GRM help needed! Challenger stranded need diag help

Hi all. Our own singleslammer is stuck in Mt Vernon il at the napa trying to diagnoes issues with his challenge xjr.

He said it was running fine but he stopped for gas, checked the oil and trans fluid, added a bit of Lucas fuel injector cleaner, and suddenly the car started backfiring under load and hardly has any power. Seems to idle fine.

He already replaced the fuel pump and filter, new spark plugs last night. What's the issue?

Jag experts? 1997 xjr with the supercharged inline6.

oh no!

I know nothing in particular about Jags. Anything else to add? CEL? Black smoke? Smells?

I got nothing, just bumping this up to keep it at the top of the latest topics. 

I just asked if there were any codes. There aren't.

He didn't mention smoke or smells.

Have him disconnect the maf/map. Should go limp mode, and determine if its sensor or ignition related 

Dusterbd13 said:

Have him disconnec not the maf/map. Should go limp mode, and determine if its sensor or ignition related 

No start with maf disconnected

Apparently it doesn't work the same as mazda and chevy.  I got nothing. 

Did it jump time? Are those chains? I'd check for spark first.

I know nothing about XJRs but backfiring usually results from spark coming at the wrong time. Could range from arcing in the distributor cap (if it even has one), to engine jumped time, to a sensor or computer malfunction. I know, that probably doesn't help much. You could put a plain old fashioned timing light on it and see if the ignition timing is on spec.

When I have a car run that runs badly after getting gas I'm always suspicious of the gas.  I'd try and look at a fuel sample and check for water.

Those things are known for the timing chain going all clickity clackity then catastrophe.  Timing chain sprockets are plastic on the early ones, a combo of plastic and metal and the next itineration and finally once Ford bought them, they went all metal.

Well I have given up. I rented a U-Haul and a tow dolly. I am going home now. I will now have to figure out how to cancel my challenge ticket

In reply to singleslammer :

Oh no!  I am really sorry. 

for what it's worth I think they will hold your entry till next year.  I thought I read that in here .  hopefully it wasn't a Dream.

In reply to singleslammer :

I feel gutted for you. Sorry to hear that.

Wow, that really super sucks. I’m sorry there’s no way I can help. 

singleslammer said:

Well I have given up. I rented a U-Haul and a tow dolly. I am going home now. I will now have to figure out how to cancel my challenge ticket

Really sorry to hear that. Don't worry about your registration. We can roll it over to next year for you if you like.

Really sorry to hear singleslammer. I am bummed for you. 

I would guess fuel related due to the recent repairs to the fuel system and the gas fill up. I am guessing you either have low flow due to a complication with recent repairs, or a clogged filter, or bad gas.

I'm really sorry you cant make it. I was looking forward to seeing that car run.

Illinois fuel?

last time I had that issue, it was an intake hose between the MAF and the throttlebody. It would idle fine, but any throttle would twist the engine enough to open up the hole to allow unmetered air in. That's all I got. Time to put a scanner on it and see what it says

Thanks for all the support. I plan to come next year so no problem there. After today, this might sit in the yard for a couple weeks for me to recover some dignity. It's a shame too, with the 4.11 gears, it hailed serious ass. I am guessing low 14s if I can get it to launch.

In reply to singleslammer :

Sorry about all this. I was really looking forward to seeing you again and maybe lining up against you. 

Oh no!!!

Aw, man... I'm sorry. I dug the car, and the "What the heck, I'm taking a Jag to the Challenge!" approach. Hope it isn't too awful to sort, and you have a triumphant arrival next year!