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91 chevy 350 TBI dies at idle
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Jdog
Novice
Apr 23, 2015, 6:02 AM
Post #1 of 12
(2846 views)
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91 chevy 350 TBI dies at idle
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I have a 91 chevy 350 TBI 252,000 miles, motor and trans were rebuilt at 204,000 back in 02. 6 months ago it started to die when I gave it gas. I ended up replacing the module on the distributor. It quit dying while giving it gas but wont idle without dying. I replaced the pickup module put
New pickup coil
New cap and rotor
New vacume lines
New coil
New esc controller
New knock sensor
New AIC sensor
New map sensor
New TPS sensor
New engine temp sensor
New computer
New fuel pump
New throttle body and injectors
All AC DELCO parts
Yesterday
I double checked the fuel filter to make sure it was on right double
checked the cap and rotor and AIC sensor got cleaned even though it is
new. Motor still wont idle and seems to have gotten worse over time. The
EGR valve has been disconnected for 14 years but I went ahead and
blocked it off but still dies at idle or when its put in gear. drives
down the road fine.
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Discretesignals
Ultimate Carjunky
/ Moderator
Apr 23, 2015, 1:51 PM
Post #2 of 12
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Re: 91 chevy 350 TBI dies at idle
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Pretty sure the check engine light is on. Enable the diagnostic system by jumpering A to B in the DLC and write down the flash codes.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Jdog
Novice
Apr 24, 2015, 6:39 AM
Post #3 of 12
(2808 views)
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Re: 91 chevy 350 TBI dies at idle
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Check engine light works and only comes on after 15 minutes of driving which is because the EGR valve has been disconnected. But Ill will try that and see what shows up. The only time it came on during all this was when it showed a code for the ESC controller and knock sensor which I changed but engine still stalls any where near idle. It has gotten worse since I started all this over the past six months.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 24, 2015, 7:00 AM
Post #4 of 12
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Re: 91 chevy 350 TBI dies at idle
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You can still check for other codes and even then they don't mean what you should replace just what it sees and YOU figure out why.
EGR? Plugged for ages. Maybe time to take plug out and take a look inside. IDK if a good kit to plug those was used or something created - you might.
Your list is a mile long already and still plain stalls is what I see. Leaking EGR (place sure would) would do that. Same as vacuum leak checking more than just hoses - all air that could get in anywhere - intake, throttle body gaskets, keep going on PCV hose and brake booster.
Think about even a good used EGR that doesn't leak. If nothing else for '91 they help with spark knock/ping with low octane fuel,
T
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Jdog
Novice
Apr 24, 2015, 7:22 AM
Post #5 of 12
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Re: 91 chevy 350 TBI dies at idle
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Yea im thinking about hooking it up again but this time I will have to keep my foot on the gas. When I took of the egr valve that been there disconnected for 14 years I noticed a lot of black on the intake behind it where I think it was leaking but I have that block off plate there now sealing that up. My old throttle body was loose but the new one is on good and tight. The pcv valve and vacume line are new but I haven't checked the brake booster at all.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 24, 2015, 7:35 AM
Post #6 of 12
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Re: 91 chevy 350 TBI dies at idle
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All that fudge under EGR block off plate isn't helping anything. You do need at least an intact gasket there that can tolerate exhaust heat. If one made up or a regular some just don't take it that long.
EGR concept is built into the system and intake manifold. Plain plugging one intended is probably causing problem if not THE problem right now.
Brake booster: Just pinch the new line and don't drive it as you'll have no power assist but if that makes it run fine again check on more like the booster, check valve and grommet too,
T
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Jdog
Novice
Apr 24, 2015, 7:42 AM
Post #7 of 12
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Re: 91 chevy 350 TBI dies at idle
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The egr block off plate from Mr. Gasket came with a gasket to seal it off. I inspected the intake where the EGR was and it was clean. The old gasket came off fine and wasnt torn. I haven't done anything to the brake booster though.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 24, 2015, 8:11 AM
Post #8 of 12
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Re: 91 chevy 350 TBI dies at idle
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Mr. Gasket! Now there's a name you can trust.
Engine has clearly been OK for you for a long time in general. Whatever "rebuilt" means for this thing I guess will never be known or who screwed with what.
I'm just focusing on EGR just because you are having troubles idling or so it seems. EGRs from the get go people instantly thought any engine would be better without one and did all sorts of things. Manifold and camshaft are expecting it along with the whole operation. Before or without an EGR cam designs would allow MORE exhaust back in by holding exhaust valve open a tad longer for intake stroke to SMOOTH OUT IDLES SO THEY DIDN'T STALL! That's a reason you hear the drag strip engines constantly rev up to keep from stalling just all things set for maxed out possible power and last 1/4 mile a few times and fuss with them till another round. Not useful for the real world.
Have to get lots older than this for the early crap to be designed in that really didn't help much or caused problem from new - not the case here.
General vintage was also a vacuum hose and devices nightmare. It's just tougher now at age and redone just what has changed now on this exact motor?
Plastic vacuum and rubber vacuum parts fail easily. If over some years just bypassed or hacked up you are paying for that now.
I guess you just need to look around for things messed up or altered like that EGR or more that it isn't tolerating anymore?
Not easy when things have been altered,
T
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Jdog
Novice
Apr 24, 2015, 8:35 AM
Post #9 of 12
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Re: 91 chevy 350 TBI dies at idle
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Well i can buy a new egr valve and vacume line for it and see what it does. I remember it was messing up and we just plugged the vacume line and the idle smoothed out but that was 14 years ago and since then the engine has been fully rebuilt, has 50 k miles on it now. A mechanic told me to put a new prom in it since the new computer didn't come with one but im getting tired of just throwing parts at it.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 24, 2015, 8:55 AM
Post #10 of 12
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Re: 91 chevy 350 TBI dies at idle
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This will be tough if nothing is obvious. Lots of water over those falls in 14 years.
OK - That day so long ago when engine ran better when hose to EGR was removed was because something was wrong that it was getting vacuum at idle and that solved it for that moment and stayed that way but the original reason not fixed and you may still have it? Can't know these things it's old AND messed with.
Hey TOTALLY REBUILT ENGINE: That doesn't mean squat really. What, old worn stuff reworked, machined up to all new everything ever sold for an engine it's far from new ever again.
What counts is issues TODAY now.
About now I'd still be checking for any and all vacuum leaks and see if you can find a sludge problem. Exhaust heat travelling in the wrong places too long will cook up the best of oils.
If this engine in general is in good compression state with working (not clogged out of site) PCV you'll see smoke go down a dipstick tube with stick lifted showing that crankcase vacuum is there as it should be. If it blow back out either PCV is messed up, engine worn again or crankcase in general has lost it's integrity to overcome blow by which is normal to a point.
You said some parts didn't fit so well - why?
I hear you that it's getting sickening and expensive tossing parts at it. Perhaps some basics to see if this has issues causing other issues finally catching up. Take lots of time to know each function is working properly and have to leave it there. It's old and messed with is about all that's needed to know so looking for a problem this late might be real tough to find,
T
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Jdog
Novice
Apr 24, 2015, 9:16 AM
Post #11 of 12
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Re: 91 chevy 350 TBI dies at idle
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No, all parts fit well, all oem and all acdelco is what I put on it. I will have to go over everything and check for more vacum leaks. I also wonder if there could be some lifters loose or something.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 24, 2015, 9:56 AM
Post #12 of 12
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Re: 91 chevy 350 TBI dies at idle
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Lifters? You really should be hearing those. No harm in looking. A simple vacuum gauge "Teed" into actual manifold vacuum could tell a lot too along with the whole check list,
T
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