91 lumina has bad hesitation after warm up

[allisonmo2]

about a week ago i thought i ran out of gas. as i was coming to a stop my car started shaking and shuddering and since i was on e i thought it was out. i was right by a station so i filled up and it seemed ok for a mile or two. then again started the shuddering. it feels as if i am driving over the rumble strips in the middle of the road. it is worst when the car gets locked in overdrive and the rpms are low and the load higher. when i coast it isn't bad and if i floor it it isn't as rough. it feels like i am on 4 or 5 cylinders. i can also smell gas i believe from the exhaust. i also have no power at all. if i shut it off and it cools down all is ok till about 10-15 miles after i start driving. i originally thought fuel filter but that would be constant. this was also when i thought i ran out of gas. i now think it was just shuddering. also when it is real rough my headlights will dim momentarily also. it feels like it is on the verge of stalling when i come to a stop. so if i rule out the fuel filter i am now thinking plugs, wires, or coil. but would one of these act up only when the car is warm? anything else i should be looking at? i am gonna dig into this on saturday and don't want to just throw a bunch of parts at it if unneeded.

[allisonmo2]

also no codes thrown. sound like an egr issue?

[allisonmo2]

on a whim i unplugged my o2 sensor and went for a rid. after about 3 miles the familiar shake was back but this time it stopped after about another mile of driving. make any sense? i'll reply again after trip to work and back tomorrow. 25 miles each way.

[allisonmo2]

so i have driven about 80 miles with the o2 sensor unplugged and it still has intermittently had the hesitation but not nearly as bad. and it will clear up quickly with some healthy throttle. today though when i was parked for about 10 minutes after a 2 mile drive, i started it and when i put it in reverse to back out of the spot it stalled. so i started it and it did it again. it took about 8 tries to get going and then everything was just fine again.

[Tech II]

Well, not good to drive the vehicle with O2 sensor disconnected....

When has the vehicle last had a complete tuneup? Plugs, wires, air and fuel filter, PCV?

Could even have a fuel pump on it's way out.....

Lack of power could be symptoms of a partial blockage of the cat.....

[allisonmo2]

i just hopped on here to post again. good timing. air filter and oil were done by me 2 weeks ago. pulled the front 3 plugs just now and they are in good shape. resistor is light tan and the electrode has no melting or breakage. no fouling or melting. gonna pull the alternator and get to the back 3. i am going to replace the plugs and fuel filter today and see what happens. the coil electrodes have no visible rust at all and the plug wires are all in great shape with no rubs or melting too.
is the correct gap really .006? it seems kinda big and on the net i see 35, 45 and 60 thousandths.
mine are currently 46-48 on the fronts

thanks

[Scrapper]

Originally Posted by allisonmo2

on a whim i unplugged my o2 sensor and went for a rid. after about 3 miles the familiar shake was back but this time it stopped after about another mile of driving. make any sense? i'll reply again after trip to work and back tomorrow. 25 miles each way.

have you took hose off of throttle body and looked at butterfly see if it's dirty it might need cleaned?

[allisonmo2]

Originally Posted by Scrapper

have you took hose off of throttle body and looked at butterfly see if it's dirty it might need cleaned?

i have not. i might do that this afternoon. took out all plugs. pita. took half an hour to figure out how to get that lower rear bolt out of the alternator bracket. replaced o2 sensor. going out for plugs and wires and fuel filter and pcv filter. will report in later. all plugs look good. biggest gap was on plug at .050 exact so only 5-6 thousandths variation. no melting or fouling or breakage.

[allisonmo2]

so changed plugs, wires, pcv valve after i finally found it, and fuel filter. drove about 15 total miles and it is still doing it. now i'm getting frustrated. i guess tomorrow if i have time i will pull the tb boot and see if it is dirty in there. i have also seen a post where someone reccomended using an extension to tap on the injectors. presumeably to dislodge a partial blockage. any thoughts on that? should i be looking at an egr or maf now? btw when i pulled the fuel filter the gas that poured out was almost black. i am hoping it was just sediment in the filter. the hard part is i leave for work at 545 in th morning and don't get home till about 715 at night so time is hard to come by. always dark when i am home until the weekend.

[allisonmo2]

how do you feel about a clogged cat? i was gonna pop it off tonight but the p.o. seems to have cemented teh front of the pipe to the downpipe. i may have to cut it off which will have to wait till the weekend.

[Scrapper]

Originally Posted by allisonmo2

so changed plugs, wires, pcv valve after i finally found it, and fuel filter. drove about 15 total miles and it is still doing it. now i'm getting frustrated. i guess tomorrow if i have time i will pull the tb boot and see if it is dirty in there. i have also seen a post where someone reccomended using an extension to tap on the injectors. presumeably to dislodge a partial blockage. any thoughts on that? should i be looking at an egr or maf now? btw when i pulled the fuel filter the gas that poured out was almost black. i am hoping it was just sediment in the filter. the hard part is i leave for work at 545 in th morning and don't get home till about 715 at night so time is hard to come by. always dark when i am home until the weekend.

when maf is bad it will usually will die when you start it and die at anytime you can try to clean the screen in the maf and egr you can clean to i have my doubts on cat but again thats the next thing to check out would be the cat but really see if that butterfly is dirty and try to add some sea foam to clean injectors since you say gas was black.

good luck...........

[93lumina3.1]

I also have a 1993 Chevy Lumina 3.1L. It has had fueling issues for a few months now. It seems like it floods out so bad that it cuts out. I have to put it in drive so the engine won't die while I'm driving. Sometimes I have to put it in neutral and keep one foot on the gas and use the other for the brake to keep it running. It seems to mess up after it warms up. Then if you keep driving it while it's messing up it will sometimes quit acting up and drive just fine again. While it's running bad though the "service engine soon" light comes on. Anyways, what you described sounds similar to what my car is doing. I'm thinking it might be bad fuel injectors sticking open, dumping so much fuel in the cylinder it can't run right. It EATS gas when it messes up. I read that you can do ohm tests on the injectors. The ohms are suppose to be 12.5 or greater HOT. Then again, they might test fine even when hot, until they start messing up. I'll post again if I figure anything out.

[rkvons]

If your service engine soon light came on, you have a code stored. Get it read and post the code.

[allisonmo2]

well i have done lots and lots with mixed results over the last few months. recently i have replaced the ecu, throttle position sensor and the manifold air pressure sensor. i finally got it to throw a code 33 which is low vacuum for map sensor. replaced it and now what i have is a great running car. sort of. starts fine, idles fine, but still feels down on power when accelerating. it will surge as i am driving like it is picking up 40hp and losing it again. and my check engine light is still on when i am coasting or braking. it does go out when i am accelerating though. sound like a vacuum leak? i am hopeful that if i can fix this last little issue i will be done, at least for now. how exactly do i go about replacing vacuum lines? do they make a set or do i just buy the right size line and replace away? how would i bend it? i see i have to remove my intake to do this. anything funny i need to know? every time i work on this thing i am so happy while half way into any task it is very easy to work on, then that quickly turns to tons of foul language and frustration as the other half of my project starts. nothing has been easy all the way through. i actually gave up on a crank position sensor because i just for the life of me just couldn't get the damn nut off. it took me almost an hour just to get the connector back on the old one. and lots of blood, dirt and grease on my hands. lots of cussing. and i am always outside in my driveway since i don't have a garage.

[allisonmo2]

also replaced all 3 coils and icm.