Decelleration, High Idle .. weird stuff ...

[Sidewayzzz]

Alright, this KA is starting to piss me off (and I am an avid sr hater...).

Don't remeber exactly when it started but i'm having some weird issues on decelerattion and my idle is fucking erratic at best. The idle will be anywhere between 700-1100...it doesn't shift extremely fast between idle, its hardly noticable most of the time, but you can hear the motor change pitches while idling. I will just stop at a light and sometimes it will idle at 750 .. sometimes 900 .. most of the time 1000. This isn't a "searching" "hunting" type idle...it will usually come to 750, then rise to 1000 and you can hear it change pitches in the exhaust... and if you stare at the RPM's and watch very closely it will shift about 100 rpm's up and down. It's very hard to notice, but I think this is important with my decelleration problem so I want to note it.

On decelerattion my car will fall extremely fast to very low rpm's .. i'm talking 300-400-500 ... and it will come back up to 750 when I come to a complete stop then rise to 1000. It feels like an atmospheric blow off on a maf based turbo car almost. If I pull the car out of gear while moving the rpm's will fall to extremely low levels .. IE 500-600.. Very rarely, the car can die if I pull it out of gear to stop, or even coast. When I come to a stop it usually falls extremely low to the point it should nearly die, then the IACV brings it up to 750...then 1000. If i pull it out of gear while coasting, it usually falls to 500ish and stays there, until I come to a complete stop, then it rises to 750...then 1000.

Today I .. uh .. took an IACV from the junkyard and cleaned it up .. swapped it .. same problem exists.

I can have checked the ECU for codes and on a few occassions it did show code 33, which is the o2 sensor circuit.

I have 3 different o2's that I have swapped and tried, they are working fine, I just had to replace my o2 actually. I've tested the o2 via the ecu test, it's working as it should. Harness/Connector falls into the aforementioned state, if the harness/connector was bad, the o2 would not give a correct resule and that would be noticable in the o2 test.

I'm on my last straw with this motor ... any help is appreciated guys, thanks in advance.

[gfisch]

That sounds a lot like a problem I had that was due to the IACV not working right. It was sticking and causing the RPMs to drop when idling or rolling to a stop. Sometimes it would die and sometimes it would recover.

But sounds like you already tried that route. Unless it is the wiring for the valve and not the valve/solenoid itself.

[Sidewayzzz]

Well today was a busy day, I took off the throttle body to set the adjustment screws for the idle and wot. I set so that when i snapped it open/close it didn't click (the way the FSM describes to do it). I figured while I had it out I should set the TPS to the correct spec, so i set it to .45 closed and rotated the set screw on the TB so that it was all the way out, and my TPS only goes to 4 volts and change WOT...I believe it should be 5, but thats not really important.

I checked the timing, it was 15 degrees BTDC which is 5 off, so I set it to 20 degrees, which is stock.

Bypassed the coolant lines, I don't need those. I also plugged the 4 vacuum lines I had previously when I had the AIV and Vacuum Canister (they were previously plugged at the end of the hoses, this time I did it right from the hard lines).

I want to make it known that I have replaced FPR, TPS, o2 Sensor, MAF, ECU, and the Plugs all within maybe 5-6 months. That's not to say they are not bad, but I have done more than a few things under the hood and this problem is just .. weird and unusual.

SO after all that mess, It doesn't try to die coming to a stop anymore, it doesn't go much lower then 600 rpms (and thats only sometimes...) when I pull it out of gear. What it does do thats strange is it idles at 1000, but if I pull it out of gear or press the clutch in while coming to a stop, BEFORE I come to a complete stop, it will idle at 750 and while i'm coming to a stop it rises and by the time I stop its at 1000.

To be more specific, I was on the 95 and doing about 65-75 and pulled out of gear ... rock solid at 750 for a good few seconds. When I came home, I flipped a u-turn to park and when I took it out of 2nd to come to a stop, it went to 750 and while I was braking it came up to 1000 by the time I came to a stop.

