Surging Idle????

[Quin]

Car has 440s, that's why the FP was bumped up (used to have a Lex as well). The PO told me it was tuned with FP and the SAFC so I left it high the whole time I had it. I'll bring my timing light up when I bring that little piece that goes inside the ISCV (originally, there was a block off plate with that piece inside, when I put an ISC on I left it off, thinking it was part of the block off), but the SAFC wiring is a very likely suspect. The PO did a very poor job of wiring it in and I never got around to redoing it, but it probably got messed up when I pulled the motor this summer. Couldn't tell you what thermostat it has in it, sorry. Never had any issues with temperature so I never messed with it. PCV system is set up like stock, not using oil rated hose (unless you've replaced it) but it was a lot better than a poorly and incorrectly done catch can. Sorry about the Lex, traded it to that guy in the silver Supra that asked you about the car while it was on your trailer for that stock turbo and the AFM on the car (lol). Figured I wouldn't be running enough boost to need a bigger than stock AFM anyway. Think that about covered most of the confusion.

I'd be happy to help you troubleshoot/rewire the SAFC this week if you've got some time in the evening. HG job on the 89 should be done tomorrow. Text or call me if you have any questions.

 

[Yeats5.0]

I have now replaced the AFM with a junk yard model and removed the SAFC. IT STILL WON'T IDLE. Surging from 1500-2200. What am I missing here? ECM?

 

[Yeats5.0]

UPDATE:

Started digging around and found two broken wires to the idle control valve - fixed those and it didnt change anything. Then I found a section of wire in the main ecm harness right above the turbo that looked like it got very hot at one time or another - I separated all those wires (many of them melted together) - ran exactly the same.

I then tried to start the engine with the IAV unplugged, I don't know what it should do, but it ran exactly the same.

Here is my thoughts, please let me know if you think differently:
1: The idle is not surging persay, it is revving up to fuel cut and back repeatedly. Probly because it can tell the throttle is closed it won't let it rev up past 2200rpms.
2: The harness melted causing wires to cross and wiped out the ECM (I have checked continuity of the wires between the ECM and each of the following sensors - AFM, IAV, TPS, ECT)

I will be looking for an ECM tomorrow. Anybody have others ideas?

 

[Yeats5.0]

Update: ECM did not fix the problem - idles the same way with the IAV plugged in or unplugged

 

[super7mgtepower]

Check your afm plug those wires get loose and back out a bit, i had that problem before.

 

[Yeats5.0]

Thanks for your post, I read about that a couple days ago and tried it. I have now removed the intake hoping to found a leak of some sort. I smoked it but I didnt know the condition of the gaskets so I thought I would go ahead and replace them.

 

[Yeats5.0]

Just wanted to finish off this thread. I ended up stripping every thing off the intake side of the motor and regasketing everything that attaches to the intake. When I restarted the motor it ran the same. I then removed the IAV and tried to start the engine with the valve plugged in and removed from the intake. It made no movement at all. I replugged in the original IAV and it moved during cranking. My thoughts: I checked the original IAV and proved it to be good but during my parts changing I had put one on from a different car (now known to be bad). I had found wiring problems at the connector for the IAV and corrected them but still had the faulty valve. After putting on the good one it idled low and rough, but at least I could drive it! I put on about 100 miles in two days on the car and it started not idling at all. I poked around on this sight, unplugged the o2 sensor and have been having a blast ever since. Thanks for all your help, I'm sure I'll need it again.:icon_bigg