lack of power when accalerating

[gorudorf]

OKay new to this website but I been working on 1993 jimmy with 4.3 vortec with the CMPI carb i have replaced every fuel part on truck from the tank all the way to the carb,also have replaced plugs ,cap,rotor ,and the control module. But still have mass lack when accalerating any help would be great.

[maxwedge]

What is a "mass lack", no such term in the automotive repair field. You do not have a carb, you could have TBI or CPFI, which is it??

[JIMMY92w]

"Mass Lack" of power when accelerating
= Massive lack of power when accelerating


You need to be more descriptive. Does your beast hesitate or stumble, engine misses, do your hear engine noises, or smell strange odors.

Maybe you need a compression test to see if your truck is with in tolerance

• Incorrect ignition timing
• Excessive play in distributor shaft
• Faulty distributor cap, wires…
• Faulty or incorrectly gapped spark plugs
• Air filter dirty
• Faulty ignition coil
• Brakes binding
• Auto transmission fluid level incorrect, causing slippage
• Clutch slipping
• Fuel filter clogged, or impurities in the fuel system
• EGR system not functioning properly
• Use of substandard fuel
• Low or uneven cylinder compression pressures
• Air leak at Carb or intake manifold
• Dirty or clogged carb jets or malfunctioning choke
• Throttle Position Sensor (TPS) faulty

[Gonly39]

Originally Posted by gorudorf

OKay new to this website but I been working on 1993 jimmy with 4.3 vortec with the CMPI carb i have replaced every fuel part on truck from the tank all the way to the carb,also have replaced plugs ,cap,rotor ,and the control module. But still have mass lack when accalerating any help would be great.

I have a 1996 Chevy Blazer that was doing this and after a 120.00 later a gas station just replaced a fuel filter saying the volume was low. That might have been part of it but the real cause was a bad 250.00 fuel pump I put in. GM also has a fuel vent check valve in the back of the tank made of plastic and a short 4 inch fuel line going to the fram this will brake if you don't find it first. I glued mine with crazy glue and good old JB weld and replace the hose with a 12 inch piece.

Ron

[gorudorf]

Okay this is where i am at with the 1993 jimmy. This is the best way i can decribe it the truck idles perfect ,but when i give it gas it accalerates fine up to 35mph after that point the motor starts to lose power,and speed begans to drop.there are no leaks no funny smells,and no noise.It has the CPI unit and i have replaced the fuel sending unit, the fuel pump,the fuel filter,and the CPI unit.I did find a wire that runs from distributor to the brain that has no power to it not sure if that would have anything to do with it .I did check compression and that is fine,timming also is good this has really got me stumped!!

[ford50killa]

i have a 95 jimmy with 4.3 I have replace the plugs, wires, rotor, and cap.also i replaced thefuel filter, egr valve, and cpi.i also bought a new muffler and put it on about 5000 miles ago.i also just had the tranny rebuilt less than 1000 miles ago.its still got a loss of power.a guy i know told me to put a pipe in where the cat is but i didnt know what to do.it has a sensor after the catalitic converter so i dont know if that will affect it?would a vacume leak cause this?thanks if you can give me info.

[94 Jimmy]

I don't believe there is an O2 sensor after the CAT on a 93, there isn't on my 94. I had a CAT melt down many years ago and caused similar symptoms. It wouldn't be to expensive to have your muffler shop cut yours out for an inspection.
A pluged CAT will make itself know at higher RPM, under load by restricting the exhaust flow, like a potato in the tail pipe(shades of my misspent youth). In any case it sure sounds like what I had, a new CAT solved the problem.
Good Luck
94

[trackrat]

Did you just buy this GMC? If so was it like this when you bought it or did it just start doing it?

More info needed.

[ford50killa]

hey guys.i bought it in the summer last year.it didnt have any problems when i bought it except it kept giving me the egr code.so i replaced it and it come back on.well i cleand it and it still poped up.so i was toldt if the cpu leaks it will cause that so i put a new cpu on it and it fixed it.but then around sept the tranny started sluipping.so then about the 1st of the year it went out and i had it rebuilt.well it ran fine for about a week and now it has no power just regular driving.but if you stomp it it still get up and go but it just uses so much more gas doing that.then just crusing when your on the highway and let your foot of the gas,the rpm goes up about 100-150 before going down.i didnt know if the intake could be leaking vacume from when i changed the cpi.also my defrost and floor are always on.it wont close the flap for the defrost to tur it off.thats what made me think of vacume leak.if you just tur the floor heat on it still comes out on top the dash board.thanks for any info.also how would i check to see for a vacume leak?