Surging with tip in...UPDATE-SOLVED!

[rusty ol ranger]

86 B2 2.9L

Cold it wont do it.

Warmed up, and just a slight tip in of the gas pedal, itll start surging bad. Doesnt do it at idle, nor above that point.

I can literally make it do it at will by holding the throttle at the right point, and unplugging/plugging in TPS.

I replaced the TPS...no change.

I should add that if i hold it long enough (about 15 seconds) and allow it to surge it straightens out.

Its just annoying cause its right about where you hold the throttle to let up on the clutch...so take offs are jerky unless you go a bit harder on the throttle

Any ideas?

 

[SenorNoob]

Dead/sticky spot in the IAC?

 

[franklin2]

You may have a problem with the neutral switch on the trans or the clutch switch. These old EFI systems did not have a speed sensor. They put the computer in some sort of different fueling strategy depending on if you are in gear or the clutch is in engaged. When I swapped a 86 2.9 EFI into my 84 BII, I ended up having to jump that computer terminal out or it would do the same thing yours is doing. I ended up permanently jumping pin 30 to ground.

I think if you google eeciv pin 30, you will get some more info on it. The early mustang guys have had problems with this also.

 

[rusty ol ranger]

Dead/sticky spot in the IAC?

I was wondering this. It seems to idle low at times. But im not sure if its actually idleing low or its just so quiet compared to my ranger its throwing my ear off.

You may have a problem with the neutral switch on the trans or the clutch switch. These old EFI systems did not have a speed sensor. They put the computer in some sort of different fueling strategy depending on if you are in gear or the clutch is in engaged. When I swapped a 86 2.9 EFI into my 84 BII, I ended up having to jump that computer terminal out or it would do the same thing yours is doing. I ended up permanently jumping pin 30 to ground.

I think if you google eeciv pin 30, you will get some more info on it. The early mustang guys have had problems with this also.

Hmm...interesting. i never heard of that before. If there is an issue with that switch wouldnt it start in gear without clutch down? Or not start at all?

But yes ill for sure keep that in mind

 

[SenorNoob]

Hmm...interesting. i never heard of that before. If there is an issue with that switch wouldnt it start in gear without clutch down? Or not start at all?

Not necessarily. Depends on where/how the circuit is broken. I need to look at that circuit myself sometime. I don't have a neutral switch so idk what the computer is thinking right now. I just use the clutch to start it.

 

[rusty ol ranger]

Not necessarily. Depends on where/how the circuit is broken. I need to look at that circuit myself sometime. I don't have a neutral switch so idk what the computer is thinking right now. I just use the clutch to start it.

That switch is down on the tranny right?

 

[franklin2]

It's up high on the trans around the shifter. You can't actually see it unless you take the shifter out. It has nothing to do with starting. The starter interlock is on the clutch pedal only. This switch on the trans is hooked in parallel with the one on the clutch. The clutch switch has two or three sections to it. One is the starter interlock. The other is this computer circuit. And then the third is for the cruise control if you have it. I am not looking at the diagrams, so this might be a little off.

 

[rusty ol ranger]

It's up high on the trans around the shifter. You can't actually see it unless you take the shifter out. It has nothing to do with starting. The starter interlock is on the clutch pedal only. This switch on the trans is hooked in parallel with the one on the clutch. The clutch switch has two or three sections to it. One is the starter interlock. The other is this computer circuit. And then the third is for the cruise control if you have it. I am not looking at the diagrams, so this might be a little off.

Anyone got a diagram for it? I dont even know what to search for on that....or where to start.

 

[rusty ol ranger]

Found this. But it looks like on a manual the wire dead ends after the clutch switch?

 

[SenorNoob]

It continues on through the box that says "Automatic only" then to splice 121 and out to the starter relay and the box labeled "solid state" Guessing that is the PCM?

So that diagram is showing 2 possible paths in that box. Depending on whether you have a manual or automatic.

 

[rusty ol ranger]

It continues on through the box that says "Automatic only" then to splice 121 and out to the starter relay and the box labeled "solid state" Guessing that is the PCM?

So that diagram is showing 2 possible paths in that box. Depending on whether you have a manual or automatic.

I think solid state is reffering to the TFI? This is confusing as hell to me.

I went out and tried starting it in gear with clutch out it didnt start.

Next time im out i guess ill try tracing the circuit. I cant say for sure but it seems like when i pulled codes something came up for a neutral switch, or clutch position switch...i ignored it thinking it wasnt important.

Pry be thursday before i get out to piss with it again, but ill scan it and see if i get that code again.

 

[SenorNoob]

There is a point in the test where it expects to you to press the clutch.

521	(R) Wheel not turned during test or PSP problem – PSP
522	(O) Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault – PNP
	transmission MLP sensor out of range in park – Transmissions
524	Problem in low speed fuel pump circuit – Power / Fuel Pump Circuits
525	(O,M) Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault – PNP
528	(M) System shows voltage at pin 10 (is A/C on ?) or pin 30 (PNP, CPP switch) – PNP

67​	Park/Neutral circuit fault – PNP
​	Transmission Manual Lever Position (MLP) sensor circuit – Transmissions
​	(M) Intermittent Park Neutral Position (PNP) sensor fault – PNP

 

[rusty ol ranger]

There is a point in the test where it expects to you to press the clutch.

521	(R) Wheel not turned during test or PSP problem – PSP
522	(O) Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault – PNP
	transmission MLP sensor out of range in park – Transmissions
524	Problem in low speed fuel pump circuit – Power / Fuel Pump Circuits
525	(O,M) Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault – PNP
528	(M) System shows voltage at pin 10 (is A/C on ?) or pin 30 (PNP, CPP switch) – PNP

67​	Park/Neutral circuit fault – PNP
​	Transmission Manual Lever Position (MLP) sensor circuit – Transmissions
​	(M) Intermittent Park Neutral Position (PNP) sensor fault – PNP

Thats probably why i disregarded it

BUT...

On my ranger i never hit the clutch and dont get that code.

Maybe i left it in 1st when i did the KOEO test?

One other question....this wouldnt possibly be an EGR issue could it? Reason i ask is i did get an EGR code when i scanned it but i found a broken wire at the plug to the pulse sensor. I fixed that assuming that was the cause of the code but never rescanned it.

 

[rusty ol ranger]

Figured it out.

It was the frickin ECM. I swapped the ECM with the one from rusty #2 (which is running an 88 ECM to get rid of EGR/Knock).

Its running like a top (so far). Zero hesitation and idles so smooth i set an empty gatorade bottle on the plenium and it didnt fall off.

I always had a feeling that old ecm was iffy. Just a gut feeling.

The bronco always seemed like it stalled easy coming off the clutch compared to my ranger. But i figured with bigger tires, more weight, 4wd and the higher mitsu 1st (compared to the TK in my ranger) coupled with the same axle ratio (3.45) was why.

ECM change took care of that too. Its literally running like a new truck.

Thanks for the help guys.

 

[bobbywalter]

yeah. sad part there.... no telling how long that will last. they are old.

ms3.