rough running 93 zj 4.0l atx

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

MudPuppy76 < - 27 Aug 2005 22:15 GMT

HELP me please.

story: bought a 1993 jeep grand cherokee with 173k
on it. i have persisting problems. not sure if
these are related?

symptoms:
hard starting, excessive cranking
rough idle, intermittent stall P to D or R
rough running attempting to pass on highway

my mistakes:
173k replaced fuel pressure regulator and fuel
pump (ouch) replaced spark plugs because some nut
put bosch quadfires in it. immediately improved
the hard starting problems.

183k replaced intake gasket for suspected vacuum
leak. no improvement. replaced spark plug wires.
no improvement. replaced IAC, no improvement.
replaced crank position sensor connector, after
which i promptly broke the sensor, and replaced
that too. no improvement.

tested and found to be ok:
tps, map, ect, iat, alternator, vacuum, coil.

ready to load the .45 i'm losing my mind here. not
sure if i should shoot myself, or the truck.

Signature

Ben Jerew AKA PolarPuppy1976
New Country Lexus of Latham, NY, USA
Amateur Off-Roader 93 YJ, 93 ZJ

Reply to this Message

Will Honea - 28 Aug 2005 05:41 GMT

> HELP me please.
>
[quoted text clipped - 25 lines]
> ready to load the .45 i'm losing my mind here. not
> sure if i should shoot myself, or the truck.

Did you also replace the cap and rotor when you changed the plugs and
wires?

Signature

Will Honea

Reply to this Message

MudPuppy76 < - 28 Aug 2005 14:58 GMT

>>HELP me please.
>>
[quoted text clipped - 28 lines]
> Did you also replace the cap and rotor when you changed the plugs and
> wires?

the cap and rotor i did not replace because it was
new just before i bought it. inside the cap is
still clean with no deposits or carbon tracking.

Signature

Ben Jerew AKA PolarPuppy1976
New Country Lexus of Latham, NY, USA
Amateur Off-Roader 93 YJ, 93 ZJ

Reply to this Message

MudPuppy76 < - 28 Aug 2005 15:07 GMT

> HELP me please.
>
[quoted text clipped - 21 lines]
> ready to load the .45 i'm losing my mind here. not sure if i should
> shoot myself, or the truck.

i remembered my kV probe and thought to myself,
why not, but then i remembered i don't use it all
that much, because all lexus now is DIS. anyways,
i measured the kV on my cherokee. my results:

coil: 10.6
1-6: 9.6, 8.5, 10.3, 11.3, 12.5, 10.6

this morning i decided to go back to my original
fix 10k mi ago. i replaced the spark plugs. now it
starts good again. i remeasured the kV:

coil: 8.6
1-6: 6.5, 7.4, 9.1, 10.2, 9.2, 8.5

what would cause the plugs to foul out so fast? or
is this normal? previously has champions in it.
now i have ngk's.

Signature

Ben Jerew AKA PolarPuppy1976
New Country Lexus of Latham, NY, USA
Amateur Off-Roader 93 YJ, 93 ZJ

Reply to this Message

DougW - 28 Aug 2005 19:29 GMT

MudPuppy76 <"<moc.rr.pacyn"@"pupralop"> did pass the time by typing:

> i remembered my kV probe and thought to myself,
> why not, but then i remembered i don't use it all
[quoted text clipped - 7 lines]
> fix 10k mi ago. i replaced the spark plugs. now it
> starts good again. i remeasured the kV:

10k is too long to wait between spark plugs. I don't
go any longer than 7,000 between replacements.

> coil: 8.6
> 1-6: 6.5, 7.4, 9.1, 10.2, 9.2, 8.5
>
> what would cause the plugs to foul out so fast? or
> is this normal? previously has champions in it.
> now i have ngk's.

spark plug heat range, stop/start city driving where the engine
doesn't get fully up to temp for long enough. CCV system plugged
up and backfeeding oil into the air intake (look for an oily spot
on the filter.

I run Autolite 3924, but that would be too cold for your
application. Go one heat range up, 3925. Also check the
plug wires, your still getting too much variance. It is
acceptable to mix heat ranges, blocks don't cool evenly.

Runs about $100 but I like to have a local shop use
a motorvac on my Jeep. (induction/rail cleaning)
http://www.motorvac.com/
Does a lot better than dumping carb/fuel cleaner into the system.

A plugged cat will also cause fouling.

Signature

-- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!

Reply to this Message