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95 Tahoe 5.7TBI - Constant issues


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Recently purchased a '95 Tahoe, 4WD, Regency conversion. Truck just hit 170,000 miles.

 

Body/paint is absolutely perfect, underbody ditto.

 

Truck ran great when we bought it 5-6 months ago.

 

Past two months or so, has had an issue that makes it undrivable. In the six months weve had it, we may have put a total of 1000 miles on it. Truck refuses to accelerate, revs up to redline in park with seemingly no issues. Stumble fall flat on it failure of a face when you truck to pick up speed. Anything past maybe 1/6 pedal makes it stumble/hesitate/clunk/knock, just do the opposite of what it should.
Replaces CTS, MAP, fuel filter Cleaned grounds, not entirely sure what my dad has done as well. Tried unpluggin battery for a couple minutes. I'm not a chevy guy by any means - This truck was for my brother for school, and it cant make it out of the driveway. The problems manifested over the course of maybe 100-150 miles.

 

Ideas what the issue could be?

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Have a look at the injectors,should have a nice cone shape to the spray pattern.Also,no dribbles.

 

Pics?

 

Check

Fuel pressure

EGR

TPS

Timing

CPS

 

Any of these things can cause problems. Unfortunately, the truck is run by computer and if any of these are bad, then you'll have these problems.

 

Would any of these go bad over the course of 100-150 miles.

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Your truck, like mine, is 20 years old. I've had things run and die the same day.

 

It sucks, but anything can happen on a rig that old. I've replaced the IAC, TPS, and EGR all within a few months on my rig... I just replaced the power steering hoses that blew out in a day with no warning.

 

 

At some point you will catch up on all the worn parts, but its never ending. You just get ahead of the curve, if you know what I mean.

 

The list of my parts: Ball joints (twice), idle and pitman arm, tie rod ends(twice), both cv half shafts, rear axles and bearings, u-joints, FR hub, 2 alternators, 2 battery, 3 radiators, 3 water pumps, too many serpentine belts to count, all the pulleys on the front, 1 trans, 1 rebuilt engine, elec window and lock switches, erg, iac, tps, fuel filter, rockers, push rods, lifters, intake gaskets, and more stuff that I can't remember.

 

 

 

I have 250K on my rig. And it yet again... runs great.

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Your truck, like mine, is 20 years old. I've had things run and die the same day.

 

It sucks, but anything can happen on a rig that old. I've replaced the IAC, TPS, and EGR all within a few months on my rig... I just replaced the power steering hoses that blew out in a day with no warning.

 

 

At some point you will catch up on all the worn parts, but its never ending. You just get ahead of the curve, if you know what I mean.

 

The list of my parts: Ball joints (twice), idle and pitman arm, tie rod ends(twice), both cv half shafts, rear axles and bearings, u-joints, FR hub, 2 alternators, 2 battery, 3 radiators, 3 water pumps, too many serpentine belts to count, all the pulleys on the front, 1 trans, 1 rebuilt engine, elec window and lock switches, erg, iac, tps, fuel filter, rockers, push rods, lifters, intake gaskets, and more stuff that I can't remember.

 

 

 

I have 250K on my rig. And it yet again... runs great.

 

I drive a 26 year old truck. I know about replacing parts. But ive not come across an issue that manifests across 150 miles, doesnt make a damn lick of sense because I've never had problems like this with the truck.

 

Found this pic....appears to be of an injector above idle,at idle mine have near that shape but not as forceful and not as well defined.

 

TesterLive5.7WEB.jpg

 

This is more what I'm looking for.

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If you have fuel pressure and the spray is good you do the following. While the engine is running, you can go around and disconnect and reconnect the sensors one at a time until you find the one that makes no change. This would in theory be your problem child. This doesn't always work, but I've been lucky with it before. Except the CPS... I'd leave that alone.

 

If none of those work, I would block off the EGR next and then run. They can get weak and allow the engine to gulp too much air.

 

Or borrow some ones scanner and run a diag. Your best bet here.

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Couldnt seem to find a fuel pressure schrader valve anywhere on the fuel rail... that would've been too easy.

Certainly isnt like a Ford in that aspect.

 

Decided to run a vacuum check on the top end, sprayed brake cleaner around and found a massive leak at the TBI base plate.

Gonna rip that out and put a new gasket in. Do they make silicone ones?

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Just replaced TBI flange gasket. No change.

Blocked off EGR vacuum. No change.

At wits end here. There isnt a way to read FP by any logical means.

 

Could TPS go bad in a short time span?

Pulled codes. Said code 12 (Everything running GREAT!!!), and 34. System lean.

Couldve told you that.

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I've had odd issues from when the ignition module under the distributor cap went out, as well as the coil going slightly bad. I think Advance could check the module, and the haynes manual had how to multimeter the coil.

 

 

For fuel pressure, you can borrow a tester from Autozone. IF it's similar to the 89 pickup, you attach the adapter to the output of the fuel filter underneath and check that way.

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