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can you hear the banjos?
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ok heres the story mandas 98 xj you start it if you let it run for a while it starts to idle bad like it has a ginormus cam in lets say 500 rpm to 2000 rpm then you put it in gear and its fine drives down road fine no problems. also if you fire it up and take off without letting it warm up it pops and backfires for a sec then runs like new :confused: i really have no idea. no codes. no obvious vacuum leaks i have no idea
 

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Did this happens after they salted the roads? If so start checking your connector for corrosion. Check the coolant sensor, air temperature and map sensor for the computer for moisture.
 

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throttle position sensor? i know the older ones are adjustable. not too sure on the newer ones. it did mess w/ my idle like that. that and the IAC might be dirty
 

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throttle position sensor? i know the older ones are adjustable. not too sure on the newer ones. it did mess w/ my idle like that. that and the IAC might be dirty
x2 Ive had that happen on an 92xj and also the wife's taurus wagon. On the wagon it got ridicules, the throttle would stick at about 2grand and i'd have to turn off the ignition and then restart it and it woulod be fine. the sensor is just 2 small bolts and a couple of conectors on top of the throttle body.
 

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OK since I might have not made it very clear did this problem start doing this after they started to salt the road or was it doing before that time?
Not if it is wet out dry or cold or warm.
Salt in the conector will cause some very strange things to happen. Most of the sensor work off resistance for the computer.
 

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ok heres the story mandas 98 xj you start it if you let it run for a while it starts to idle bad like it has a ginormus cam in lets say 500 rpm to 2000 rpm then you put it in gear and its fine drives down road fine no problems. also if you fire it up and take off without letting it warm up it pops and backfires for a sec then runs like new :confused: i really have no idea. no codes. no obvious vacuum leaks i have no idea

I've never had a problem with the idle, but my 99 has that same backfiring issue. I've never done anything about it other than curb my "start up and drive" habits. I don't think it's the TPS. I had this issue with mine before and after swapping a TPS.
 

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can you hear the banjos?
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Discussion Starter · #8 ·
I've never had a problem with the idle, but my 99 has that same backfiring issue. I've never done anything about it other than curb my "start up and drive" habits. I don't think it's the TPS. I had this issue with mine before and after swapping a TPS.
now i let it warm up and thats good but need to figure this out. throttle pos tests fine so we are good there
 

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Iac
 

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Rad Racing
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Not sure if this is your issue, but I had this with my '00 XJ before I went to larger injectors with the stroker. I sleeved my #3 injector and the rough idle after startup was gone.

Here's the TSB that was sent out about an issue very similar to what you are describing. I know you said hers is a '98 and this covers '99-04, but it may be the same problem. Hope it helps.


TSB
1803103 - 4.0L ROUGH ENGINE IDLE AFTER RESTART FOLLOWING A HOT SOAK
Date: 09/05/03 (supercedes 1802702 dated 09/06/02)
Model Year(s): 1999-2004

Description: NOTE: This bulletin applies to vehicles equipped with a 4.0L engine. This bulletin involves the installation of a fuel injector insulator sleeve.

Details: Customers may describe a 20 to 30 second rough idle following the restart of a heat soaked engine. This condition may be most noticeable when the engine is restarted following a prior 10 to 20 minute heat soak in hot ambient conditions of approximately 32 C (90ºF) or higher. This condition may be consistent with short city stop-and-go driving trips and can be aggravated by the use of fuel with a high ethanol content. Depending upon various conditions a MIL may occur due to DTC P0303 - Cylinder #3 Misfire.

This condition may be caused by heat from the exhaust manifold that following engine shut down migrates to the area around injector #3 and causes fuel vapor to form within the injector. This in turn may cause a momentary misfire of cylinder #3 until the fuel vapor is cleared of injector #3. The insulator sleeve lowers the injector #3 temperature to a point below which the fuel will not normally vaporize.

If vehicle exhibits a rough idle, and if a misfire of cylinder #3 is observed following a 10 to 20 minute hot soak, perform the Repair Procedure.

Parts required:
56028371AA Ignition Wire Shield

Repair procedure:
1. Cut insulator sleeve, p/n 56028371AA, to make two (2) insulator sleeves about 25-30 mm (1 in.) in length. See diagram.
2. Install one sleeve around injector #3, with the slit on the upward facing side of the injector. Install the other sleeve with the slit on the downward facing side of the injector.
3. Confirm sleeve is flush to intake manifold surface around injector.
4. Check injector #3 wire and ensure that the injector is rotated to a 2 o'clock position (from driver?s side of vehicle).
 
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