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Old 05-04-2019, 01:30 PM   #1 (permalink)
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5.0L Backfiring and Missing/Low Power

The 5.0L in my beater Bronco II has been running like crap since I bought it last summer, but it has at least been drive-able until recently. I believe it is an '86 F150 engine based on the computer part number (as well as others that support an '86 model year) and the SPOUT connector.

When I bought it, it had a bad hesitation and would cut out completely under hard acceleration. It probably had a bit of a miss too, but the hesitation/cutting out was the most obvious. I ended up replacing both the fuel pumps which seemed to fix the hesitation/cutting out problem for the most part. The in-tank had a dead short and was popping fuses, and my fuel pressure was still dropping really bad on acceleration after I replaced it, so I replaced the high pressure pump as well.

The last time I had it out after replacing the high pressure fuel pump, it seemed to run run more or less alright for a few hours, but then a miss started that kept getting worse as I was towing a busted Toyota off the trail back to the tow rigs. By the time I got back to the trailer it was backfiring too and barely running good enough to load it onto the trailer.

When I got it home, I checked the plugs, wires, cap, and rotor. The plugs looked textbook good and were all gapped ~.44-.46. The wires all ohmed out good (the worst was ~8K ohms) and I didn't see any arcing when I fired it up at night. The cap and rotor had a good amount of carbon build up so I replaced them with no real change except maybe a bit smoother idle.

I checked the base timing and it was ~14, so I set it back to 10 with no real change. With SPOUT connected it seems like it wants to sit at ~24 with the base set at 10, which seems low since the repair manual I was looking at said it should be base timing + 203. The timing seems to jump around a bit with the SPOUT connected, and when I goose it, it sometimes drops below 10 and has a really bad backfire.

Just to experiment, I set the base timing to 20 since it seems like it is retarding too much and causing the exhaust backfire. It seemed to run a little better (still undrive-able), and didn't backfire coasting down a small hill in 3rd gear (NP435, so really more like 2nd gear) like it did with 10 base timing. I also experimented with ~5 base timing, but as you might expect that was even worse.

My vacuum is really good, ~15-16 inHg rock solid depending where the timing is set (I am at 7K feet, and my DD with 90K miles only pulls 14-15inHG).

The misfiring and backfiring also seems to be really sensitive to engine load, because when I rev it in neutral, it almost seems like it would be drive-able, but when I drive it, it misses and backfires really badly, and I can't build any speed trying to drive up a slight incline in 3rd gear at full throttle that I should have no problem lugging up in 4th.

I pulled codes and here is what I got:

KOEO
67 - Improper signals received from neutral safety switch
87 - Fuel pump relay circuit failure

KOER
41 - Oxygen sensor signal always lean
34 - EGR fault

The neutral safety switch was bypassed, so I reconnected it and it seems to work, but after leaving the battery disconnected to clear codes and retesting, I am still getting the code. I don't think this should affect anything though. The fuel pump relay was deleted by the previous owner who swapped the engine, so my pump runs constantly. I don't think this should affect anything either.

The 41 code seemed like a smoking gun, so I replaced the O2 sensor, but no change in the way it runs and I am still getting the 41 code. The EGR system seems to still be intact, but I am not sure how the EGR system would cause the engine to be running like this anyways.

So after all this, my gut feeling is that the distributor/ignition module has crapped out on me, but I don't have another laying around to test it, and I hate throwing parts at a problem hoping it will fix it.

Any ideas of what else I should test or look at? I am a 5.0L dummy so there could be something obvious I am missing. I am having trouble finding a good distributor/ignition module test method.

Edit: I forgot to mention that it fires right up no problem when I start it.

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Old 05-04-2019, 01:48 PM   #2 (permalink)
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Check fuel pressure 30 at idle 40 under load or no vaccum to the regulator.

Motor will Usually start breaking up with fuel pressures under 25 under load.

Ignition modules that go into limp mode will caues low power, you should be carring a spare, better spare is the whole distributer in case the pickup goes bad, speeds up trouble guessing.



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Old 05-04-2019, 02:01 PM   #3 (permalink)
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Quote:
Originally Posted by ransil View Post
Check fuel pressure 30 at idle 40 under load or no vaccum to the regulator.

Motor will Usually start breaking up with fuel pressures under 25 under load.

Ignition modules that go into limp mode will caues low power, you should be carring a spare, better spare is the whole distributer in case the pickup goes bad, speeds up trouble guessing.



