have a knock at idle - JeepForum.com

 
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post #1 of 14 Old 09-23-2010, 08:10 PM Thread Starter
yadamean316
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have a knock at idle

hi i have a 98 cherokee 4x4 4 door with a 4.0 and i have just replaced the tps and i has a idle problem and has a pretty loud knock at idle once warmed up an once u give it a little throttle it goes away but if you are driving when you come to a stop u here the knock and it dies any ideas

thanks mathew

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post #2 of 14 Old 09-24-2010, 05:55 AM
cruiser54
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If it has an auto trans, the torque converter to flexplate bolts are probably loosening up on you. Easiest and cheapest thing to check first.
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post #3 of 14 Old 09-24-2010, 06:29 AM
c0ncEpT
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Check your flex plate.

Could also be piston slap. About 75% of the 4.0's I have heard have it and it just seems to get louder with age.

95 XJ. Longarm'd, Geared and Locked on 35's
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post #4 of 14 Old 09-24-2010, 10:29 AM
Millermagic
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If it does it in neutral is it the flexpate issue?

2000 XJ - 3.5'' Lift & Skinny Mudders.
Previous: A CJ, Few TJs and JK.
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post #5 of 14 Old 09-24-2010, 11:56 AM
Mikeand
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Yes, the flexplate turns all the time, neutral, drive, whatever...Ive had the bolts come loose on both my jeeps. That would be the first place Id check.

1996 Cherokee Sport -4.6L Stroker, TB Spacer, Cold Air Intake, APN Header - D30 front / 8.25 Rear -RC 3" Lift -Dakota Leaf Pack -Rough Country Discos / -31" General Grabber A/T2s on 15x8 Cragar Soft 8s -Diamond plate rear quarter panels -Front bumper with hoop - IRO Double shear Track Bar and HD tie rod -Homemade light bar
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post #6 of 14 Old 09-24-2010, 01:21 PM
Mkonyn
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Get some lock tight, tighten the bolts and you'll be good.
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post #7 of 14 Old 09-24-2010, 02:28 PM Thread Starter
yadamean316
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ok that seems right but what about the dieing issue and it only does it when it is warmed up
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post #8 of 14 Old 09-24-2010, 03:16 PM
cruiser54
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Normal maintenance could be an issue. Plugs, wires, cap and rotor, if equipped. Clean the throttle body and IAC motor.
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post #9 of 14 Old 09-24-2010, 03:53 PM
FairlanePhil
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Mine does it too.
Changed my oil the 1st time since I bought it and it clatters like crazy. Give it gas and it goes away.


I pulled the valvecover and its not the rockers or a busted valvespring.
Oil pressure is good, runs cool and is OK on power.
I think its piston slap or a rod bearing. I get guys telling me to drop the pan and check the bearings but my buddy is a Jeep tech. He said to either leave it alone and drive it or rebuild it. Popping caps off can cause them to spin a bearing pretty quick

Haven't checked the TC bolts yet. Ive been driving like this for a month and saving for an $1800 reman from Autozone. Ill probably cjheck the bolts tonight since its cool and not raining finally

Current: 99XJ 6.5 lift-Bought 2015
Sold: Patriot Blue 00 XJ.
'sploded: 01 stock-0331 head victim
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post #10 of 14 Old 09-24-2010, 04:54 PM
smokinlib1
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Quote:
Originally Posted by yadamean316 View Post
hi i have a 98 cherokee 4x4 4 door with a 4.0 and i have just replaced the tps and i has a idle problem and has a pretty loud knock at idle once warmed up an once u give it a little throttle it goes away but if you are driving when you come to a stop u here the knock and it dies any ideas

thanks mathew
Quote:
Originally Posted by yadamean316 View Post
ok that seems right but what about the dieing issue and it only does it when it is warmed up
I agree it sounds like your flexplate bolts may be loose. Did you ever overheat the engine? If so you could have shrunk a piston skirt or two. Did you set your new TPS with a VOM? Do a search for TPS and you will find plenty of info on how to install it correctly. The TPS is NOT plug and play.

1990 XJ Cherokee
1995 XJ Cherokee
1990 YJ Wrangler
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post #11 of 14 Old 09-24-2010, 08:00 PM Thread Starter
yadamean316
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thanks guys for your help but i pulled the head off and found that cylinder 5 and 6 had blown the o rings and the pistons have destroyed the walls no lie but if one of yall have a motor for sale let me know really need one i only have this and my motorcycle and its going to get cold soon ya send me a message at matkid@gmail.com thanks
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post #12 of 14 Old 09-24-2010, 09:59 PM
FairlanePhil
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Quote:
Originally Posted by yadamean316 View Post
thanks guys for your help but i pulled the head off and found that cylinder 5 and 6 had blown the o rings and the pistons have destroyed the walls no lie but if one of yall have a motor for sale let me know really need one i only have this and my motorcycle and its going to get cold soon ya send me a message at matkid@gmail.com thanks

yeah I am betting mine is the same inside

I bought a $350 used motor that "had 20K on the reman when the jeep
rusted through" The mill was pretty clean and had reman tags on the
head and block and it came with a trans and Tcase.

I pulled the head and it had a blown HG.

All the yards here want $800-1300 for high mile motors and I got two quotes for a rebuild $2900 and $4200

Just bust out VISA and get a $1800 warranted reman from AutoZone
Your Jeep will only be down a weekend then

Everyone on here will tell you $100 running 4.0s fall outta the sky but
just try to find one. Particularly for a 00-01. I've been looking for 4 weeks.

Current: 99XJ 6.5 lift-Bought 2015
Sold: Patriot Blue 00 XJ.
'sploded: 01 stock-0331 head victim
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post #13 of 14 Old 09-25-2010, 04:14 PM
tjwalker
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Garage
*Check your local salvage yard and have them do a search
*Craigs List, etc.

There were a lot of 4.0 engines manufactured. Should be able to find one if you pound the pavement and the interweb a bit.

99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!
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post #14 of 14 Old 09-26-2010, 12:33 AM Thread Starter
yadamean316
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thank you for your help yall i will find one and i will le u know how it goes
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