96_xj

for the past month I cannot get over 3500-4000 rpms under full throttle. under 1/4-1/3 throttle i can operate just fine and reach 5000 rpms but the moment you go to stomp on it (getting up a ledge offroad, passing on the high way, fast start) it will cut out, wait a second or so then kick back on and repeat as long as you are pressing on the pedal.

(please see youtube links for video of what is going on)
light/normal throttle:
http://www.youtube.com/watch?v=http:...?v=9M8NR3fj5HA

heavy throttle:
http://www.youtube.com/watch?v=http:...?v=S6PqEyR9Qew


New parts include:
TPS (new as of today)
IAC (replaced 3000 miles ago)
CPS(new as of today)
upstream o2 (new as of today)
Fuel filter (about a week old)
full tank of gas with a bottle of seam foam to make sure there is no water in the system (1/3 tank gone).
no CEL codes stored or active


did the fuel pressure test and got the following results:

light/normal throttle: 50 psi constant
http://www.youtube.com/watch?v=http:...?v=0pzJ8uECQ2U

heavy throttle: 50 psi that drops down to 40-45psi
http://www.youtube.com/watch?v=http:...?v=_lGMnCk5d9w


I am thinking now either the fuel pump or fuel pressure regulator (which is one unit). or (that was mentioned to me) the distributor and/or the crank positioning sensor

any ideas?

96_xj

I went to a very good local auto shop today. he test drove it with me in the jeep and we replicated it pretty well. for $35 he is going to hook it up to the scanners and give me all the print outs and information to help me diagnose it:

I go in tomorrow morning to get readings and print outs like such:

XJ Stryker

Well seems like you are finally seeking professional help.

Cherockee

Someone else on the forums here had trouble like this recently (said his exhaust manifold was getting ornage hot too) and he found his distributor hold down bolt was loose and allowed the distributor to move around. Maybe check that.

96_xj

I am just now at a loss with everything.... it has been a month.... the thing has been on a multimeter for every sensor (volts and ohms readings), mechanical gauges and Yet nothing is coming up and I am sick of throwing parts at it. Testing it (in my driveway) is free parts are not lol.

The Map sensor I am going to retest. It was tipped to me to test it since after 80% throttle it takes over (from what i hear).

So I will try that and look into the Distributor timing(retard and advance) today as well .


I am still looking for advice in any shape or form however.


I will check that out thanks. and exhaust is fine, and engine temp is 200-210 never above....

Cherockee

Just curious, that thing sound pretty mean... what for exhaust are you running? Is it a stroked motor? Wish mine sounded like that (without cutting out of course).

Do you know anybody your could swap a ECM with? Sounds electrical to me, but what do I know...

96_xj

it ended up being the speed sensor. anything past 1/2 throttle it would register i was going 200+ mph(high voltage) resulting in it cutting out then it would cut back on when i was at a normal speed (normal voltage) and so forth.

new speed sensor and BAM! works perfect....

radio flyer

How did you pin it down to that?

96_xj

as per post #2

i took it to a local shop. for 2 days it was hooked up to a Dyno and all sorts of computers. it read and mapped/graphed everything that was going and what the ECM was reading and they just saw that speed sensor was not correct or not even giving a reading at some points. so I bought them a new one they installed it and everything was good to go.

$56 to get full dyno print outs and full diagnostics and to have them instal the part (not that doing 1 bolt is hard lol)

dukie564

NICE!