throttling issues.. searched and replaced many parts!! -
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post #1 of 4 Old 02-25-2013, 12:10 AM Thread Starter
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1996 XJ Cherokee 
Join Date: Sep 2009
Location: wilmington, de
Posts: 254
throttling issues.. searched and replaced many parts!!

hey guys im hoping someone can help me out here... ive been battling with this issue for well over a month and have done a ton of research and even looked on here (which means IVE SEARCHED N SEARCHED SO DONT FLAME). basically heres a description of whats going on and what ive replaced already. now issues have changed slightly both for the better and for the worst with replacing different parts. i basically replaced one part at a time more or less so that i could eliminate what it could have been... but heres the deal..

my xj usually struggles to start up when its warmed up, and then when driving the throttle tends to hesitate or while idling at a light it will peak a little then drop down to around 500 or lower and sometimes just get crazy and then shut off.

heres a list of all the parts that i have replaced over the last few weeks trying to get it straight:
cps, tps, map sensor, upstream o2 sensor, new air filter, new cap and rotor, new plugs and wires (twice), new fuel pump, fuel pressure regulator, fuel filter external and also the sock on the fuel pump, rewired the faulty wiring in the fuel sending unit, rewired a baked area of the o2 sensor harness after the connection, cleaned the throttle body really well, cleaned the iac valve really well, and also replaced the ignition switch and lock cylinder....

so this is why i am lost. ive done so much research and spent more than enough money on the issue and would really like to move onto replacing the cooling system but this issue is holding me back from it. i noticed this morning though that the canister vacuum valve solenoid was making a tapping noise inside the housing. thats on the list for replacement now just have to order it. but i honestly dont see how that could be the issue to the problem. so please, if anyone has any insight on what could be my problem please let me know. any ideas are welcome!! and btw i have a 96 xj classic with the inline 6. (change over year)

thanks ahead of time!!

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post #2 of 4 Old 02-25-2013, 07:35 AM
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1999 XJ Cherokee 
Join Date: Jul 2011
Location: Canton
Posts: 3,548
You may have a clogged exhaust (Catalytic Converter ?).

Try hooking up a vacuum gauge to your intake manifold and check for a clogged exhaust. Refer to these sites for vacuum diagnostics.

This one shows a clogged exhaust in scenario 14:

Another site:

There are several Youtube vids showing vacuum diagnostics that you may want to check out. You can also Google 'Vacuum Gauge Diagnostics'.
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post #3 of 4 Old 05-02-2013, 05:28 PM Thread Starter
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1996 XJ Cherokee 
Join Date: Sep 2009
Location: wilmington, de
Posts: 254
just to put it up on here... i have gotten to the point where i have literally replaced everything dealing directly with the fuel system specifically. the only parts that i havent at this point is the tank, sending unit, and hard lines... did a diagnostic on the xj at a shop and all systems are good. mechanic thinks that its the ecm thats sending incorrect info so its causing an incorrect throttle response. invested so far- $1500.. ecm- $300... damn it! thought id post just so if anyone else comes across the same issue itll save them a ton of time and money
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post #4 of 4 Old 05-02-2013, 06:34 PM
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1996 XJ Cherokee 
Join Date: Feb 2010
Location: Mesa, AZ
Posts: 589
I'm with CCKen on this one - a vacuum gauge may well be your best view into what's going on with your motor. A leaky intake manifold gasket might fit your scenario pretty well, too (you can usually find that by spraying WD-40 or similar around the engine - manifold junction, where a leak will ingest the spray and cause an increase in engine speed, usually).
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