1987 Bronco II--transmission problem, or??

[teknurd]

I have a problem that has yet to be resolved...
History:
I purchased a low mileage (76k) 1987 BII, non-running. It had been sitting for a long time and required a bit to get it running again. New head gasket, new fuel tank and sending unit, lots of new sensors, new radiator, new filters, the list goes on.

The engine runs strong. My problem is with uneven power. What I mean by that is if the truck shifts into 4, I will never get above 45MPH, floored. If I shift it down, the engine has a higher RPM and will gain speed. In addition, if I take off from a dead stop in 1st, it is VERY sluggish until the engine's RPM gets higher (sorry, don't have a tach so I don't know what the magic RPM level is). It starts really taking off at higher RPM.

My thought is that perhaps I have a bad torque converter (could it go bad due to sitting for 10+ years?), or maybe the entire trans. The truck shifts between all gears just fine, so I suspect that the tranny is fine. Do you have any suggestions on what to check or where to look?

 

[RonD]

Welcome to TRS

Reads more like lower compression or spark timing issue, assuming new fuel filter

1987 2.9l will use a TFI ignition which uses the engine computer to replace the "vacuum advance" used on older ignition systems

The system will have a SPOUT(spark out) connection near distributor on passenger side of lower intake usually
This is the "vacuum advance" signal from computer to TFI module
It has a connector that must be unplugged to set Base Spark timing at 10-12deg BTDC, then plugged back in for best power
If it was left unplugged or ???, then engine will run fine with RPM advance but lack power

So I would find and check SPOUT connector, reset base spark timing and see how it goes


You can test compression just to take that off the table, 2.9l ran 9:1 ratio so 145-155psi with cold engine


I wouldn't think bad torque converter with described issue, if RPMs were going higher without increase in speed then could be torque converter is not locking up
You have an A4LD automatic with a locking torque converter, the computer locks the torque converter above 35MPH for better MPG so you should feel direct engine connection at that time, i.e. when you take foot off the gas pedal going downhill the engine rpms don't drop to idle, engine stays connected to transmission so rpms stay high until MPH gets lower

 

[teknurd]

@RonD Thank you so much for your response! I appreciate the assistance. I will check the timing, there has been so much that has been done to the vehicle that it could indeed be off. I will keep you posted with my progress! Thanks again!

 

[Shran]

I agree with Ron that it sounds like a timing issue. Let us know what you find.

 

[teknurd]

@RonD @Shran are you able to clarify for me which timing mark I should be using? The balancer has two marks on it. From the front of the engine, is TDC the left mark or the right mark? I don't know if you're familiar with what I'm referring to, but I am told that the left mark is TDC, and the right mark is 30 degrees BTDC. So, if that is correct, should I paint a mark 1/3 of the way between the two notches in order to be 10 degrees BTDC? I really hope this makes sense. The Haynes manual has very little info on what the marks represent. Thanks for any help you can provide!

 

[RonD]

Have a look here: https://www.therangerstation.com/fo...0-degrees-before-top-dead-center-issue.81074/


The 2.9l pulley should have a T|C line and then smaller lines every 2deg to the drivers side, on some there will be a 1|2 for 12deg BTDC

You can use emory cloth, steel wool, scotchbrite, ect......to clean off the pulley then wipe it down and put some paint on it, then wipe off the paint, it should leave paint just in the lines making it easier to read with timing light

 

[teknurd]

@RonD you rock! I took some steel wool to the pulley and BLAM, there the 1|2 was, staring me right in the face. Thank you for helping a "YouTube Mechanic" in figuring this out LOL. Sometimes I think I should stick to computers, that's what I'm really good at!

It started snowing (spring has not yet arrived in Colorado), so I'll dig into this when it's a bit warmer, probably in the next day or two. I'll keep you posted, and thanks again!

 

[teknurd]

Hey guys. So the base timing was smack on T|C. I adjusted it to 12 deg BTDC, and it is much, much better!
Hopefully this is the last little gremlin on this truck. You guys sure were helpful, so thank you!

 

[RonD]

Good work

Thanks for posting what worked, it will some someone else one day