2nd Generation S-series (1995-2005) Tech Discuss 2nd generation S-series (1995-2005) general tech topics here.

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Old Feb 28, 2013 | 05:25 PM
  #11  
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ran fuel trim test about an hour ago and LONGFT2(%) went from -11.7 to a steady -14.3
LONGFT1(%) -7ish

MAP readings at idle are holding at 10inHg
 
Old Feb 28, 2013 | 05:48 PM
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I wonder if the two are related... Your fuel regulator may be leaking, allowing excess fuel by, hence the bad fuel economy. It could in turn be causing fouling issues with your O2 sensors and possibly catalytic converter. (thinking out loud)
 
Old Feb 28, 2013 | 06:02 PM
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i would rather it be a fpr, although it is new (came with spider upgrade), than a fuel pump. Im not sure I'd understand bad fuel economy with a bad fuel pump, seems like it'd be running lean with a bad pump. I think the negative trim indicates its trying to cut back on fuel? right?

I live in Ohio and I'm waiting till the weather warms up a little before I take the top of the intake off to check for leaks. Like I said before the fuel pressure jumps to 60 key on engine off, but loses pressure to 0 in less than 5 sec. With engine on its maintaining a steady 50-51psi. Runs fine everywhere but idle. and rpms only float +/-50 just eats gas crazy and doesn't idle as smooth as it used to
 
Old Feb 28, 2013 | 06:52 PM
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That's what I was thinking, it may be a bad fuel regulator/ injector assembly causing all your grief. Your pump seems to be fine, but without going through the entire diagnostic procedure it's hard to be sure. The spider upgrade is good to do either way on the '96, so that's a good place to start.
 
Old Feb 28, 2013 | 07:14 PM
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Actually, I have already done the spider upgrade. I replaced it in the Fall due to a cylinder 1 misfire. I'm not saying the FPR that came with it isn't faulty, but it is relatively new.


Only code I get frequently after continuous deleting: P0420 catalyst operating below threshold.
 

Last edited by ramairblazer; Feb 28, 2013 at 07:47 PM.
Old Feb 28, 2013 | 09:08 PM
  #16  
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Fuel pressure is at bare minimum and leakdown is excessive. You need to isolate the pump and check maximum pump output pressure and leakdown to determine where the leak is, and if the pump is weak. Fuel trim is indicating very rich, negative fuel trim indicates the PCM is trying to lean it out. Timing at negative 20 is a problem. Most likely camshaft retard is off.

EDIT: P0420 will not affect performance and it may go away after all the other problems are taken care of.
 
Old Feb 28, 2013 | 09:23 PM
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I did change the distributor cap and I thought for sure it was on right. What do I need to do to check or fix the timing issue.
 
Old Feb 28, 2013 | 09:34 PM
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Your scan tool shows how many degrees of advance the PCM is applying, it should never be negative. Timing lights are obsolete on this engine, they won't tell you a thing. Checking and or adjusting camshaft retard requires a scan tool capable of accessing the streaming data, usually in the misfire menu on high end scan tools. The el cheapo $500 jobbies can't access it. Adjustment is done by slightly rotating the distributor. Desired spec is zero degrees + or - 2 degrees, not something you can do "by ear", or "seat of the pants"
 

Last edited by Captain Hook; Feb 28, 2013 at 09:38 PM.
Old Feb 28, 2013 | 09:38 PM
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The cap is on tight, but has a little play if twisted left or right. Is this normal?
 
Old Feb 28, 2013 | 09:41 PM
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Cap shouldn't move. Be careful when tightening the screws, the distributor housing threads will strip out or the ears will break off.... time for a new distributor either way.
 



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