Random Idling Issues

[SargeRX8]

Hey all, been a while since Ive posted here. Having some issues when I'm idling and I think its AFM related.

Its an intermittent issue, happens sometimes, then can go away for days then comes back. Anyway driving feels and seems fine, power on boost seems fine too. When I come to a stop the car will idle but seems to pull less vacuum than usual and my AFR gauge goes from the usual 12 on idle to about 17 and as you can imagine it feels really rough. Once you start moving or give the car a tiny bit of throttle, even while idling and stationary, the issue goes away, AFR's come back down to about 12 - 13. Its only when completely stopped and off the accelerator. I popped the bonnet open and the engine was running and just fiddling around with things I noticed when I jiggled the socket on the z32 afm the problem went away, jiggling it again and it came back. Jiggle again and it went. Seemed consistant enough.

Today I stripped the wiring and checked all the harness joints, patched them up and taped them and started the car up. Still has the issue. I then read about dry solder joints. After cracking the AFM around the top cap, I finally got it off only to see perfect joints, none were loose, none were cracked, none were just touching. They were strong complete solders and rather than risk damaging it by heating it up unnecessarily I put it back together. Now while I wait for it to dry, I have been looking for a new loom, I suspect there may be some brittle wire close to the socket but am unsure.

Questions to ask here, do these issues seem consistant with a AFM issue? The only thing I got is the fact that jiggling the wire will often rectify the problem. Just because I can't see(I also did use a little probe to poke at the joints to check their stiffness) dry solder joints, could those joints be a problem? Is it odd that it only occurs on idle? Should I just buy another known working AFM and loom?

Cheers guys.

If anyone here is in Sydney near Parramatta and can let me borrow an AFM for like a day, free bottle of smirnoff vodka.

Edited April 17, 2012 by SargeRX8

[SargeRX8]

An interesting, and very stumbling observation. My car, as long as I have known, has always had idle control issues when coming off load into neutral such that the rpm will drop to about 500rpm then climb back up to their usual rpm. I thought this was normal... When my afm starts "failing" the car actually works much better. Coming off boost revs drop and hold properly at 750rpm. The ONLY issue is it seems to run leaner in this state. I am actually thinking my AFM wiring was dodgey before hand and now I have actually fixed the problem. If I give the car more fuel on idle, it will pull more vacuum, and be much more stable.. Actually sounds like this is a solution to a problem(almost stalling vs a lean idle(on boost is perfect, power delivery is perfect)).

Going to hook up the FC Edit tomorrow and drop more fuel in on idle and if that brings the engine burble down and a smoother sounding idle, I may have well and truely fixed my never ending idle hunting issues. Maybe it wasn't necessary for me to make so many intake pipes due to my suspected reversion issues which could have been AFM wiring issues.

Edited April 17, 2012 by SargeRX8

[DVS JEZ]

Yes set the idle up to 13.2afr. This is where torque doesnt change and will help stabilise the idle alot.

So when i tuned it last the afm was good idle was good etcetc. But the when u changed the intake pipe do u think the wiring has been damaged?

[wolverine]

Sarge, I have also seen perfect looking soldered joints on old afm's that were known to be faulty. I resoldered them anyway and fixed the issues. Just food for thought if the issues continue.

[SargeRX8]

Yes set the idle up to 13.2afr. This is where torque doesnt change and will help stabilise the idle alot.

So when i tuned it last the afm was good idle was good etcetc. But the when u changed the intake pipe do u think the wiring has been damaged?

When we tuned it yeah, it was fine. Remember how I told you I changed the intake pipe and since then it was always coming close to stalling? I must have rooted something and it caused everything to run a little richer but never felt it was down on power. I'll give it some more fuel for comfort and see how it goes.

Sarge, I have also seen perfect looking soldered joints on old afm's that were known to be faulty. I resoldered them anyway and fixed the issues. Just food for thought if the issues continue.

I just read a few places and what you are saying seems true. I glued the AFM back together because it appears to be fine now, so incase this issue arrises again, ill strip it and resolder those 4 points and also get a new loom incase the it is the fault.

Either that or if funds permit, ill go with a new ECU.

[DVS JEZ]

Link

[GTSBoy]

It would seem wise to resolder, at the very least, the joints on the AFM board for the plug's pins. Those are the ones that would be most likely to have sustained damage from you moving stuff around during inlet pipe work, and the most likely to change performance when you wiggle the wiring loom.

Or....beg or borrow a known good Z32 to test.

[SargeRX8]

The problem seems to have gone now, it seems more consistant(touching the wires now doesn't change anything). It runs leaner on idle(13.8 when cold and 15 when warm). If I can add fuel to make it a little richer, it will pull a little more vacuum and run smoother.

[SargeRX8]

To add to these symptoms, I also had a popped plenum chamber gasket(the one between the plenum and the runners). I took out the old gasket, cylinder 3 and 4 were egg shaped and when fitted in the car they were sticking out from inbetween the components causing a pretty big leak. Fixed all this up and now my idle is back to where it was. Seems fine now just a tad rich now after compensating for the leanness before lol.

WARNING TO ALL: CHANGING THE PLENUM CHAMBER TO RUNNERS GASKET IS A f**kING JOB AND A HALF! Undoing the piece of shit took the best part of an hour and alot of cut fingers. Putting it back together and tightetning the bolts up, in the right order(and f**k me if I didn't tighten them enough!) IS ABSOLUTE HELL.

[DVS JEZ]

Good u found the issue. How did u diagnose it

[SargeRX8]

I was driving the car as I always do, like a bitch. Then came to a point where it was necessary to hit some boost and get around some traffic, so I done so and all seemed fine. Then I pulled up at the light and my idle went rough as shit and I was leaning out to the point my ratios were 18.0+ I thought while driving that it can't be the AFM anymore and it seemed only to occur after I hit boost. So I pulled over and switched the car off, looked under the bonnet and didn't notice anything popped. Got my mrs to start the car for me while I was under the bonnet and my ears immediately heard the PSSSH sound you hear on an intake leak then I noticed the black rubber gasket between the plenum and runners was sticking out, I gave it a little touch and I could see the actual O openings and air was gushing in which was causing it to lean on idle. I loosened the manifold, jammed it back in with a screw driver, tightened it up and it seemed alot better but I could still hear the psssh from around the plenum so I thought it could be busted on the inner side too. Drove home, ordered the parts and pulled it all apart while I waited.

Its running way too rich now, at points 10.5 on idle. After I fixed it, I took it for a drive and everything was fine on little load and little tiny boost. I then pushed it all the way, the power was there, the boost was nice and consistant, but then at about 6500rpm I see the engine light and hear a pop under the bonnet, then it idled weird and shut off on me. I thought I just destroyed my car, it was that fat hose that runs from the cross over pipe to the plenum, I forgot to clip the clamp thing back at the right place. Hopefully that ping reading was the noise of the pop pssh bang hose coming off. Its never pinged on me before on low boost and Ive already pulled out a fair bit of timing so it didn't ping on high boost.