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Thanks for the input. I haven't checked the fuel pressure since I swapped out the high pressure fuel pump since it seemed to cure the the cutting out/hesitation problem. I rented the fuel pressure gauge I used earlier, but maybe I should just buy one since they are available on Amazon for ~$25.

As I said, am leaning towards pulling the trigger on a distributor, but I would really like to be able to test it in some way to confirm it is bad before blowing money on one. Sure, they aren't that expensive, and having a spare may not be bad, but costs start adding up quickly when you start just throwing parts at things.

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Old 05-04-2019, 03:18 PM   #4 (permalink)
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So, I decided to double check the firing order and the firing order is 1-3-7-2-6-5-4-8 which is the '94+ firing order. I was told the engine was out of a '95 F150 when I bought it, but there is no MAF sensor, and all the external parts seem to be older (lots of E4 and E6 part numbers).

Here is a picture of the computer:


Here is a shot of the engine from when I drug it home:


So is this a '86 Mustang computer and distributor (E4ZE-12131-AA) on the engine?

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Old 05-04-2019, 04:04 PM   #5 (permalink)
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Im trying to solve a miss in my 5.0 swapped ford ranger myself.

Your motor is non ho if its a truck block. That will change firing order. Try the non ho firing order see if it gets better.
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Old 05-04-2019, 06:33 PM   #6 (permalink)
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I’m trying to solve a miss in my 5.0 swapped ford ranger myself.

Your motor is non ho if it’s a truck block. That will change firing order. Try the non ho firing order see if it gets better.
I've read your thread with great interest hoping to get something useful for my situation out of it. As far as the firing order is concerned, it is correct since it would only be firing on 4 cylinders if it weren't. This engine was running more or less fine for a while, then started running worse and worse over the course of about an hour of driving.

After playing with it some more, the timing is actually retarding as revs increase. I don't have a tach, but when I rev it, the advance actually drops to ~10-15 at what sounds like 3,000+RPM with no load. Is there a sensor that would prevent proper advance with RPM? Like I said earlier, when I goose it, the timing goes way retarded briefly, like below base timing retarded

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Old 05-04-2019, 08:31 PM   #7 (permalink)
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Originally Posted by '84 Bronco II View Post
I've read your thread with great interest hoping to get something useful for my situation out of it. As far as the firing order is concerned, it is correct since it would only be firing on 4 cylinders if it weren't. This engine was running more or less fine for a while, then started running worse and worse over the course of about an hour of driving.

After playing with it some more, the timing is actually retarding as revs increase. I don't have a tach, but when I rev it, the advance actually drops to ~10-15 at what sounds like 3,000+RPM with no load. Is there a sensor that would prevent proper advance with RPM? Like I said earlier, when I goose it, the timing goes way retarded briefly, like below base timing retarded
I believe the pickup would cause timing to not advance correctly. Im still a newb at engines. Hopefully someone in the know will chime in.
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Old 05-05-2019, 10:46 AM   #8 (permalink)
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I believe the pickup would cause timing to not advance correctly. I’m still a newb at engines. Hopefully someone in the know will chime in.
After further research, it looks like you really need an oscilloscope to properly diagnose distributor/ignition module problems, which I don't have.

I also found this thread where a guy seemed to be having pretty much the same issues in his '91 Mustang: https://forums.corral.net/forums/5-0...-clueless.html

He said swapping the ignition module out from a gray one to a black one fixed the problem. He said replacing the distributor as well as the gray ignition module didn't do anything, but the black one was the cure. I know there are 4 different Ford TFI modules (black or gray, 6 pin or 9 pin). I am not sure what the difference between the black and gray modules is, but I believe the black one is for newer applications.

I can get a brand new Cardone distributor (https://www.rockauto.com/en/moreinfo...133840&jsn=474) for ~$75 from Rock Auto, so I am thinking I'll just take the leap and get one. The only problem is I am not sure if I should get a gray or black ignition module, and whether I need the cast iron or steel distributor gear. If the longblock is indeed a '95 f150, it should be a roller right? And an '86 Mustang 5.0L H.O. would have had a roller cam, which is why the distributor works on my engine, right? More research is needed.

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Old 05-05-2019, 12:22 PM   #9 (permalink)
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I thought the black one was for the remote mounted TFI

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Old 05-05-2019, 12:43 PM   #10 (permalink)
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So it looks like I have a F1SE block with a date code of 4G28 (right above the starter).


