gmbchef

No vacuum leaks..stock ECU.
I set the duty cycle to 45 fluctuating. Beautiful idle.
After driving for a few days, the idle leans out. Or..if I get on the car it may happen in a day. Have you ever heard of the mixture screw vibrating in one direction?
I reset the mixture, and the same thing happens.
I'm totally stumped.

smoking10v-urq

sounds like you and i had similar problems.

1. did you change any parts recently on the car?
2. where did you test the duty cycle? at the test site or at the freq. valve?
3. at what rpm does the car lean out at?
4. does the car misbehave on cold start? hot start? after it is at idle?

i found out that my leaning out problem was a three-fold problem. 1. my fuel pump wasn't up to the task, it was remanufactured and wasn't original. -> i bought a new fuel pump and put a relay in at the battery before the fuel pump. 2. my warm-up regulator <- this should really be renamed fuel-pressure regulator was putting too much pressure on the plunger of the fuel distributer, therby causing less fuel to be distributed. 3. the sleeves of my injectors were cracked causing a massive vacuum leak at higher engine speeds and incorrect fuel-air mixture.

1.now, how did you test for vacuum leak?

2.did you check your o2 sensor?

please reply and let me know what you have checked and what you haven't checked, also tell me what modifications you have done to your car,

thanks,

ben

rally4s

Look for a vacuum leaks. Chek elbow on inlet to turbocharger.

gmbchef

Dies immediatley when I pop the oil filler cap off.

gmbchef

I just did a complete overhaul of the bottom end, gaskets, seals, hoses clamps etc.
I do the DC test at the test connector, and checked the O2 sensor. It checks out fine.
Fuel pump is a brand new Bosch unit. Recent filters also.
All the sensors and switches are doing their jobs. No 4000 rpm cut out. It doesn't really lean out at a certain rpm, it seems like it leans out after a certain volume of air has gone into the engine, and then the problem is only at idle and with cold starts.
This has been plaquing the car since I've had it (8/01) and the rebuild has put a huge dent in the issues I was having before.
Tomorrow I'm checking fuel pressure at all stages.
What you said about the control pressure regulator makes sense to me.
Thanks

smoking10v-urq

i still think you should make sure of vacuum leaks . . . .old school method: take some silicone spray and while your engine is running spray on and around each hose. if there is an rpm drop then you should suspect that hose . . . worst case scenario you end up with shinny hoses.

please answer my other questions if you want me to help you.

thnaks,


ben

gmbchef

BTDT with any and all vacuum leak tests,beatin a dead horse.

fusilier

Try putting some of that thread locker on top to lock it to the Fuel Distributor housing. They you can see if the distributor vibration is messing up the Duty Cycle.

What does the DC do if the O2 is unhooked while idleing lean? That should throw the F/TCU into open loop and run the DC at near 50% stable unflucuating.

BTW, what is the DC when its idling lean?
Is it as high as 90%? Listen to the Frequency Valve and check for an intermittent buzz.

gmbchef

I thought the screw was doing that. So..I set the DC so it was spot on, then I turned the screw c-clockwise to the stop, counting the turn til it stopped. 7 1/2 turns. TOXCHEAP can verify that!!
So I always go back to that setting when I'm having probelms.
DC reads around 68 when its leaned out. But that doesn't seem to affect the way the car runs otherwise, only the idle. I've seen it go to 90, but that was before I tore the car apart. I have to perform some more checks, like the O2 sensor checks.
Thanks

gmbchef

I am going to email him and see how far he would be willing to drive/tow his car for a UPG meet in the future...maybe 2005 or 2006. Wouldn't it be cool to have you towing your rally car AND Colins Sport with your 83??
kiddin.