Got a 84 Z28 carbed LG4 Im tinkering with came in with the connectors on the carb unplugged. The ECM was toast I couldent even get a code 12. I replaced the ECM and connected the MCS and TPS and it ran fine but the SEL came on shortly after and I'm pulling these 3 codes, 21, 23 and 45. All the ground wires and as far as I can tell are intact. To me this indicates the MCS and the TPS are shot making it run rich. Can anyone verify my diagnosis before I change the carb?

Thanks!

 

Sounds like you might be needing a new GM p/n 17078448 (TPS). The MC and O² errors could result from a failed TPS, since the ECM relies on the TPS and MAP for determining correct MC duty cycle rate. The O² is just telling you what it is measuring. Since you're probably going to have to at least remove the top of the carb to replace the TPS, you might as well remove the two nuts in back, remove the carb, and inspect the main well plugs for leakage while you're at it.

 

Thanks Vader.

 

How long did it take to gewt those codes ? A 45 is a mixture code and doesn't pop right up. TPS isn't a critical deal but can cause some slight mixture problems but most will be done through the M/C solinoid or dirt in the carb.

Before you do anything clear all codes and retest with out even starting the car, see if you have a hard code (one that comes back imeadiatly after you clear them ). If you didn't get a code, drive it and see if one comes back. The 45 should take a little driving to reproduce. That carb is fairly sensitive to dirt build up internally and could be casting a 45, it's very common.

Test it... test of the tps with an ohm meter. and if you can remove the M/C solinoid from the car without loosing the seal on the bottom power it up with 12 volts and a ground , it should open. Resistance with an ohm meter is I believe about 32 ohmson the M/C also..

 

Yea I tested as much as I was willing to. I did reset the new ecm and they poped back up. I just poped my Fbirds old CC carb on it and the codes never showed back up. I think the reson the MCS was disconnected is because it went full rich so they just unplugged it.

 

There is a limiting/stop screw under the MC solenoid to adjust for maximum enrichment on most of the E4MEs, if I recall correctly.