engine stumbling loss of power (please help) - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 03-04-2004, 06:48 PM   #1
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Default engine stumbling loss of power (please help)

ok it all started with when fuel was low and made a turn especially a right hand turn would cut out or die - I actually solved this with replacing the fuel pump and pickup screen even though seemed ok and fuel pressure tested ok.. saw that other people also had this problem. Then sometimes if washed the engine bay would stumble and run rough for a few days, then got to where it would most the time run ok at idle but whenever try to accelerate especially once boost was kicking in would completely lose power and start to stumble, I did notice if I put transmission in a lower gear would still do it but not as bad but once got rpms up was ok but accelerating was a major problem. If you started up a hill would just fall on its face.. Also around the same time had to replace battery and alternator and disconnect antenae which was constantly trying to retract..

Anyway - I replaced the fuel pump and fuel filter and cleaned out tank seemed fine, fuel pressure is good. It is currently not showing any codes and most of the time did not. However, once showed map sensor which did test bad. I replaced MAP and MAF sensor with no change. Acted like clogged converter had muffler shop test they said ok. Thinking computer control related started testing indiv. sensors - so far MAF, MAP, Throttle position sensor, o2, idle air control, idle air temp, all test ok was planning to test knock sensor, crank and camshaft sensors and continuity to ecm between sensors - also was going to do a wrap test on ecm while engine running they say that is the only way to tell if ecm itself is bad - however hard to get to and could not find ecm so decided to test some other things it was then that all hell broke loose.. 1st resistance of injectors was ok and they seemed to firing evenly went to do a test where you put plastic jars under each injector and crank engine when it developed a fuel rail leak and burst into flames.!!

So now I have major problems, I have to at a minimum rewire some things that melted and possibly change fuse box and a few of the expensive sensors - just to get back to where I was. So does anyone have any tips on building or buying wiring harnesses or repairing such damage. Oh I have always had a short in the dash as well and my low water level light comes on sometimes although did this even before I had any driveability problems.. Also does this sound like the ecm or ignition module and coils? Oh I forgot to mention I had prev. replaced spark plugs and wires and they always seemed to firing even when under load. However, when I got a tester that could test the strength of the spark sometimes it failed. Never could trace this to a specific wire or coil and then could not get it to act up again so I had ruled this out..

Also is the stinking ecm behind the glove box and any tips on checking continuity? No leads will reach.. seemed if sensors or bad connection would throw a code but some talk like not necessarily especially on this OBD1 type car?. Did just prior to fire notice some bear wires on injector wiring. so again need to find the problem as well as rewire at least part of the car.... help!!!!!!!!!! thanks ????
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Old 03-04-2004, 09:32 PM   #2
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This will be a huge undertaking, but you're going to have to start by telling us what year and trim level you have. Please put that in your signature.
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Old 03-05-2004, 10:33 AM   #3
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Default engine power loss, stumblling

Yes, I should have mentioned it is a 1993 SSE supercharged Bonnie. This is OBD1 which I realize much limits the info and the acuracy of what you can tell just by looking at codes or trusting the output of the ecm. I keep thinking if it was ecm related, it should tell me with the codes, yet some people have told me not necessarily. The OBD1 does not show any info. on the spark like if it is misfiring and such... at least that is what I remember. Oh also in addition the only other info I have is once or twice it did throw a code for running too lean but does not do this consistantly. One reason I was trying to check the actual spray pattern and flow of the injectors was sometimes at idle it will miss and hunt (rpm going up and down) and when I had a scan tool on it, it would alternate between rich and lean at idle.

From my testing it seems the spark at least most of the time holds up under load, and the fuel pressure stays good even under load. So I keep thinking has to be ecm related...? The dealer suggest that especially with this car it would not be uncommon for that to be the problem.. Do you know where the boost guage measures its signal? I have wondered if the supercharger is not actually producing the boost the guage is reading.?

Where is the sensor that sends the low water level thing and could that be causing it to run in limp in mode even though it only does it once in a while...?

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Old 03-09-2004, 06:22 PM   #4
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Default Re: engine power loss, stumblling

Quote:
Originally Posted by raffmanlt
Where is the sensor that sends the low water level thing and could that be causing it to run in limp in mode even though it only does it once in a while...?
It'* mounted in the radiator in the end tank on the passenger'* side, about 1/3 of the way down directly below the radiator cap. Look for a squarish black plastic thing with a two-wire connector on it. No, it won't cause limp-home mode; it just turns on the warning, and they're known for giving frequent false alarms.

Despite what your shop told you about the convertor, I'm not convinced that you can rule it out. What exactly did they do to reach their conclusion? (Thumping on it doesn't count. )
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Old 03-10-2004, 10:17 AM   #5
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thank you so much for that info! You know I have been suspicious of the catalytic converter all along and I know they can cause this exact same kind of problem. What he did was make a hole in the exhaust prior to the converter and I believe just after it and he used a guage to test the back pressure. He told me it was normal.. I have been tempted to go back down there and have them cut off my exhaust and drive it just to make sure... or hey maybe a good excuse for a cat back exhaust system huh??
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Old 03-10-2004, 12:37 PM   #6
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You won't find a cat-back exhaust for your car, and you don't want one. The factory tubing is the ideal performance diameter, is stainless steel, and is mandrel-bent.

raffmanlt, can you pick one topic and post all your info in that one? You have 6 topics that are all related, and it'* very difficult to keep track of what is being discussed in all of them.
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