HELP - Hard start, dies, stumbles driving, buuuurg on heavy pedle

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goingcrazy2fix

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Its a : 1995 gmc c1500 2 door sierra 8' bed 5 speed manual v6 4.3l TBI
with aprx 223k miles.

problems & symptoms :
must start 9 or 10 times. rumbles & shakes, Bruuuup sound on peddle press
when taking off or it dies. When it was running last -Jerks and sounded
congested - no power, couldn't get over 25 mph.

problems are more constant and increasing - just sitting there now.

In the last 3k miles I replaced with "new"

1.) ehaust from cat to tailpipe - everything.
2.) rotor, cap, plugs & wires
3.) engine coolant temp sensor
4.) map sensor
5.) throttle possition sensor
6.) oxygen sensor
7.) egr
8.) egr vacuum solinoid
9.) idle air controll valve
10.) TBI rebuild kit
11.) fuel pressure regulator rebuild & new spring
12.) vehicle speed sensor in transmission
13.) ignition coil
14.) water pump & lower hose - fresh dexcool 50/50 mix
15.) starter w/ solinoid
16.) flushed radiator & overflow container
17.) changed fuel filter.
18.) oil & filter 35 miles ago. - fairly dirty after 3,500 miles-
been using mmo (1 qt) + mobile super high millage 5w-30.
19.) tensioner & idler pully bearings.
19.) unpluged computer and cleaned pins with crc qd circut / contact cleaner
and jiggled wires while it was running - nothing changed.

Additional info :

swaped fuel relay with a new one and no difference - reused old.
Fuel pressure test 11-13 psi. <- autozone loan a tool 2 test first gauge = 0 psi.
I checked vacuum when it was at least running a while back- 19.5 & 20 @ idle
and steady - no flux, dips, etc. <- engine was warm / opp temp.

Currently have 3 new parts "NOT" yet installed :

1.) oil pressure switch ( controlls fuel also ??? - says some internet info )
2.) ignition controll module.
3.) fuel pump - full assymbly - everything on it. <- if its this, Im screwed.

*** when it was running - Oil pressure 60 cold / 40 warm & 20-25 hot @ idle.
oil pressure Still 60 cold start while working on this beast.
Never over heated.

reciently i began to smell heavy gas from time to time but found no leak.
Fuel millage from the day i got it was 13-14 mpg avg driving hwy & not.

Additionally, I have no Idea where the knock sensor(s) are other than people
saying on the side or rear of engine.... videos show close ups only.
Some real exact location information would be helpfull.

I also have no idea where the oil pressure switch is / goes - exactly.

This thing is killing me.... I am not a mechanic.

Any and all help would be greatly appreciated.
 
Your issue sounds to be fuel/air/vacuum or exhaust back pressure related.

Did your TBI rebuild include a new injector?

Have you changed the air filter?

Have you had your cat checked for plugging/blockage?

Your mention of a fuel smell leads me to believe it could very well be the injector in the TBI being worn and leaking extra fuel which would cause everything you mentioned as it is flooding the engine all the time.
 
2013denial ... Thanks for a response -

fuel/air/vacuum or exhaust back pressure ?
Thats anything and everything.

No new injectors yet.
air filter on or off no difference.
cat new - whole exhaust is new y-pipe to tail pipe.

working on ground wires. 2 off the battery to block &
& quarter panel, 1 from somewhere to the thermostat housing,
another one from somewhere to another part the block
and.....
just found out 2 more exist on the back of
the enigine to the fire wall. = 6 seperate ground contact points.

So the diagnostic plan for now is :

1.) finish checking ground wires.
2.) test the new fuel pressure regulator I just put in.
3.) check injector spray with timing light (evening / dusk).
4.) ck basic hoses off TBI for vacume leaks - again.
5.) install new ICM on distributor and check base ignition timing.
6.) check Canister Purge Valve.
7.) get a camera shot above gas tank to check ground
wire on the fuel pump, filler hose, etc. for possible issues.

then see what if anything is better... What do you think ?:confused:
 
It's a 1995 so it's a single coil. I doubt this issue is spark related.

I say fuel issue and I suspect the injector in the TB is the cause. You've addressed or checked almost every other thing it could be. If you check the injector spray and it looks good then I would check to make sure the injector isn't stuck on. This would also cause a flooding situation that could result in the symptoms you describe.

Have you done a compression test on each cylinder? Maybe you just have a very worn motor or cracked or broken rings that are not allowing you to get the power out of the cylinder while accelerating?

Oh and check your firing order and plug wire order connections as well.

Hope something in that helps.
 
JMC12... thanks for the post - the ignition coil is new.

2013denial..

I am thinking fuel also. I have two injectors and a new distributor coming in the mail . about all that left is a knock sensor and new engine.

I had to stop working on it for now - tbi is off the motor.
Anyway - I figured a while back the vacuum gauge diagnostic was good so I never did a compression test - should have done before replacing everything huh ? I did use a chemical tester on the radiator a few months back to check for a blown head gasket and the chemical never changed color.

Someone is coming to help - I hope - and check a few more things.

Odd thing is, when it was running somewhat, if I hit a bump in the road it would run better. If I hit a bump again it would run worse ??? untill it just started feeling and sounding so bad at start up I stopped starting it.

I do appreciate your input and will repost any new results after the new injectors and distributor arrive.
 
UPDATE on repairs.

I rebuilt the TBI and installed two remanufactured fuel injectors and replaced the diaphragm and spring in the fuel pressure regulator.

Still not running fully correct but noticeably better.

The distributor is next.
 
The hitting bumps on the road sounds like a ground issue. Maybe not for the fuel pump but possibly for the ECM.
 
KTOWNLOUDOG .. Ground to ECM ?

-- > Any Idea where the ECM ground wire starts & ends ???
I haven't been able to find all the ground wires in the form of a list and I am not real good with electrical schematics.

Also, it seems that Emissions and vacuum line routing are also 2 different things because the vacuum to the brake booster is not shown in emissions schematic..... makes me wonder if previous owner remove any T's in vacuum lines and something that should be under vacuum isn't.
 
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