1999 4.0 OHV engine troubles

badams21523636 · Feb 9, 2018

I have this 1999 extend cab ranger, it’s a 4.0 OHV, 4x4, auto. I got the truck intending to flip it but found that I really like the damn thing and have decided to keep. Thus, the heartache begins. I put an engine in it and all seemed well. It was hard starting but ran ok other than the lean codes. Found the fuel pressure at 40psi. (not good) replaced the pump and filter and got 70psi upon cycling the key. Starts well now. The truck has had a miss since I got it on the road. After doing some investigation I found that the miss only happens in the 2500-2600 RPM range. It happens in all gears and can be duplicated in park with no load on the engine. Searching the forums I have looked into all the usual culprits and just can not resolve this miss. I have done the following;
New pump and filter
New plugs (motorcraft SP-500’s)
New Motorcraft wires and coil
New IAC
Mass Air Flow cleaned, reading within specs and seems to be responding
TPS checked and is within spec and responding
Ran Techron through it 3 times
Nothing has changed the miss, I pulled wires off one at a time and ran the engine at the affected RPM the miss was always present. I know my way around an engine but I’m at my wits end with thing. The computer never shows a code, doesn’t register a misfire even when I disconnected the wires and ran it. No injector faults are shown. Passes the KOER and KOEO self tests. Any ideas would be great.

Thanks,

adsm08 · Feb 9, 2018

Do you have access to something that can show you the misfire monitor in real time?

The misfire profile may not be learned well enough to set a code yet, and an active miss can lengthen the time it takes to learn it. But it will not affect the graph of the power balance.

At this stage you pretty much need to start by knowing which cylinder is causing your problem.

A compression test would be the next step if you can't get a good scanner with access to the power balance.

badams21523636 · Feb 9, 2018

I have an older OTC scanner and have monitored the individual cylinder missfire counts, as well as injector faults and nothing has showed up. i am going to grab my friend Snapon ethos scanner monday and see if there is anything else it can show me. The odd thing, is that when unhooking plug wires, MAF, and the IAC at different times this evening and running the truck for awhile. no check engine light was ever set throughout the testing. i will check compression in the cylinders in the morning, my thought right now are either injectors or possibly the PCM.

its very strange thats for sure

adsm08 · Feb 9, 2018

The ethos may do better than your OTC. I haven't used the OTC scanners, but my Solus can get me the info I am talking about, and my Solus is old, about on par with my one buddy's ethos.

A mechanical injector fault won't show on the PID. So if it is blocked or jammed that won't show.

You probably aren't setting codes because none of the monitors are set yet. I mean you should be getting circuit codes, but sometimes those act funny and clear themselves as soon as the circuit is put right.

I went through this on my Explorer last summer with a MAP code, I spent two and a half days dicking with the MAF, unhooking it KOER and all, all to have no codes set, before I remembered that my MAP sensor is part of the EGR valve.

badams21523636 · Feb 10, 2018

adsm08 said:
The ethos may do better than your OTC. I haven't used the OTC scanners, but my Solus can get me the info I am talking about, and my Solus is old, about on par with my one buddy's ethos.

A mechanical injector fault won't show on the PID. So if it is blocked or jammed that won't show.

You probably aren't setting codes because none of the monitors are set yet. I mean you should be getting circuit codes, but sometimes those act funny and clear themselves as soon as the circuit is put right.

I went through this on my Explorer last summer with a MAP code, I spent two and a half days dicking with the MAF, unhooking it KOER and all, all to have no codes set, before I remembered that my MAP sensor is part of the EGR valve.

I was able to run the contribution test and found that #’s 1 &2 had short dips in contribution. Up to -14. I suspect injectors but am going to check compression in 1 & 2 for kicks.

Sent from my iPhone using Tapatalk

badams21523636 · Feb 17, 2018

Finally Solved it!!!!!

Well, After a lot of head scratching and brainstorming with other techs I finall found the problem. My new Autel Scanner showed a pending code for the cam circuit that the snapon scanner would not show for some reason. So i decided to replace the synchronizer. As i was performing the service I found that the synchronizer that was installed in the truck was setup for the 3 pin stator, but the truck was wired for a 2 pin stator. The wron signal was getting to the PCM.
this engine came from a parts truck, so it looks like it was not the stock engine to the parts truck. when the previous owner found the sensor mismatch they just swapped the 2 wire sensor for the 3 wire one. with the proper synchronizer installed the phantom miss has gone away.

1999 4.0 OHV engine troubles

badams21523636

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adsm08

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badams21523636

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