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fatshady
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Aug 23, 2006, 8:00 AM
Post #1 of 7
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Stalling and Stumbling
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Its a '92 sierra pickup with a 350. Several times lately it has stalled after coasting to a stop at a signal. Always has cranked right up and taken off immediately afterwards, kinda with a pukey smell. this morning it stumbled a couple of different times while cruising at 60 but then kept going. There is no engine light though the light works fine when ignition first on. All other times it has its usual great power and smoothness. i know this could be a lot of things and its such a pain that i can't get codes for it, but any direction would be much appreciated.
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DanD
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/ Moderator
Aug 23, 2006, 8:52 AM
Post #2 of 7
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Re: Stalling and Stumbling
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In 92 they still used a vacuum operated EGR (exhaust gas recalculation) valve and it maybe intermittently sticking open at idle. You’ll find the valve bolted to the intake manifold; it is designed to allow exhaust gases back into the engine to be reburned to lower NOX emissions. The valve is commanded open by the ECM at cruising speeds or like load conditions and should always be closed at idle. Carbon can break off from somewhere in the engine and cause this valve to stick partly open if the carbon gets inside the valve.
This is just a guess due to you saying the “pukey smell”; a stuck open valve will cause a smell and the poor running.
To confirm this you could unplug the vacuum line at the EGR and plug the hose; do this while the truck is running “normally” and drive it for a couple of days.
This may cause the check engine light to come on if the ECM decides to do a functional test on the EGR system but no big deal because you know that the hose is disconnected.
You also may notice an engine ping with the hose disconnected but for the short time the hose is off to do the test; it shouldn’t do any damage.
Dan.
Canadian "EH"
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fatshady
User
Aug 24, 2006, 6:01 AM
Post #3 of 7
(2700 views)
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Re: Stalling and Stumbling
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I disconnected the egr valve before driving home yesterday and closed the open ends of the tube etc. I made one stop for about an hour and it died immediately after restarting. It started right back up and stumbled once on the 15 mile drive home. The engine light did come on, and I did have the pinging. I reconnected the egr last night and the engine light went off, and there was no symptom when I drove in to work this morning. I am thinking this should mean the egr is not the culprit, but i wonder if there was a residual problem in the valve that may have self corrected while it was detached- like a piece of debris that shook loose. I'll keep you posted. If there is a next usual suspect I should look at please let me know. It has never faltered during acceleration- maybe I just need to drive faster. Thanks.
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DanD
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/ Moderator
Aug 25, 2006, 2:19 AM
Post #4 of 7
(2691 views)
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Re: Stalling and Stumbling
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You’re right if the truck still had some of the same issues; the EGR valve is not at fault. If the truck seemed better while the valve was disconnected; it’s because the valves operation wasn’t aggravating the root cause? I’m trying to think of other items that may cause an intermittent problem like this and can’t come up with anything that doesn’t take test equipment to verify.
Low fuel pressure or volume, poor connections, a sensor going out of its parameters; but not so far that it’s setting a code? I’m not sure without getting under the hood and trying a few things; as in monitoring sensor data with a scan tool while it’s doing its thing?
Maybe start with all the basics of a tune up; plugs, wires, fuel and air filters and a good quality concentrated fuel injector cleaner. It may not do anything for this problem but you won’t know unless you do it and it sure won’t hurt anything.
Dan.
Canadian "EH"
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fatshady
User
Sep 16, 2006, 8:09 PM
Post #5 of 7
(2635 views)
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Re: Stalling and Stumbling
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The truck has now run normally for the last couple of weeks. I think i remember it stumbling very slightly a time or two since i reconnected the egr valve, but it seems to be fine now. Maybe the egr was purged of a little dirt or something. Anyway, thats how it is. Thanks again for the help.
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fatshady
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Feb 4, 2007, 12:19 PM
Post #6 of 7
(2383 views)
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Re: Stalling and Stumbling
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After a few months of symptom-free service, the same problem seems to be back again. It starts and drives normally most of the time but will stall sometimes at lower highway speeds (45-60ish) and doesn't stall at higher speeds. It seems most likely to stall when slowing from highway speed down to a stop. It has always re-started and will typically run fine after a restart, but will sometimes stall again once or twice then go and keep running till I get somewhere. It has never stalled during a good acceleration.
I put a new fuel filter on it yesterday and haven't driven it much yet. The old filter spilled out some sediment but didn't seem to be entirely clogged. I think I replaced it a few months ago when this happened before. I cut the filter open and it was a little nasty but I don't know how bad they get before they cause trouble. I'll do some more checking and keep you posted.
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fatshady
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Apr 3, 2007, 8:55 PM
Post #7 of 7
(2240 views)
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Re: Stalling and Stumbling
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And again. The same symptoms returned a few weeks ago and i dropped the tank and found a very nasty fuel strainer. I thought about putting a pump on it while i had it out but decided not to at the time. The strainer did not fix it so I did put a new fuel pump in it last weekend. I thought maybe I had it fixed but my friend who borrowed it today said it quit 3 times on him. It still has never set a code though the message center checks out when connected. it seems like a sudden electrical disconnect with no other symptoms than suddenly dying. And it still always restarts with a few cranks, the longest maybe the better part of a full minute's cranking, but usually within seconds. Could this be a worn ignition switch? The truck has 195,000. I wonder if there is another most likely connection that would be losing contact when the vehicle slows. when it was cutting out more frequently a couple of weeks ago i found that i could usually downshift and it would relight if i was doing 45 or better. The transmission is working fine.
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