What does this mean?

ohecht · 05-29-2002, 05:06 PM

My 82 SC was running perfectly, but now it stumbles off of idle, but only when between very cold and fully warmed up temperatures.

It starts right up and idles fine for a while, but between the point when the temp needle starts moving until it gets to operating temp (about 180) the idle is low, irregular, some backfiring, and a sever stumble as I move out in first gear. Power is fine after that and everything returns to normal once it reaches operating temperature.

I have checked the mixture, timing, plugs, cap, rotor, and cleaned the air sensor plate.

I did get gas from a different station then usual, and the fuel pump was momemtarily starved going around an entrance ramp at high speed with an empty tank (necessitating the unplanned fuel stop) Could bad fuel cause such a specific symptom?

Olivier

Talonz82 · 05-30-2002, 02:41 AM

I am working a problem that began that way. When you first start your car the fuel system and its components are in what is known as the open loop system, your ECU uses a cold start valve, thermotime switch, thermo switch warm up regulator auxillary air valve, fuel distributor (and maybe others I am unaware of on an 82, I have an 80) to provide a certain fuel air mixture for warm up, once engine warms to a certain point the thermo switch places the system in the closed loop, which uses the o2 sensor in combo with the frequency valve to refine certain air/fuel values and provide the engine with the correct fuel air mixture.

The back firing tells me possible vacumne leak, improper mixture adjustment, cold start setting of WUR.

To pinpoint you will need a CIS fuel test gauge to check primary pressure and system pressure (to set WUR cold pressure)

A gastester to check mixture. Let me know how you make out,

ohecht · 05-30-2002, 03:37 AM

Thanks. I am running with the O2 sensor unplugged now, so the car should be staying in open loop. I do have a Gastester to set the mixture, but the readings drift a lot after I clear the sensor to see if it will return to the baseline reading. It never does, so I suspect those settings. I did the last setting using the duty cycle of the O2 sensor instead, but that was since the problem started.

I also have a fuel tester that I want touse, but I am having trouble finding all the washers I will need to replace as I open connections to put in the tester. Looking for a vacuum leak is a good idea, too.

Olivier

rstoll · 05-30-2002, 03:56 AM

Check the relay under passenger seat. Start the engine, unplug relay and listen for a change. Plug it back in. If no difference, change relay. Can you hear the frequency valve buzzing?

ohecht · 05-30-2002, 03:12 PM

The relay under the seat is working, because the car almost died when I unplugged it. I will try to check the frequency valve. I can't say I've ever heard or felt it, but wouldn't the fact that the control circuit being interrupted almost stalls the car mean the valve is working as well.

The temperature part of the symptoms is the weird part. The idle is low and rough between the first and second temperature marks (120 and 180), but above and below it idles fine.

Olivier