Hi all! I've been browsing your website for about 2 hours now looking for possible solutions to the problem my boyfriend is having with his 1994 Lumina Euro 3.1L. Have learned a lot of valuable info, but haven't seen any posts from anyone with the exact same problem. NEED HELP FAST! (and cheap!).
OK, here goes....The car has about 186K on it, routine maintenance done regularly. Plugs were replaced about 8 months ago. No major problems, good running car until recently. The car starts fine, but sometimes engine backfires upon starting. Will run OK for first 10-15 minutes at highway speed, then starts choking and bucking, wanting to quit. Stays running, but continues choking and engine backfire and typically won't go above 15-20 MPH. Shifts fine. It re-starts OK after shutting it off, runs OK for a few minutes, then the problems start again. Seems to have no problems at idle, only on the road and after it's warmed up. Boyfriend says he can hear the fuel pump running, but not always really steadily, when key is turned. Has a mild odor coming from the engine area after turning the car off, but neither of us recognize it. Both of us know a lot about cars, but have never smelled this odor before. A few people have suggested replacing the fuel pump. If it's the fuel pump that's faulty, wouldn't that be all the time, not just after the car is warmed-up and at speed?
We replaced the heater core about a month ago, and check engine light was on after that. Discovered a vacuum line that had broken while doing the heater core, and replaced it. CEL went off, and hasn't come back on. The current problems started about a week later, and continue to get worse. Possibly related??? We don't think so, the problems it has now seem fuel-related. Have tried fuel-injector cleaner to no avail. Friends have suggested numerous causes including plugged catalytic converter, dirty EGR valve, faulty IAC valve, clogged fuel filter, faulty fuel pressure regulator, and faulty crankshaft position sensor. That's a lot of stuff to start replacing! Would like to at least narrow it down!

PLEASE HELP!!! :banghead:

I would suggest diagnosing the fuel system before replacing the pump on a hunch. A new fuel filter wouldn't hurt, but test the fuel system pressure after the car has been driven and is at normal operating temperature. If the pump is failing, it should show low pressure ( at least 37 PSIG) or not move adequate free-flow volume (at least one pint in 15 seconds).

The other common possibility is the ignition amplifier/switch module under the coil packs. They frequently begin to fail after heating, then "heal" themselves after a cooling off period.

OK... Here's an update to the problem. Seems to me that it's an electrical issue that may be affecting the fuel pump. After the car was driven for about 15 miles last night (all the same problems occurring for the last 5 miles or so), we put it in the driveway and tried to figure it out. With the car running and lights off, you can hear the fuel pump humming steadily. If you put the brakes on or turn on the headlights, it seems to put a strain on the fuel pump and it slows down considerably. Also, the dome light dims momentarily when something else is turned on and the headlights dim slightly when you tap the brakes.
Blue Bowtie, does this sound like a bad ignition amplifier/ switch module problem? I don't really know a lot about electrical systems and am not sure what this part does. Can't find any info anywhere else on the 'net. Browsed around parts stores websites and can't find anything called "ignition amplifier/ switch module" but found "replacement ignition module" Same thing?? Also found replacement ignition coils and ignition switch. Thanks for your last reply and any additional info would be GREATLY appreciated.

Sounds similar to an issue I had on my old Cutlass. Might want to check those plug wires you replaced 8 months ago. One of them may have gone bad.

My lumina for a long time had a problem with loosing power on the highway, mostly above half throttle, on hills, etc. I replaced fuel pressure reg. filter, and numerious other sensors, map, tps, temp, etc. Wasnt worried cause it prob needed them anyway. But problem persisted for over a year, well last month, fuel pump quit completly, i put a new pump in, and a new tank only because it was rusted, and that age old problem was gone.
So... a fuel pump doesnt always quit all at once, they can be weak and not give enough fuel at heavier engine loads. So yes, check that fuel pressure !
Headlights dimming ever so slightly, just noticable, just a blinking then back to bright? or are they dimming a lot and staying dim?
Might want to have altanator checked for proper output, battery checked as well, or loose/dirty battery cables (check both ends of both cables) just not the battery end

((yes,replacement ignition module is the same thing))

Be aware of this, i bought a Ign. modual at Advance Auto, and 2 coils, the Ign.modual quit within 2 weeks, they gave me another, it was dead when i put it on, gave me another, and its been working over a year now.
Also, one of the new coils died within a year.So i put a coil on from a junk yard car and its still working.
As for the smell, if its backfiring, running lean,getting hot, whatever, may give you smells you never smelled before as well.

I'd check the battery, cables and alternator before trying anything else. Since the fuel pump slows as electrical load increases, I'd suspect a low system voltage problem over a fuel pump or ICM issue.