Performance issues... 4.0

[lil_Blue_Ford]

Ok, so my Choptop. 1989 Bronco II and I swapped in a 4.0 OHV years ago. Pretty sure the engine harness is from a 91 Ranger. I had run it on an automatic transmission computer for years and it got 12-14 mpg and ran rather rich. Couple months ago I bought a reman manual transmission computer for a 91 4.0 Ranger and a new oxygen sensor. After putting both in it ran better than ever and fuel economy jumped up. I'm not sure how much because I was on a partial tank when I did the swap and before I was able to do a full fill up things went bad. Exhaust is headers to 2.5" stainless single with a universal cat and Flowmaster 10 series (I had asked the exhaust shop to supply the cat and requested a Flowmaster 40 or Super 44 but they did what they wanted).

I also decided to install a heavy duty headlight harness upgrade which resulted in discovering that my radiator was leaking again. The repair there was to go to an aluminum rad and an electric fan because, well, I had them. Originally I had planned on putting them in my 88, but needing to keep this thing on the road, so yeah. I don't know if that had an influence on things or not.

Fuel tank, pump, lines and filter were all replaced within the last year to year and a half. IIRC it's an Airtex pump assembly. Plastic tank. New vent and grommet. fuel lines are -6an PTFE and 3/8" aluminum. Vent line is 1/4" Ni-Copp.

When I connected the battery back up after doing all of the electrical, it ran rather rough for awhile. I want to say that it did that when I replaced the computer as well and it took a drive cycle to smooth out but I'm not sure. I don't remember when I last replaced any sensors but most have been replaced at some point or other and I probably put a new thermostat in when this motor went in which was about 2 years ago. Sensors were off the previous motor though. I can warranty out sensors though.

No CEL showing but I pulled KOEO codes. I got a 23 which is a TPS error (I'm not having drivability issues and the TPS was replaced years ago), and a 67 which is an AC clutch issue.

I did pop open the reman computer and take a look. Didn't see anything obvious. Board looked a lot different than the old computer with a lot more surface mount stuff.

Right now it's stupid cold out so I'm waiting to try replacing some sensors and doing diagnostics. Right at the moment just trying to build a plan of attack to figure this out. It's getting really annoying not having this doing what it should. I'll take suggestions on what to check and diagnostic information at this point and will report back as I figure things out in between the weather being crap. I do have a decent set of diagnostic tools.

 

[lil_Blue_Ford]

@bobbywalter , sorry I didn't get this posted yesterday, things happened.

 

[bobbywalter]

temp gun on cylinders.

valve event check.

91 assumes bank fire no cam sensor possible bap sensor.

bap sensor can definitely affect power delivery.

 

[lil_Blue_Ford]

temp gun on cylinders.

valve event check.

91 assumes bank fire no cam sensor possible bap sensor.

bap sensor can definitely affect power delivery.

Temp gun is no problem.

No cam sensor is correct.

I’m also working on exploring my electrical connections from back when I put the 4.0 in the rig and trying to clean some stuff up on it. May not be THE problem but it is a problem. This thing is a bit irritating, I fix problems that have existed for awhile and things work better for a little bit then go back to the way they were or worse and I’m suddenly chasing another problem.

 

[bobbywalter]

will still be operationally more reliable longer than anything rolling off of a production line today.

i am ok with good enough more than i should be i suspect.

 

[lil_Blue_Ford]

will still be operationally more reliable longer than anything rolling off of a production line today.

i am ok with good enough more than i should be i suspect.

I guess I should be amazed that so many problems were apparently masked by other problems for an incredible amount of time and the dang thing mostly did what it was supposed to other than eating motors.

 

[Shran]

You know to do the normal stuff... fuel filter, clean the MAF, inspect plugs, correct vacuum leaks, fuel pressure test when running and see if it leaks back over time, etc

I would zero in on that TPS code first. Check your voltages there, sensors do go bad but could indicate a grounding issue or sensor out of alignment.

I googled code 67 and it sounds like that's a clutch pedal/neutral safety switch thing...? Probably ignore that for now.

 

[lil_Blue_Ford]

You know to do the normal stuff... fuel filter, clean the MAF, inspect plugs, correct vacuum leaks, fuel pressure test when running and see if it leaks back over time, etc

I would zero in on that TPS code first. Check your voltages there, sensors do go bad but could indicate a grounding issue or sensor out of alignment.

I googled code 67 and it sounds like that's a clutch pedal/neutral safety switch thing...? Probably ignore that for now.

Filter should be good since it was replaced not long ago. I’ll go through things a bit though.

Interesting that you mention the clutch switch, in trying to sort through my spliced wires apparently at least one of my splices is a wire for that. May be some of my problems just in old splices.