hard start, very rough idle, lots of problems

[Metro]

Ok, I finished my swap about a month ago. Car was running great, sounded great and I was having a lot of fun. Now I just want to shove a stick of dynamite in the motor.

 

Setup:

Stock '81 L28et in a 1976 280z ~ 5psi

JSK fuel rail

Stocker fuel pump since I had loads of problems with my walbro pump

Aeromotive RFPFR set to 37psi and the vacuum line isn't hooked up.

N42 instake manifold w/ no air regulator.

1G DSM BOV - recirculating

New NGK bpr6es plugs - factory gap, I forget it atm

MSA downpipe into ghetto 3" mandrel exhaust.

 

 

Last week the car had been running rough at idle, but drove fine. Just seemed like it kept getting worse. Meanwhile I had several leaking (on the manifold) injectors, so I replaced them. After reading up on possible causes, I realized the start signal was wired wrong - it was going to a constant 12volt signal. So sometime around disconnecting that and replacing the injectors it all went to hell.

 

It will barely start now and idles extremely rough. It's missing real bad, but I can't tell which cylinder(s) is doing it. When I press down on the throttle hard, it causes the motor to die and backfire a little in the intake, which makes me think it's running rich or the timing is bonkers. The plugs are black and sooty, but no worse than when I checked them before.

 

Weird thing is, once it has warmed up it will idle much, much, better. Almost to where it's driveable. I was watching it today and it was like a switch was flicked, all of a sudden it was running much better. I don't know if it was switching modes or what.. I've also never seen the green LED turn on, ever, but then I didn't know my ecu had it until a week ago.

 

As for the timing, I can't get a good signal to check. No matter what plug I hook it up to, it's very sporadic. I checked the cap and cleaned the contacts, but that didn't do anything. When I can get a signal, it looks like the timing is around 23-25° at idle.

 

I test fired the injectors and the pattern looked consistent between all six, no problems there. Double checked all the connections and wiring to coil and swapped coils. AFM is mounted sideways, but opens and closes just fine.

 

Kinda rambling on here, but if anyone can think of anything else I should check, please let me know.

[Guest bastaad525]

hmmm... check for vacuum leaks? all around the manifold, also the rubber boot between the afm and the turbo. They like to crack... I've replaced two already, but you can usually just use some silicone or something for a temporary fix.

 

For your EFI, though it's usually associated with a differerent problem, but you may want to try the old 'clean the wires' trick. It's practically free and only takes a few minutes.

 

If you're injectors are working fine, then most likely it's a sensor problem or a shorted wire. AFM may be out of adjustment. A bad head temp sensor can definately cause the car to run all kinds of erratic.

 

Do you still have an EGR valve? Sometimes these like to stick open and cause a horrible idle and car runs like crap. May need to be cleaned or replaced.

 

About the car 'switching over' yeah mine does this too, you can hear it very clearly after the car's been running for a few minutes, right when the temp needle starts to move. The idle will raise like 100-200rpm and will run much smoother. You can also see the timing change dramatically. When cold, it's like 10-12* BTDC, then when it 'switches' it jumps to 22*.

[Metro]

No EGR valve, no vacuum leaks, went over the manifold with a hose, couldn't hear anything suspect.

 

I cleaned the plugs last night and that helped a tiny bit.

 

But as far as I can tell, something is wrong with the ignition. When the motor is cold, the timing is at 10° and runs awful. When it warms up a bit, it goes to around 35° idles better, but can't rev up. THen 10-15 minutes later, it will drop to 25 and run decent. When it's running ok, the green LED on the ecu is on, doesn't flicker, just on steady.

 

No matter what I try to change the timing, it's set. Messing with the CAS adjustment and even rotating the dizzy does nothing.

 

So, what should I start replacing: O2 sensor, HTS(I tested it and it appears fine), forget what else can affect the timing/ecu.

 

Well, back to the archives I go.

[R0N]

I think you may have damaged your ecu when you had the wiring hooked up wrong. Also the best way to test for leaks is using one of these http://www.stealth316.com/2-pressuretester.htm I got my parts from home depot. I think your using this method but posting the link just incase.

[Guest bastaad525]

Be sure you are disconnecting the TPS when you're adjusting timing (as per the Haynes manual).

 

A bad or dirty CAS on the '81 turbos can cause these kinds of problems as well.

[Metro]

Ok, I think I've solved the majority of my problems. I still have a rough idle, but not nearly as bad as before. I can live with that.

 

I'm not actually sure what fixed it, but yesterday I aligned the CAS, adjusted the valves, and replaced the fuel filter at the tank. It was after I replaced the fuel filter I noticed the clip was off the #3 injector. So it could be anyone one of those three things that did it.

 

I'm still looking into getting a 82 dizzy just in case though. If anything, it will make megasquirt a little easier in the future. Is $150 a decent price for one?