93 rough run and pop 4.0 no check engine light

[FEandGoingBroke]

I have experienced many form of injector failures and fowling, this truck follows non of those parameters.
Anyone have an ECM test procedure to check if it’s failing to send or receive a signal from one or more components?

 

[FEandGoingBroke]

Mr super cab, let me reiterate. I mis spoke.

Mathis issue was here prior to installing new plugs, prior to replacing bad capacitors in the ECM, prior to fixing the coolant leak, and prior to the new coil pack and crank position sensor.

man’s it does not run like there’s an issue with the MAF, in which case the overall runability would diminish greatly in my experience.

still no check engine light.

 

[FEandGoingBroke]

compression test…. Yeah I’ll do that if you can tell me what benefit it would reveal.

 

[2011Supercab]

Yeah I’ll do that if you can tell me what benefit it would reveal.

To eliminate any mechanical problems.

skip fire and pop chug on mild to hard acceleration

And it could be something as simple as a dirty fuel filter

 

[FEandGoingBroke]

The fuel filter is seven days old. And mechanical issues shown by a compression test rarely let an engine run so well, yet misfire.
but for posterity I will do that and ohm the wires tomorrow.

 

[FEandGoingBroke]

My roomate stole the truck for the day, I’ll get compression test tomorrow I reckon.

 

[FEandGoingBroke]

Also I’m going to add that clogged fuel injectors are clogged all the time and not only while driving down the road and having bumbles and burbles have n maintains speed, erratically and the occasional pop and miss through the intake while accelerating hard.

perhaps the new coil pack is shorting identical to the original one from 93, but that’shighly improbable.

perhaps this is all happening from a poorly acting MAF sensor, but that also would likely set a check engine light, as would a bad crank sensor, which is also new….

so many possibilities yes not enough of a miss to code out or point a specific occasional failure.

 

[2011Supercab]

would likely set a check engine light,

I have to ask,

Does your check engine light work ?

Key on - engine off , light should be on.

 

[FEandGoingBroke]

Yessir super cab, that was the first place I checked when my buddy brought it over. 1-1-1. And 1-1-1. All clear no codes.

 

[FEandGoingBroke]

Checked it after cleaning MAF with the proper cleaner, and again after the other repairs. Will re check for codes tomorrow because although the light isn’t on when running, I replaced the three bad ecm capacitors a few days ago to no change in running condition. But didn’t re run code test.

 

[FEandGoingBroke]

93 4.0 no check engine light….

thinking the ECU was hammered I put new capacitors in it today, one diode had an iffy solder arm that I touched up, (the rest of the three layer board was perfect) thinking that the hesitations and popping that happened on occasion while hard acceleration but are more normal now we’re coming from the bad PCM.
this occurred after replacing the plugs, properly gapped to .052, crank sensor the coolant temp sensor the throttle position sensor and the thermostat, while pulling the motor apart and fixing the lower intake leak and the timing cover leak….

So either the ECM is bad still, or the whole skip fire and pop chug on mild to hard acceleration is due to a bad MAF sensor….

But there’s no codes detected by the ECM.

loan me your thought friends!

Tested MAF, it’s spot on in its parameters.

still no check engine light, computer flashed no problems.

so I’m going to 44k this piece of crap, and out yet another new fuel filter in.

current Koeo fuel pressure at rail is 34 initial and holding at 32.
Koer idle pressure is 26 psi. And 26 psi at 2500-3000 rpms.

so I think I’ve located the issue beyond the bad capacitors in the ecm!

the friggin weak fuel pump, or the in tank pressure regulator causing poor pressure while running.

what do you all think? When I tested the fuel pressure last week 34-32 psi is within specs, but I failed to test it warmed up and running because I ASSumed it was fine…

 

[FEandGoingBroke]

145 max 125 min. As shown in the other thread. Some would say that’s terrible. But the issue is intermittent spark interruptions.

I have removed the column mounted ignition switch and testing it digitally tomorrow, checking for fluctuations or loss of power signal to ecm with minute movement imitating driving conditions.

after that I will remove and map out every part of the ecm dealing with spark control. There MUST be a correlation within the lower ignition switch and ecm OR the ecm and the edis 6, OR the edis 6 and the new coil pack, OR the new crank sensor and the ecm.

Miya gotta be something, and with the actual hours into this truck he could have almost bought a great running replacement. He’s a friend, so I’m doing everything I can to keep his costs down.

I came here for suggestions because of the entirety of the communities knowledge in the same place, but haven received any suggestions that haven’t been eliminated by testing or by brand new parts (some swapped for additional new parts under warranty in case of assembly errors)

thanks guys.

 

[2011Supercab]

Thanks for taking the compression off the list.

How is the harmonic balancer ?
Just wondering if the rubber is starting to go and causing the airgap to the crankshaft sensor to get to far out of spec at the higher RPMs

 

[FEandGoingBroke]

The balancer is a perfect circle while running, the rubber is smooth and untracked and solid.