I have an 89 with a 5.7 with 220k miles. I just finished replacing the the fuel injectors because I had a slight miss. That seemed to resolve that problem. Now im getting a check engine light, error 33 for the MAP sensor or vacuum problem. Vacuum seems fine, I have a reading of 20 at idle. Also my temperature gauge no longer works. I'm not sure if both problems are related. Maybe there is a connector somewhere that pulled apart. I have yet to solve either problem. Is the MAP sensor under the plenum? I think the temp sender is in the front of the block under the theomstat by-pass. I don't think both sensors went bad at the same time. Other wise, the car seems to run fine. Any suggestions. Thanks.

 

Sorry I can't really help you with the MAP issue but the sending unit for your temp gauge is located on the drivers side cyinder head. It looks like a brass plug and should have one green wire going to it. The sensor that you are refering to on the front of the block is the coolant temp sensor which is not related to your gauge.

 

Thanks, for the info on the temp sender. I just had a Chevy dealer verify that there isn't a MAP sensor on 89 TPI's. I'll be checking the MAF again.

 

to verify if the MAF sensor is bad, you'll need to do some testing. Here is the link to the test......https://www.thirdgen.org/forums/tpi/...uble-code.html

 

I changed the plug on the MAF harness and that was it. Runs even better. It had a corroded pin. Temp gauge started working. I don't know. Now if it will pass emissions. Needs a new CAT every year. Thanks alot for the TS flowchart.

Dennis

 

Good deal. I had the same problem too. But what I did was take off the MAF. I got my Dremel and cleaned off the little 5 pins inside the MAF housing down to its brass color. Then I got a little flathead jewelers screwdriver and inserted into each female prong on the wiring harness. I then gave it the tornado twister to clean off the corrosion inside. Then I touched it off by applying some Permatex Dielectric Grease. It cured my troublecode 33.