From what I can figure out online that works out to a thunderbird block cast on July 28 of 1994. Man this engine is a real bastard Although it looks like the Thunderbird casting may have been used in the trucks post 1991 since I don't see a truck 302 casting number for the 1992-1996 truck models (E4AE is listed for '84-'91 truck)

So it looks like I should have a steel distributor gear (roller cam & H.O. firing order). The difference between the gray and black TFI ignition modules is how the dwell is controlled. Black is computer controlled dwell and Gray is controlled by the TFI module (https://www.stangnet.com/mustang-for.../#post-7673973). So since I have an '86 speed density computer it looks like I should go gray. The distributor gear should be steel since it looks like I have a factory roller cam motor.

I am going to go ahead and pull the trigger on the distributor and hope I guesed right and it solves my problem

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Old 05-05-2019, 12:45 PM   #11 (permalink)
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I thought the black one was for the remote mounted TFI

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So from my research, that is the 6 vs 9 pin TFI module. 9 pin is distributor mounted and 6 pin is remote mounted. See my previous post for gray vs. black.
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Old 05-05-2019, 03:32 PM   #12 (permalink)
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Okay, latest update:

From my research, I had concluded that my motor should be a roller cam motor, but when I pulled the distributor, it had a cast iron gear!




It looks a little chewed up, but nothing catastrophic. This dis-congruity led me to tear into the engine and pull out a pushrod to confirm that the motor was indeed a roller cam. Per this post (https://www.ford-trucks.com/forums/1...l#post12071619) it looks like I have a roller cam (6.25" pushrod vs. 6.75" pushrod for a flat tappet camshaft).



I am going to go order a gray TFI module, steel gear distributor. I will update when I get it installed. Hopefully this fixes it, this has been such a fucking headache

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Old 05-05-2019, 11:39 PM   #13 (permalink)
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the gear is possibly worn enough to potentially cause some issues..


push start module is somtimes a factor.. ccd/tfi.


if the pcm is reflashed/reman then its program may be different. the nds issue could be burned trace as well.


assuming it is running speed density, and the injector harness is wired right bank left bank as well...maybe just a bad connection on 58 or 59 pins..
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Old 05-09-2019, 05:01 PM   #14 (permalink)
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Well, my distributor came in today and I put it in after I got home from work and I still have the same symptoms

Back to the drawing board...
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Old 05-11-2019, 07:25 PM   #15 (permalink)
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Check fuel pressure 30 at idle 40 under load or no vaccum to the regulator.

Motor will Usually start breaking up with fuel pressures under 25 under load.

Ignition modules that go into limp mode will caues low power, you should be carring a spare, better spare is the whole distributer in case the pickup goes bad, speeds up trouble guessing.



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I threw a fuel pressure gauge on the truck today since I never checked the fuel pressure situation after replacing the high pressure fuel pump, and I wanted to rule it out as a cause.

KOEO was ~41 PSI
KOER was 35 PSI
KOER fuel pressure regulator vacuum line disconnected was 42PSI

When driving, it would hold at 38 PSI full throttle under load, and drop to ~30 PSI coasting in gear. When revving it it out in lower gears without much load, the pressure would crest 40 PSI. It was only when I gave it all it had it would drop to 38 PSI.

The strange thing is that after driving the engine long enough to get it up to operating temperature, the pressure dropped across the board and stayed down It idled at 30 PSI at that point and would go up to 38 PSI with the vacuum line to the regulator disconnected. Under heavy load, the pressure was in the 33-35 PSI range, and would drop pretty bad on a full throttle upshift (I think I saw it drop as low as 25 PSI). It seems like a pretty consistent 4-5 PSI drop across the board. Could the fuel pressure regulator be regulating the pressure inconsistently? It seemed to run a bit worse when the fuel pressure dropped to this lower range.

After driving it, I checked for leak down. After 5 minutes, the pressure didn't drop at all.

The other thing is that as I drove it, it seemed to start running better as the engine reached operating temperature and went into closed loop operation I presume. It is to the point that it is getting close to almost being drive-able, but is still running like shit. It is still backfiring pretty badly and down on power, but it at least has some pull under acceleration now.

I noticed when I disconnected the fuel pressure gauge that the gas looks pretty bad. It is amber in color and stinks like old gas. I've been topping off the tank every time I take it out since the fuel gauge doesn't work, but I have only been putting in a few gallons each time. I haven't given the tank a major fill up since I bought it in August last year, so who knows how old some of the gas that is still mixed in there is.

