Runing rough, idle rough, cylinder #4 misfire - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > TJ Jeep Wrangler Forum > TJ General Discussion Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 05-24-2008, 09:31 PM   #1
Jeeper
 
Join Date: Jul 2007
Posts: 24
Runing rough, idle rough, cylinder #4 misfire

I could really use some help on this one! Here's the basic info:

1997 Wrangler Sport 4.0L, only mods are 10.5X31 tires on wider 15" wheels. 139,XXX miles, just bought it a couple of weeks ago from first owner. It had been sitting for approx. a year unused, but drove fine on the test drive etc. Commuted to work in it (90 miles round trip) a couple of times, no issues.

Decided to do basic maintence on it since it had been sitting:

1. Did basic maintenance, changed oil/filter, changed air filter, ran Lucas injector cleaner through a couple of tanks. Replaced, plugs with new Bosch Platinums. Took it on a road trip and got a check engine light after a burst of hard accleration in 2nd gear to 4900 RPM or so. Jeep still ran fine, just CEL on, so drove it home 4 hours. Checked codes at home with OBDII scanner, got misfires in cyl #1 and cyl #4. