1995 Buick Lesabre Limited

Hello, I'm new to the forum. The Lesabre that i bought for my son is a 1995 with the 3.8 engine and appox. 90'000 miles. The reason that i'm posting is that when traveling down the interstate at about 65 to 70 mph, the speedometer will jump down to about 35 or 40 mph and the lights on the dash panel will light up like the car has stalled, but this only happens for a split second and the car runs normally after. on a trip of 20 miles this might happen once and then once on the return trip, this car has also stalled on occasion at a stop light , but will restart and run fine. it is currently at a repair shop, the mech says that the computer he hooked up was working but received no codes, and then computer stopped working and would not work again, we are both scratching our heads, so i figured i'd come to this forum for some input. he checked throttle position sensor and said it was working fine, he does not want to start putting parts on to run up bill, i know that there have been similar posts on here, so if anyone has any ideas i would sure appreciate them thanks

BAsed on your description of the symtoms I woul dhave looked at the TPS and ECM. Since the TPS is "OK" and the ECM is acting erratically I woul dbe checking all the main connections / wiring.

thanks i'll pass info on

Yeah, I've heard of the bulkhead connectors, the BIG clip of wires that are bolted through the firewall can come loose, get corroded etc and cause these issues.

Just my input, and not to be taken as an expert one because I'm far from being a mechanic, but I have a 94 LeSabre, and for a long time it showed that weird symptom you talk about, speedometer going crazy and warning lights flashing for a split second and then everything back to normal. Whenever I took it to an autoparts store to get the codes there were no codes at all. But it did not only that, but also sometimes it would cut the engine off after that occurrence. Eventually I replaced the alternator and it didn't do that anymore. If you have somebody you can borrow an alternator of the same kind from, perhaps you can give that a try.

'95 LeSabre? Like this one?

http://72.19.213.157/files/1995LeSabreLF.jpg

That actually has a PCM which should store and display as lot more data than an old ECM. Wright is correct about the C100 bulkhead connector and PCM connectors. The PCM can be affected by moisture and corrosion, so checking the connectors is probably a good idea.

SeaBass also brings up a good point./ Have the technician cycle the "L" terminal for the alternator through the scanner (with the engine running) to see if the symptoms occur.

yes, it looks like that only light blue, thanks for input i'll pass it on

I believe the 94 & 95 were OBD 1.5. Do you know what scanner the mechanic is using?

i'm not sure what scanner he's using but i'll see him this morning and pass all info on, thanks everyone.

well if anyone is still reading this the tps and ecm both checked out so if anyone has more suggestions please reply:banghead:

The phenomenon probably had less to do with the speed being traveled and more to do with heating and/or time the engine had been running. Rogue problems like this are frequently due to marginal electrical connections. The disturbing part is that the ECM would not communicate with the scanner, indicating a problem with ECM power, or possibly the ECM itself.

If the ECM connectors and bulkhead connectors have been inspected and found to be intact, there may be problems with other connectors. Unfortunately, that could be in any number of places. I’d suggest checking all the main power connections from the battery to the main power distribution under the hood. The ignition switch and its connectors are also suspect. I’ve had a similar occurrence in a couple of other vehicles and discovered resistive connections at the interior fuse panel and connection problems at the instrument cluster base.

Again, it might be helpful to try to cycle the L terminal at the alternator to see if power quality has an influence on the phenomenon.

Good luck.