Diagnostic assistance needed

[CollapsedNut]

As I have no personality I'll skip the small talk and get to it

95 Ranger XLT 4.0 SOHC 4x4
None EGR engine.

Here's what I've got. Intermitent issue of hessitation/low power, some days it runs fine. Issue goes away when wide open throttle is applied(WOT), but if you come off the throttle even a little bit it returns. To describe the issue in terms most can relate to, it feels like your clutch is worn and slipping a small amount while under load, ie: climbing a hill. I'm get slight jerks, and not enough power to pull a hill unless you got to WOT, then it's like the turbo finally spooled and lays you back. RPM makes no difference. I can be 2k 5th gear on the highway going up a hill, WOT will make the issue go away immiediatly before RPM can even raise. Stumbling and hessitation taking off from a stop, so you floor it and BAM vtec kicked in.

KOEO Codes:
172 - lean bank 1
177 - rich bank 2

KOER Codes:
137 - rich bank 2

Steps and tests performed:
Fuel filter replaced
Fuel pump replaced
Air filter replaced
Cleaned MAF
Plugs replaced (old plugs looked great)
Plug wires replaced
Fuel pressure test: ~32psi idle. 30psi @2k. 38psi with FPR unplugged from vac. I ran it with the FPR unhooked for a day just to see how it did, no noticable change.
Checked for vacuume leaks, none found.
Feel test of injectors, I can feel them all clicking.
Exhaust is removed about 4" behind the cat(long story) no smoking of any color straight out of cat.


My general thought is this is an electrical systems issue. I need to check timing, but I dont see that being it unless this system dramatically changes timing at WOT. I need to check resistance of the injectors, but again I dont see how going to WOT would resolve an injector issue. I should check and adjust the TPS also, but I would think if it were out of adjustment I'd get a code. Could it be O2 seners maybe... I've never had a system that would adjust fuel and timing off of O2 readings to the extent that it would cause a noticable issue, and again wouldn't go away at WOT.

Thoughts? Thanks for your time if you made it this far

 

[RangerSVT]

95 started OBD2, but the 3 digit codes you listed are OBD1. What is the actual build date of your truck? How many miles are on your truck? At a quick guess I'd say your oxygen sensor(s) need replaced. You may have multiple issues, though. Your tps/iac could be malfunctioning.

SVT

 

[CollapsedNut]

No door sticker as the driver door has been replaced at some point. It is an OBD1 system though, with no EGR. Sitting around 246k miles right now.

IAC. Hmmmm. I need to study how it works on this engine, I seem to recall an electronic IAC on the manifold. But yeah I see where you're going there. Good thought.

 

[alwaysFlOoReD]

I'll also call O2. The computer uses no O2 readings when engine is cold [one or two minutes] and when under WOT.

Richard

 

[CollapsedNut]

Good thinking. Maybe I will justify replacing them.

 

[CollapsedNut]

Just ran a quick test on the o2's.Test shows I'm either running way rich, like above 1volt rich(.45 is the magic number on 14.7:1 afr) on bank 2 or the sensor is bad. Bank 1 was sitting around .48-.51 which I'd say is acceptable. I think if I were running that rich I'd smell a lot of fuel in the exhaust.

 

[CollapsedNut]

Update: Replaced o2's, they really did need replacement but the issue is still there. Bank 2 still runs really rich. Ideas?

 

[SenorNoob]

Stuck open injector maybe? Bad wiring to injectors or o2 sensor?

 

[CollapsedNut]

Can someone confirm that the signal wire for bank 1 o2 is red with a black stripe. Looking at a diagram on a 94 4.0 none California spec.

 

[RonD]

For wiring this is a good page to bookmark
http://www.autozone.com/autozone/re...epairGuideContent.jsp?pageId=0996b43f802c54bb

Figure 26 is for the 1994 ranger 4.0l non-Calif

Yes red/black for sensor 1

 

[adsm08]

Wait, is this a SOHC transplanted into a 95 body? That might be relevant.

 

[CollapsedNut]

Well guys, I'm still stumped. It's a ohv to correct myself, not an ohc. I was getting voltage on the red black wire so I traced it for a short, none found. Opened up the ecu and found a capacitor bad, replaced it and now my voltage issue is gone but nothing changed.

 

[RonD]

There are 3 O2 sensors on V6/V8 engines
Bank 1 sensor 1 (exhaust manifold)
Bank 1 sensor 2 (this is behind the Cat converter)
Bank 2 sensor 1(exhaust manifold)

Bank 1 sensor 2 is often confused with Bank 2 sensor 1, and a rich condition on this sensor means Cat converter isn't working right

 

[BRUTUS_T_HOG]

Sounds like you are having an ignition misfire. Without any test equipment and data my best guess would be the coil pack is bad. The coil pack has 3 coils in it and if one of them shorts it will take out 2 cylinders.

I wouldn't really worry about the codes right now because a misfire can cause rich and lean codes.

 

[CollapsedNut]

Update:
I was checking voltages and such looking for bad componets. I found an odd voltage on the bank1 O2 signal wire for the PCM, traced it al the way back to the PCM. Basically the PCM was sending out a voltage that it shouldn't have been. Took it out and opened it up, found a capacitor leaking so I soldered in a new one and that seems to have fixed that issue but no change in the driving condition. Still getting the same codes.

Before I replace the PCM would someone mind checking a voltage on their truck for me? It's the red/blk wire on the top left of the connector pictured below. You can ground to the battery and just back probe on the connector. Perform the test with the engine off, key on, preferably cold engine. If someone could do that it would really help me.
https://drive.google.com/file/d/0B00GVCxk-F-Fbl9KUXMyaFpjMEU/edit?usp=sharing
https://drive.google.com/file/d/0B00GVCxk-F-FVTJUUlRKNWlzNlE/edit?usp=sharing