91 s-10 needs help

[TUFFBONNEVILLE]

this truck is my brother-in-laws it a 91 s-10 4.3l with 147,124 the problem is it wont stay running at idle it just dies also when your driving it has no power just stumbles and falls flat on its face when floored if you give a 1/4 gas its ok but still has the stumble. i have changed map sensor,tps sensor,egr valve,rebuilt tbi unit, intake gasket,plugs,wires,cap,rotor, the cat is newer maybe 3 or 4 years old. the only thing i can think of is the timming chain has slop in it and dont want to stay running. any ideas would hlep me. thanks

[J Wikoff]

Have you checked for big vacuum leaks? Do you have a real-time data scanner to see what the fuel trims are doing? Does it have MAF sensor?

[BlackHawk99]

What are the fuel pressures? Age of the pump? Age of the pressure regulator?

[TUFFBONNEVILLE]

no vacuum leaks and i have a snap on scanner mt2500
it does not have a maf sensor.

for the fuel pump could be oem have know idea. the fuel pressure regulator a few months ago.
and how do you check for fuel pressure their is no valve to tap into

[J Wikoff]

There isn't a pressure port anywhere?

Can you scan to see if it's really lean or rich at idle? Or maybe pull a plug or two and "read" them.

[TUFFBONNEVILLE]

im at work so when i get home ill check it out
thanks

[crash93ssei]

Was the problem the same before and after changing the pressure regulator? A friend of mine had the same problem and the spring inside the pressure regulator was broken in five pieces.

[TUFFBONNEVILLE]

yes it was the same before and after changing fuel pressure regulator.
i will scan it when i get to work this afternoon

[TUFFBONNEVILLE]

ok i scan it and i have a code 44 lean exhaust
and i must of broke the coolant temp sensor cause
that code is 15 coolant temp signal high or low
so open the hood and the temp sensor is broke
also the truck was scaning the truck at 191 degrees.
but i leaving out of town tonight and ill be back monday night
thanks

[TUFFBONNEVILLE]

so iam back on this project again put new temp sensor in cleared codes
so i scaned it again no codes ill give you the run down what the readings on the scaner was
1) exhaust oxygen was going back and forth lean/rich
2) tps (v) 0.66
3) iac position 43
4) o2 crosscounts on the low side i saw was a 17 and on the high side 23
5) map(hg) 11.0
6) map(v) 1.58
7) coolant temp was around 155 and getting hotter

[xX3800Xx]

Vacuum looks a little low at idle i would think it would be more around 20. It would appear you have a vacuum leak.

[TUFFBONNEVILLE]

well took it out for a test drive on lunch and scan it
at 191 temp
exhaust oxygen was going back and forth lean/rich
tps (v) .056
iac position 43
map(hg) 9.0
map(v) 1.12
o2 crosscounts where going back and forth from 0 to 1
oh and now it kinda stays running at idle only when it warms up and then
the rpm goes up and down like it going to die then the rpms go up and it still acts the same
when you floor it falls flat on it face

[TUFFBONNEVILLE]

put all new vacuum lines on and that didn't help
i wish i could test the fuel pressure

[Mopar Man]

Check the fuel filter?

[TUFFBONNEVILLE]

fuel filter maybe 6 months old
i think its time to drop the tank and put a fuel pump in it to see if that makes
it any better if not my brother in law can pick it up and take it to a shop

[xX3800Xx]

put all new vacuum lines on and that didn't help
i wish i could test the fuel pressure

What about intake gaskets? Brake booster 1 way checkvalve? modulator for the trans?
throttle body gasket? Bad IAC?

[tpulliam79]

the fuel pressure can be tested, you need a tbi fuel pressure tester, I think autozone has them it hooks up between the supply and return lines to the tbi, or you can get a fitting to go where your fuel filter is. kind of a pain but beats replacing a pump if not needed. also did you clean or replace the iac?

[TUFFBONNEVILLE]

i did clean the iac when i rebuilt the tbi could be bad i guess ill have to unplug it to see if it does anything. also ill check the one way check valve and modulator.thanks for the tip about the fitting at auto zone ill check that out when i get off of work.

[tpulliam79]

also have you checked the timing?

[TUFFBONNEVILLE]

i have messed around with it made it run real bad so i just put it back to stock
and i do know about the wire you have to unplug under the pass side of the dash
wont be able to look at it tonight but tomorrow morning ill be lookin at the truck ill let you guy know what i find out. thanks