Recently I had replaced the head gaskets on my 94 Camaro, it's the 3.4L V6. That fix was successful on my overheat problem. However, after a day or 2 after driving it, the check engine light comes on whenever I idle in a stationary location, whether in park or at a red light. The car seems to have a low pulsation at a constant rate when its stop, but it goes away when driving. The idle is at around 600-700rpm and struggled when accelerating slowly. I thought it might be a vacuum leak, since I just did a head gasket job, but I couldn't find any. I also thought it may be a misfire, so I put in new spark plugs and wires today, since I didn't do that when I put back the car after the head gasket job. The new plugs sort of helped, there is hardly any struggle to accelerate, but the weird pulsating idle comes back when I let it run in park( but it is softer). I can't get the codes off, and Autozone can't scan my car since its OBD1. Any ideas on what may cause the light or car to idle oddly? I also lost fuel economy because I noticed I don't get the same miles on a tank as before, it went from 20mpg down to 14mpg, if that helps. Oh, and when I start the car in the morning, I can smell exhaust. Appreciate any help

 

With that much of a drop in fuel mileage and the smell, it sure sounds like your car is running extremely rich now. Easiest thing to check first I think would be the MAF sensor. It was probably removed durinng the head gasket fix and could potentially be dirty. A dirty MAF can cause a drop in fuel mileage. Next thing I would look at, if that doesn't help you, would be the 02 sensors. Dirty or fouled 02 sensors can also cause your car to run rich and get poor mileage. Not sure on your car, but generally most will have at least 2 02 sensors; an upstream and downstream one. The upstream one is the one you would want to look at and will be located right after your exhaust manifolds or in the y pipe.

 

I have not checked those yet, but I will check the MAF sensor tomorrow. Hopefully it's as simple as that. I do believe there are 2 o2 sensors, so I will check those out when I check the MAF sensor. How would I know if they are bad from a visual inspection?

 

Failed basically got it spot on. Only as I recently found out, we only have a MAP sensor, not a MAF. But check it out anyway as it would still be disconnected on a head gasket job.

Also, SOME 3.4l's have a downstream by the cat. But both of mine stock didnt. It seems like most 3.4l camaros have one on each header. (where all the pipes connect at the down pipe)

 

Excessive carbon built up on the tip/extremely burnt. If you have a post cat 02 sensor, you can try swapping that one with your upstream sensor.

 

Kinda been a while, sorry, school has had be busy, but here is what happened:
The MAF is connected and I never removed it from the intake plenum during the head gasket job. I tried replugging the connector just to be sure, but it still runs the same. I haven't had a chance to take a look at the O2 sensors yet since I don't have a deep 7/8 socket, but I'm hoping that I can finally find the problem

 

bad temp sensor can also cause this issue.

 

Got a mechanic friend to scan my car, got a code 44, saying the left O2 sensor was lean. Replaced the O2 sensor today and car runs fantastic(: It was really easy to change

 

fd nailed it