SR Idle Problem

[Fahaka]

I posted this in the SR forum but I didn't get much response...

I have and SR that will not idle.

I performed the swap about a year ago, and have searched all forums for a possible solution.

I will first start with the basics.

The car is an '89 automatic coupe.I swapped the ka and auto transmission for a '94 blacktop and 5 speed transmission.I replaced the t25 with a gt2871r.other mods include:650cc injectorsFMIC300zx mafs3" turbo back exhaustBikiRom daughter board tuned by CG tuning.

With the stock sr mafs, injectors and ecu the car would not idle. Specifically when the motor is started it will rev up to ~1500 rpm and then drop down to 750 with a bad misfire and then die. Above 1500 rpm the car is fine and runs quite well.

I swapped the sr mafs for a sohc mafs, with the same result. I tried another brand new sohc mafs and it still did not fix the problem.

I sprayed an entire can of carburetor cleaner into the idle air control valve in an attempt to free up a possible stuck valve with no change in idle.

Once we changed to the 300zx mafs, 650cc injectors and bikirom tuned daughter board the car would still act the same way (For the record I was not expecting a change, but I was hoping that this would do something). Still above idle the car ran well and made good power (See also no traction in first or second gear at 20 psi).

In November, due to a faulty actuator I cracked a ring land and decided to remove the motor and rebuild. I machined the block installed cp pistons with eagle rods new bearings freeze plugs, head gasket etc, and while I had the motor out and the manifold off I changed the idle air control valve for a known working used one hoping this would fix the persistent idle problem. It did not.

I have now installed a known working ecu, still no change.Swapped harnesses with a known working harness, no change.Replaced all rubber fuel lines in case one had an unseen leak, no change.reinstalled stock injectors, sohc mafs and stock sr injectors, still no change.

I have run out of possible solutions with the exception of replacing the iacv with a brand new unit.

With the wide band connected the af ratio sweeps wildly between 11/1 to 22/1, obviously it gets very rough above 17.5/1 and usually dies around 22/1.

If any SR experts who have encountered a similar persistent idle problem could chime in on this subject I would greatly appreciate it.

Also when I disconnect the mafs the car idles fine.

[180fan]

Set it back to as stock as possible.

What's the vac and fuel pressure set to?

I suspect the mafs wiring. I had a similar problem with my idle when I put in my dunno my second one? Turned out to be related to the wiring. If you've got anything else tapping any of those mafs wires, now may be the time to pull those and reconnect those wires and test. Are you using shielded wire at the mafs extension and also checked over the grounds for the mafs as well?

[Fahaka]

The car is currently running stock injectors and a sohc mafs, with a gt2871r set to 10psi and a stock computer.

Mafs wiring is good, when it is disconected it will idle because the computer is dumping a ton of fuel and keeping it pig rich and it wont rev past 2500rpm. When the mafs is connected the car runs great, it just wont idle. If it were wired wrong, it wouldn't rev past 2500rpm.

I have removed my entire engine harness and replaced it with a known good harness and the problem doesn't change.

I can't tell what the vacuum and fuel pressure are because the car won't idle and they oscillate with the idle.

[180fan]

I'm convinced it's a mafs issue or a mafs grounding issue. add another ground to the mafs and see if that clears up the issue.

[xXtouge_beastXx]

well im not too sure

but maybe its ur fuel controller?or lack of one?