98ZJ 4.6L Stroker Build

[purple_jeep]

Got the fuel pump and pressure regulator replaced yesterday, glad I ran the tank down as that would not be fun with a full tank!

I got the Wallbro GSS342 (255LPH) and the install kit 400-869 which has everything you need to rebuild the stock pump module. Also purchased a BWD filter regulater which actually had a chrysler part sticker with the right Mopar part number on it so they must be the OEM supplier?

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Dropping the tank was no problem only thing that took a while was disconnecting the electrical connector as it was full of dirt. Once out I cleaned off the top of the tank before opening removing the fuel pump module as I did not want to get dirt in my tank . Fuel in the tank looked clear, no crap in the tank but the fuel caught in the pump module was a brown color so I dumped that out. Pulled apart the module per the instructions with the rebuild kit.

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Then cleaned the module and reinstalled the new parts and put it back in the tank no problems

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Once I had the tank back installed I purged the fuel rails and got a steady 48-49 psi with the new pump and regulator fired it up and under idle the pressure still bounces a little bit but when I increase the rpm's it stabilizes.

https://www.youtube.com/watch?v=9FrDTpu ... KROzqppDtw

Took it for a drive and it seem a little better LTFT seems to be more stable around 10%.

0-60MPH took just under 10s on the one attempt I made, on Thursday prior to fixing the pump it was just over 12s.

Still need to get that AFR meter also what should the MAP be on idle? I will check compression and manifold vacuum next

Cheers

Chris

[jeepxj3]

I got the Wallbro GSS342 (255LPH) and the install kit 400-869 which has everything you need to rebuild the stock pump module. Also purchased a BWD filter regulater which actually had a chrysler part sticker with the right Mopar part number on it so they must be the OEM supplier?

Nice, Where did you buy these? How much?

[purple_jeep]

Amazon
Walbro GSS342 - $69.53
Walbro 400-869 - $15.21

Pep Boys
BWD Fuel Pressure Regulator 23079 - $84.99

Cheers

Chris

[purple_jeep]

Well I measured the vacuum in the intake with a Mityvac vacuum tester. When idling it flutters around 14inHg and when I rev it drops down to single digits and then when I release the throttle it jumps to just above 20 then starts to fall back down to the idle position. Idle vacuum seems low so I will look for leaks and isolate the other vacuum components.

Another thing I noticed was that in Park or Neutral the RPM's can sometimes get stuck higher then normal at idle. For example normal idle in Park or Neutral is 770ish but if I rev the engine up to just over 2k rpm and then release the throttle the RPM's may drop back only to 1200 at idle no lower unless I go into gear (drops to 700 RPM) and back out then it will go back to 770.

What could cause that?

Cheers

Chris

[purple_jeep]

Hi All,

I have ~1500 miles on the engine now and other than still not been happy with the performance and a funny high idle after driving and putting it in Park or Neutral it seems pretty happy

Pulled the spark plugs again this last weekend and did a compression test all 6 cylinders read 160psi plus or minus 5 psi. I forgot to chock the throttle wide open for this test so the numbers might be off but they are even which seems to indicate all cylinders are fine.

Spark plugs all look good I think but maybe someone can comment on them (big pictures this time SilverXJ for some reason I thought the forum required images to be 800x600).

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For the high idle I will check my IAC and the TB plate I don't think I have a vacuum leak but its possible.

Cheers

Chris

[purple_jeep]

Still not sure what is causing my high idle the intake smells of gas but i am not sure if that means anything...

I have a AFR on its way and ordered a Tune from FlyinRyan so that handheld should be on its way also

Maybe these will help with the performance and high idle.

Cheers

Chris

[SilverXJ]

You have to have a vacuum leak. Did you check the TPS? The hanging after revving the gas is a classics symptom of a faulty tps. Also, check the throttle body bearings for play and/or leaky seals. AIC possibly acting up too. Put a playing card or business card over the IAC port above the throttle blade and see what happens. Check the throttle blade to the bore as well. There should be a small gap so it doesn't touch when closed. Are you using the stock throttle body?

[purple_jeep]

I will check for leaks again tomorrow morning, I seem to recall you used an unlit propane torch? What should be the effect if I hold it to the leak?

TPS and IAC were replaced in 2011 with Mopar parts but I guess it is possible it has an issue but on the OBDII reader it reads the same at normal idle as at high idle.

Stock throttle body, I will take a picture of the blade to bore gap if there is one. Will also do the playing card trick and look at the bearings/seals.

