HT4100 4.1, 4.5, 4.9 Discussion, '85 Seville HT 4100 MAP location & mystery connectors ? in Cadillac Engine Discussion; Hi folks,
After cleaning the engine on my newly acquired '85 Seville (distributor & TBI plastic bagged, sensors & connectors ...
After cleaning the engine on my newly acquired '85 Seville (distributor & TBI plastic bagged, sensors & connectors avoided) I seem to have a problem. The next day the car started hard, ran rough for a few seconds and then cleared up and ran fine. I drove it to work, parked it and when I returned, no start. Had to come home on a roll-back and began diagnosing the issue.....no spark!
I've removed the distributor and replaced the pickup coil, condenser, ICM, coil, cap & rotor (at 74K miles I figured it was time anyway). It now tries to start, but runs rough for a few seconds and dies. I indexed the dist drive gear and replaced it as it was, and also indexed the dist location and replaced it to the same position....still no joy. I unplugged every ign connector and blew them out with air (no signs of moisture). If I unplug the ICM connector it starts and runs smooth for a few seconds and dies (I'm guessing the ECM is shutting off the fuel pump due to no ICM signal?), and when I plug it back in the hard/no start condition returns. I've checked all the other components I can find...vacuum & wires to EGR, TPS etc. I've ordered a Haynes manual but it has not arrived yet.
In Googling the issue I see references to the MAP sensor as a possible culprit and have looked at online parts lists which show a pix & price, but I can't find the darn thing on the car! I did find a 3 pin connector hanging loose near the back of the A/C compressor, but nothing to plug it into within the reach of the wires...???? Also found an orphan green connecter near the air compressor (marked with blue tape) Any ideas as to the function? The 3 wire connector near the TB has what looks like a cap on it...maybe a diagnostic port?
Any expert advice appreciated before I throw more parts at it or have it towed to the shop. I have experience working on old Detroit Iron, but the electronic management gee-gaws have me stumped.