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Unread 01-08-2016, 05:29 PM   #1
Belizejeep
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Rebuilt 1995 Wrangler YJ 2.5 MPFI

Hi everyone, I just rebuilt a 1995 wrangler yj 2.5 MPFI. I have replaced all sensors with Standard brand devices all except O2 and IACV. was having acceleration hesitation problem but after the sensors were changed all acceleration issues went away, all good right. Now after resetting ECM I have an idle problem, it just idles rough, but accelerates and drives great! Just idle issue, do I replace IACV? Also my timing light when I hook it up to #1 and shoot to crank pulley, the mark flashes past zero clockwise, is that supposed to be like that? I repeated distributor installation and it still flashes past the zero mark CW.

any ideas any suggestions?

Thanks for your time everyone,

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Unread 01-08-2016, 06:55 PM   #2
Drednot
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Start by cleaning the IACV and the throttle body passages. New gasket and o-ring.

Put a new O2 sensor in it. Are the plugs new?
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Unread 01-08-2016, 07:24 PM   #3
Belizejeep
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did a clean to TB an IACV before changing sensors, but I will remove and redo. gasket an o-ring are good new. yes new plugs. O2 sensor seams good no code, am thinking I should change em out too. Thanks Drednot

any thought on the timing light, when the strobe flashes the pulley mark should be aligned to the zero on timing chain cover right?
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Unread 01-09-2016, 06:28 PM   #4
Belizejeep
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update...cleaned TB IACV...now she idles great! However she's terrible on acceleration it's rough on acceleration. O2 sensor still original.
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Unread 01-09-2016, 06:46 PM   #5
Louie4
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Did you get any codes out of it? I'm not 100% sure about the 2.5L but I think the ECM does the timing and you cannot clock the distributor since it only has one position. You just have to make sure the distributor is set to the #1 cylinder at TDC. But I assume you didn't make any changes to that. If you get a new O2 sensor, go with a Denso, I believe they were from the factory versus the Bosch, just a preference though.

Again, get the codes out of it first and go from there.
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Unread 01-09-2016, 07:22 PM   #6
Belizejeep
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no codes... yes 2.5 MPFI is set by ECM so I figure distributor position is good. hope to get O2 sensor sometime during the week. wondering if the ECM is going bad now? as all the sensors are new except IACV n O2.

thanks Lou n Drednot
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Unread 01-10-2016, 02:05 AM   #7
SailerMatt
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Make sure that your spark plugs are copper.
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Unread 01-10-2016, 05:23 AM   #8
Belizejeep
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yes autolite 985 copper core

thanks SailerMatt
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Unread 01-10-2016, 09:48 PM   #9
Drednot
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I try to change out the O2 sensor with every other spark plug change. They get contaminated with fuel deposits/additives and any kind of silicone spray/fumes kills the sensor.

As far as the timing mark, it's possible the outer ring is slipping because of a loose/rotten rubber ring in the harmonic balancer. They dry rot and break loose causing the timing mark to drift from its correct location
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Unread 01-11-2016, 08:10 AM   #10
Belizejeep
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Ok Drednot, so I will pull the #1 plug an do a physical TDC on #1 to see if timing mark is off. Yeah the rubber on HB is dry n cracked on the outside facing radiator, so if it has slipped, then I guess I'll need a new or good used HB. Thanks
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Unread 01-11-2016, 08:50 AM   #11
Que89YJ
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There is no point in checking the timing mark like that. Its computer controlled and you were running good the timing is correct. The thing you might need to worry about is a stretched timing chain. If it has slipped a compression test is a better way to diagnose it.
This video shows how to check for timing chain slop:
http://www.youtube.com/watch?v=4_f5ukZVri8
Do what Dred says before doing anything else. The O2 sensor is important. Note if your issue on acceleration is any different hot/cold.
Use this thread and post your fault codes:
http://www.jeepforum.com/forum/f12/h...codes-1257145/
Use this link and download the service manual:
http://www.youtube.com/watch?v=bsLQSA5L5B8


Your in good hands with Dred.
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Unread 01-11-2016, 11:20 AM   #12
Belizejeep
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Ok got the O2 sensor this morning Parts store here in Belize only has Standard brand O2. hooked it up n verified my TDC on #1 and gave her a try. she briefly ran great good idle good acceleration took her for a spin in the yard and seem when she get above 100* this problem comes back. it was hard restart and when she fired up good idle and bad acceleration again. Am all for suggestions here put lots of $ into it and no change. Is this an ECM issue? Or What? Thanks
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Unread 01-11-2016, 11:42 AM   #13
Que89YJ
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What you just said is extremely important. It ran well then started acting up. You said you replaced all the sensors. You are not listing them so I need to know for sure you replaced the intake AIR temp sensor? The symptoms match you issue.
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Unread 01-11-2016, 11:42 AM   #14
Que89YJ
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Also check your codes and post them. I linked how.
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Unread 01-11-2016, 12:00 PM   #15
Belizejeep
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que89yj thanks for quick reply, I have replaced TPS MAP CPS distributor PickUpCoil and today the O2. Am getting temp sending unit because the base where connector connects rotates, it's located on the head driver side rear of engine, i do have it in a sweet spot where I get a reading on the gauge at least . Intake air sensor has not been changed. Also I notice the yj manual you linked has a different image on cap plug positions than the chiltons, Chil shows #1 right behind a/c compressor @3 o'clk n the one I just downloaded shows #1 @ 6 o'clk. Which is right? as I switched my wires around according to that manual I downloaded and she does not start.
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