My Misfire,popping Saga "Please Help"

My on going Saga

Now that the "Urgent Help forum" is shut down it hurts the one's that need help the most. I had Mark, Ron, Jerry helping to figure this issue out the best way they could. Today I had a hell of a time trying to start my truck it turned over slow. I gave it a little throttle as it tuned over it almost fired up. I pulled number 3 and 6 plug out both fuel fouled. I cleaned them and tried again with an extra battery hooked up with jumper cables it fired up it wasn't easy. I did put a filter in line with the PVC a Fram white plastic one but the line is same as a small vacuum line. Today I see oil buildup in the bottom of the filter. My friend gave me a Fram HPG-1 fuel filter canister to use with bigger ID line bigger canister

The darn thing pops misfires bogs now all the time it use to be off and on. I have changed the Ignition Module, MAP, TPS, Ignition Coil cleaned the IAC and put a new Borg Warner dist cap and rotor on and new Napa plug wires. The spark plugs are AP 105's I have changed the fuel filter high valume fuel pump as well. I have also done a vacuum test and compression test all good no issues. I am kinda lost on this and ran out of ideas to fix it any help is very much appreciated

Pull the fuel pump relay out
Crank engine a few times to drain fuel pressure

Pull off the intakes air tube
Open throttle and spray some gas or Quick start(ether) into the intake and then try to start engine
Just seeing if engine is flooding out from problem with injector system.


Second thing
TFI spark system like other distributor systems has a START and RUN power wire.
This is done to extend the life of the coil
A coil can give good spark with 9volts and it will make it last longer
But on cold start with starter motor turning the system voltage can drop below 10volts, so a resistor in the coil system would make it 6volts which is a weak weak spark.
So there has always been separate START and RUN power wires for the coils.
On the old 4 post starter relays(solenoids) there was the "I" post, it ran to coil + to give coil full power when cranking engine, after start up(key moves back to RUN) that power was cut and coil got 9v via ignition switch.

Common symptom for a failed START wire was no fire up while cranking but a pop or almost start when you let off on the key.
When key moves back from START to RUN coil gets power so you get spark for that moment.

TFI info here, check out the START wire: http://www.therangerstation.com/tech_library/TFI_Diagnostic.shtml

As a quick test you can run a jumper wire from Battery Positive to Coil +
Then try to start engine, a basic Hot Wire, lol, prior to locking steering wheels

RonD said:

Pull the fuel pump relay out
Crank engine a few times to drain fuel pressure

Pull off the intakes air tube
Open throttle and spray some gas or Quick start(ether) into the intake and then try to start engine
Just seeing if engine is flooding out from problem with injector system.


Second thing
TFI spark system like other distributor systems has a START and RUN power wire.
This is done to extend the life of the coil
A coil can give good spark with 9volts and it will make it last longer
But on cold start with starter motor turning the system voltage can drop below 10volts, so a resistor in the coil system would make it 6volts which is a weak weak spark.
So there has always been separate START and RUN power wires for the coils.
On the old 4 post starter relays(solenoids) there was the "I" post, it ran to coil + to give coil full power when cranking engine, after start up(key moves back to RUN) that power was cut and coil got 9v via ignition switch.

Common symptom for a failed START wire was no fire up while cranking but a pop or almost start when you let off on the key.
When key moves back from START to RUN coil gets power so you get spark for that moment.

TFI info here, check out the START wire: http://www.therangerstation.com/tech_library/TFI_Diagnostic.shtml

As a quick test you can run a jumper wire from Battery Positive to Coil +
Then try to start engine, a basic Hot Wire, lol, prior to locking steering wheels

Click to expand...

Thank you Ron

You don't know how glad I am to get help I was stressing when I couldn't get it started. I am dealing with snow storms and having to get my mom back home from the hospital the 31st. After I got it running I got back home at 4pm I fired it back up at 12 midnight let it run 20min. This morning it fired up as I gave it a little throttle but loaded up. Its still popping under a load and misfire tick at idle. I took it to Oreilly Auto Parts they looked it over herd the misfire and pop there telling me its a valve sticking. I got home put my Fram filter canister in line with the PVC I went over to check the drivers side vacuum tube to valve cover as it mybe plugged up. I found it half way out of the grommet real easy slipping it up and down. I pulled it out the grommet was shot mushy gooey I bet that was a good vacuum leak. I took a new one from a 390ci valve cover modified it to fit snug with my high speed grinder. I fired it up still popping at quick throttle but not as loud as its ben

I think my Napa battery maybe to weak I got a battery charger for the next heart pounding moment. The Alt light still comes on and off at times I need to get some ether quick start and do what you said. The darn thing pops bogs but once I put my foot down on the throttle and it goes into low gear it revs up and gets going I don't let it get over 3500rpm's I let it go into high gear than popping bogging again. I pulled number 3 plug still black carbon dry deposits. It looks to be firing looking between the tip and strap looks clean

New issue Stalling

Well guys fun never stops I had a stalling issue each time I put into gear it would stall. I fired it up and had to give it a little throttle as I put it into gear to get going. I changed the IAC valve ran like crap for a while than cleared up ran fine smooth idled great. I drove it up the highway grade popping missing again all the way to town 11 miles. I shut it off for 20min fired it up running great again. The strange deal is it ran perfect all the way home all up hill 11 miles first time its ever done this. The bad part 1/4 mile before getting home coasting down the highway grade it stalled I pulled over started it up it was chugging trying to run I put my foot the floor it reved up than sputterd and died it did this three times I let it sit and hour fired it up running fine again. This morning I drove it up the highway grade didn't pop or miss but a few times acted like it wanted to bog or a sudden loss of power off and on than back to normal. This thing is going to leave me stranded I can't trust it anymore what is going with this truck? I know changing the IAC it don't pop as much but now likes to stall and when re-starting rev up with my foot to the floor than sputter chug and stall after running perfect for a while

Well you have checked everything else, and problem is intermittent, so can't be mechanical.

