AZ Ron Posted August 7, 2017 Share Posted August 7, 2017 My 88 has always had lousy gas mileage (16 mpg) and recently has been stalling as I back out of the garage just after a cold start. I bought a new Magnavox coil pack from AutoZone as they had one in stock with a lifetime warranty and I had enough credit to get $20 off. History: 117,500 miles. The car was always serviced at the Buick dealer that it was purchased at when new (before I bought it ). I replaced the cam position sensor, the crank pulley, the cam magnet, plugs and wires recently. I took the car for a 30 mile test drive and got 26 mpg with a smooth idle and it was running good. The next morning it had a hard time starting. I took in a movie and had a hard time starting afterward and it was hesitating with acceleration. The directions with the Magnavox coil pack stated that I should also replace the ICM when a coil pack was replaced. Since both the coil pack and the ICM's plastic filler looked discolored and were beginning to get mushy I bought a Magnavox ICM from Autozone too. I went for a test drive. Started great, ran great and after 15 miles the AC stopped working and I got a warning that the compressor shut off due to the engine overheating. The temp gauge read HOT. I was near home and pulled into my garage to let the car cool down. Now, even on the very hot days here in AZ (117 F) the car never gets over 204F. Previous owner recently installed a new radiator and hoses and had a full flush done. I installed a rebuilt water pump recently too when I did the cam magnet. Could a bad ICM cause the car to overheat? I topped off the antifreeze after the car cooled and drove around about 5 miles and it overheated again? Link to comment Share on other sites More sharing options...
2seater Posted August 7, 2017 Share Posted August 7, 2017 Both fans are working when a/c is on, correct? Did it run at the expected temperature after the water pump was replaced and this only occurred after the ICM replacement? I am not certain about the Reatta, but I know a '93 Buick Century will shut the a/c down not just for engine temperature, but when the fan failed, it shut off the a/c due to the hi-side pressure spiking high from lack of cooling. If the engine is running well, mileage is up, I don't see any connection with the ICM. Are there any codes? Link to comment Share on other sites More sharing options...
AZ Ron Posted August 7, 2017 Topic Author Share Posted August 7, 2017 The only change was the new ICM. Water pump has been installed for several months with no problems afterwards. I took the ICM back to Autozone this evening and they gave me another one with no hassle. This one was in a new box that had not been opened and included the insulator that goes in before the wiring harness is bolted in and the 6 screws that hold the coil pack to the ICM. These were NOT in the box with the first ICM they gave me. UNFORTUNATELY I broke one of the spade connectors at the coil pack. :S I gave up for the night and will practice my soldering skills tomorrow morning. :rolleyes: Both the coil pack and ICM that were on the car appear to have been replaced at some time in the past. The ICM had one non-metric nut jammed on the top bolt and the coil pack had marks on the insulation that showed which color wire was supposed to go to their respective tabs. Seriously love this stuff. Pretty much having fun in the garage these past few days - wish it was air conditioned though. Link to comment Share on other sites More sharing options...
Ronnie Posted August 7, 2017 Share Posted August 7, 2017 IF, and this is a big if, the ICM was causing the timing to be severely retarded it can cause the engine to run hot. But if that was the case the engine should run so bad that you would notice it right away. A friend of mine installed a "Timing Tape" on his harmonic balancer incorrectly. When he set the timing it caused the timing to be retarded. After a couple of passes at the drag strip the engine was running hot, the headers were cherry red and performance was way down. I'm looking forward to hearing whether or not putting on a new ICM fixes the overheating problem. I'm doubting it will - but I'm hoping it does. :) Link to comment Share on other sites More sharing options...
2seater Posted August 7, 2017 Share Posted August 7, 2017 That is bizarre, but we do find new failure modes occasionally. It would take something seriously odd for the module to place extra load on the engine. If ignition timing is late it will increase exhaust temperatures but I don't see that overheating the engine that quickly. Link to comment Share on other sites More sharing options...
