Hi I have a 1987 Iroc 305 that is giving me a code of 33 MAP sensor but I can't find it. Does it have one or just a MAF sensor? I also have a 1989 that is giving me a code of 36 MAF sensor I know where the MAF is but I can't find a MAP on my 89 either it has a 350. I have looked in all the locations that I know of and the closest that I found looks similar on the drivers side firewall but there is no vacuum hose on it? Please let me know.

Thanks
Bill

 

The error code will vary depending upon the model and year. For an '87 TPI engine, a "33" is a high MAF reading. A "36" is a MAF burn-off cycle failure. If your '87 happens to be one of the few with a carb, a "33" would be a MAP/BARO sensor signal low.

What is the fuel system, and what modifications, if any, have been done?

 

Thanks they are both TPI Engines with no mods the 87 is a 305 and the 89 is a 350.

 

For the '87 with a "33" code, the ECM is receiving a higher than expected signal from the MAF sensor at a given TPS voltage and engine RPM. This can be caused by a TPS which is not properly adjusted. If it hasn't been cone in a while, it may be helpful to clean the throttle body and IAC air passages, check/set the throttle minimum air position (in case someone has been tweaking on the stop screw) , and readjust the TPS to the lower end of the range, probably something close to 0.50V at the closed throttle position.

For the '89 with the "36" error code, verify that both the MAF power and burn off relays are intact and providing voltage to the MAF sensor on the appropriate pins at the correct times. In some rare cases where the problem persists after the MAF power and burnoff circuits are proven correct, the auxiliary oil pressure switch (for the fuel pump) may have intermittent connection problems, which will interrupt the burnoff cycle after engine shut-down and cause the error code to set.

In either case, about all you will need is a good set of schematics and a working DMM to check voltages and resistances.