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New XJ in the family need some help

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THE MENACE View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote THE MENACE Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2018 at 12:49pm
Seems like a lot of people overlook the fuel filter on XJ's for some reason. It's above the rear diff.

Injectors get clogged. A great upgrade for 91 up 4.0L XJ's are Dodge Neon injectors. They are a simple direct replacement (no mods) for the OE injectors and are pretty common to find at the bone yards, at least around here. Get them ultra sonic cleaned and they work like new. My 91 XJ ended with better acceleration and slightly improved fuel mileage with the Dodge Neon injectors.
    
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1970 AMX 416,EFI,5 speed(Mine)   
1970 Javelin 401, 727 (My Wife's)
1969 AMX,390,Auto,Go Pac (My Mom's)
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Pdok View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pdok Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2018 at 8:01pm
This link is useful for MPFI troubleshooting:


Symptoms could conceivably be caused by:

erratic fuel pressure or regulator
Erratic fuel delivery (as mentioned, injector clogged), or more rarely, injector wiring faulty ground
injector problems will usually throw an OBD code, however, even if intermittent.  I've found that to be true anyway.

Ignition coil issue
O2 sensor (engine never gets past open loop warmup)

We're sure no valves are sticking?  No vac leaks, intake/exhaust tight and gaskets good?

Best of luck, wish I could fly down and drink a beer while you fix it...
76 Grem X 258/904,4.0 head/MPFI, Comp X250H cam, Hughes springs, Clifford header, serpentine swap.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2018 at 8:05pm
Originally posted by Pdok Pdok wrote:

We're sure no valves are sticking?  No vac leaks, intake/exhaust tight and gaskets good


I think I will start with this stuff and a compression test, then move onto the electronic stuff.
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70 Donohue 390 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 70 Donohue 390 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2018 at 10:50pm



It's currently for sale on The Medford Craiglist


I bought my 172k mile 96 from the original owner after she totaled it. I rebuilt it and have put 12k miles on it the last 18 months. It was running rough, when I first bought it. so I ran a can of Marvel Mystery Oil down the carb and 90% of the miss was gone. Then I wanted a smoother idle and better gas mileage so I changed my cap, rotor & wires. Get the better heavier cap (I think that may have been my main problem) My E3 type plugs are very clean but the wires were showing their age. Keep an eye out for a leaking oil pressure sending unit. They blow the back off and oil on hot pipes is ugly.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Oct/11/2018 at 11:15pm
I should update this, replaced the rear main seal and oil filter adapter O-rings, fixed a small vacuum leak in the PCV system and the thing has been running fine ever since.
I've finally given up drinking for good...........now I only drink for evil.
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73Gremlin401 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 73Gremlin401 Quote  Post ReplyReply Direct Link To This Post Posted: Yesterday at 2:23pm
Originally posted by WesternRed WesternRed wrote:

I should update this, replaced the rear main seal and oil filter adapter O-rings, fixed a small vacuum leak in the PCV system and the thing has been running fine ever since.

Sometimes it is the simplest of things that makes them run right!  AMC 6s in general are super sensitive to vacuum leaks, so this repair makes sense. Glad it's doing well.
73 Gremlin 401/5-spd.
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