Ronnie Posted August 7, 2017 Share Posted August 7, 2017 Yeah, I agree 2seater. We took a while setting the timing at the track with the engine idling without the engine overheating. It took 2 hard passes down the track before he noticed that the engine was getting a lot hotter than normal. Raising the hood at night and seeing the headers red is what gave us a clue to what was going on. Link to comment Share on other sites More sharing options...
AZ Ron Posted August 7, 2017 Topic Author Share Posted August 7, 2017 The engine ran very smooth and acceleration was good after I changed it out. The only thing I did different was to remove the belt so I could get at the upper mounting bolt for the ICM with vice grips. Previous "mechanic" had forced a non-metric nut on there. I also had to move the pipe that runs under the mounting plate so I could get a ratchet wrench on the nut closest to the engine. When the car first overheated I lost almost 1 gallon of coolant. That was odd as the overflow tank was not empty. I checked the belt to make sure that I installed it per the routing diagram on the shock tower. I also watched after I started it up to make sure it was tracking smoothly. I have a couple of chores to do this morning and then I will try to finish the install of the new ICM. It would defy logic to find that something else just randomly happened to cause the car to suddenly run hot. Link to comment Share on other sites More sharing options...
2seater Posted August 7, 2017 Share Posted August 7, 2017 I had a somewhat similar experience when we were breaking in the new cam on my sons off road car. Got the timing "close" before starting the engine and didn't want to shut it down after starting the break in. High idle speed, 1500-2000rpm, and the headers started to smoke and then a dull color change. Darn Chevies and that rear distributor made it tough to get at quickly but turning it to add advance cooled it right down. Didn't run long enough to get the water temp very warm but I would imagine it would eventually. I know it is a moot point now, but I wonder if the timing would indicate properly in diagnostics or not? I've never heard of crossed plug wires causing heating trouble? Link to comment Share on other sites More sharing options...
Ronnie Posted August 7, 2017 Share Posted August 7, 2017 I have a couple of chores to do this morning and then I will try to finish the install of the new ICM. It would defy logic to find that something else just randomly happened to cause the car to suddenly run hot. The outcome of this is going to be interesting. ;) Link to comment Share on other sites More sharing options...
2seater Posted August 7, 2017 Share Posted August 7, 2017 The outcome of this is going to be interesting. ;) 10-4 on that. I imagine the pipe that was moved is the power steering return line which should have zero effect. :huh: Link to comment Share on other sites More sharing options...
AZ Ron Posted August 7, 2017 Topic Author Share Posted August 7, 2017 The replacement ICM fixed the overheating problem. I drove around town for about 10 miles. Stop and go driving. Highest temp was 197 but mostly around 188 when moving. Outside temp is 95F, low humidity. I shut it off and it started right up again. Happy camper! ? Link to comment Share on other sites More sharing options...
Ronnie Posted August 7, 2017 Share Posted August 7, 2017 This may turn out to be something as simple as a stuck thermostat and changing the ICM was just a coincidence. Link to comment Share on other sites More sharing options...
2seater Posted August 7, 2017 Share Posted August 7, 2017 I'm glad it is fixed and I would guess we'll never know exactly what went wrong. Coincidence? Maybe. It seems like an unlikely candidate as the villain, but I would guess this ICM may have been returned, for some reason, since the included parts were missing. If it was the cause, let's hope it doesn't get recycled back into the system for the next unsuspecting customer. Link to comment Share on other sites More sharing options...
Ronnie Posted August 7, 2017 Share Posted August 7, 2017 This may turn out to be something as simple as a stuck thermostat and changing the ICM was just a coincidence. AZ, I didn't see your post that you had fixed it when I wrote this. I'm glad the ICM fixed it. Link to comment Share on other sites More sharing options...
AZ Ron Posted August 7, 2017 Topic Author Share Posted August 7, 2017 The counter guy at Autozone said my old one was going in the trash bin and would not be returned the factory. I wanted to make sure no one else got stuck with it. I think I will buy a new thermostat just to be safe though. Worth the money to have peace of mind on my next trip to Las Vegas. 1+ hours each way with lots of steep mountains in and out of the Hoover Dam area. I'll gamble on other things but not the Reatta ;) Link to comment Share on other sites More sharing options...
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