XJ XJ8 / XJR ( X308 ) 1997 - 2003

P0102

 
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Old 06-11-2019, 06:57 PM
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Question P0102

Y'know, if it's not one thing it's something else....
After running flawlessly for several hundred miles, today the car died at a traffic light while my wife was en route to work. She called me in a panic, saying it would crank and start but immediately die. After a while, she could get it to run long enough to try and move it but as soon as she put it out of Park it would die. This was accompanied by the check engine light and the Restricted Performance warning.
I had the car towed home...
Tonight, I went out with my OBD reader and it came up with P0102 and no other codes. Before I wrote this post, I searched the forum and found some good advice on a few things to check. The connector is clean and firmly plugged in, the fuse is good (replaced it anyway), the air filter has only 8,000 miles on it and is visibly near-perfect. I ran a smoke test over the weekend for a different issue, and found the full-load breather to leak at the cam cover as well as the intake seal at the throttle body leaking. Both parts have been ordered, but both also had been leaking probably since before I got the car running and on the road in October. In that time and mileage, the MAF code has never come up.
Also, strangely, I discovered when I took the intake apart to clean the MAF 2 weeks ago (with CRC MAF cleaner) that 3 of the 5 wires at the MAF connector were frayed and likely shorting against one another, and a fourth (the black one) was broken altogether. The white wire was the only one that was intact. The really weird part is that I was getting no codes with this clear problem going on. I repaired the wires, secured them with shrink tube, and re-wrapped the whole thing with new tape. We've since put probably 400 miles on the car without incident until this morning.
I hate to jump to a conclusion, but I'm kind of thinking the MAF was maybe near failure and fixing all the wiring caused it to die altogether -- does that seem plausible?
Also, is there an electrical test I can run to look for incorrect resistance or lack of voltage at the plug? I checked the factory manual, and what I found was a short section on how to replace the MAF and nothing about troubleshooting it.
I did try resetting the code after unplugging, cleaning (with a can of air), and plugging back in the connector and changing the fuse. As soon as I start the car the light comes back on with the code. Also, even after resetting and before the code comes back on start-up the restricted performance message remains.
Any ideas?
Thanks
-Steve-
 
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Old 06-11-2019, 07:02 PM
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If it helps, I was able to pull freeze-frame data. When the code occured, STFT was at 0 for both banks. LTFT was 7.8% on Bank 1 and 9.0 on Bank 2. IAT was 109.
Live data without resetting the code showed STFT at -0.7% Bank 1 and -2.3% Bank 2. LTFT Bank 1 was 7.8%, Bank 2 was 9.3%. IAT was 100
 
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Old 06-11-2019, 07:29 PM
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I think the connections to the throttle body are in that same circuit? It seems a few years ago I had similar symptoms and cleaning the throttle body electrical connections helped. I eventually had to replace the throttle body with a rebuilt one; that has eliminated the problem for years now.

Yours could be something completely different, but that’s what came to mind when I read your posts.
 
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Old 06-12-2019, 11:19 AM
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Go back to the MAF wiring: sounds like one of the wires may be loose or still grounding out.
 
 
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