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LOOK AT MY NIPPLES!
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Discussion Starter · #1,442 ·
I’ve put some miles on the truck this week, and things could be better. There’s a major misfire I’m having trouble tracking down. First and second gear are ok, but higher gears, at higher rpms, it misses bad. I wrecked a couple of the old plug wires back when I swapped the head. So I made and installed new ones. No difference. Pulled the plugs, and they all looked good. Light grey/tan, no deposits, no soot. They only had maybe 5k on them. I decided to replace them anyway.

New vs old. Seems I’ve been running the wrong plugs the last few years. I figured this was my answer. Nope. Replaced the coil, as I had a new one on hand. Still no real change. It does seem to improve very slightly as I drive it, so I’m thinking maaaaaaaybe it’s an issue with the EFI, and it just has to learn? But it’s definitely an ignition misfire. I can see the AFR on the screen, and watch it drop from 13-14:1 down to 9:1 as rpms increase until it finally misses so bad it stops accelerating. If I push through, it’ll eventually smooth back out most of the time. If I downshift and get the rpms way up, it immediately stops and runs fine. I’ve got all the stuff to get rid of the ignition module and vacuum advance, and run the timing off the EFI, so I think that’s my next step. If that doesn’t help, I’m really lost as what to do next.
 

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B4U Task Force Admin
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30,347 Posts
I’ve put some miles on the truck this week, and things could be better. There’s a major misfire I’m having trouble tracking down. First and second gear are ok, but higher gears, at higher rpms, it misses bad. I wrecked a couple of the old plug wires back when I swapped the head. So I made and installed new ones. No difference. Pulled the plugs, and they all looked good. Light grey/tan, no deposits, no soot. They only had maybe 5k on them. I decided to replace them anyway.

New vs old. Seems I’ve been running the wrong plugs the last few years. I figured this was my answer. Nope. Replaced the coil, as I had a new one on hand. Still no real change. It does seem to improve very slightly as I drive it, so I’m thinking maaaaaaaybe it’s an issue with the EFI, and it just has to learn? But it’s definitely an ignition misfire. I can see the AFR on the screen, and watch it drop from 13-14:1 down to 9:1 as rpms increase until it finally misses so bad it stops accelerating. If I push through, it’ll eventually smooth back out most of the time. If I downshift and get the rpms way up, it immediately stops and runs fine. I’ve got all the stuff to get rid of the ignition module and vacuum advance, and run the timing off the EFI, so I think that’s my next step. If that doesn’t help, I’m really lost as what to do next.
how about Holley Tech Support?
 

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Registered
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56 Posts
There isn't much I'd consider parting ways with for "Clarice". (Yes my trucks get names somehow) But that little half ton is very good candidate. Good look, very good look.
 

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Boozebag
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9,968 Posts
Pants... is it easy to put the carb back on and run it that way temporarily? If it cures the missfire issue, you have a head start on the next step to a solution (?)
I think Pro ^^^ has the symptom down.
 

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LOOK AT MY NIPPLES!
Joined
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3,743 Posts
Discussion Starter · #1,448 ·
Carb has looooong been sold. I took it on a long highway run Saturday, and it’s been improving since then. Yesterday I downloaded the EFI software to a laptop, and logged the data while making a couple runs. I need to familiarize myself with it some, but so far it doesn’t really tell me anything I didn’t know. AFR drops as rpms increase in higher gears, until it misses. I’m gonna give it a few more days and see if it is just an EFI learning curve.
 

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1991 Irregular Cab Short-Short Bed
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370 Posts
Does it have to be put into a special "learn mode" in order to do the self tuning? Or does it try to learn all the time?
Seems to me that it should be able to dial out the 9:1 AFR pretty quickly.
 

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LOOK AT MY NIPPLES!
Joined
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3,743 Posts
Discussion Starter · #1,450 ·
It’s constantly learning and adapting. It learns a base fuel map pretty quickly, but things like WOT and other parameters can take a while to dial in. Last year, the issue was it going super lean and wanting to stall as I came down to a stop. But it hasn’t done that once yet this year.
 

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Boozebag
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9,968 Posts
If you still have a problem, I can lend you a carb to experiment, but it seems as though the system will self correct.
Time will cure all hopefully.
 

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LOOK AT MY NIPPLES!
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3,743 Posts
Discussion Starter · #1,452 ·
Very productive day. Finally got the misfire issue solved! Bad ignition module. I think it’s been weak for quite a while, as I always had these symptoms, just at higher rpms. I just thought it was valve float, with the beefy cam and stock valve springs. I guess at higher loads the spark was getting weaker and weaker until it got so weak or the mixture got so rich it just stumbled and bogged. Now it’ll rev to 5k, and be happy to do it.

Finally got to replace the window channel rubbers.

35 year old dried out garbage.


New not dried out garbage. No more rattling windows and wind noise, and water leaks every time it rains.
Not nearly as easy of a job as I hoped. Had to pull the door panels back off. Half a can of silicone spray, a couple hours, several cuts and scratches, and it was done. Worth it though.
Then I spent the rest of the afternoon giving it a deeeeeep clean.

Interior has never been this clean. Seats look just about new.



Scrubbed all the dirt and mildew out from the grille and underside of the hood.
Then gave the rest its usual scrub down. This truck has never been this clean. In the literal, dirt-free sense, and the overall neat and tidy, finished sense.

It’s embarrassing to think I used to consider this ‘low’…
Going to a big show tomorrow at the local racetrack. Should be fun.
 

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Boozebag
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9,968 Posts
Pantaloons - Has the FI learned enough to graduate kindergarten? 🤪

Seriously, how has the head and other recent engine mods added up?
Interested to know if there is a substantial difference in performance.
 

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LOOK AT MY NIPPLES!
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3,743 Posts
Discussion Starter · #1,458 ·
EFI is doing fine. I haven’t really got on it since replacing the ignition module. It’s got a little more balls, but definitely not $1800 worth. I should’ve just put stiffer springs on the EFI head and installed it. Live and learn, I guess.
 

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LOOK AT MY NIPPLES!
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3,743 Posts
Discussion Starter · #1,459 ·
Got started on the inside of the bed yesterday.
Started with some off the shelf trailer fenders.


Opened up one corner and closed in the other to more closely match the shape of the wheel openings.



They ended up not being as wide as I really needed. Luckily the original pair that FedEx lost 3 weeks ago, that the company sent replacements for, showed up Friday afternoon. So I was able to cut one up and widen them a few inches.


I’m feeling extra lazy today, so I’m not sure if I’ll get any more done. Maybe just trim down the front of the fenders, set them in place and mark where I need to cut the bed. Fuel cell needs to be moved forward a couple inches, but is still half full. I don’t feel like getting covered in gas today.
 

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Boozebag
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9,968 Posts
^^^ I know the feeling too well.
It's been 100*+ here for the last 6 days. 105* yesterday. Probably seen it on national TV.
I really feel like sweating like Niagara.
At least I installed 1/3 of the A/C in my truck. :rolleyes:

There's always next weekend Monsieur Pontalons...
 
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