Well, my buddy used his db1 scan tool and we come to the conclusion I crossed the number 5 and 6 plug ,so we thought easy fix so we made it right the truck ran a hundreds times better but now its doing the same ol thing. Im out of ideas, maybe change the egr and the coil pack.
Jimmy

 

Maybe unfasten the coilpack from the intake manafold, insulate it with a thick piece of plastic or wood & see if it runs better. If it does, suspect it may have cracks underneath thats breaking down to ground on the intake manafold.

Most autoparts stores can bench test the coil pack for output.

If you don't want to do that, use an inductive type timing light on each plug wire & see if you can find any that are missing spark, in time with the felt engine miss.

Do you now have any cyl misfire codes, if so look to those cyls first.

Seeing as how it ran better after you got the plug wire hook up straightened up, are you sure the plug wires are still snapped on good & tight & the plug ceramics aren't cracked????

 

PawPaw
Im heading out to a local salvage yard and finding a coil pack and egr valve, will let you know.
Jimmy

 

found a coil pack, a TPS sensor a Idle something sensor and replaced them all, still the same...arggggggggggggg could it be the egr sensor?
Jimmy

 

Just out of curiosity, have you done any of the things that were suggested in post #17? Seems to me pawpaw is trying to get you to actually test the parts, not just throw more untested parts in. At the moment you're running around in circles, wasting money, and getting nowhere - slow down, take your time, and start testing things.

 

Done it already, we did the light miss thing, replaced the coil with a good one.
No crack plugs, no wire caps off.

 

Any one have a SIMPLE vacuum wire diagram for dummys maybe?

 

If it's a vacuum leak you're suspecting, those can sometimes be found with a can of starting fluid (I've also used carb cleaner but ya gotta be mindful of the fire risk) - just spray it around where you think the leak is and listen for changes in your RPM. I found a bad gasket once by doing this - it didn't seal down right and was causing rough running issues.

 

FIRE! wish me luck, Im at the point if it does catch fire I'll just let it burn. LOL
Thanks Furious
Jimmy

 

OK, we aren't mind readers here, so a little more feedback detail would be helpful in aiding you in your trouble shoot.

How is the vehicle behaving now???? Still missing under load????

If so, what did you discover, or learn from the inductive timing light test???? Were any cylinders found to be missing???

Are you now Certain that you Now have all of the plug wires connected properly to the correct positions on the coil pack & routed to the correct spark plug?????

Coilpack plug wire layout positions, looking at the engine from the radiator.
3 4
2 6
1 5

Engine cylinder layout, looking at the engine from the radiator.
3 6
2 5
1 4

If your now certain that the plugs & wires are put right, what trouble shooting have you done on the OBD-1 codes you posted earlier on page one, P158, MAF sensor above maximum voltage (1991 on) & P181 Adaptive fuel rich limit reached at part throttle, system lean cyl bank-1 (1990 on) ????

These codes suggest a fuel trim problem likely being caused by a problem in the MAF system.
So you need to use your friends scantool to measure the MAF sensors operating voltage & the MAF sensors PID output to the computer at idle & at about 2500 rpm, to see if the MAF Sig Return rises with rpm, from about .2-1.5 volts at idle, to about 2.0 volts at 2500 rpm. The signal return voltage should rise with increased RPM.

If you don't now have the scan tool, disconnect the MAF sensors electrical connector & probe the VPWR pin with your multimeter for B+ at KOEO.
If thats ok, plug it back in, start the engine & back probe the MAF connector to measure the MAF sensors Sig Rtn voltage at idle & at 2500 rpm, it should be as posted above.

Let us know what you find.

 

I did a cylinder fire check by removing each plug wire from the coil, they all worked fired fine until I pulled wire back far enough where the spark could not jump, I then would notice a change in the way it ran so I assume all the cylinders are working as they should. The wires are ran correctly from the coil to the cylinders, I rechecked.

You quoted
P158, MAF sensor above maximum voltage (1991 on) & P181 Adaptive fuel rich limit reached at part throttle, system lean cyl bank-1 (1990 on) ????

Yes, thats what it read if memory serves me correct.

