I have an all stock ‘81 with the 350 small block with 58K miles. It has the stock Rochester carb. It’s an automatic transmission. It’s always started hard since I’ve owned it but something is really wrong with it.

I took it for a ride last weekend and it was fine. It sat idle for 3-4 hours and when I tried to start it, it just cranked until it eventually started but the engine shook. When I had to stop for a light, the rpm’s fluctuated between 300 and 500 and wanted to stall, this was after 10 miles of driving. It seemed to run fine after it that.

I took it out again today and the same thing happened accept this time the engine had a ping after it started hard. It had the rough idle at a stop like. If it was going less than 25 MPH without my foot on the accelerator, the car seemed to surge.

Here are a few things that I’ve noticed or have done over the last few weeks that may or may not be contributing to the problem.

- I can smell coolant but can find a leak, I did replace the radiator cap

- The fuel gauge is pinned at full. This probably has nothing to do with the problem but I thought I’d mention it.

- I’ve been driving it in 2nd gear around town. Same comment as the previous bullet.

My brother seems to think it has something to do with a bad spark plug wire.

I’d appreciate any suggestions of where to look for the problem.

Thanks

 

Hi, did you find an answer to this? My 81 recently did very similar, I also had check engine light coming on and off. I deleted the EGR and now runs very well and no light.

 

Yours is the first suggestion and I haven’t been able to revisit the problem since I posted it.

A couple of years ago I did replace, not delete, the EGR and it ran better but I wasn’t having the problems that I’m having now. I do recall that the valve and block were full of gunk. I vacuumed out what I could because I didn’t want to loosen it up and have it clunking around in there. What did you use to plug the EGR opening?

I think I’m going to start with replacing the pickup sock in the tank while I’m trying to figure out why the fuel gauge is pegged at full.

Thanks for the suggestion.

 

I always suspect ignition systems. Wires fail and HEI's can fail under heat. I would do cap rotor and wires plugs to establish a solid baseline.them set the carb and timing by the book.

 

Ya know, John S, that sounds like a better idea than the pick up sock because it ran great one minute and a few hours later the problem started on the next start up.

I’ve heard nightmare stories about replacing spark plugs wires on the C3’s, I hope my patience isn’t tested.

Thanks for the advise.

 

It will be. On at least one of the plug wires a pissed off GM engineer thought it would be nice to route one of the plug wires under the starter. 😡

 

Might be a vacuum leak. The surging is a lean condition. Look for a cracked or disconnected hose around the carb..

 

Could be fuel related, could be ignition/timing... don't just throw parts at it. Suggest lopoking at the simpoliest, most likely culprits... my first though is fuel starvation, easy enough to change the fuel filter, when clogged enough it'll cause the symptoms described.
Take off the air cleaner & look for anything out of place, is fuel squirting from acc pump when bumping throttle... Or dribbling out?
When driving, hit the gas hard, does it completely stumble, fall on it's face, or backfire? These are all clues to what the issue may be... if it backfires, likely timing is too retarded... stumbles, then carb secondary/spring adjustment & possibly card rebuild (which never hurts with today's gas). Vacuum leaks will be most apparent at idle, not so much when normal driving & accelerating. Check these things first & then follow-up here... chances are there's a vacuum leak in addition to whatever the primary problem is.

While many of us can provide suggestions (and remember it's the internet so you get more bad suggestions than good ones), with these older cars, good basic mechanical knowledge is needed to keep them running.

 

I recently bought a low mileage 81 that was sitting in an airplane hanger for close to 20 years. The carburetor was sent out to a recommended shop that does high end restorations. After completely going through the car and getting it back on the road it wasn't running 100%. I looked for vacuum leaks and anything else that would give it a rough idle,everything I looked at was fine so I figured it had to be the carburetor. After isolating all vacuum sources and capping all ports on the carburetor the the car still had the rough idle. The shop that rebuilt the carburetor didn't replace the O rings on the idle air bleed valve, I replaced the O rings and that was the issue,car now runs 100%.