that would normally throw a code, like "214".
 
I would guess that bad plugs would show up more under boost, due to the added resistance. I wonder if it could be O2 sensors?
 
ok plugs were replace with factory motorcraft double platnum
cam shaft sensor new
new dis
and battry has been off several times
 
O2 sensors arent throwing codes but i changed one way in the past. Will it even throw a code if they go bad though? One code i am getting is no knock sensor sensed during dynamic responce test. Code 25 doesnt throw a chck engine light, but it came up the first time I pulled codes before I changed the IAC TPS and coil pack. And came up again in the most recent test about a month ago. Any thoughts
 
Well, for code 25 - I would check to make sure that the sensor is plugged in to the harness (it's right above the passenger side of the oil pan).

O2 sensors don't always throw codes - I mean, they can respond slowly for a while without being bad enough to throw a code.
 
No ideas huh. This baby is my daily driver im kinda getting worried. Like i said the iac and tps are like a week old. Are their any calibrations i need to do or do they set themselves?
 
The IAC is controlled directly by the EEC, so you can't tune that without an EEC tuner or chip.

The EEC does adjust for whatever the base TPS reading is when you start the car (so I have been told). So the TPS has some self-correcting capability, but it should read in a certain range.

I think the TPS output voltage should be from 0.7 to 1.0 volts with the throttle closed, and 4.5 to 5.0 volts at WOT. If you have an analog voltmeter, you should also watch the needle sweep as you slowly open and close the throttle. It should move smoothly with no dips or jumps. If the reading is off, you may be able to slot one of the screw holes in the TPS sensor itself and move it slightly to compensate - but you shouldn't have to do that under normal circumstances.

It's a bit of a long shot, but you may want to check that the minimum idle is set correctly. Unplug the IAC and try to start the car. It should be able to hold an idle around 600 rpm. If it dies, turn the car off. Got back under the hood and turn the minimum idle screw so as to open the throttle a little tiny bit. Try again until you get there. (Don't adjust the screw with the engine running or IAC plugged in, because it will try to compensate.)

It really sounds like a bad IAC, but I know you changed it already. Maybe your wiring is loose or corroded? Or maybe the EEC is getting a bad signal from the cam or crank sensor.
 
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the crank sensor was replaced, but a long time ago and seeing that the other parts are so new mabey it went bad again. Are ther anyway to test it
 
I don't know if you can test it or not. Maybe if you used a frequency meter. But what would you compare it to? I mean, if the crank sensor is giving bad readings, can you trust the tach?

Here's a thought - how about your fuel pressure regulator?
 
I am having the exact same problem on my 93 5 sepeed after installing the 75 mm PP Throttle body. TPS was set at .94 volts. IAC works and bleed screw was not touched. I may try the unplug the IAC thing but I think that may make it idle Hight I have between 18-19lbs of vacuume and no leaks that I can tell.
 
:-( I am having the same problem

Please let me know what you find out, I have had this problem for the past month or so and can't seem to find what it is either. :confused: I haven't done anything in or around that time frame, so I am puzzled also. If I find anything I'll let you know.

Thanks,

Cristy
 
when I unplug my IAc it dies , so no leaking air into the system, maybe a bad IAC or sticky one oir maybe I need to let it relearn a bit longer I put on quite a few mods at once. 85mm Maf 75 mm TB magnesson S port with teflon rotors 89 pulley and ported 94-95 plenum and CIA with cone filter and divider. It's really stout now I hit the upshift light in well under .5 miles from a standing start. AND I smoked an SE r Altima last night from a roll, and it was a sweet looking Altima too. I'm Pushing 15+bs of boost at WOT witha stock 89-93 pulley and a very open exhaust . Kudos to the GTP rotors>>>>>
 
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