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Originally Posted by bobbywalter View Post
the gear is possibly worn enough to potentially cause some issues..


push start module is somtimes a factor.. ccd/tfi.


if the pcm is reflashed/reman then its program may be different. the nds issue could be burned trace as well.


assuming it is running speed density, and the injector harness is wired right bank left bank as well...maybe just a bad connection on 58 or 59 pins..
How can I tell if the ECM has been reflashed and if so what calibration it is running?

I figured that I could rule out the injectors with a cylinder balance test, but I haven't been successful in getting the computer to run a cylinder balance test when in diagnostic mode. I am not sure if there is an issue preventing it from running, or if I am just doing it wrong. The test manual I have says to wait about 10 seconds after the KOER test completes, then goose the throttle to get the engine at or above 2,500 RPM to initiate the cylinder balance test. As I mentioned earlier, I don't have a tach, so I am just doing it by ear, so maybe I am not quite revving high enough I also read a post on a Mustang forum that said you need to goose it immediately after the KOER test to initiate the cylinder balance test, so maybe I need to try that. The other thing that could be causing me issues is that my manual says to not go 100% throttle except for '86 models only. I have tried it both ways, but maybe I didn't hit 2,500 RPM when I was only doing partial throttle.


After doing a bit more research, it looks like the timing advance is affected by the EGR position sensor, and since I am getting a code 34 (EGR fault), it may be worth diagnosing the EGR system. From my reading, it also seem that the code 41 (Oxygen sensor signal always lean) may well go hand in hand with the EGR code. Still, the lean code has me puzzled since it seems to be running rich due to the exhaust backfires and the fact that is smells a bit like gas while it is running. It seems like it thinks it is lean and is way over-compensating with a really rich mixture.

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Old 05-12-2019, 11:39 PM   #16 (permalink)
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reman sticker would have a calibration number on it....the pic i see is a stock tag, speed density with rv code. any other stickers?


how is the engine wired? is it sefi or bank?







that computer looks like a truck computer to me based on the rv..... rv as i know it is a 5.0 bronco with manual trans. i remember rv...because i had one with a rv cam swap....that did nothing for the nutless pos.......lolz...

so if it is stock.... it is bank fire truck/bronco computer and wont respond to sefi cyl balance test. 4 injectors are pin 58...four are pin 59.


is there any other stickers? if it is a reman it should say who remanned it

and a flubbed injector or two is a bit more tricky to figure. and firing order may or may not be 351. there are regular firing order roller cams.


sorry to add more confusion...
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Old 05-13-2019, 05:34 PM   #17 (permalink)
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reman sticker would have a calibration number on it....the pic i see is a stock tag, speed density with rv code. any other stickers?


how is the engine wired? is it sefi or bank?







that computer looks like a truck computer to me based on the rv..... rv as i know it is a 5.0 bronco with manual trans. i remember rv...because i had one with a rv cam swap....that did nothing for the nutless pos.......lolz...

so if it is stock.... it is bank fire truck/bronco computer and wont respond to sefi cyl balance test. 4 injectors are pin 58...four are pin 59.


is there any other stickers? if it is a reman it should say who remanned it

and a flubbed injector or two is a bit more tricky to figure. and firing order may or may not be 351. there are regular firing order roller cams.


sorry to add more confusion...
Thanks for the info. I am an EFI newbie, so I am not sure id it is SEFI or bank, but based on the inability to do a balance test and the computer it sounds like it is bank. I am pretty sure the computer doesn't have any other stickers on it, but I will take a look at it the next time I am screwing with it.

I had an "aha" moment thinking maybe the timing chain was worn out and was causing my timing fluctuations and maybe it even jumped a tooth, but when I went out and checked crank rotation vs. distributor rotor rotation, I only have about 2 of total slop. That doesn't preclude the possibility of the chain jumping a tooth, but that is probably unlikely given how tight it is. Besides, my timing fluctuations are way bigger than just 2.

I am a TFI dummy, so maybe there is something I am not grasping here, but I set the base timing to 10 with SPOUT disconnected. When I rev the motor, the timing retards significantly, especially if I close the throttle quickly. Like 10+ significantly. My understanding is that with the SPOUT disconnected, there is no computer control of the timing. I also believe there aren't any flyweights in the TFI distributor like a mechanical advance setup. So why the hell is my timing changing with revs, and particularly, what is causing it to retard?

