'07 Ranger 3.0L stumble on WOT, backfire, random misfire

[Derf_the_Mule]

The key cylinder was moving a bit in the housing ...They were all wrong and had I not listened my truck would have bee on the road month earlier

Playing with it and recording the results is a fair diagnostic strategy. Quite a bit of scientific discovery has used that methodology (mind you the lab techs or scientists were actually playing with the equipment). Thanks for your input. I'll try and see what happens.

 

[Maggie may]

Believe me I have heard women don't belong in a bodyshop for many years now, and how I am to small to do mechanics. So much so that I no longer work in the field,

 

[Maggie may]

Scan toolalso coded open circuit that was also in there column the main harness connector had been damaged at some point in my trucks long life

 

[Derf_the_Mule]

I played with the keyswitch (pushed, pulled, up, down, circles) and hit the steering column hard to jar any loose wiring. It had no obvious effect on the way the engine is running. Let me know it there is something else to check.

All symptoms I started this thread with are still present (stumble on snap to WOT, random misfire, rough running, backfire out the exhaust) with one additional (high idle, IAC slowly reduces idle when closing, it has bumped the idle to the rev limiter) and the backfire is back. The truck sat in the garage for 5 days undisturbed.

The Actron scanner tool I rented from Autozone broke so I took it back. Looking for a good bi-directional tool (anybody know any good ones?), but will be awhile before I can afford to get one.

I have previously discounted a major vacuum leak because the MAF showed corresponding increase when the idle went up. Additionally, if a leak were present to idle up to the rev limiter, I am assuming the engine would stall with that much unmetered air. LTFT1/2 have always been positive and at there highest less than 10% and usually within 2-3% of each other. STFT has been +/- at about the same rate as the O2 sensors. I don't have a scanner with live data anymore so I cannot check anything else.

I am diagnosing this as a PCM problem (with possible addition of fuel pump or regulator) because there is not a short in the control voltage for the IAC that I can find. Either a bad IAC (just replaced), short in the signal wire, or a short in the power wire will cause this (not limited to these). I was limited on the testing I could do according to the PC/ED manual because I could not access all the PID's (specifically IAC duty cycle) with the Actron, and I do not have access to an oscilloscope (nor the money to invest in one).

 

[Derf_the_Mule]

Believe me I have heard women don't belong in a bodyshop for many years now, and how I am to small to do mechanics. So much so that I no longer work in the field,

Bigotry is a major stumbling block to innovation. I have seen it in my own field as well. Too bad for the industry.

 

[Maggie may]

Bigotry is a major stumbling block to innovation. I have seen it in my own field as well. Too bad for the industry.

I see you mentioned seafoam, I know it is an excellent product . did you run it through your vacuum lines as directed? This is almost as good as placing injectors through the machine to clean them. I advise anyone I know to use this, and it works equally well for diesel,or gas engines. Did you unplug the shorting bar also called PIP? try disconnecting neg cable for 5 mins to clear codes as well when u reset PIP.

 

[Maggie may]

Fuel pressure regulator could be some of problem

 

[Half Nuts]

Kiss

Let me start by saying that your fastidious attention to detail in this thread is both monumentally impressive, and more than a bit intimidating.
I had a similar problem with rough running, stumbling, and backfiring on my truck. In my case, it was microscopic cracks in the casing of the ignition coil. The coil looked good at a glance, but under my pocket microscope it was clear as day. Incidentally, driving around on a broken coil for so long had burned up all my exhaust valves, and so a tear-down and trip to the machine shop was necessary.
Finally, do not be intimidated by the prospect of tearing down the 3.0.
If you've had experience on 20-year-old motors, remember that your motor's design is now 30+ years old!
Happy hunting!

 

[Derf_the_Mule]

I see you mentioned seafoam, I know it is an excellent product . did you run it through your vacuum lines as directed? This is almost as good as placing injectors through the machine to clean them. I advise anyone I know to use this, and it works equally well for diesel,or gas engines. Did you unplug the shorting bar also called PIP? try disconnecting neg cable for 5 mins to clear codes as well when u reset PIP.

I had the upper intake manifold cleaned at a Valvoline Quick Lube place thinking I was getting a fuel rail flush (run the vehicle off the cleaner itself). I then found I needed to pull off the upper intake plenum to change the gaskets on it. I pulled the injectors and had then ultrasonically cleaned and flow tested and baskets replaced. Only a slight improvement that removed the bouncing of the needle on the fuel pressure gauge. I think 2 injectors were sticking. I also cleaned out the plenum when it was off.

I have no idea what a shorting bar or PIP is. I have looked for the terms and could not find by googling them.

I have cleared the KAM numerous time now. The last was not entirely intentional when I was checking for shorts in the IAC control circiut (grey w/ orange stripe). After resetting the KAM it runs fine for a short while then the PCM activates the IAC too much and very slowly dashpots the idle.

Fuel pressure regulator could be some of problem

I am fairly confident the fuel pressure regulator (in the tank with the sending unit) is dying. My mechanical maintenance insurance should cover it, but I have to take it to qualifying mechanics. The short holiday weeks and illness have kept me from those repairs.

 

[Derf_the_Mule]

Let me start by saying that your fastidious attention to detail in this thread is both monumentally impressive, and more than a bit intimidating....motor's design is now 30+ years old!
Happy hunting!

I try to approach things in a manner so that anyone that reads can see clearly what I have done. I don't want to waste time by repeating recommendations, repairs, or tests that are available elsewhere.

The mechanics of tearing down my engine are not what is intimidating me. It is the cost and ability to complete the work where I live. I also bought a mechanical repair insurance from my credit union that will cover the repair. The PO had the engine 2.5 quarts low on oil. (I should have run away then). I figured it would cover one major repair if needed. And it needs. I will try to get my cheap Chinese bore-scope into cyl #4 to check for a burned valve. I do not know what a burned valve looks like.

 

[Maggie may]

PIP otherwise known as profile ignition pickup it is most likely by the test pport , or near the ICM..

 

[Maggie may]

I was thinking the pressure reg. On the fuel rails.

 

[Derf_the_Mule]

PIP otherwise known as profile ignition pickup it is most likely by the test pport , or near the ICM..

This engine does not use this type of ignition system. It uses a camshaft position sensor on what used to be the distributor (called camshaft syncronizer). I replaced the syncronizer already and the sensor was not damaged (I think it is a variable reluctance sensor). It tested OK as well. I did reset the KAM after cleaning the MAF and resetting the CMP. The timing is read by the crankshaft position sensor (CKP) and the injector timing (not pulse width) is read by the CMP.

I was thinking the pressure reg. On the fuel rails.

This truck has a mechanical returnless fuel system. The bypass is at the filter and is controlled by the pressure regulator (in the tank, of course). The components of the sending unit/ fuel pump assembly are not available separately for this vehicle.

 

[Derf_the_Mule]

...I had a similar problem with rough running, stumbling, and backfiring on my truck. In my case, it was microscopic cracks in the casing of the ignition coil. The coil looked good at a glance, but under my pocket microscope it was clear as day. ...

You mean like this? It looks like a scratch to me.

 

[Derf_the_Mule]

I took a close look at the coil pack with a high power magnifying glass. Those are indeed cracks in the casing of the coil pack. Funny, it tested fine with OTC HEI spark testers.

I also looked into Cyl-4 with my borescope. I think I got a picture of the exaust valve wich was open. The picture is out of focus and up-side down (possibly mirrored as well). I had to take video then capture an image. There is a bunch of carbon buildup, even after 3 fuel treatments. I'll give it a nice long drive after it is fixed.