Hi all,

Need some help on getting this truck running right. I've got a 95 f150 that originally came with a 5.0 4r70w. Came across a "deal" on a 5.8 from a 92 and it quickly turned into a nightmare.

Current situation: I had a reputable shop install a jasper 5.8 as I was in somewhat of a time crunch (impatience). They seemed to have done good work, but it never really ran right after start up. Initially it ran really rough and they backed timing back to 8 degrees.

Since then, it runs relatively well but has a sputter/miss when accelerating. Especially after getting to normal operating temps. Since the new jasper engine, I have personally replaced the injectors (south bay rebuilt Bosch III), alternator (2g motorcraft), all vac lines, intake plenum (had a small crack) and gaskets (including TB), spark plug wires (verified routing to avoid crossfire), new intake air temp sensor (standard as nor MC available), new TPS (motor craft). Haven't replaced the ECT sensor. It was replaced a few years back.

Additional/random info:

1. Noticed that there is what looks like an air temp sensor in the lower intake of the new engine. It has a sensor and is plugged in. This is in addition to the newly installed sensor in the air box. Not sure what to make of this.

2. The injectors were replaced due to a long crank after shutting the truck off warm. I figured one was leaking. This fixed the long crank and the truck seemed to idle and run better. Still has the sputter/miss when accelerating after warm.

3. I've noticed that the oil pressure gauge seems to fluctuate at times. Never drops into the red, but normally stays between the "n" and the white line before the red zone. 4. It's seemed to run warmer since the new engine. It was flushed and all new coolant. One day it started blowing coolant through a new cap when idling after a while. I ended up replacing the fan clutch and installing a new cap. Haven't had an overheating issue since, but still seems to run warmer than my 94 5.8. The 94 never makes it past the "o" in "normal" the new engine in the 5.8 seems to hang between the "m" in "normal.

4. All emissions were deleted. Tab/tad solenoids are there and vac lines plugged. EGR valve is there and plugged in, but it has a block off plate behind it to ensure no leak. Smog pump was deleted and bypass bracket is in place.

5. Running the KOEO test, I only received a 332 in the CM. 111 in the active memory.

6. Sometimes (prob more often than not) on cold start up after the idle comes down from 1k to about 800, the engine idle will bounce as if an IAC issue. Never really does it again after start taking off.

Honestly, I'm at a loss and am debating throwing a pimpx or squirt on it. Maybe that would help pinpoint what is causing the issue? Thanks in advance to any help y'all can offer.

 

‘95 was probably mass air (air sensor in the air box ) and the ‘92 5.8 would have been speed density (air sensor in the intake manifold) so what did they do ie what system are you using? I assume the ‘95 computer because you need that the run the transmission so is the mass air meter still there? You kind of lost me with the Jasper engine thing… is that engine still in the truck or the ‘92 engine?

 

Sorry, I should have clarified. It's still running the 95 5.0 MAF system. The air sensor I meant was the act or iat. It's on the lower intake manifold.

The jasper engine (roller f4te stamped) is in the truck. The original swap, a 92, ended up losing oil pressure. That's why I ended up going with the jasper.

 

So all of the engine wiring is original to your truck?

WIth the IAT in the airbox there would not be anything in the harness to plug into a lower intake IAT, so what have they done? Did they splice that sensor into the existing sensor wires so there are now 2 sensors in parallel? If so that is not going to work, I'd suggest you unplug that sensor.

 

Hello? OP, did you figure out the answer to this question?