What could possibly cause the base timing to retard with the SPOUT disconnected? That seems to be the key to solving my problem.
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Old 05-14-2019, 08:49 AM   #18 (permalink)
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Your computer says:
E6TF-12a650-V1A

E = 1980
6 = 6
T = Truck
F = Electronics

You have a 1986 Ford F150/Bronco computer (barf).

that would go with your E5TE distributor (1985, close enough for ford).

The block F1SE is
F =1900
1 = 1
S = Thunderbird
E = Engine
1991 Thunderbird (also barf).

A thunderbird (non HO motors) and 5.0 truck (again not HO motors) use the non HO firing order.
1-5-4-2-6-3-7-8

I'd start by correcting your firing order.
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Old 05-15-2019, 11:47 AM   #19 (permalink)
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Your computer says:
E6TF-12a650-V1A

E = 1980
6 = 6
T = Truck
F = Electronics

You have a 1986 Ford F150/Bronco computer (barf).

that would go with your E5TE distributor (1985, close enough for ford).

The block F1SE is
F =1900
1 = 1
S = Thunderbird
E = Engine
1991 Thunderbird (also barf).

A thunderbird (non HO motors) and 5.0 truck (again not HO motors) use the non HO firing order.
1-5-4-2-6-3-7-8

I'd start by correcting your firing order.
I agree with you as far as the computer and distributor are concerned. What makes the truck/Bronco distributor bad (or barf as you put it)? I can understand the truck computer probably having a milder tune than say a Mustang computer, but what is the difference in the distributor? Regardless, I bought a new Cardone distributor through Rock Auto using an '86 Mustang as the application to get the steel distributor gear.

I disagree with you on your assessment of the engine though. Casting part numbers only got changed when design changes were made, so the casting part number is not necessarily indicative of the date of manufacture. According to the date code cast into my block, it was manufactured in July of 1994, which jives with the 1995 F150 5.0L claim the previous owner made. I already discussed this in my previous post, but you are correct that F1SE decodes as a Thunderbird casting but I believe this casting may have been used in the trucks as well since I can not find a truck-specific casting number for the '92-'96 model years. Not to mention the engine has a truck intake and it would be an odd piece to swap onto a non-truck engine. Again, I mentioned this in my previous post, but my shop manual states that '94+ trucks had the HO firing order and pre '93 had the non-HO firing order. My engine is definitely the HO firing order. The firing order doesn't magically change and cause a good running truck to start running like crap. Besides, if the firing order were wrong, the engine would only be hitting on four cylinders, and I doubt it would even start.

My engine fires right up and idles fine. It runs like crap because the timing drastically retards with RPM/load for some unknown reason. My harness is pretty hacked together so I am thinking my problem is some kind of short/grounding issue.

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Old 05-16-2019, 08:00 AM   #20 (permalink)
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If you fully believe it's a timing issue, I'd check the "Start" wire on the the TFI, to ensure it's ONLY getting power during cranking.
Then also check the Spout wire the runs from the TFI to the ECU for brakes or issues.
That and the computer, are all I can think of that control timing.
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Old 06-21-2019, 11:22 AM   #21 (permalink)
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If you fully believe it's a timing issue, I'd check the "Start" wire on the the TFI, to ensure it's ONLY getting power during cranking.
Then also check the Spout wire the runs from the TFI to the ECU for brakes or issues.
That and the computer, are all I can think of that control timing.
Man, it took way to long to get back to dealing with this. I was frustrated, so I just put this on the back-burner and have been busy with other things lately.

Anyways, this turned out to be my issue. I had full battery voltage to the "start" wire going into the TFI module while the engine was running I pulled the "Start" pin out of the connector for now and it is back to being drivable again and the timing doesn't drastically retard anymore. From what little I've read, it seems this is an ignition switch issue? It starts up fine with the "Start" wire disconnected, but I would like to fix it properly instead of just leaving the wire unhooked.

It is still backfiring out the exhaust a bit, and seems a little sluggish, but I am thinking it must be running a bit rich. Maybe it is the old gas Regardless, the truck is actually drivable now, so it isn't as big of a deal, but the backfire is annoying.
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Old Yesterday, 08:11 AM   #22 (permalink)
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If I recall right, that start signal sets it back to base timing, but I am not entirely sure, you need it hooked up however, then you can chase down the other issue, or hope they are related.
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