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Loud electrical buzzing? (erratic idle)

Ok so heres an update:

 

'91 NA 300zx: hesitation problems, erratic idle and stalling.

 

- Disconnected maf made no difference other than a slightly higher erratic idle.

 

- Cold ambient air makes the problem worse. (less than 5c)

 

- No air leaks found.

 

- PCV valves are pretty clean (replaced one with a new one).

 

- Throttle bodies cleaned.

 

- Touching the coolant temp sensor connector would increase revs, this was fixed by cleaning the connector.

 

- Hesitation mostly gone and in most cases car accelerates faster than it ever has in my ownership.

 

- Car no longer stalls and hesitation cure might be because of the warmer weather?

 

New discovery:

Car idles fine for 5 mins, then there is a loud electrical buzzing noise which appears to come from the back of the engine, when this happens the revs drop to 500 and the erratic idle kicks in for about a minute until the engine stabalises again. No loose connections found.

The problem happens randomly but can easily be recreated by switching from demister to auto (eco).

 

I cant pinpoint where the buzzing is coming from but i think all the idle control stuff is in that area, im assuming a loud buzzing would indicate a major problem? or does the unit usually make a noise?

Featured Replies

Ok so heres an update:

 

'91 NA 300zx: hesitation problems, erratic idle and stalling.

 

- Disconnected maf made no difference other than a slightly higher erratic idle.

 

- Cold ambient air makes the problem worse. (less than 5c)

 

- No air leaks found.

 

- PCV valves are pretty clean (replaced one with a new one).

 

- Throttle bodies cleaned.

 

- Touching the coolant temp sensor connector would increase revs, this was fixed by cleaning the connector.

 

- Hesitation mostly gone and in most cases car accelerates faster than it ever has in my ownership.

 

- Car no longer stalls and hesitation cure might be because of the warmer weather?

 

New discovery:

Car idles fine for 5 mins, then there is a loud electrical buzzing noise which appears to come from the back of the engine, when this happens the revs drop to 500 and the erratic idle kicks in for about a minute until the engine stabalises again. No loose connections found.

The problem happens randomly but can easily be recreated by switching from demister to auto (eco).

 

I cant pinpoint where the buzzing is coming from but i think all the idle control stuff is in that area, im assuming a loud buzzing would indicate a major problem? or does the unit usually make a noise?

 

 

 

i have same idle and stalling problem, (only starts stalling after 15 miles or so when nice and warm + i dont have buzzing noise) i know that the knock sensor is faulty on mine but also there is a yellow connector block of some sort at the back passenger side of the engine (not sure what it connects to yet) but when i wiggle it, it idles fine! will be cleaning connections and hopefully replacing knock sensor monday.

think the click is coming from your fast idle control valve or the idle valve next to it take it off (4 small bolts) take the barrel shape peice apart & clean out with some carb/brake cleaner & replace... another less work method is to remove the hose going to the valve & spray wd40 inside as engine is running this will help clean it too ..also check the connectors are clean,

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