Thanks for the ideas!

Cheers

Chris

[SilverXJ]

An unlit propane torch will make the idle go up if it is waved over a leak. Also, a spray bottle of water will help as well. The water will make a crackling sound when it hits a leak.

When you looked at the TPS via OBD, was the sweep smooth as you moved the throttle?

[purple_jeep]

Ok so yesterday I did some more testing to see if I could Isolate the high RPM issue. To recap the issue is as follows:

• Driving normally, come to a stop at a light jeep will idle at 1,000rpm instead of 750ish
• If I put it in Neutral or park at that point Idle will jump up to between 1,500 and 2,000
• If I blip the throttle while holding the brake I can get the idle to drop back down to 750ish
• Can reproduce in the garage by starting the car, normal idle then in park blip the throttle up to 2k and it will stick high alot of the time
• Seems to be happening more frequently

Here is a video of it happening when stopped at a light, I was just idling and then I put it in Neutral to see the rpm jump.

So this weekend I pulled the air tube off to check the throttle body and it looks clean there is some space around the throttle blade where it is sucking air. When the car is idling at the 750-770 mark putting a playing card over the IAC does nothing it appears to be fully closed. After bliping the throttle to get it stuck at the high rpm the IAC is open and putting a playing card over the IAC port brings the throttle back down to normal levels???

Does this mean my IAC is faulty or is its position driven by another sensor which could be faulty? Is it normal for it to be closed at normal idle?

I did check for leaks with propane nothing.

IMG_20141115_111510.jpg

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Cheers

Chris

[SilverXJ]

When the car is idling at the 750-770 mark putting a playing card over the IAC does nothing it appears to be fully closed.

That should be expected when you have a vacuum leak

After bliping the throttle to get it stuck at the high rpm the IAC is open and putting a playing card over the IAC port brings the throttle back down to normal levels???

That is a bit unexpected. But if teh shaft is sticking causing the TPS to be off closed value that could do it.

When this is happening what is the TPS reporting?

Does this mean my IAC is faulty or is its position driven by another sensor which could be faulty? Is it normal for it to be closed at normal idle?

I wouldn't jump there yet. I'm leaning toward a problem with the throttle body. Sticking butterfly, perhaps bad or loose bearings.

The second pic you posted shows quite a large gap between the bore and plate under the IAC port while the opposite side looks about normal.

Get it stuck at the high idle then try to play with the throttle body shaft. Try to close it a bit further and try to move the shaft up and down. Don't open the throttle. Basically just see what happens when you try to wiggle it a bit. Your symptoms are similar to what happened when I had faulty throttle body bearings.

[purple_jeep]

Ok I think you might be on to something, looks like the throttle plate is sticking off closed. When idling correctly it reads 19.2% and 770-790 rpm when idling fast it reads 20.4-20.8% and 1700 rpm.

I turned the throttle plate shaft more closed while it was idling fast and it slowed down to the 770-790 rpm and read 19.2%.

Is the throttle body bearings and seals replaceable or do I replace the whole throttle body? Maybe I can spray some lube on the bearings?

Now the IAC been fully closed at normal idle speed you say indicates a vacuum leak? Maybe I have 2 issues :p

Cheers

Chris

[jsawduste]

Chris Purple, the symptoms your describing closely matched a series of TB issues I was having.

The old TB had worn pivot components and leaky seals. The blade would bind at time within the bore. Then even with it seated the airflow was unregulated due to the seals being bad.

Installed a Jeepers Creepers unit and the hang up went away but no amount of fiddling could fix the excessive plate to bore clearance. The customer service was top notch with them sending 3 TB`s to try.

In the end a BBK unit fixed everything and is all I use now. High quality, close tolerance.

The stock TB`s can have bearings replaced but you may find the shaft itself is worn.

[SilverXJ]

You need a special bearing puller to remove the bearings and the bearings can be a bit difficult to find. The bearings you need are INA SCE 67PP. Also sold by Torrington under by JTT67. They need to have o-rings on each side.
The tool looks like this:

[purple_jeep]

OK I will look at work to see if any of our pullers would work, might need to make the adapter for the end to fit the bearing. Can you tell me the part number of the kit you bought?

http://www.amazon.com/Koyo-Bearingd-200 ... B007EDO9DA seems about right?

or http://www.ebay.com/itm/JTT67-TORRINGTO ... 1e9453b025

Otherwise a new TB per jsawduste could be on the cards although I would want to do the 68mm one then...

Cheers

Chris