Hey everyone, I have a 98 disco one that is driving me up the wall, it has negotiable fuel trim at - 24.5 percent on both banks but still seems like it is running richer than my wallet, thats when it starts might I add, when you turn it over it'l sspudder and spudder but you can hear all of the combustion happening in the tail pipe and she smokes like a God damn freight train, and burns your eyes from the gas fumes, I've had all injectors out and are all good, no leaks, fuel pressure is a healthy 40 psi on the nose, maf has been changed, throttle body has been cleaned, new plugs, newer wires, ( last year), new fuel filter and pump, vacum lines have all been capped off for testing so I didn' h to worry about leaks, when it finally does run it runs ok, smokes pretty good of unburnt fuel, and it melted out a pair of cats, 2 brand new ones in there now and also new muffler, put a spark tester on it and under no compress will spark close to 3/4 of a inch, I'm lost and looking for advice, I hate throwing parts at things and these motors are picky and eaily uupset, put it this way, this thing has been on its period since I got it and I really want it to calm the hell down for a bit, haha, thanks on advance

 

What about fuel pressure regulator? It's been awhile since I've messed w GEMS but I believe it's still got the vacuum line to the intake. I'd make sure the return line isn't clogged. I'm assuming you've done a compression test? I don't see you mention O2 sensors. They are a big part of the fuel mix situation.

 

The hose is hooked up on the regulator to the plenum,, holds pressure good, I haven't touched the o2 sensors, reading good and consistent with one another but it is at the point where it won' s cold, the o2 sensors haven' e started reading yet, I'm going to be changing the 2 upstream ones in the next week but atm it just fires in the tailpipe, the waste spark seems to be ignighting the fuel when the exhaust valve is open, but not in the cylinder that needs to fire

 

a lot of the "AEL" vehicles seem to have trouble with the fuel tank pressure sensor>>used as part of the evap system.....when it shorts out (or the wiring to it) it can take out the throttle position sensor and even the IACV since they all share the same circuit....all with no cel codes.........roll up the carpet in the back and get to the fuel pump....un plug the sensor and see if it makes a difference.......my 98 acted the same way yours is ..nplugging tat damn thing made an instant difference....it's worth a try,and cheap

 

I'll definitely give that aa try in the am, did change the fuel pump so something might have happened, easy to accss n I cut a hole in the carpet and foam and Velcroed it down just in case in the future I needed in there again

 

This is a very good thread. Can the moderators move this to the D1 section?

 

That would be my bad, sorry, read alot off of this forum but first time posting and I thought that's where I was supposed to post it, my bad

 

No luck on removing the gas tank pressure sensor, checked spark on all 8 and is very consistent, fuel pressure holds 40psi while turning over, fluctuates a bit but consistent

 

is the maf you changed to a known good one ?......,try unplugging the maf and see how it acts

 

AbnMike had similar troubles. I don't recall how he ultimately resolved his issue but it may have been an ECU re-set.