Hi, Appreciate any ideas any of you may have to a mystery regarding my engine. I have an 83 z28 with a 4 barl. carb. The car has 66k orig. miles. I have had it for a year and a half, and have replaced the plugs, and new carb filter. The car has always ran very well. It just passed smog last month. When I got in to go home today after work, it ran really bad...I thought maybe the chocke got stuck, pulled the air cleaner, and it was wide open , I had to limp it home...it would idle down around five hundred, when it normally runs around seven hundred and fifty rpms. As I would try to accelerate it almost seemed as if it were chocking, so I would upshift to keep it going till I got home. I took the air cleaner cover off, and while running, shoot some carb cleaner down the barrels, thinking maybe something was clogging it, but seems about the same, am mystified??? Could this be something with the electrical..I understand my car does not have points and condenser, but something like a powerful coil?, or could it be something with the smog equipment, like an egr valve???, or could it be with the computer(I am assuming I may have one, because there is a plug in place under the dash, I think for the hook up for diagnosis equipment. I looked under the hood also for any hoses that looked disconnected, but all looked ok, have not touched anything myself lately. Could this also be the carb, or a fuel pump??, not sure how one would act if going bad, except for running poorly, but if it were either of these two, would it not slowly go bad, instead quickly as it did today? Again, thanks for your help, Dennis dennisgramm@netzero.com

 

Welcome Aboard!

Yes, that connector under the dash (ALDL connector) is for connecting diagnostic equipment. That can include a data logging scanner to retrieve running sensor data, or a code scanner or paper clip (jumper wire) to retrieve error codes.

In stock form, there are no points or condenser, but there is a distributor cap, rotor, secondary wires, and coil. That is the typical HEI ignition system.

A sticking EGR is a possibility, as is any other vacuum leak or carbuertor problem that would alter the fuel mixture.

Just to clarify, is the Check Engine lamp on while the engine is running?

If you can, test vacuum at warm idle. This may help diagnose a sticky/leaking EGR valve. It may also help with other diagnoses.

The problems you are experiencing could be related to many possible causes, and it would be easiest to split the list in half by determining if the cause is fuel delivery or ignition system. My wild guess is that you have a fuel mixture problem.

Do you notice any particularly strong suel odor in the exhaust? Are the spark plug electrcdes and insulators white, tan, or black?

 

Hi Vader, Thanks for your quick reply, and all the good info...to answer your question...there was no engine light on dash on. but the good news is ....I think we may have figured out what may have caused it...last week I filled my car up at the local Vons gas station, normally use 76 gas...a local mechanic and I put our heads together, and think it may have been that, yesterday when I went to start the car it came right up, drove it to mechanic, still little rough in primary, but continuing to improve, he talked with me, told me to take freeway drive, I did, and it was almost back to normal...when I got back into town, I noticed first and second still had a little dead spot, so I sprayed more carb cleaned down throat of carb, drove it to the 76 station where the mechanic was told him what it did, and we decided to drive it for a while and see what happens...well, while I was there, I filled up with 76 gas, and we did some in town shopping in the pm, and it feels like normal again...maybe just some bad gas...gonna keep a close eye on it, hopefully that was it, the car just really runs good, we love it, something funny...everyone thinks it looks like nightrider car, cause it is all black...was kidding my wife one day when the new star wars movie was on, and said, hey lets put a small sticker on the back and call it VADER...we laughed, but decided not to, but last week I stopped to get some coffee and a local Burger King, and they had all the latest star war figures, so I bought a Vader, and he proudly sits on the little dash above my radio...thought you might get a laugh of that...well, my first time trying a reply, hope you get this ok, love this web site, hope the2007 Camaro makes back, the new artist conceptions are just awesome. Thanks again Vader for all your help, take care, Dennis

 

Glad you got it solved. Part of it may have been poor fuel, some may have been old fuel if it has been stored for a while.