Very rough running, missing until warm

[rs6er]

When I start my car, it runs very rough- popping, backfiring, missing. It feels like it is only running on 5 cyls. This continues until I have driven for a while and thoroughly warmed up, at which time it runs fine.

I had a total rebuild a few years ago and the car ran perfectly for a while.

What should I be looking at?

[Scott R]

You should be looking at your cold control pressure first.

[rs6er]

Sorry. Do you mean fuel pressure?

[crepen2002]

john i have a 82 sc and i have the same problem i figure it must be my wires but i really dont know.

[rs6er]

I changed them to Magnacors a few years ago.

[Scott R]

Yes, sorry for the brief response. I would hookup a set of CIS gauges and get the numbers when cold, and then warm and note how long it takes to go from cold to warm control pressure.

It could be as simple as not having voltage to the wur, or it could be a dead heating element inside the wur. If you have +12V's at the plug on the wur with the fuel pump running, then it's likely a problem in the wur. You can check that by getting a resistance reading on the heating element.

Sometimes you just need to adjust the WUR a bit as they get older. A lot of threads on how to do that here.

[Scott R]

Sorry somehow I missed the running on five cylinders... ignition issue first before CIS. Which cylinder is dead? Have you isolated it?

[rs6er]

Thanks Scott. That sounds like a good place to begin. I will check firing tomorrow.

[sancho]

if it was an ignition issue wouldn't the car be driving rough when cold and warm?
I think it is fuel related issue, i would check WUR as it is a common thing on cars with CIS, I had the same problem with mine,,,,,

good luck

keep us updated

[T77911S]

if you have gages, still check the cold and warm pressures. its always good to rule those out.
make sure the ignition is is good working order, cap, rotor, plugs and wires. you could have a bad plug that shows itself when it is cold. also, MCA put on a new set of plug wires and had a bad set, so even though the wires may be new(ish), they can still be a problem. but, i think his car ran bad hot and cold.
check the fuel flow and spray pattern of the injectors. you could have one that runs rich/lean.
air leaks. if you have several Orings/injector sleeves that leak, you could compensate by making one cylinder run rich, fouling plugs.
you can have 5 cylinders that have air leaks. so to make it run right, the good one might be too rich. its not always the one with the problem that is the real problem.
i would even do a compression test if you cant find out whats going on.

pull the plugs, look for one that might be running rich, might help you isolate the problem.