'77:

Normal, every single time until today: Put it in neutral, turn the key, listen for FP, hit the ignition, starts immediately and assumes a cold idle around 1200 and I usually let it idle for 5-10 minutes before driving. No smoke. Note: My foot never goes anywhere near the throttle during all this.

Today: Fired right up, but REALLY rough and chugging. Sputtering up and down around 400-500. Seems to be missing really bad and had a tone to it (I had the hood up) like one of the cylinders was hitting something. Smoke starts coming out the tail pipe. I rev it up slightly with the linkage, but it does not smooth out. It continues the same skip. I reved it to maybe 2000. Really smoking at that speed, and running REALLY rough. By now it is starting to get warm but when I take my hand off the linkage, it drops to 200 and JUST BARELY stays alive. Hmmmm...

I shut it off and scratch my head. Doesn't make sense. Ran perfectly last week. Hit the ignition again without touching the throttle. Starts instantly and assumes a perfect idle. No smoke. Let it warm for a bit more and take it out for a flawless, spirited run.

Huh?

steve77

sounds like you lost some spark in the cylinders. Check your plugs for fouling. Might be a head gasket too, just do some more mechanical inspection before you take it into a shop.

Sounds to me more like it could be a problem in the cold start circuit.

Water temp switch, thermo time switch or the cold start valve (injector), or it could be the air temp sensor in the AFM. It might be either only working intermittantly or it could be just that the one time it either over enriched the mixture or didn't richen it up at all. There is also a cylinder head temp sensor that's involved too. UGH. Lots of things to check. You didn't say what color the smoke was, I'm just arse-uming it was black? Just in those few things, between all of them it's about 300 bucks for new.:mad:

I'd check the wire plugs to all of them first, then using the service manual as a guide (hopefully you have a factory manual) you can check all the switches operation in the plug to the ECU. I'm pretty sure it tells which pins or for which. Sorry, I sold the 280 the other day so I don't have the 75 service manual anymore to use as a reference.