So at this point I would disconnect battery and pull out the PCM(computer), make sure connector and wires are good, then pop the top on it and have a look at the circuit board.

Here is what it should look like: http://www.auto-diagnostics.info/ford_eec_iv

When they get older the capacitors can leak and cause circuit issues by the loss of capacitor and the leaking fluid.

Remanufactured PCMs run about $75
You need an 1988 for a 2.9l
And if automatic trans then it needs to be for an automatic
I don't think 2.9l used EGR valve in '88 but that must also match, with EGR or without EGR

Computer issue would explain the "chasing" of ghost problems
And the "it works" and "it doesn't work" problems

And last place you go when all other parts have been looked at, tested or replaced
Could still be the wiring to/at the PCM so check that first

RonD said:

Well you have checked everything else, and problem is intermittent, so can't be mechanical.

So at this point I would disconnect battery and pull out the PCM(computer), make sure connector and wires are good, then pop the top on it and have a look at the circuit board.

Here is what it should look like: http://www.auto-diagnostics.info/ford_eec_iv

When they get older the capacitors can leak and cause circuit issues by the loss of capacitor and the leaking fluid.

Remanufactured PCMs run about $75
You need an 1988 for a 2.9l
And if automatic trans then it needs to be for an automatic
I don't think 2.9l used EGR valve in '88 but that must also match, with EGR or without EGR

Computer issue would explain the "chasing" of ghost problems
And the "it works" and "it doesn't work" problems

And last place you go when all other parts have been looked at, tested or replaced
Could still be the wiring to/at the PCM so check that first

Click to expand...

Thanks Ron

I pulled the cover off the computer and checked the circuit board under a bright light. I see no issues of leaking or discoloration looks nice the wiring to the computer all looks good. It also at idle sitting will all of a sudden drop in rpm's than go up and back to 800rpm's. I gone this far I guess change the computer and cross my fingers the only place that I can get one is at oreilly auto parts

Only way to change idle on fuel injected engine is to change air flow.
Vacuum leak raises idle, so dropping idle should be IAC Valve closing, could be loose throttle plate but long shot.

IAC valve works by PCM pulsing its Ground wire
It has 12volts one one wire(red) with key on, other wire runs to pin 21 on PCM(grey)
With key on PCM grounds pin 21 and IAC Valve should open all the way.
Without touching gas pedal, when you start a fuel injected engine it should REV to about 1,500rpm, IAC valve is open all the way, then computer starts to close it by pulsing ground, so RPMs start to drop, and PCM set cold or warm idle RPM based on ECT(engine temp) sensor

On a volt meter you can't see the pulsing ground, you do see lower voltage, usually 8 to 11volts, lower volts = lower RPMs

If overall voltage in system(charging system) dropped then that could lower RPM
Charging System with engine running should be 13.5volts at the battery after running a few minutes, 14+ volts just after starting, recharge voltage, then it should drop to 13.5volts so battery doesn't get cooked.

RonD said:

Only way to change idle on fuel injected engine is to change air flow.
Vacuum leak raises idle, so dropping idle should be IAC Valve closing, could be loose throttle plate but long shot.

IAC valve works by PCM pulsing its Ground wire
It has 12volts one one wire(red) with key on, other wire runs to pin 21 on PCM(grey)
With key on PCM grounds pin 21 and IAC Valve should open all the way.
Without touching gas pedal, when you start a fuel injected engine it should REV to about 1,500rpm, IAC valve is open all the way, then computer starts to close it by pulsing ground, so RPMs start to drop, and PCM set cold or warm idle RPM based on ECT(engine temp) sensor

On a volt meter you can't see the pulsing ground, you do see lower voltage, usually 8 to 11volts, lower volts = lower RPMs

If overall voltage in system(charging system) dropped then that could lower RPM
Charging System with engine running should be 13.5volts at the battery after running a few minutes, 14+ volts just after starting, recharge voltage, then it should drop to 13.5volts so battery doesn't get cooked.

Click to expand...

Ron

I went ahead orderd a Cardone PCM computer $102.99 from O'reilly Auto Parts Napa don't sell them anymore. Its back to pooping bogging again I hope this corrects the issue. I changed everything els it should be here in a couple day's

Have you checked for vacuum leaks? A vacuum leak can cause all sorts of operating problems. Even the cruise control can malfunction due to vacuum leaks.

wildbill23c said:

Have you checked for vacuum leaks? A vacuum leak can cause all sorts of operating problems. Even the cruise control can malfunction due to vacuum leaks.

Click to expand...

Wild Bill

I did a vacuum test on the engine using a vacuum gauge it all checked out good. This on and off popping bogging surging and stalling running rich and running perfect it must be the main brain computer? I spent a lot of money thus far just to be kicked in the face but this now another $102+ dollars. I have no real hope I feel its going to be another waste of money with same results

Another failed attempt


I changed the computer fired it up running rough and surging idle each time I started it the engine would die. I took it on the road popping bogging no change runs like crap. I took the new Napa IAC off put the old Ford IAC on fired it up no surging idles at 800rpm's. I did everything changed everything the dirty dog bites my Azzz each time. I am going to switch number 3 and number I plug wire on the cap see if it runs better. I don't know its a shame the truck is real clean I hate to junk it