Ford Driveability Problem

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  #1  
Old 07-13-04, 02:29 PM
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Ford Driveability Problem

98 E250 4.2 This is a well maintained fleet vehicle with about 100K. Truck came in with complaint of very sluggish and check engine light on. Hooked up scanner, no communication. Check fuses and found #23 20amp burnt out. Replaced fuse, now have communication but truck runs the same. Scanned for codes and found lean O/2 S1B2 and lean O/2 S2B2. Checked data, found 0 voltage from both sensors, even pumping throttle. Everything else looks normal including trim. Swapped sensors around and took reading right at sensor, truly no voltage. The PCM seems to recognize enough to set a code but otherwise, everything is business as usual. The PCM isn't responding to this condition in any way excepting setting the code. The fuel trim is riding right around zero with no correction taking place. Everything just seems to point to no fuel in the left bank. It's not missing but very sluggish with occasional intake backfire. I'm leaning toward a bad PCM but I wanted to hear some of you guys opinions. Already tried a MAF, no change.
 

Last edited by Desi501; 07-13-04 at 05:34 PM.
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  #2  
Old 07-13-04, 05:47 PM
Johnc280
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That is very odd that fuel trims are not changing, especially short term. Are the O2 sensors getting 5v ref signal from the pcm?

I know you said there is no change when you snap the throttle but have you tried to richen the mixture with some intake cleaner to see if you get some action from the sensors.
Does freeze frame data show anything?

I have read about Ford having a problem with fuse 23 blowing because of the wiring harness rubbing on something(can't remember what) and shorting it.

Those are just a few quick thoughts I will read your post again and update any ideas tomorrow.

Good luck,

Johnny
 
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Old 07-13-04, 06:13 PM
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Originally Posted by Johnc280
That is very odd that fuel trims are not changing, especially short term. Are the O2 sensors getting 5v ref signal from the pcm?

I know you said there is no change when you snap the throttle but have you tried to richen the mixture with some intake cleaner to see if you get some action from the sensors.
Does freeze frame data show anything?

I have read about Ford having a problem with fuse 23 blowing because of the wiring harness rubbing on something(can't remember what) and shorting it.

Those are just a few quick thoughts I will read your post again and update any ideas tomorrow.

Good luck,

Johnny
The short term will jump around a little but the long term is pretty steady at center. What 5v reference are you talking about? Never seen a reference signal used on an O/2 sensor. It has B+ and ground for the heater. I haven't really had any reason to look at freeze frame since the only codes are hard codes and the current data tell the same story. Lean O/2s on the left bank are the only codes I'm getting. I haven't really done much to richen the mixture except pump the throttle a little. Access is a bit of a problem on this thing and it uses a MAF. I'll try that in the morning.
 
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Old 07-14-04, 05:10 PM
Johnc280
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Sorry Desi,

Just before I made a reply to your help request I was posting about a Dodge Truck with a 5.2L on iATN. I was still thinking Dodge even though you said so clearly Ford Van. I actuall had written quite a bit more but then realized I was talking about the wrong vehicle. I deleted it all, only I missed that part about the 5v at the O2 sensor. It is actually called a biasing voltage that you will see at 5v on late model Dodges when the O2 sensor is dead.

When I am asking about freeze frame data I am really just curious if there are any other parameters out of whack. Here's the way I am thinking:

A bad PCM will not cause an O2 sensor to have no voltage output.

Bad O2 sensors will not cause a vehicle to run bad. They will mess up fuel/air ratio which of course will make it run bad but you have stated that fuel trims are not changing. Do you have any means to determine if it is actually running rich?

I am very curious to know what the results of this one are. You seem to have the capability to figure it out. Please post it when you do or give me an update on any new information.

Wish I could write more but I need to shut down the pc until this thunderstorm passes.

Johnny
 
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Old 07-14-04, 05:25 PM
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Thanks John
I didn't have much chance to mess with it today but I was able to rule out the PCM and the Cat. It fires on all six at idle but goes into a smooth miss under load. I may be heading in the right direction with the wiring but I have to look a little closer. I'm off tomorrow but I'll dive into it Friday.
 
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