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00 GPGT multiple codes

FordMan77

Active member
Alright, tired of messing with this and want some 2nd helpful opinions. I've noticed a decrease in mpg and actually made it ping once pretty bad when I got on it hard. It also has a strange idle issue when it gets super cold out and first start of the am the rpms will fluctuate between 2k and almost dying (~500). Once the motor warms up the idle is fine and it won't do it again all day, even after sitting 8 hours at work. Drives just fine other than that.

Since the MIL bulb is out, I broke out the scan tool and got 5 codes back as follows:

P0137- O2 low voltage sensor 2
P0171 (twice)- Lean bank 1
P0405- Sensor A EGR circuit low input
P1404- EGR stuck open?

What I have done so far:
Checked +5v reference at the gray wire of egr plug. Have +5v with key on
Removed EGR valve and checked pintle operation- not stuck at all- moved freely
Checked gas cap- the seal has small cracks starting to form in it, could be a bit loose fit on the neck
Checked wiring to rear O2 sensor- Not damaged as far as I can tell but it's f'n cold and I didn't actually probe it with a meter and I don't know where to check it, lol..
Replaced the upstream O2 sensor a few months back

What I do know is that I must have a crack in the rear manifold somewhere as when I first start it up I can hear an exhaust leak. It stops as it heats up. Have a leak in the resonator that I just found. Original cat on it as far as I know, which now has 360K on it along with the rest of the exhaust. I banged on the cat with my hand and heard what sounds like a loose washer or something bouncing around. Will have to jack it up so I can see if it really is something in the exhaust or just a loose/rusted part outside the cat rattling around. It's possible that there is gravel trapped somewhere as I live in the country and frequent gravel roads, but I've been suspecting the cat for a while now.

To start out, I plan on replacing the gas cap and clearing the codes and see what comes back. If it comes back for EGR, is there a re-learn for it? I swapped on a spare one I had at some point but didn't do anything other than bolt it on and go.

How do I check voltage at the rear O2? I should probably just replace it as when I got the car it had this code so I stuck an O2 sim on it to clear it. The O2 sim died and I reconnected the O2 sensor again.

My scanner can read live data so if there is anything you want me to look at then please let me know and I can post it up.
 


Ok, will do. I guess I'll start with that and see what codes pop back up. I have a spare one lying in the garage I can use if it's not a POS too. Time to break out the PB blaster!
 
It can be via my insulated coveralls and 50,000 btu heater. I just hope the rear gasket is in good shape or I might have to hit up the parts store for a new metal one. Really don't want to mess with it more than once.

Are fel-pro gaskets all metal? They don't look like it.
 


Alright, before I start tearing this apart I used my new inspection mirror to check things out back there. The only place I see anything wierd is around the top edge of cyl #2 where there appears to be some white soot creaping out around where the tube meets the flange on the head. The other 2 cyls do not show this. I would assume this is the leak?
 
most likely. with a cold engine fire it up, put your hand by that area, you should feel some air hitting your hand.

or sea foam it. the smoke will come out the leak area.
 
Well, I fired it up cold and could not feel anything coming from there, but there is a small leak further down the exhaust (past the upstream O2). It's faint but there so I didn't bother to tear up my hands removing the rear manifold just yet.

I did however ohm out the pins on the clear and blue connector from the ECM to the egr connector and both showed up. I put everything back together, cleared the codes and took it for a drive. Pulled the codes again and got the P0171 and P0405. I think my next step is to scan my 95 Bonneville for codes and if no EGR codes show up on it I'm gonna hijack that one and swap it into the GP for a quick test to see if the EGR code clears out.
 
To update: I replaced the EGR valve today, removed the TB and cleaned the junk out of it (it was sticking) and cleared the codes. Took it for a drive and then rescanned it when I got back. The only code showing now besides the MIL light code (my bulb is out) is P0171 Bank 1 lean.
 
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