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94 Grand Prix starts but stalls
My 94 Grand Prix starts, revs up to about 3000 rpm, and stalls withing
a couple seconds. I've got fuel and spark, but it still stalls. Mass airflow sensor, or maybe O2 sensor? Can someonepoint me in the right direction? Thanks for any help/info. Tim |
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#2
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94 Grand Prix starts but stalls
Sounds like a catastrophic vacuum leak to me, or it's not sensing intake air volume correctly, as you said...Make sure the PCV or other large vacuum lines aren't unplugged, depending what motor you have it could have a massive intake gasket leak... But you're on the right track, they throttle way up like that when there's too much air in the cold start mixture. Could be the IAC also, not being able to get it into a rich cold engine start idle...can you keep it running by giving it throttle or no? EGR stuck open would also do this... -- jeffcoslacker ------------------------------------------------------------------------ jeffcoslacker's Profile: http://www.automotiveforums.com/vbul...?userid=219638 View this thread: http://www.automotiveforums.com/vbul...d.php?t=583098 http://www.automotiveforums.com |
#3
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94 Grand Prix starts but stalls
Forgot to mention it's a 3.4L. And, working the throttle only just
barely keeps it running and running very roughly at that. Thanks for the help so far. jeffcoslacker wrote: > Sounds like a catastrophic vacuum leak to me, or it's not sensing intake > air volume correctly, as you said...Make sure the PCV or other large > vacuum lines aren't unplugged, depending what motor you have it could > have a massive intake gasket leak... > > But you're on the right track, they throttle way up like that when > there's too much air in the cold start mixture. Could be the IAC also, > not being able to get it into a rich cold engine start idle...can you > keep it running by giving it throttle or no? > > EGR stuck open would also do this... > > > -- > jeffcoslacker > ------------------------------------------------------------------------ > jeffcoslacker's Profile: http://www.automotiveforums.com/vbul...?userid=219638 > View this thread: http://www.automotiveforums.com/vbul...d.php?t=583098 > > http://www.automotiveforums.com |
#4
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94 Grand Prix starts but stalls
Well you can rule out the O2, because it ignores that signal until the engine warms up. What you need to find out here is if it's too lean or too rich that's causing the condition. When you say it runs up to 3000 then dies, is it smooth and strong sounding until it checks out? And does it woof and backfire through the intake when you try to keep it running with the throttle? Or just chug like it's flooding? Any sooty exhaust as it dies out? A defective Coolant Temp Switch will sometimes make something like this happen on cold starts, but usually causes overfueling and sooty exhaust and strong fuel odor, along with fuel fouled plugs. The MAF could concievably cause this, you can have someone thump on it while you attempt to start it, if it reacts to being bumped, it's bad... The 3.4's did have lower intake gasket design problems, sometimes the gasket would disintegrate and cause leakages. Usually there was coolant loss involved too when this happens. This is the SFI SOHC 3.4, right? Not the DOHC? I don't even know if they put those in Grand Prix, but they were a headache. -- jeffcoslacker ------------------------------------------------------------------------ jeffcoslacker's Profile: http://www.automotiveforums.com/vbul...?userid=219638 View this thread: http://www.automotiveforums.com/vbul...d.php?t=583098 http://www.automotiveforums.com |
#5
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94 Grand Prix starts but stalls
Thanks again, Jeff, for the info and help.
