88 2.9L Misfireing/backfireing issue

Spott said:

It's to the right of the passenger's footwell behind a kick panel, just ahead of the passenger's door. You have to unbolt a large connector to get the computer assembly out, and then you can take a cover off and inspect it. IIRC, the entire circuit board is dipped in a gray epoxy-coat, so any overheating, cracking, or component damage should be easy to spot.

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Thanks for info on the computer

I think I may have found the issue "I hope" I fired it up drove it to town ran perfect. Now on the way home its down the grade 6 miles coasting. I turn off to our road it starts popping missing I pull over shut it off install the scanner and fired it up popping missing. I put it on test the first code was (42) than the two others (74) and (77)

The code (42) is exhaust gas oxygen (EGO) sensor voltage signal always "rich" (high value) does not switch. I did the scanner test twice shut it off than fired it up first code was (42) again. Is this the sensor in the exhaust manifold that is bad? the popping is to much fuel? I have my original one I took off in 2002 we thought was the issue but it was the Ignition Module. I think the one I put on was for a 1990 3.8V6 T-Bird never had an issue until now

Maybe the sensor is bad, but maybe the sensor is just fine and your engine is running rich. How is your fuel economy? Does your exhaust smell like gas?

Just because the computer says a sensor is reporting an out-of-range value, doesn't necessarily mean the sensor is bad. Sometimes something else is wrong and the sensor is reporting that fact with valid values.

Spott said:

Maybe the sensor is bad, but maybe the sensor is just fine and your engine is running rich. How is your fuel economy? Does your exhaust smell like gas?

Just because the computer says a sensor is reporting an out-of-range value, doesn't necessarily mean the sensor is bad. Sometimes something else is wrong and the sensor is reporting that fact with valid values.

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Still popping issue

I changed the EGO sensor to the original one no change still doing the same. One thing when I put the scanner on I get code 12 unable to bring engine rpm up now that is strange why changing the EGO sensor do that. I notice after starting it up it drops to 800rpm's quick. I got another used Bosh sensor looks more newer not rusty looking. I will change that and I got some new Denso IT20 spark plugs my friend gave me. I will change those and the MAP sensor back to the new Napa one

Today I fire it up popping/missing I ran it up the back road 5 miles pulled over shut it off for 4 min. I than started it up gave it a couple reves than started off no popping/missing driving and stopping a few times. It only does it on the way home down the freeway as soon as I took the turn off it started popping/missing

I had always thought that popping and missing were timing issues? Especially since it's a fuel injected engine. And off and on issues are almost always a electrical in some way. You're probably gonna have to go through and make sure there's no bare wires or other issues.

bronco2fan said:

I had always thought that popping and missing were timing issues? Especially since it's a fuel injected engine. And off and on issues are almost always a electrical in some way. You're probably gonna have to go through and make sure there's no bare wires or other issues.

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Thank you

I appreciate any help on this issue it seams to be running to rich. The tail pipe is dark black as it use to be gray inside. Also when it starts popping I can smell fuel real good. I changed the MAP sensor 02 sensor or EGO sensor. I did a fuel pressure check when popping it held at 35-36psi. I checked the FPR for gas in the vacuume tube nothing there

Could a bad Dist cap due this? maybe jumping spark between cylinders. If it was I would think it be doing all the time not on and off like it is. I got new plug wires and spark plugs I never touched the cap. I think I better check the wires from the EGO sensor up to where ever it goes maybe the EGO is not working? I am grasping at straws I know

"Slammed again hard by the Napa know how team"

My on going issue at hand has turned to TRS the know nothing station. These guy's are pissing me off "Big Time" there terms for Ford are I hate to say. Anyway I would love to shove there SOB Chit back in there face lets try to figure this issue out

Question (1)
Can a bad Dist cap make this issue?

Question (2)
If the EGO sensor is not working electrical wise could it make this issue?

Yes, I am a Hillbilly I don't have the funds to have a certified mechanic check it out. I have a scanner that is it and you great folks to help these three Napa dude's are Toyota TRD off road racers. Ford is built tough just like all you TRS folks in my book

Have you checked the computer yet?

Mark_88 said:

To answer the question: Yes, the distributor can cause these symptoms...

To clarify...it is not likely the physical distributor because it is like an switch...it either works...or it does not work.

I am still betting it is either the TFI or the wire harness feeding the ignition (or spark to be more specific) that is wonky...as in you are hitting a bump or otherwise jarring the harness and it simply stops feeding the spark to the plugs.

Did you actually move the TFI off the distributor and locate it on a heat sink away from the stock location?

If you have done that already then time to focus on something like the wiring under the hood.

I again refer you to this document in the Tech Articles...I did not see where you had done this...

http://www.therangerstation.com/tech_library/remote_tfi.shtml

If this was done or is not the problem then I can only say that it is something acting in a similar fashion because it is too sporadic to be a "fixed" part like the distributor.

