Grab a cup of coffee and a bagel because this is a long one!
I've had some codes that pop up alot when I'm on the highway. When I pull over to check the codes, I get three of them. I get 12, 33, and 44. Of course I know that 12 is nothing to worry about. It is the code that sets when you are reading codes. Code 33 reads as MAF sensor and description is Poor electrical connection, open or short circuit, defective MAF, defective ECM. Code 44 reads Lean Exhaust, and description is Lean condition caused by malfunctioning injectior, vacuum leak, low fuel pressure, poor electrical connection, open or short in circuit, defective MAP / MAF, defective oxygen sensor, defective ECM.
Well since both codes said MAF sensor, I replaced it. The fuel pressure is at 47 psi, I have adjustable regulator, Vacuum seem to be holding at 21 inches at idle and kinda surges closer to 24 then back down again. I have switch ECM's from my 86 TA and my brother's 88 Camaro and code keeps popping up with or without my chip in the ECM. What the heck?
I'll be replacing oxygen sensor today but what is going on here? What could be going wrong? Any ideas would be very helpful. Thanks in advance and hopefully someone will have some input.

 

I dont know if I can help. First of all, I will assume that you have a 305 TPI.
You have the dreaded 33 error code, it is the most difficult one to fix or identify the root cause. There are many posts on this matter, please do a search.

The 33 error code is set when all three of the following are true:
1) engine speed under 2000RPM,
2) over 45 gms/sec air flow thru the MAF, and
3) less than 25% throotle.

After I modified my 350 TPI back in the mid 90s, I could set the 33 error code at will, and I did it on the expressway time & time again. I could watch the engine RPM climb to just above 2000RPM as I increased speed on the expressway, and sure enough, I would feel the engine booble, then the SES light would come on, and the engine started to run like crap. It was the 33 error code. The ECM would go into "limp home mode" everytime that I set the 33 error code. I changed out MAFs, I changed the burn off switch, and relay switch. I work with the TPS setting. Nothing help. Finally, I learned how to "burn" my own Eproms, and by setting two items to different values, I killed my 33 error code forever !!!!!!

It is very rear for a 305 to set the 33 error code, you are lucky! I would install a new O2 sensor as you plan (these should be changed out on a regular basis anyway). You could buy a scanner,,, these things are very helpful in tracking down problems, especially on these TPI cars.

 

Thanks for the info. It does happen to me around 2000 rpms. The only difference is that my car came stock with a 350 and after the rebuild it was built 30 over with forged internals. My car isn't a 305. I will change o2 sensor but what did you change on the prom to stop this from happening. I was looking into prom burning but it seems to be a little difficult.

 

What temp thermostat are you running?

jms

 

If your car is an '86, it did not come from the factory with a 350. 350s started in '87.

 

I'm running a 180 degree thermostat. My car is an 1989 Pontiac Firebird formula. On the door it says formula 350 which sucks cause everyone knows it's a 350. It has a 700r4 trans with a trans go shift kit. I have edelbrock runners and manifold with a ported plenum and AFR heads. I was going to get the edelbrocks but got a deal on the AFR's. I don't know if my mods are the problem but it would be nice to fix it. I replaced the o2 and codes keep coming up. What the heck? Why is my car being so dumb?

 

Put a 195 or 200 degree thermostat back in it.

Then clear the codes by pulling computer fuse in fuse block or disconnecting battery cable for a few minutes.

I had a similar problem several years ago and the computer was reading engine speed versus amount of air coming in versus water temp.

During cold weather with my 170 degree thermostat, the water temp would not get warm enough to satisfy the computer versus the amount of airflow it was seeing.

Just my experience and it is cheap to try.

jms

 

As pointed out above, when you make a change, you must clear the current error codes. You do this by disconnecting the black ground cable on the battery.

 

OK, thanks for the help. I'll get a stock thermo back in the car tomorrow. Thanks again for the help because this has been a major pain in the ***.