[Sidewayzzz]

bump...anyone?

[Dream240]

I have a somewhat similar problem. Mine started right after my 5-speed swap.
I have an idle jump from 800 all the way to 1500, it's steady there for about 2 seconds, then it gradually falls back to 800 then it's fine.

This problem occurs when slowing down but, not until until I reach an absolute stop. Then bam idle jumps to 1500 rpms. I'm lost!!!

It also always happens the instant I touch the gas from a stand still. No matter what gear I'm in, even reverse and neutral. I initally thought it could be due to the auto ECU I still have. I'm thinking the ECU is trying to compensate for the auto downshifting into 1st at a standstill like when it was an auto tranny. Maybe the ECU is confused because I unplugged all those tranny connectors except the one for the speed sensor and back-up lights. Oh I also removed the Auto ECU under the dash (little green box).

My other guess is the AIV. I'm gonna check that tonight. I'm wondering if the fact that this car sat for 6 months has anything to do with this. I only did an oil change, and put in a new Cat with the new cat-back exhaust before my first 5-speed start up. Strange.

Sorry for the threadjack. Maybe we can both get some answers.

[AuburnRyan]

Idle and decelleration issues should be textbook EGR issues... however, as other suggested, I think I cleaned my IACV with success.

Honestly, remove all of this emmisions/recircualtion crap, clean, and replace and your issue should be gone. find an FSM to help you out on removal, or search here.

here's the EGR to start:

http://www.flickr.com/photos/icex01x/82556947/

[Dream240]

Well a while back before my car went into hibernation, I was getting an intermittent CEL, turned out to be the EGR. I took it apart, cleaned it thouroughly and hadn't had the problem since. I also wiped the codes back then too. I have a feeling it's the IAV. I'll be cleaning it tonight. Let you guys know.

Thanks.

[Dream240]

UPDATE:

Okay I got the IACV totally disassembled and got all the carbon gunk cleaned out. I flipped the little vanes inside over to give the clean side some use. The other side has got some slight build up left on it despite my best cleaning efforts.

I found that the small diaphragm that is secured to the top of the IAV by two small screws was clogged!!!! The little air hole was rusted shut and the spring grinds badly inside when you turn the lower portion. So now I need to get a new one of those from Nissan. That should help. The problem still exists for now though. Actually it got a little worse since I messed with the bad Diaphragm part.

I went ahead and bought a manual ECU, gonna test out my theory as soon as it gets here. I'm thinking the high idle issue is from the auto ECU trying to compensate for an auto tranny in 1st gear at a stop. Kinda hard to explain so we'll see.

C'MON GUYS.......NOONE HAS ANY (HELPFUL :) )INPUT FOR THIS PROBLEM?

[ThE_BoMB]

egr directly effects the idle. when the throttle is closed the egr should be on. If its as bad as you say they realistically thats probably your problem. Im having problems with my car revving and dying at idle and Im about ready to disconnect my egr. I would get a new one but what a pain in the ass to replace one of those suckers. Ive cleaned the IACV multiple times. only thing I have left is egr. and that only effects performance at idle. Last time I checked you could disable it by disconnecting the vaccuum hose to the BPT valve (other disc above the egr.) Probably the vavle is stuck open and lets too much air in and the ecu goes nuts and eventually kills it. And or compensates with a higher rpm.

No egr no problems :).

[miklos]

""Last time I checked you could disable it by disconnecting the vaccuum hose to the BPT valve (other disc above the egr.)""

Does this work?

[93nismo]

the high idle issue is most likely the egr. i just put a header on and i cut the egr tube/line that connects to the stock header. immediatly afterwords my ide was anywere from 800-1200. i pluged up the line with a peice of hose and a big ass bolt. temp fix untill i get a block off plate. but the egr is prob the idle issue. and the idle when comeing to a stop issue is something i have too, and the idea youve got about the ecu makes alot of sense. so if that fixes it let me know:) i dont like wasteing my gas just stoping... LAME.

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