Spealtrong

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?

Test Results: Last night, Air temp -1c, engine cold: 1250 revs (stable), engine warm: (300-1200 revs on idle) car stalling, revs all over the place, very poor acceleration (compareable to a 1l corsa). Today, Air temp 7c, engine cold: 1250 revs (stable) engine warm: 700 revs, after 10-15 mins the problems begin: Revs drop to 300, car revs itself to 1250, revs drop to 400, rise to 800 then level at 700 then stable. Repeats every 1-2 minutes. (Note: if the demister is on the revs are perfectly stable at 1000 revs. Air con belt was removed last year due to broken air con pulley) Without MAF: Enging revs perfectly stable at 1000 revs, never changes. But when i push the brake pedal the revs drop to 800 then rocket to nearly 2k revs and flucuate until settling at 1000 revs again. (cant test acceleration problems that appear after 3.5k revs for obvious reasons.) Is this info of any use?

checked the maf and maf connection the other day, the look like new. Okies ill give them a check, so i just unplug the coil packs whilst the engine is running and listen for a note change? and if there isnt a note change that one isnt working? (yes i am an idiot when it comes to this kinda thing :-P)

havent had any engine based work done to it in about a year. only brakes and wheel based repairs. Its hard to tell if there is white smoke with the temps been so cold all the time but once the engine warms up the steamy exhaust gas goes away, and the engine still runs like shite. Feels like its just constantly flooded with fuel no matter what speed, but its the stalling with the braking thats leading me to the pcv valves, or do other parts cause that too?

Well after spending the weekend looking for a vacuum leak and being unable to find one and playing around with the maf to no effect a new symptom cropped up today. The car really struggles to accelerate now in any gear, at any speed, at any revs. When i brake the engine cuts out, and when cold the oil pressure is nearly off the top of the guage. Am i right in thinking that this is a definate sign of PCV valve failure? Im crap when it comes to mechanics and so are my local garages, wanna make sure that if i am going to attempt to replace something its the right part. Looking at the how to guides its pretty straight forward, but just a pain.

Well i took the maf out to give it a quick clean and noticed it was damp so left it out to dry. Seems that when i put it back in i didnt plug it back in. The car ran sweet as a nut all the way home but as soon as i got home the idle went back to low and erratic again :-(

oops my bad, nevermind. Mods can delete this post and no one ever needs to know of my mistake :whistling:

connectors are clean, but the mesh has a fair few holes in it :-S dont know how thats happened. (and i dont mean the holes that are meant to be in the mesh lol). Who do i contact on 300zx.co.uk to get one? need it pretty quickly lol.

how fragile is the maf? there was a bit of dirt in the housing so i gently blew it out, could that have broken it? or is there a good chance that that was the cause of the erratic idle and ive just pushed it over the edge? Also, where can you get replacement mafs from?

Hey all, I posted a while ago about an erratic idle and hesitation whilst driving, on my lunch today i checked the maf and maf connections to make sure it wasnt loose or dirty, and now the car wont go above 2500 revs :helpsmilie: Have i fooked something or do i need to reset something? :-S

if it were an air leak wouldnt the problem be continuous rather than intermittent? are afm's an expensive part?

same here zedhed, going through fuel at a crazy rate, guess over fueling would be the obvious issue :-S, jeff ill keep an eye out for the black smoke. How easy would it be to locate and fix an air leak?

about 2 days ago my car ('91 NA Jap Spec) stalled when i was changing gear (from 3rd down to 2nd, but before i lifted my foot off the clutch the engine was dead). Sometimes the idle can be perfectly stable at around 800 revs but other times it really fluctuates and drops to 400 revs (when it drops below it stalls), there doesnt seem to be a pattern as to when it happens, eg hot vs cold engine etc. Also i have to accelerate really really gently as if i try to accelerate a decent amount (when joining onto a fast road) the car really loses performance and feels like driving a 1l corsa, you can really feel the resistance (almost as if the engine isnt getting enough fuel). I think the first thing im going to try is injector cleaners, are any recommended? or should i start replacing things like fuel pump and filter etc?

Battery light has now come on so it looks like the alternator is fooked either way, only problem is im having trouble locating one? Anyone know where i can get an alternator for a '91 Z32 NA Jap spec quickly? Ive checked ebay etc but no joy (except a z32 that some guy is breaking but he is on holiday until december which is no use).

lol i had some friends over today to try and pinpoint the problem, one said its the alternator bearing, and the other said its the air con pulley. Problem is it seems like i have to get under the car to get access to either or remove the radiator :-( (im assuming the aircon pulley is the one which is bottom right when looking front on and the alternator is bottom left?)