does the idle vary when you turn the idle screw. your iac could just be dead mate, quite common really.
yeah chages when i turn the screw, when its fully in idle is 700rmp, atm its unscrewed a bit to make idle 1000 so it never stalls
Following quote taken from: http://www2.zhome.com:81/ZCMnL/PICS/hesitation/hesitation.html "I've had this problem ever since I bought the car ('91 TT) 3 months ago. The engine cuts out under hard braking (normally from 55+ mph) with the clutch pedal fully depressed. ( I guess the clutch not getting fully disengaged could cause the RPMs to drop too low - but I don't think this is the case.) If I engage the clutch again or turn the key, it will start right up. It's pretty scary when this happens while going around a curve, since it causes the power steering to cut out as well. Doesn't do too much for my confidence! Somehow this problem never occurred during the (fairly long) test drive, but started to happen 2-3 hours after I took possession. (Actually, it may have once, but at that I think I may've thought (!) it was something I'd done wrong.) The dealership that sold me the car said they were unable to duplicate the problem since they were unable to take the car over 55 mph. (At that time the problem occurred only at above 70 mph.) They did agree to let a service guy ride with me while I tried to duplicate the problem, but we never got around to it since I moved out of town the next day. The service guy at the next dealership I took it to immediately told me it was a problem with a transistor that was causing this to happen, and that it would be fixed under a recall. Well, the work they did seems to have done something, since it doesn't happen as frequently anymore. However, now that I'm not able to duplicate the problem at will, it's harder to show them what's happening. Has anybody had (or is having) a similar problem with their late-model Z? I'm planning to take it to a different dealer, but it'd be nice if I knew what the problem was, so I could tell them exactly what I need done." Could it be the PTU? I guess I should try cleaning those connections as well. Looks like I'll have to invest in conzult and run some tests otherwise.
Another thing I was going to mention: Don't think this is completely related to the same problem but i've noticed that when starting the car from cold (generally) the rev's sit up around 1500, once the car warms up they'll sit on 1000/1100 If i turn the car off and start it again the rev's will sit a bit lower and go up and down between 800 900 I'm guessing my IACV is sticking as people suggested earlier - or would this be something different? Still yet to fix the coasting to stall/braking at lights to stall problem.
In my car, the car hesitates a little when I rev the car when warm. When its cold I've noticed that it doesn't do it, but it's sometimes very lazy about dropping the revs after you take the foot off the pedal. Quite often it may take 5 or more seconds to drop the revs from around 1500rpm downwards. Unfortunately I've also got a leaking turbo seal and it loves to show the world its white smoke at this rpm
Going to give this a try: http://www.300zxclub.com/showthread.php?t=59296 Will update on how it goes.
I'm going to try doing the same thing, only see if I can get away with a liberal use of 100 mile tape instead of splitting hoses.
Ok, on the weekend I cleaned the IACV (the lazy way, while still connected to the car). Straight away the rev's were all over the place, so I drove to the local shop and sprayed some WD40 in there afterwards, then went for a 30min drive or so. The difference was noticeable. I didn't fix the problem, but the car still felt a bit smoother a tiny bit more responsive anyway. Before I went home I stopped at a Supercheap and picked up hose clamps - I remembered that the hose had been replaced at AMEC and no hose clamps were put back on. This actually made a fair difference as well. It may have just been in my head, but I think the combined effect really helped. My girlfriend has taken the car to work today, so she'll be able to confirm/deny. I didn't get a chance to clear the ECU or anything though. I'd like to adjust the TPS as well, but I'm missing a screw for that...
if your missing a screw on your tps it would most probably be the reason as it wouldnt be giving a correct reading
Reading should be fine... it just means that I can't adjust it without moving the unit ever-so-slightly. I'm missing the bottom one if anyone has any spares
I dont think you really need the bottom screw, I dropped mine into the engine when replacing my tps so far just the top provided its nice and tight has been fine. You can adjust it with just the one screw.
Yeah, maybe. I kept having the problem where the reading would be perfect, I'd slowly tighten the screw, check again, continue tightening and check again and the value is wrong. After the 4th time that happened I gave up
so you have it set slightly wrong, then tighten, so when its fully done up it is sitting on the correct value
Yeah, thats what I ended up doing at the time. It was almost perfect... I drove it around for a week or so and checked it again and the value was slightly different, so I figured it had probably moved.
Just an update: I cleaned my IACV today with Nulon Throttle Body & Carby Cleaner via the lazy way detailed here - http://www.300zxclub.com/showthread.php?t=59296 After I changed the hoses over, i had a look down the tube and it was like new, beforehand it was completely black so it's done something. I went for a drive, still getting the RPM drops when I pull in the clutch, but for some reason it doesn't seem as bad, it doesn't drop low enough for the engine to cut out. Still not sure what it could be though it only happens when I give it a bit of throttle, when it's boosting I guess. Idle RPM still sits between 800-900-1000 and it'll go up and down between that every 30 seconds or so. I think I'll give cleaning the throttle bodies a go, using the same stuff from Nulon via this method - http://www.300zxclub.com/showthread.php?t=91931 I'll just connect a hose up to each nipple under the TB and do them seperately.
whats the AAC value via consult when the car is warm and idling, with the aircon off (not that u have it on in winter). if its significantly above 30 then this could be cause (not the AAC so much, but idle screw being set to idle too low and therefore AAC has to compensate...cause its compensating so much, it has less room to move to 'catch' engine when revs drop quickly). could probably also verify by seeing what happens when u enter base idle mode (e.g. free conzult has it, maybe obd scantech also). if car stalls then its probably also indicative.
if this input helps at all i had the same problem towards the end of last year. revs did the same as your vid shows. I went over all vacc hoses, didnt fix it. I got a new air filter, checked AFM tightened all hoses. No change. I did an in situ clean of the IACV. No difference. It had the correct resistances and stuff as well, so I figured it was ok. Then when I still couldnt find it I took the IACV out of the car completely, cleaned it part by part, pulling every little screw and things out as written up in the tech section. Then as I was about to put it back in the car I noticed the black connector on I think the ACC valve it was? It looked a bit slanted. On closer inspection, it turned out the black conenctor had broken on one side, but stayed on somehow, and someone had gone over it with black tape which concealed it very nicely. I took teh tape off and saw some corrosion around the electrical bits. Then I bought a second-hand IACV unit, took off the AAC cylinder with the connector on it, put it on mine. And the problem was gone Shortly after though the problem started coming back, and I found out the IACV unit itself was leaking. In a weird spot. Can be seen where in this picture below: So I got another unit of a member, and it had been sealed around the location mine leaked, with a resin of somesort. Works fine now well... worked fine until my engine died.. a few months so my fix was both IACV unit and AAC valve
now that u mension the knock censor, the mechanic told me that the car was low in psi and reading around the tech and forum when the knock censor is failling the psi is not the same as it should be as the censor is not sending the imformation to the ecu and etc. so he should check the censor i having the same probleme i give i litle touch to nthe acelerator and it goes down and then up in a second, i havent have time to check the censor morocer i try to test it but not idea ...
