'86 B2 2.9 miss at ~3200 RPM

[G8orFord]

Got the TPS installed. No difference. I'm lost on this one. Any help is appreciated.

Edit: One other thing of note. If you floor it in the shop, it goes right past the miss RPM. I haven't tried to see if it will hold against the limiter, because I'm not sure it even has one and I don't really want a block with windows.

 

[rusty ol ranger]

Got the TPS installed. No difference. I'm lost on this one. Any help is appreciated.

Edit: One other thing of note. If you floor it in the shop, it goes right past the miss RPM. I haven't tried to see if it will hold against the limiter, because I'm not sure it even has one and I don't really want a block with windows.

I wonder if you got an injector being screwy maybe??

 

[G8orFord]

I wonder if you got an injector being screwy maybe??

Anything is possible I guess, but they're brand new injectors and replacing them made no difference from the originals. Which I learned after the fact had already been cleaned.

 

[RonD]

Warm up the engine shut it off and then unplug the SPOUT connector
Restart and go for a drive
There WILL BE a hesitation as there is no "Vacuum advance"/Load spark advance when accelerating so slowly get up to speed, 2,500rpm and see if missing is still there, or at any higher RPM

The TFI module does RPM spark advance on its own, like old distributor's did with springs and spinning weights
Vacuum advance was Load advance, and the computer does that with TFI via the SPOUT wire

This would be an ODD failure, Computer's load spark advance causing an issue that is RPM specific

But grasping at straws here

 

[G8orFord]

Warm up the engine shut it off and then unplug the SPOUT connector
Restart and go for a drive
There WILL BE a hesitation as there is no "Vacuum advance"/Load spark advance when accelerating so slowly get up to speed, 2,500rpm and see if missing is still there, or at any higher RPM

The TFI module does RPM spark advance on its own, like old distributor's did with springs and spinning weights
Vacuum advance was Load advance, and the computer does that with TFI via the SPOUT wire

This would be an ODD failure, Computer's load spark advance causing an issue that is RPM specific

But grasping at straws here

I'll give that a shot, but it'll have to wait a day or two. Just a FYI though, this is the second ECM, with no change. Both Autozone parts. However, I don't know if either one was the correct ECM since I never saw the original. Not sure how many strategies or whatever there may have been back then.

 

[RonD]

I missed the changing of the ECMs so an even longer shot, lol

 

[rusty ol ranger]

I'll give that a shot, but it'll have to wait a day or two. Just a FYI though, this is the second ECM, with no change. Both Autozone parts. However, I don't know if either one was the correct ECM since I never saw the original. Not sure how many strategies or whatever there may have been back then.

Should just be manual/auto and fed/cali emissions

 

[G8orFord]

Could the O2 sensor have any effect on this?

 

[rusty ol ranger]

Could the O2 sensor have any effect on this?

Doubt it

 

[G8orFord]

OK, pulled all of the plugs and re-gapped to 0.043". They were all about 0.060" and all look fairly new and clean. Ran a compression check on all cylinders while the plugs were out. The numbers ranged from 140 to 160 psi. Put my new plug wires on just for sh!ts and giggles. The ones on it were basically new. No change.

I truly believe this is spark related, but unless the new distributor I installed has the same problem as the original one, I can't figure out how it can be spark. Still open to suggestions.

 

[Uncle Gump]

I think I would probe the TPS signal wire and ensure there is no flat spot.

Being that it happens during light load... I would ensure the vacuum line to the MAP is good... then try a new MAP.

I didn't re-read the thread... maybe you already did this.

 

[rusty ol ranger]

Youve checked for intake leaks havent you?

 

[G8orFord]

I haven't probed the TFI signal. Not even sure I'd know how. I have replaced the MAP sensor, but checking the vacuum to it sounds like a good idea.

 

[G8orFord]

Youve checked for intake leaks havent you?

Yes, as best as I can, but it's hard to believe an intake leak wouldn't show its face until 3000 RPM. I'm not ruling anything out at this point though.

 

[rusty ol ranger]

Yes, as best as I can, but it's hard to believe an intake leak wouldn't show its face until 3000 RPM. I'm not ruling anything out at this point though.

Ive had carb base gaskets not leak untill up in the RPM's....not saying thats the case here but it might be worth a look.