Jeep Wrangler Surging

Michael Mobile Technician Utah Posted   Latest  
Discussion
Driveability
2006 Jeep Wrangler Rubicon 4.0L 4-spd
P0203 — Cylinder 3 Injector "A" Circuit
P0205 — Cylinder 5 Injector "A" Circuit
P0206 — Cylinder 6 Injector "A" Circuit
Lack of Power

I have a new customer that gave me a project. He thinks the computer is bad. It is a possibility but I am thinking something else. The Wrangler develops the injector circuit codes for multiple injectors. These appear soon after starting but are not a hard code. What I mean by that is that they will stay clear until the vehicle is running. I scoped the injectors and they all have a textbook injector trace. My theory is that these codes are generated by an algorithm and not by actual circuit voltages. The vehicle is constant lean and goes extremely lean when RPMs are around 2500 RPM. I did not have a way to test fuel pressure when I was there. It looks like the PW at idle is over 4.5ms which is almost double what I would expect. Even at that it is still running lean. This is why I suspect the fuel pump module. I am wondering if anyone out there has seen this before and can point me in the right direction.

diag​.​net/file/f2nqthzyr…

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Robert Diagnostician
New York
Robert Default
 

It is difficult to see on that pattern but it appears the closing pintle hump may be missing. Chrysler commonly uses the inductive kick to verify injector operation. If the closing pintle kick is missing , erratic or not strong enough it may be skewing the modules perception of the injector circuit. Do all 6 patterns resemble his one? How is the current pattern? On the current side watch for…

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Michael Mobile Technician
Utah
Michael Default
 

Hi Robert, Thanks for the reply. All the patterns are like this one. I think the pintle hump issue is more the limitation of this scope than it is missing. If you look closely it is camouflaged by the second grid line up. I like your point about the current flow. That could be it. One thing I did not mention is that the longer I ran the vehicle, the more injectors showed with the same variety…

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Dave Mobile Technician
Ohio
Dave Default
 

I would want to make sure that the Jeep had the correct injectors and pcm before going further.

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Geoff Diagnostician
Hawaii
Geoff Default
 

I'm wondering if someone else has already installed AM injectors that are flowing the wrong amount of current...(and maybe fuel too!).

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Robert Diagnostician
New York
Robert Default
 

How’s the charging system? AC ripple OK? I would still check current as it will show you the rest of the picture. There may only be one faulty injector and due to internal circuits in the module it may set codes for multiple injectors.

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Samuel Technician
New Jersey
Samuel Default
 

Agree...I saw a case study on a Toyota that had one bad injector, caused system lean and multiple misfire. Current would definitely help narrow the possibilities.

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Phil Technician
Oregon
Phil Default
 

Have you scoped the throttle position sensor? It used to be pretty common that a dirty signal on the TPS usually around cruise speed would set injector codes like that. If I recall the rapid change in the TPS signal would cause the PCM to go into acceleration mode when it shouldn't.

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Scott Technician
Wisconsin
Scott Default
 

Did you volt drop any of the injectors harness? You might try a FRTD and watch the O2's on WOT to see how the fuel pump is performing. Hope that helps.

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Scott Owner/Technician
Missouri
Scott Default
 

Look closely at the inductive kick on all injectors. The only ones I have seen were related to the height of the kick.

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Dennis Owner/Technician
Michigan
Dennis Default
 

I know you said you didn't have a way to test fuel pressure​.​What about a current ramp test with your meter.

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Ray Diagnostician
Ontario
Ray Default
 

These captures are from an 06 Jeep 3.7L CH A is injector 1 volts CH D is a WPS500 on one side of the fuel rail. The low fuel pressure drops are from the injectors on the far bank. HTH

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Matthew Mobile Technician
Illinois
Matthew Default
 

Here are the things I would check based on what I have seen in the past. Do a TP sweep, what happens is right around that 10-20% throttle range the voltage may spike to double what you would expect. The PCM quickly increases the PW and sometimes it sets injector circuit codes. The PCM of this era did not do a good job coding for TP sensor issues, especially without a MAF they probably could not…

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Alex Diagnostician
Australia
Alex Default
 

Hi there it looks like the inj spike is clip at 69v which is good. I will assume all are equal. Current ramping all inj for common looking ramp wld be a good confirmation that they are ok electrically. I wld doubt an actual inj fault but there may a common feed resistance. on V side check all inj and being pulled down to 0 v on turn on. it does not sound like one inj but all if it is the inj, so…

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Michael Mobile Technician
Utah
Michael Default
 

Thanks all for the comments. We will see if the customer calls me back. They were going to check fuel pressure at the rail to see if it is low. It seems that there is a filter and bypass regulator in the module assembly. Maybe something there is haywire. I do appreciate all the comments on the wiring and injector problems. Lots to go with here. We will see how it sorts out. BTW the engine runs…

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Robert Owner/Technician
Virginia
Robert Default
 

We have had several that had bad connectors on injectors .we have been replacing all .

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