I have a 1984 4 cylinder Fiero. It has the same problem as my 1988 four cylinder Fiero. It runs fine for a few minutes, then runs VERY rough. The CHECK ENGINE light comes on every few minutes. The car seems to run BETTER when the light is on.

I had a private mechanic fix the 1988 Fiero. I was charged $930. They said the problem was a loose wire. I took the 1984 Fiero to a Pontiac dealer. They told me they would charge me unto they fixed it or I ran out of money - whichever came first. They begged me to take the car home.

I brought the car to a private mechanic. He replaced the ECM, the plugs, the rotor, distributor cap and spark plug wires. No help.

ECM code is 44. Any ideas?

O2 sensor

44 is lean mixture

Possible causes in addition to the O2 being bad.

1) A bad ECM ground. on the BLACK ecm connector there is a tan wire (pin 15) make sure it is grounded.

2) Low fuel pressure.

3) Ground in the O2 sensor circut

4) Stuck open EGR valve.

Thanks.

I got two votes for the O2 sensor so that is where I will start. I think it's at the top of the block with a purple wire on it. It looks nice and clean so I didn't suspect it.

Apparently the ECM thinks the mixture is too lean and richens the mixture until it becomes way too rich. Because this problem seems identical to the problem I had in my last Fiero, I believe there is some common cause. Do Fiero's have a more frequent history of problems with the O2 sensor itself or the wiring?

The dealer had the car several times before they gave up. You guys seem to have put your finger on it right away. Why is every mechanic terrified when you drive up in a Fiero? It's a fabulous car.

quote Originally posted by productepi: Thanks. I got two votes for the O2 sensor so that is where I will start. I think it's at the top of the block with a purple wire on it. It looks nice and clean so I didn't suspect it.

It is not in the block itself, but in the exhaust manifold. FWIW: Mine has a black wire.

quote Originally posted by productepi: Thanks. I got two votes for the O2 sensor so that is where I will start. I think it's at the top of the block with a purple wire on it. It looks nice and clean so I didn't suspect it. Apparently the ECM thinks the mixture is too lean and richens the mixture until it becomes way too rich. Because this problem seems identical to the problem I had in my last Fiero, I believe there is some common cause. Do Fiero's have a more frequent history of problems with the O2 sensor itself or the wiring? The dealer had the car several times before they gave up. You guys seem to have put your finger on it right away. Why is every mechanic terrified when you drive up in a Fiero? It's a fabulous car.

Yes
I have had O2 sensors break or shatter internaly. Once it is broken the O2 sensor will throw a lean code even though it is barfing out black smoke.

The wire that the O2 plugs into (on the 84 anyway) is purple. It runs to the BLACK ECM connector (pin 8). The purple wire is fairly well protected and may not be the fault. The connector itself may be bad.

I removed the connector from the PCM and confirmed the tan wire was grounded. I checked continuity between the ECM and the O2 sensor and found it was good. I replaced the O2 sensor (purple wire on the old one, black wire on the new one, crossed my fingers, and took a ride. It ran fine for a few miles, then chugged. It chugged one more time and the Check Engine light went on. Then it ran perfectly for the next 20 miles or so and was still running fine when I shut down. The new failure code was 13. Something has changed but it is still not fixed. The wire which runs between the connector on the O2 sensor and the ECM looks like a suspect. People keep mentioning the tan wire on pin 15. Is there a history of problems with that wire? Where is the other end of the tan wire?

The next step I plan to take is replacing the purple wire. If that doesn't help, any ideas about what to try next?