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Mark thanks for the help again

I left the TFI or ignition module on the Dist I did change it three times. I also checked all the wires from there even to the 02 sensor I found nothing. I did pull all the plugs today Motorcraft plugs. They all looked good no wet or fouled one's after pooping you think one or two would be black. I did put brand new set of Denso plugs in on first fire up popping you can hear it more in the intake plenum. The weird deal is after 60 seconds of running it cleared up ran smooth. I get on the freeway again going 65mph stating up the 4 mile grade it dropped to 45mph than popping came in. Well it stayed going into town shutting off three times all the way back home popping


Now I took the dirt road last time it stated off pooping it is very rough bouncing up and down. Than the paved smooth part some 3 miles steep up hill all climb still popping I pull over on the crest level part shut it off for 60 seconds re-start let run the same give it two quick throttle jabs it clears up runs fine going into town shutting off re-starting three times no issues until going home. I am going to pull the Dist cap in the morning maybe change the O2 sensor I got one used Bosch left?

Hagan said:

Have you checked the computer yet?

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Thanks for checking back

I haven't checked the computer yet I am not real good with electrical stuff. I am afraid if I move it I might mess more up. I feel what is going on is electrical and effects the spark of the plugs. What feel each time it is popping I can feel it in the throttle peddel its like it is running on 5 cylindars real hard bogging power loss. I do push the throttle down it goes into low gear brings the RPM's up but not moving very quick like 35mph not firing on one cylinder or two

So, you have evidence that the engine is running rich, but you're insistent that the problem is spark? And on the side, you're avoiding checking things that may be the actual source of the problem, because you're afraid you don't understand them?

Please take a step back and review the logic here. If you really want this fixed, you have to be systematic, and you absolutely must test things, not just replace them, especially not just replace them with random untested junkyard parts.

You've started 3 different lengthy threads, spent months, and thrown hundreds of dollars of unnecessary parts into this vehicle. Everyone keeps asking you to test things and report the results.

If you had, instead, put that much time and money into educating yourself on basic electronics and the use of a multimeter, you could teach vocational electronics at the local high school by now.

If you won't get a multitester and do the tests, you'll never fix this truck, except maybe by accident.

Don't worry if you don't understand it, all you have to do is follow basic instructions and report the results. But first and most importantly, you must commit to approaching the electrical parts of the problem.

Spott said:

So, you have evidence that the engine is running rich, but you're insistent that the problem is spark? And on the side, you're avoiding checking things that may be the actual source of the problem, because you're afraid you don't understand them?

Please take a step back and review the logic here. If you really want this fixed, you have to be systematic, and you absolutely must test things, not just replace them, especially not just replace them with random untested junkyard parts.

You've started 3 different lengthy threads, spent months, and thrown hundreds of dollars of unnecessary parts into this vehicle. Everyone keeps asking you to test things and report the results.

If you had, instead, put that much time and money into educating yourself on basic electronics and the use of a multimeter, you could teach vocational electronics at the local high school by now.

If you won't get a multitester and do the tests, you'll never fix this truck, except maybe by accident.

Don't worry if you don't understand it, all you have to do is follow basic instructions and report the results. But first and most importantly, you must commit to approaching the electrical parts of the problem.

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Thank You

You got a good point there I spent way to much money on this and have gotten no where. I got a Napa & Oreilly auto parts here in town see if I can get a Multitester or Multimeter. Once I get one what should be tested first? once I figure how to use it right

I'd start by testing the battery voltage with the engine off, then while idling when warmed up, and then while misfiring. Get a basic digital multimeter, set it to 20 VDC, and put the red probe on the + battery terminal, and the black probe on the - terminal, then note the displayed value in each case.

Also, pull the computer, take the cover off, and visually inspect for damage or discoloration.

Let us know the results and we'll provide further suggestions.

Thank you guy's so very much

I bought a digital Multimeter and did the battery test as Spot said. Here are the results below

Motor off cold 12.51
Motor running normal temp 14.23-24
Popping normal temp 14.21
Alternator light on 14.19-20

Popping cold was 14.42-46 it misses on one cylender it seams like number 2. It pops at 800rpm's once I give more throttle it smooths out sitting. The pop noise sounds like a pop in a can sorta. Also my Alternator light comes on and off but the volts seam to not drop off to much. I still need to check the computer

Make sure to pull the battery terminals before removing the computer

Hagan said:

Make sure to pull the battery terminals before removing the computer

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Thank you Hagan

I appreciate all of you taking the time to help on this issue. I will disconnect both terminals before doing anything. I will get it out remove the cover look it over real good. Once I do will post here I wish I had a way of taking in depth photos and posting them here. I am on dial up computer and have a 1980's push button phone no cell service its like the dark ages here in the sticks