1990 240SX fluctuating idle problem

[jerryk]

I own two 1990 240sx. Both are on the road. I have a fluctuating idle problem with one of them with 177K on the engine. It is scheduled to be my final car. I know what the idle is supposed to be a bit above 730 because my other one with 220K has a perfect idle. The fluctuating /hunting idle goes between 780 and 950 when warmed up or at a stop. Sometime it fluctuates worse then others but it never goes below780 and is always moving. I just made a trip to PA and the road mileage is, I swear 31MPG, but in the city, it ranges between 21 and 23, which is costly these days. The other car gets 25MPG in the city and 30MPG on highway. I have both cars at a mechanic and he has been swapping parts.

Air regulator
AICV
MAF meter
EGR valve

I would appreciate any ideas.

[Captain_Ron80]

Search... there is a thread on this site that explains the problem and the fix.

[cotbu]

check your ecu for codes!
I'm thinking CTS.

[fairladysx_s13]

Theres also an idle regulator under the throttle body on the right side. Theres a bolt that moves forward and back that u can tighten and loosen. Try to play with that and see if ur idle levels out.

[Vernal]

i had that on my de. The timing was off though. If its a smooth idle but just high then adjust it. If it hunts and bobs then its your timing or a vacuum leak or both.

[SilviaSR20DET]

ive actually had this problem for quite some time now, mine usually does this when im using a defroster. I wonder myself what might be the problem behind this. Ill have to check my timing since i havent done so in like 3 or 4 years ago.