Rough idle and hesitation when cold

[groovydude]

I have a just-received 1982 SC with some cold idle issues. The car has 116k miles (verified), and had a top-end rebuild at 97k mi.

I had the car inspected before purchase, and the mechanic told me it needs a new WUR. However, I had another thread started, asking for opinions about rebuilt WURs, and there were some comments that suggested it could be a couple of other issues.

I've had a chance to delve into this a bit further, now that I actually have the car! Here are the exact symptoms:

Cold (or warm) start up - no problem. Car starts right up and revs up tp around 1700 for about a minute. Then it settles down to around 700, but very rough. If I hit accelerator it's extremely slugish. After a few minutes the car warms up (temp guage starts to move), and the idle settles in at around 700, and throttle response is normal.

Engine RPMs decrease if I open the oil filler cap.

I'll replace the fuel filter and the fuel accumulator (just because I might as well - it's a bit pricey but I think it's not a bad idea to replace any part that's 33 years old). If the problem persists, I'll try Tony's loaner WUR.

I have the Bently book, and it looks like it could be a few other things as well. Does anyone have any thoughts on what else could be checked, things that are more likely than others to be the problem?

Thanks for all your help!

[Bob Kontak]

Originally Posted by groovydude

After a few minutes the car warms up (temp guage starts to move), and the idle settles in at around 700, and throttle response is normal.

Engine RPMs decrease if I open the oil filler cap.

Check oil cap idle drop after car warms up. How much do the rpm's drop?

At first blush, cold control pressure may be off. Too rich may cause a surging in your idle. If lean, you probably know what else can cause that. False air.

Make sure the electrical connections on the WUR and aux air regulator are solid. AAR is that unit between #5 and #6 intake runner. It allows extra air in when cold. It can be bench tested.

[john walker's workshop]

Start with a proper, known CO adjustment when it's at normal temp, then see how it is cold and warmup.

[Bob Kontak]

Originally Posted by john walker's workshop

Start with a proper, known CO adjustment when it's at normal temp, then see how it is cold and warmup.

groovydude is right down the street from you.

I say money well spent for a new owner to get a potentially minor, but annoying bug swatted.

[Jdub]

John typically sets my '78 to 3.5% though your car with O2 sensor will be different. If you call John and let him warm up his machine he can check and adjust. Bring beer at a minimum...

[groovydude]

Cool. Thanks for pointing out the proximity, I wouldn't have looked.

[groovydude]

I replaced the oxygen sensor relay and that took care of most of the problem!