Quote
If you don't now have the scan tool, disconnect the MAF sensors electrical connector & probe the VPWR pin with your multimeter for B+ at KOEO.
If thats ok, plug it back in, start the engine & back probe the MAF connector to measure the MAF sensors Sig Rtn voltage at idle & at 2500 rpm, it should be as posted above.

I am by no means a upper end technician on this stuff and am a little confused my apologies. I found 2 02 sensors at a local salvage yard and replaced them (you can use your own imagination on just how that went) I accomplished it with no difference in the way it runs.

Jimmy

Jimmy

 

MAF = Mass Airflow Sensor - Mass flow sensor - Wikipedia, the free encyclopedia

KOEO = Key On, Engine Off

Sig Rtn = Signal Return - don't know where you'd find that...

And, I'm thinking he's having you check the voltage at the VPWR pin to make sure the sensor is receiving the correct signal to begin with.

 

OK, good feedback, so your now certain the plug wires are all routed properly & securily connected to the coil pack & plugs, so we can put this one aside for now.

On the trouble codes you posted, they suggest you have a MAF sensor problem. In your first post you said you cleaned it, but you didn't say how, or what with!!!!
This info is important because if you cleaned it with a product that left residue on the sensor when it dried, or poked the sensor with the wand of a spray can, cotton swab, ect, the sensor may be damaged, or contaminated, or it may have gotten dirty on reinstallation, or if you didn't remove it when cleaning, you may not have been able to get it clean, or residue may have dripped on the sensors heated wires & baked on & that could corrupt it's output reading to the computer, for which you have a trouble code, Whew!!!!!! lol SO, we need to know exactally how & what you cleaned the sensor with.

Did you have the P158 trouble code Before you cleaned the MAF sensor????

 

first I cleaned it with radio shack electronic cleaner, the second time I sprayed (lightly) with throttle body spray.
Jimmy

 

The rule is to work & put right the lowest number trouble code first.

I'm not clear if you cleaned the MAF sensor in place, removed it so you could get to it from all sides & keep it clean while it dried????
Nor certain about the recipe of those products & if they're plastic safe & residual free of deposits when they dry???? They may be ok & the MAF sensor may be as clean as you can get it & if all that is so, the computer says you still have a problem with the MAF sensor.

If your uncertain about the MAF sensor cleaning, or the products used, CRC makes a non residual plastic safe recipe, just for cleaning MAF sensors, as well as several other mfgrs.

All that is important, as Any deposits remaining on the MAF sensor heated elements can bake on & corrupt it's calibration & PID output to the computer & that'll cause the computer to get the wrong info about the true air flow into the engine & miscalculate the fuel injectors squirt time & thus corrupt the air/fuel ratio, for which you have a trouble code on bank one.

It's not clear for sure just yet what the root cause of the P181 bank 1 code is however, because a number of things can cause that kind of lean code, like a problem with the MAF sensor, for which you have a trouble code, a vacuum leak & the 4.0L of your vintage was known to have intake manafold gasket leaks, with the vintage of your ride, you could have a lazy bank 1 O2 sensor, or fuel injector problems, or an acting out TPS figuring in, but for sure you have a MAF system code that could be figuring in on the lean code, & that could figure in on the part throttle driveability problem you have, so the MAF code needs to be run down & put right first, then work the lean code, if it's still around after the MAF code is put right.

If your uncertain how to do the MAF sensor voltage checks I outlined above, a repair manual like Haynes, Clymer, Chiltons, ect, available at most auto parts stores, WalMart, or your Library, will offer up illustrations & instructions, or a repair CD will give even more detail if you need it. Before you buy a manual, or CD, check out the Libary & look over the different publishers offerings, to see if they have the format & detail you need & want. The library may have repair CD's to check out, or maybe have a Mitchells online subscription that you could access for the detail info you need.

I know you've posted that you've thrown a bunch of parts at this problem with no joy & are frustrated, but those salvage yard parts are unknowns too, so it begins to complicate how to think through your trouble shoot with so many untested variables tossed in at one time.

So begin with what is known & that is that you have two trouble codes, one for the MAF system & a part throttle lean code for bank 1.