Car started dying at red lights with the a/c on. It's my grandpas car and hAS around 75000 miles on it. Stumbles at low rpms but runs better as the rpms go up. Exhaust tips seem to have a lot of extra soot in them. He keeps the car very clean and noticed this when washing it.

Now it's hard to start and I think it's in limp mode. Fans come on at start up, a/c isn't working and the trans seems to be shifting weird.

It threw one code but they reset the computer and now it isn't throwing any. I don't know what code it was as the car is at my cousins shop and he's doing the work on it.

My cousin thinks it's the opti but my grandpa doesn't want to spend the 700+ to pay him to fix it if he's not 100% sure that's it. I'm not working on the car because I don't have the time and don't want to chance scratching it or something. Lol.

The car is mainly driven below 45 miles per hour and is rarely able to stretch it's legs. I'm almost wondering if the cats could be stopped up from such slow driving but it would be unlikely with such low miles. The air filter looks like new.

Any ideas?

Ps. We tried the icm from my car and it didn't make a difference

 

unplug the MAF and see how it runs.

 

How long since the plugs/wires have been changed? When I bought my LT1 it had about the same amount of miles on it, and acted similarily. I swapped my plugs/wires, and she ran like a champ.

 

I believe it probably has original plugs and wires. I didnt think of that because its not skipping but theres a good chance of it being the plugs. I bet they are gunked up due to being driven so easily all the time. I talked to my grandpa this evening and he said they took the car down the road and held it in second at 4500 rpms for about a mile and it cleared it up alot.

can the engine detect poor ignition from spark plugs using the oxygen sensors putting the car into limp mode? Grandfather had this same problem about a year ago driving in the mountains and a few WOT runs fixed it.

I doubt its maf because the car is still in open loop when its running bad.

I really dont think its the opti neither because it doesnt buck and sputter at high rpms.

 

check the plug and sensor in the water pump.