Fixer Upper trouble shooting

[acreature]

*FIXED* Fixer Upper trouble shooting

1996 Xtra Cab XLT 4x4 4.0l OHV

Bought as a fixxer upper, possible flip dirt cheap. A couple hundred bucks for a running and driving truck.

Needed all four leaf spring brackets replaced from rusting off, but runs and drives, with a rust free body and 4wd works, to boot.

Motor ran rough, but would keep running with a surging issue that would stall out occasionally, but fire right back up. No knocks. No smoke. No smells.

-Changed the plugs out, used ones showed normal wear; no oil or carbon.

-Checked vacuum leaks via starter fluid, none found. Problem Code 1504. Tested IAC, worked fine, but replaced anyhow. Ruled out failing vacuum inside of brake booster.

-MAF and TPS tested fine.

-Did one spray can of Seafoam. Didn't do a damn thing, so I then removed Throttle Body and Upper Intake, cleaned and replaced with new gaskets. TB & plenum had a lot of carbon buildup. Butterfly had obvious sticking because of carbon on backside. Lower intake showed buildup, but did not remove and clean.

-Fuel pressure tested at 28-30# at idle. No great change in pressure with gassing her to 3k - change was maybe 2-4#. No fuel pressure drop after shutdown, rose to low 30s# and held.

-EGR tested good: stumbled with vacuum applied and held the vacuum. (Not using a vacuum tester, mouth and hose tested, lol **EDIT, got my hands on a vacuum tool. Tested via same and EGR is good.

Runs smoother, albeit not perfect. No hesitation when accelerator applied, but left idling, will start surging. Gassing it a couple of times gets her to smooth out for a bit. Runs great on the road, just when idling.

I am leaning fuel pump/bad gas/fuel filter, but "feel" it would be constant rather than random, if so. I know, change the fuel filter and break open the old one... just haven't yet.

Thoughts.

 

[Bgunner]

Retest the TPS (throttle Position Sensor). When these start to go they often have a symptom of surging idle speeds.

 

[acreature]

Retest the TPS (throttle Position Sensor). When these start to go they often have a symptom of surging idle speeds.

.93

Smooth increase to 4.63, then smooth back down to .93

 

[acreature]

Random single clicks also noticed

https://youtu.be/op0C1Izhax4

 

[fastpakr]

You mentioned that you'd tested and replaced the IAC. How exactly did you test it?

 

[acreature]

You mentioned that you'd tested and replaced the IAC. How exactly did you test it?

The default unplug the IAC and watch her stumble/shut off, then ohm meter tested within tolerance.

 

[fastpakr]

At this point I'd be more likely to blame a loose connection between the ECM and the valve. If you could find the correct pin assignments at the ECM, you ought to be able to do a wiggle test to check for any issues. Also - is P1504 still present?

 

[acreature]

Negative. Code cleared and hasn't returned. Only code was for EGR after doing vacuum tests, that also cleared.

Question... the random single click that is occurring sounds similar to a solenoid or relay. Is there one driver side motor? I've not seen one.

 

[acreature]

At this point I'd be more likely to blame a loose connection between the ECM and the valve. If you could find the correct pin assignments at the ECM, you ought to be able to do a wiggle test to check for any issues. Also - is P1504 still present?

Loose connection between ECM and "valve"?

 

[fastpakr]

The IAC valve.

 

[acreature]

The IAC valve.

I'll do some checking when I get back to her, but as a note, I've manipulated the IAC and connections to it while idling and no changes were observed whether at a smooth idle or rough.

 

[acreature]

TPS, IAC, DPFE, Valve Control, all tested good. Including the 5v signal from ECM holding before & during stumble/surging. Still a random stumble/surge. I have the upper plenum off again, just for more inspection and cleaning. EGR tube rubber gaskets/O rings that go into plenum still like new, great seal.

 

[acreature]

Good talk

Fuel filter changed & was able to apply pressure toward engine without resistance into the old filter. No change. Have new fuel pump on order since pressure was 28lbs. With the starting issue taking 3-5 tries before she catches and hold an idle, I figure a new pump wouldn't hurt.

Did everything to drop the tank, but that 20 gal bastard won't come out.

Ext Cab 4x4 with bed off.

I tried body jacked as high as possible with suspension free hanging and also with axle and body jacked.

Only option I see is to drop the rear axle or force the rear half downward (bending the overhang front portion). I am going to leave her as is and clean while still on the body unless some superhero knows how to wrangle that tank out of an ext cab.

 

[Denisefwd93]

you aren't taking the bed off???

 

[fastpakr]

+1. Take the bed off.

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