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i need help again


 
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b_radley_05
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Joined: 25 Jul 2007
Location: Spanish fork, tah

PostPosted: Sun Oct 05, 2008 8:47 pm    Post subject: i need help again Reply with quote

ok so i have a 90 jeep cherokee, 4.0, auto trans, 4x4. it had a blown head gasket. so i pulled the engine and did the head gasket. no big deal i have done them before and had no problems. i got it all back together and it started right up but it runs like crap! it runs like the timing is off. i didnt tuch the timing chain or distributor. i am geting spark to all my sparkplugs. i checked my sparkplug wires and they are hooked up right. i am getting plenty of fuel, but i couldn't think of a way to check each of my injectors without making a big mess. i pulled the fuel rail and turned of the motor over. the injectors seemed to be working fine. does anyone have any ideas????
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1999amethyst
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Joined: 12 Aug 2008

PostPosted: Mon Oct 06, 2008 12:07 pm    Post subject: Reply with quote

ide check the timing chain and the distributor, just because you never knwo and its not hard to check. also its alot easier to rip the motor out atleast to me.
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Toliver09
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Joined: 16 Oct 2007
Location: Central Illinois

PostPosted: Mon Oct 06, 2008 1:59 pm    Post subject: Reply with quote

did you make sure to reconnect the map sensor? I've done this before haha
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Brad The Best
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Joined: 14 Jan 2007
Location: Kamloops B.C Canada

PostPosted: Mon Oct 06, 2008 7:37 pm    Post subject: Reply with quote

ya that little vacuum line to your fire wall can mess it up a bit
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b_radley_05
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Joined: 25 Jul 2007
Location: Spanish fork, tah

PostPosted: Mon Oct 06, 2008 8:44 pm    Post subject: Reply with quote

i checked the timing chain and distributor they are both fine. i chang the cap and roter. that did not help. i checked the map sensor and vacume line. they are hooked up. i also checked all the other electrical and vacume conections. they were all hooked up. i checked compression. it is good. i am pretty sure its a sensor. does anyone have a good electrical diograms of the OBD 1 computer hook ups? that shows what prong goes to witch sensor? so i can test with just a volt meter. i do not have access to a diagnostic computer. so i have to do it old school.
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DavidXJ
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Joined: 07 Sep 2006
Location: Visalia, CA

PostPosted: Tue Oct 07, 2008 6:43 am    Post subject: Reply with quote

Just thinking outside the box, but I remember someone on this forum having an engine that ran like crap after they changed the header because they hadn't gotten it tightened up correctly and it was leaking. Weird, but just another idea.
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b_radley_05
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Joined: 25 Jul 2007
Location: Spanish fork, tah

PostPosted: Tue Oct 07, 2008 7:40 am    Post subject: Reply with quote

tightend up where? i am up for any ideas. i am not the biggest fan of electrical, so if its something else that would be great.
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DavidXJ
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Joined: 07 Sep 2006
Location: Visalia, CA

PostPosted: Tue Oct 07, 2008 7:48 am    Post subject: Reply with quote

They were talking about the bolts that hold the intake manifold and exhaust manifold on. Pain in the but to get to some of them, so it's easy to not have them tightened properly. Since the some of the same bolts hold the intake and exhaust tight, it could cause a leak in both.

In their case it was the rear bolts. The intake was leaking and causing it to run like crap.
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b_radley_05
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Joined: 25 Jul 2007
Location: Spanish fork, tah

PostPosted: Tue Oct 07, 2008 8:40 am    Post subject: Reply with quote

oh i got ya now. i will duble check them but i had the engine out on a stand so i think i got them all. thanks tho for the help. keep the ideas coming
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djgrayxj
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Joined: 26 Sep 2007
Location: Southern California

PostPosted: Thu Oct 09, 2008 11:53 am    Post subject: Reply with quote

HOW TO TEST INFORMATION
By Jeep Garage Free
Owners Manual Section
http://jeepgarage.free.fr/ownersmanual.html

1988 COMPUTERIZED ENGINE CONTROLS SYSTEM INFORMATION
ON JEEP 4.0L MPFI 6-CYLINDER ENGINES
4.0l cec system.pdf 570 Kb
http://jeepgarage.free.fr/OWN/4.0l%20cec%20system.pdf
Component Testing Information Starts on Page # 7 of above

THROTTLE POSITION SENSOR DIAGNOSTICS CHART See P# 13

Coolant Temperature Sensor (CTS) See P# 7

Coolant Temperature Sensor (CTS) See P# 7

Oxygen sensor must be tested with System Tester (M.S. 1700). P# 8

Oxygen Sensor Heating Element See P# 8 & 9

Knock sensor must be tested with System Tester (M.S. 1700). P# 9

Speed Sensor P# 9

"Synch Pulse" (Stator) P# 9

EGR Solenoid Valve P# 10
More info on EGR SOLEOID
ECU-CONTROLLED SOLENOID VALVE is used to control EGR valve function.
From EMISSION CONTROL on P# 5
The ECU electrically controls Exhaust Gas Recirculation (EGR).
An ECU-controlled solenoid valve is used to control EGR valve function. This valve is located on the left inner fender panel and is operated by the ECU in response to coolant temperature; throttle position, and manifold pressure.
Under conditions of engine warm-up, engine idle, wide-open throttle, or rapid acceleration/deceleration, the solenoid valve is energized, blocking vacuum to the EGR valve. At normal operating temperatures with engine speed above idle, the solenoid valve is deenergized, allowing normal EGR valve function.
NOTE: If the electrical connector is removed from the EGR solenoid,
EGR flow will be allowed at all times.

Relays - General Testing P# 10

Starter Motor Relay P# 10 & 11

Design & Function of Relays P# 11
Hope this helps from DJ
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b_radley_05
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Joined: 25 Jul 2007
Location: Spanish fork, tah

PostPosted: Mon Oct 13, 2008 6:43 pm    Post subject: Reply with quote

the crank position sensor wins again. it tested fine but i changed it anyway and thats what it was. thanks again for everyones help.
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djgrayxj
Member


Joined: 26 Sep 2007
Location: Southern California

PostPosted: Tue Oct 14, 2008 4:51 am    Post subject: Reply with quote

Glad you got it fixed but hear is some more info on same subject
Set of diagnostic for early 4.0
Article contains information courtesy of Eric Giordan (JabaThaHut).
This page contains an easy to follow set of diagnostics for your early model 4.0L Jeep Cherokee with RENIX based (NON-HO / early)engines & sensors.
http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

Clean the Flywheel or Flexplate
From: ILOVEJEEPS.com Forums
http://www.ilovejeeps.com/forums/showthread.php?t=17451

You might want to try to scrape/clean the flywheel (flexplate). I had this problem with a few xj's. Changing the cps won't make a difference if the flywheel is rusty/dirty, because the cps is magnetic and needs to read the metal spaces. Rust and dirt will make it hard to read. You can try cleaning it through the cps hole, using a small wire brush and some wd-40/pbblaster. Disconnect the fuel pump relay or unplug the coil battery source. While having someone cranking the engine place a slender wire brush against the flywheel. crank/brush for 15 seconds then spray with wd-40/pbblaster. You may have to do this a few times until shiny. Then reinstall cps and fuel pump relay/coil plug and start. You can also remove the trans and polish the flywheel. These things work just like a lawn mower if you leave them in the weather they rust and won't start.
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b_radley_05
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Joined: 25 Jul 2007
Location: Spanish fork, tah

PostPosted: Wed Oct 15, 2008 8:26 am    Post subject: Reply with quote

ok i will chack it out. thanks again
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