Has anyone have this happen?

Started right up without foot on the gas this morning, ran great till I stopped at a gas station for a newspaper, then stalling and sputtering when giving it throttle. Parked again then sputtered about half a mile then ran better but not like the first drive. Seems to like the cool gas in the am. Pump probably getting hot, then not working so good. All this with the map sensor hose plugged.

Doug in P.R.

90 Silverado said:

Started right up without foot on the gas this morning, ran great till I stopped at a gas station for a newspaper, then stalling and sputtering when giving it throttle. Parked again then sputtered about half a mile then ran better but not like the first drive. Seems to like the cool gas in the am. Pump probably getting hot, then not working so good. All this with the map sensor hose plugged.

Doug in P.R.

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If the map sensor disconnect doesn't seem to be helping, why not plug it back in? I'm thinking you have fuel delivery issues as well. I try to put acdelco or delphi parts in whenever possible, but I've had pretty good luck with spectre fuel pumps from rock auto, they are pretty cheap too! In my experience, most fuel pumps are Chinese made, regardless of brand.

Used to get that a idle surging deal , will try it plugged back in tomorrow morning and see what happens.

I did run it in overdrive instead of third today also.

It's a big improvement so far, I still have Seafoam in the tank.

Doug in P.R.

90 Silverado said:

Yes no change either with it unplugged or plugged in.Cleaned underneath also. No change with propane test either.

Doug in P.R.

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That's not good enough Doug. What I've found a lot of times in the past is the EGR valve will stick open. I't a mechanical failure of the valve itself. The line plug in or not plugged in won't make any difference. You need to see if the valve is allowing exhaust gas to flow at idle or low RPM. Sometimes it's obvious with a visual inspection, sometimes not so much.



It should look pretty similar to this with the valve off. If you can blow air, flow water etc from one hole to the other with the valve off it's stuck open and can give you the symptoms you describe. Sometimes they can be cleaned out with solvent and working the diaphragm but often times they just need to be replaced.

Really good write up here .

http://www.chevytalk.org/fusionbb/showtopic.php?tid/258416

I actually just recently had mine go bad. Kinda similar symptoms. However no matter what, it would run terribly. First start, 1 mile, or 10 it wouldn't change. It's a cheap thing to fix and a pretty easy one. I would go ahead and check the valve and see if it's the issue you are having . Heck I think you could just plug the egr port on the tbi really quick when you're having a hard time starting it, and if it starts right up you have found your issue .

Edit. I still think it's your fuel pump though.

Knuckle dragger, I have read that these go bad and when you floor it the truck hesitates. My truck has been doing that for months. I also read that these TBI trucks need this part or you'll have more problems running too lean. So you just can't block it off till you get a new one is this true? Also you need a AC Delco one as cheap ones don't work?

I took mine off last week and it had oil residue in it. Nuts were loose also so I cleaned it up with gas and reinstalled it.
Doug in P.R.

90 Silverado said:

Knuckle dragger, I have read that these go bad and when you floor it the truck hesitates. My truck has been doing that for months. I also read that these TBI trucks need this part or you'll have more problems running too lean. So you just can't block it off till you get a new one is this true? Also you need a AC Delco one as cheap ones don't work?

I took mine off last week and it had oil residue in it. Nuts were loose also so I cleaned it up with gas and reinstalled it.
Doug in P.R.

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When the EGR goes bad all kinds of stuff can happen. There isn't just one thing that gives it away. What you describe is consistent with a partially stuck EGR. It's not a solid diagnostic but it's something you should look at. I'm not exactly sure why anyone would say the lack of EGR will cause a lean condition. Without EGR operation the ECM timing advance may become less aggressive due to detonation issues but likely not a major problem. People have been blocking off the EGR for years and years. The easiest way to eliminate the EGR as your problem would be to block it off and see if it runs better. I personally would replace the valve if it proves defective but some people run without then with no issues.

Keep in mind there are other issues that can be causing your problem. You really do need to check fuel pressure when it's acting up. Chevy ignition modules fail with heat sometimes too. They run well cold and then get all kinds of weird issues as they warm up. Take a logical step by step approach and see what you find. My checks would be EGR, then fuel and then spark.

Making a block off plate this weekend, disconnected the vacuum hose to the egr from the manifold this time but no change.( Supposed to stall out?)

Seen a video on YouTube last night, guy disconnected the fuel pump relay and the truck stalled , said the oil pressure switch was bad since it should still run with the relay disconnected, tried it on mine, truck died so I jumped the switch's wires, can hear the pump run. Not sure if it's my problem since his truck was a later TBI with the fuse box under the hood but his wiring diagram was the same as the one in my Haynes manual.

Doug in P.R.

Installed egr block off plate, no change. On to the fuel.

Doug in P.R.

Here's a question for you now, is it throwing a check engine light light now? I believe it's code 32 . Let us know how the whole fuel thing goes too.