When I get it started, it revs up to 3000 hard and fast and smoothly, then dies jsut as quickly. Not sure about the sooty, exhaust; car isn't here, so I can't try it. I will get back to you. As for the MAF, I haven't looked at my library's Chilton yet, so I'm not completely sure where it is located. Can you point me to it? Again, without the car here, I can't be 100% sure, but I believe it IS the DOHC. As I recall, the decals on the fender say something like "3.4L twin DOHC" but I will check that too. Thanks again. Tim jeffcoslacker wrote: > Well you can rule out the O2, because it ignores that signal until the > engine warms up. > > What you need to find out here is if it's too lean or too rich that's > causing the condition. When you say it runs up to 3000 then dies, is it > smooth and strong sounding until it checks out? > > And does it woof and backfire through the intake when you try to keep > it running with the throttle? Or just chug like it's flooding? Any > sooty exhaust as it dies out? > > A defective Coolant Temp Switch will sometimes make something like this > happen on cold starts, but usually causes overfueling and sooty exhaust > and strong fuel odor, along with fuel fouled plugs. > > The MAF could concievably cause this, you can have someone thump on it > while you attempt to start it, if it reacts to being bumped, it's > bad... > > The 3.4's did have lower intake gasket design problems, sometimes the > gasket would disintegrate and cause leakages. Usually there was coolant > loss involved too when this happens. > > This is the SFI SOHC 3.4, right? Not the DOHC? I don't even know if > they put those in Grand Prix, but they were a headache. > > > -- > jeffcoslacker > ------------------------------------------------------------------------ > jeffcoslacker's Profile: http://www.automotiveforums.com/vbul...?userid=219638 > View this thread: http://www.automotiveforums.com/vbul...d.php?t=583098 > > http://www.automotiveforums.com |
#6
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94 Grand Prix starts but stalls
> wrote in message ps.com... > Thanks again, Jeff, for the info and help. > > When I get it started, it revs up to 3000 hard and fast and smoothly, > then dies jsut as quickly. > > Not sure about the sooty, exhaust; car isn't here, so I can't try it. > I will get back to you. > > As for the MAF, I haven't looked at my library's Chilton yet, so I'm > not completely sure where it is located. Can you point me to it? > > Again, without the car here, I can't be 100% sure, but I believe it IS > the DOHC. As I recall, the decals on the fender say something like > "3.4L twin DOHC" but I will check that too. > > Thanks again. > > Tim > > jeffcoslacker wrote: >> Well you can rule out the O2, because it ignores that signal until the >> engine warms up. >> >> What you need to find out here is if it's too lean or too rich that's >> causing the condition. When you say it runs up to 3000 then dies, is it >> smooth and strong sounding until it checks out? >> >> And does it woof and backfire through the intake when you try to keep >> it running with the throttle? Or just chug like it's flooding? Any >> sooty exhaust as it dies out? >> >> A defective Coolant Temp Switch will sometimes make something like this >> happen on cold starts, but usually causes overfueling and sooty exhaust >> and strong fuel odor, along with fuel fouled plugs. >> >> The MAF could concievably cause this, you can have someone thump on it >> while you attempt to start it, if it reacts to being bumped, it's >> bad... >> >> The 3.4's did have lower intake gasket design problems, sometimes the >> gasket would disintegrate and cause leakages. Usually there was coolant >> loss involved too when this happens. >> >> This is the SFI SOHC 3.4, right? Not the DOHC? I don't even know if >> they put those in Grand Prix, but they were a headache. >> >> >> -- >> jeffcoslacker >> ------------------------------------------------------------------------ I had the DOHC 3.4 V6 in a '92 Olds Cutlass Supreme. It also started revving to about 2500 when started. Checked for vacuum leaks, closed off the IAC solenoid port, no help. I finally took a coaster and completely plugged the intake and the engine still ran at 1500 rpm. Turned out to the be intake plenum gasket was cracked in 3 places. It's not that bad of job to replace and if that's your problem, check the big vaccum rubber line to the brake booster while you've got the plenum off. It's bad about deteriorating and sucking closed causing a loss of brake boost. You can't hardly get to it with the plenum on. Hope this helps. Garrett Fulton |
#8
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94 Grand Prix starts but stalls
Philthy - can you point me to the proper scanner to get the fault
codes. I keep getting told that OBD2 scanners won't work on my 94 GP. But, surely, SOMETHING can be plugged into the OBD connector and tell me what's wrong. Thanks so far for all the info. Tim philthy wrote: > bad injector killing the pcm driver > failed oil pressure sensor causing fuel pump kill > factory alrm system shutting down puter failure to properly maintain vehicle such as plugs, > wires and air filter, fuel filter too > but the first thing to do is pull fault codes > > wrote: > > > Forgot to mention it's a 3.4L. And, working the throttle only just > > barely keeps it running and running very roughly at that. Thanks for > > the help so far. > > > > jeffcoslacker wrote: > > > Sounds like a catastrophic vacuum leak to me, or it's not sensing intake > > > air volume correctly, as you said...Make sure the PCV or other large > > > vacuum lines aren't unplugged, depending what motor you have it could > > > have a massive intake gasket leak... > > > > > > But you're on the right track, they throttle way up like that when > > > there's too much air in the cold start mixture. Could be the IAC also, > > > not being able to get it into a rich cold engine start idle...can you > > > keep it running by giving it throttle or no? > > > > > > EGR stuck open would also do this... > > > > > > > > > -- > > > jeffcoslacker > > > ------------------------------------------------------------------------ > > > jeffcoslacker's Profile: http://www.automotiveforums.com/vbul...?userid=219638 > > > View this thread: http://www.automotiveforums.com/vbul...d.php?t=583098 > > > > > > http://www.automotiveforums.com |
#9
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94 Grand Prix starts but stalls
Garrett-
The booster rubber vacuum line - is it about 3/4" in diameter? I was looking around and I saw that this line was swelled, and is spongy to the touch. If I have to tear it down to replace the gasket, I'll be sure to replace the line too. Thanks for the tip. Tim gfulton wrote: > > wrote in message > ps.com... > > Thanks again, Jeff, for the info and help. > > > > When I get it started, it revs up to 3000 hard and fast and smoothly, > > then dies jsut as quickly. > > > > Not sure about the sooty, exhaust; car isn't here, so I can't try it. > > I will get back to you. > > > > As for the MAF, I haven't looked at my library's Chilton yet, so I'm > > not completely sure where it is located. Can you point me to it? > > > > Again, without the car here, I can't be 100% sure, but I believe it IS > > the DOHC. As I recall, the decals on the fender say something like > > "3.4L twin DOHC" but I will check that too. > > > > Thanks again. > > > > Tim > > > > jeffcoslacker wrote: > >> Well you can rule out the O2, because it ignores that signal until the > >> engine warms up. > >> > >> What you need to find out here is if it's too lean or too rich that's > >> causing the condition. When you say it runs up to 3000 then dies, is it > >> smooth and strong sounding until it checks out? > >> > >> And does it woof and backfire through the intake when you try to keep > >> it running with the throttle? Or just chug like it's flooding? Any > >> sooty exhaust as it dies out? > >> > >> A defective Coolant Temp Switch will sometimes make something like this > >> happen on cold starts, but usually causes overfueling and sooty exhaust > >> and strong fuel odor, along with fuel fouled plugs. > >> > >> The MAF could concievably cause this, you can have someone thump on it > >> while you attempt to start it, if it reacts to being bumped, it's > >> bad... > >> > >> The 3.4's did have lower intake gasket design problems, sometimes the > >> gasket would disintegrate and cause leakages. Usually there was coolant > >> loss involved too when this happens. > >> > >> This is the SFI SOHC 3.4, right? Not the DOHC? I don't even know if > >> they put those in Grand Prix, but they were a headache. > >> > >> > >> -- > >> jeffcoslacker > >> ------------------------------------------------------------------------ > > I had the DOHC 3.4 V6 in a '92 Olds Cutlass Supreme. It also started > revving to about 2500 when started. Checked for vacuum leaks, closed off > the IAC solenoid port, no help. I finally took a coaster and completely > plugged the intake and the engine still ran at 1500 rpm. Turned out to the > be intake plenum gasket was cracked in 3 places. It's not that bad of job > to replace and if that's your problem, check the big vaccum rubber line to > the brake booster while you've got the plenum off. It's bad about > deteriorating and sucking closed causing a loss of brake boost. You can't > hardly get to it with the plenum on. Hope this helps. > > Garrett Fulton |
#10
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94 Grand Prix starts but stalls
> wrote in message ups.com... > Garrett- > The booster rubber vacuum line - is it about 3/4" in diameter? I was > looking around and I saw that this line was swelled, and is spongy to > the touch. If I have to tear it down to replace the gasket, I'll be > sure to replace the line too. Thanks for the tip. > > Tim That's the guy, Tim. My wife also complained, along with the high idle problem, that sometimes she seemed to loose brake boost and had to really stomp on the pedal. My line on the engine was dead soft and a real pain to get to with that plenum on. Good luck. Garrett |
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