Idle dip 1990 NA

[jawolf518]

I have a 1990. Ok guys so before I was having an intermittent idle and idle dip. Replaced TB, ISCV, AFM, and all associated gaskets. Cured the intermittent idle. The iscv gasket was ripped in a couple places and as hard as a rock. Reinstalled everything and no intermittent idle. Now I just have an idle dip issue (which was present before from time to time) when warmed up and driving when I release the clutch pedal and go from a gear to neutral it drops way down to around 400, then slowly comes back up ... sometimes I even have to blip the throttle to get the idle back to 850. The ECU idle is set and is the same as the cars idle. So I rather not increase ECU idle to compensate ... I rather find out whats going on. 65,000 miles .... Am I looking at bad 02 sensor? Coolant temp sensor? Fuel injectors? Fuel pressure regulator?

Anything else I forgot to mention? Thanks so much

( and I have read every post on this issue on miata.net, club roadster, etc etc .... unfortunately just a lot of pissing in the wind and when people solve their issue they never really explain what solved it. And the thread ends ... Thanks for any input, guidance, help.

[— kung fu jesus —]

Did you clean the TB? Try readjusting the throttle under 10/GND conditions.

[jawolf518]

Did you clean the TB? Try readjusting the throttle under 10/GND conditions.

I sprayed half a can of CNC TB cleaner thats safe for coated throttle bodies into it .... And when adjusted under 10/gnd .... the idle is a match.

[— kung fu jesus —]

I have experienced it before. One of the times, it was ISCV related. They are finicky when they get dirty or damaged. Check carefully for split air hoses and vacuum lines, too.

[jawolf518]

I have experienced it before. One of the times, it was ISCV related. They are finicky when they get dirty or damaged. Check carefully for split air hoses and vacuum lines, too.

Pretty sure I sprayed the hell out of the engine and air box tubing with carb cleaner to find a leak and so far nothing .... Will try that again too to see if I can track down a leak. Even sprayed near injectors ...

[— kung fu jesus —]

If you can make the car stumble consistently, try unplugging the electrical connector to the ISCV to see what happens.

[jawolf518]

If you can make the car stumble consistently, try unplugging the electrical connector to the ISCV to see what happens.

Drive around the block a few times with it unplugged to see if it helps?