Issue/advice.

[B12]

Have a 1988 ford bronco 2 2.9L. Recently I purchased it from an individual who used it as farm vehicle for awhile. I ran into one issue I can’t figure out myself. When I turn on the headlights or A/C, the vehicle will not go over 2000rpms and will basically backfire or hesitate bad. When I turn the headlights or A/C off , it will go over the 2000rpm limit but won’t go over 2500rpm. I have replaced the TPS sensor, MAP sensor, in tank fuel pump , fuel filter, on line fuel pump, battery, alternator, starter, headlights, idle air sensor, plugs, plug wires, cap. Any advice on this situation?

 

[superj]

Are all your grounds good? Grounds being dirty, or missing, can cause some odd issues

 

[B12]

Only grounds I have cleaned/replaced was the negative on the battery. Had the alternator and battery tested this evening and everything checked out. I’m not sure if something else I can’t see is grounded somewhere.

 

[rumblecloud]

Quote from RonD on Grounds:

Ground Straps

Just as a heads up, ALL the metal parts of a vehicle are painted BEFORE assembly, and alot of the panels have rubber washers/grommets when assembled, so they are NOT grounded just because they are bolted together

The engine and transmission sit on rubber mounts so the main ground cable on the engine doesn't give the frame or body any ground connection

Battery negative is the Ground of course, its larger cable should go to the engine because the starter motor and alternator use the largest AMP loads

There should also be 1 or 2 smaller ground wires on negative terminal, they go to the metal inner fender and metal rad support, they are for headlights, horn and engine fuse box relay grounds

The back of the head ground to firewall is important as that grounds all the cab electrics

There should be a ground strap under the cab to the frame, and a ground strap under the bed to the frame, both on drivers side frame rail
These pass the ground from the engine/firewall to the frame

You can add a ground strap from engine to frame at the motor mount or where ever you can find an easy place to do it
Engine moves of course, so strap needs to have slack
This will give a double ground path for the cab and tail lights

The ground on the bed is for safety, i.e. no static charge when filling up

A Ground is only as good as its connection, need bare metal, no rust or corrosion
Best practice is to sand area(bare metal), put on ground strap then paint over it as needed

The main ground is usually on starter motor bolt, and that area can get oily, so wipe it down as best you can, the bolt and the surfaces and the cable end, so it will have a good bare metal connection

 

[B12]

Thank you , I will look at everything this evening.

 

[dvdswan]

Welcome to the site.

 

[4x4prepper]

First thing I would have done is put a known good TFI module on it. Because when it goes bad, it can cause a bunch of weird codes to be thrown or cut out like the older (bad) duraspark modules would with no codes or just simply die. Though with the older DS module, if you let them cool off, you could still drive okay.

Run some test leads from the battery to a DVM inside the cab and see if your problem is voltage related when hitting the 2500 rpm limit, even with the new alternator.

If an automatic, I would make sure the TQ converter clutch is working properly. Manually shift through the gears from a dead stop and see if 2nd is out. It may be a bad torque converter.