wtf??? Problem related to every sensor the truck has????

[tinksmartbstupid]

So I just got this car from a friend of mine. He's getting rid of it because of this stupid intermitten problem.

it's a 1994 eddie version (can't spell the last name). 86000

these be my symptoms::

Car stalls when starting until slightly warm, once warm car has no power before 1500rpms. for me to drive the car I have to hope it get's above 1500rpms, and then keep it between 2000-4000rpm's to get it up to speed.

once driving it the car will all of a sudden lose power, but turing the car off and on again (20mhp and up jumpstart for auto's) the car has power back.

if I let the car sit for more then 10 minutes, and try to start it, it will studder, and fail. only does this after the car has warmed up.

if I floor it, you can hear the throttle open (loud from the air cleaner box) but the car dies. if you floor it and take your foot back just a bit, it will fly up if it's warm and running, and will studder up if it's cold and running

the codes I get are 116, 136, 172, 412, 538 (All KOER tests)

the car runs rich, not lean.

now I know 538 is usually a user error, except that when I floor the car it stalls, so I can't say it's my fault that happened.

Fuel pumps been replaced, fuel pump relay's been replace (yes there's voltage there, although I couldn't read any current flowing from one to another). no I do not hear the pump prime when I put the key in the on position.

Idle air speed sensor (IAC) was just replaced.

MAF was just replaced, along with the connector because the wires were falling out of it. all codes were erased and I tried driving it again. no luck, same problem.

now I know a lot of people have been posting this, but no one seems to have the same, or similar answer to it, if they get the answer at all.

I have a decent amount of car knowledge, AND I'm an electrical engineer, so I have enough knowledge to trouble shoot and repair, even the computer if necessary.

as far as I have so far checked, I do not have a vacuum leak.

no the computer does not display any codes.

yes the car runs worse if I disconnect the TPS, not by much though, so maybe something with that?

if I disconnect the MAF, there is no change. If I disconnect the IAC, idle falls to 500, sometimes stalls.

most of the time when it's being a pain, if you give it gas, when you let go of the gas the rpm's jump, and when you put your foot on the gas it stalls.

now things I could think could cause this problem:

MAF
O2
TPS
AIC
Ignition module
coil(s)
fuel pump
relay's
ecu
wiring?


does anyone have any idea as to which way I should go? because I really don't feel like replacing everything just to fix the problem.

help please?

 

[Turdle]

I know it is a different year, however, mine developed bad connections to the relays--not the relays bad, but the connectors in the power box.
The PCM relay in mine was intermittent. No power to PCM= no fuel pump relay, or fuel pump.

 

[tinksmartbstupid]

The computer has power, The fuel pump is running, I get spark, I am getting gas cause I can smell it, but the car still doesn't run. I'm going to either borrow or go rent a fuel pressure gauge to see if I'm getting pressure. *shrugs* any Ideas?

 

[KillerB74]

Have you tried just the basic tune up items? Make sure the simple things are working first. Replace the air filter, fuel filter, spark plugs and wires and see if that helps.

 

[tinksmartbstupid]

Just did that, new wires, new plugs, new air filter, fuel filter I didn't replace, but it's not that old, and I took it out and checked flow (flow meter at work).

now I came across something interesting. I talked to my mechanic friend and he says it sounds like the injector pulsewidth is bad, which could be a couple things. to go along with that though, the warmer the car gets, the better it runs. so the only two things I know of that mess with fuel injector pulse is the temperature sensor (I have a bad thermostat, I'm replacing it this weekend) and the oxygen sensors. MAF and IAC have been replaced, I'm going to test TPS and I know I have to check EGR too, but that's last on my list (and probably part of the problem).

the oxygen sensors are the original OEM O2's. so I'm going to start here, because I've got no where else to go with this, any idea's?

 

[Doubt Incarnate]

fuel pressure regulator?

 

[tinksmartbstupid]

I haven't check fuel pressure yet, yeah I know I should, but I haven't had the time to go get the tool. I checked each injector, each one is firing, although I did get errating firing on cylinder 6, but when I unplug that injector, the car idles even ruffer, so that's no the problem.

Now if I unplug injector for cylinder 2, there is no change in idle. I am getting spark to that cylinder, the injector is firing, the injector resistance is in spec. (it's 17ohms, spec says 11-18ohms). hmmm I wonder.

another thing, there is some kind of sensor that looks like a vaccum sensor, only it is pressurized with the pulsation of the engine. when I disconnect this hose, I notice that what looks like some gas comes out a bit. there is also gas in the oil, as if the truck is running rich.

Now I'm getting some new codes too

MAF sensor circuit open. ::: I just replaced the MAF

Fuel system at part throttle rich adaptive limit, system lean (Rear Side). (yeah I know, check fuel pressure)

Closed loop injector pulse width longer than expected. (WTF?)

Fuel system at part throttle rich adaptive limit, system lean (Front Side).
(same as above).


Should I....replace fuel injectors???