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1994 Chevy Silverado 4.3 270,000 miles no power


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Wingnut8999
New User

Jan 23, 2016, 3:03 PM

Post #1 of 7 (831 views)
1994 Chevy Silverado 4.3 270,000 miles no power Sign In

I have a 1994 Chevy Silverado with a 4.3 tbi engine. It starts and only idles in park at about 400 rpm. It doesn't miss when idling. Has a strong fuel odor. I have changed plugs,plug wires,distributor cap and rotor. Also the egr valve and throttle position sensor. It had a whistle so I changed the tbi gasket. It has no power under acceleration and a miss at speed. Only idea I have is oxygen sensor. Any help would be greatly appreciated. Ty in advance. Chris


kev2
Veteran
kev2 profile image

Jan 23, 2016, 3:14 PM

Post #2 of 7 (824 views)
Re: 1994 Chevy Silverado 4.3 270,000 miles no power Sign In

lets try some easy fast checks to get started...


1994 you should get the codes easy this model year- do you know how?
Remove air cleaner top - turn on key do not start - are injectors leaking?
Check EGR should be closed at idle- check the vacuum lines for leaks.
Can you do a exhaust back pressure test- either a BP gauge, a vacuum gauge, or noisy as hell remove o2 sensor and idle...


Wingnut8999
New User

Jan 23, 2016, 3:22 PM

Post #3 of 7 (823 views)
Re: 1994 Chevy Silverado 4.3 270,000 miles no power Sign In

I was told the code is read by the check engine light flases. I don't think mine works. It has a new egr valve. I have checked for and haven't found any vacuum leaks. I don't know how to do back pressure test.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Jan 23, 2016, 4:01 PM

Post #4 of 7 (815 views)
Re: 1994 Chevy Silverado 4.3 270,000 miles no power Sign In

If original miles it's open to anything.
Back pressure testing with vacuum gauge: Find a port to "T" into with a vacuum gauge. Miles or not hold idle at a real idle like 700 or so and read vacuum. Should stay steady at about 18Hg or so not much less unless at high altitude. Now rev and hold at about 2,000 RPM without load on engine it should be the same - if lower it's exhaust is restricted.
CEL - Bulb check. Turn key to run without starting it, it should light up. If not bulb blown or missing so put a good one in.
Vacuum leaks. If you can get it to idle worth a damn spray carb cleaner at all areas and hoses that should be tight including intake manifold, hose to brake booster - all of it. If no change in idle means that area not suspect and if a change there's a leak there.
Back to vacuum check is also indicative of valve timing. If steadily too low may have jumped valve timing so proceed with a compression check which would show all too low.


Start some conclusive testing and I'd keep investment low if that many miles. I don't hear of many that aren't plain worn out even with care at that high miles,


T



Wingnut8999
New User

Jan 23, 2016, 4:11 PM

Post #5 of 7 (812 views)
Re: 1994 Chevy Silverado 4.3 270,000 miles no power Sign In

Ty for the reply. I'll check those things out. I was in the same thinking as far as investment with that many miles


kev2
Veteran
kev2 profile image

Jan 24, 2016, 7:27 AM

Post #6 of 7 (794 views)
Re: 1994 Chevy Silverado 4.3 270,000 miles no power Sign In

checking for vacuum leaks- us carb or brake cleaner spray any area that could leak engine sound and RPM will change if you spray on a leak area.
Check those injectors as I posted- first KOEO then eng running - they can have wiring problems at air filter wiring pass through, just leak, spit dribble, over spray it can be seen.
OK a new EGR valve - confirm pintle is not held open by a piece of carbon, that there is NO vac to valve at idle,
You changed plugs- anything about old plugs - were they WET, BLACK, dry, tan?
Have you worked on engine timing?
Do you have -vacuum gauge? compression tester?
I am not sure IS there a fuel filter you can change- I think yes in 94? I could look it up but its Sunday.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Jan 24, 2016, 8:38 AM

Post #7 of 7 (789 views)
Re: 1994 Chevy Silverado 4.3 270,000 miles no power Sign In

Just notes: Yes it has a fuel filter that if not done in a long time or not really requires flare nut wrenches and care not to bust lines off on frame rail.
Check inlet end what junk may be in them just because.


Read container for brake clean if used. The brand "BRAKLEEN" is fire proof as good as a fire extinguisher - others are flammable. Just know what behavior to expect as that brand would stall out on a vacuum leak, others not nor carb cleaners. Like that method for finding vacuum leaks first myself,


T







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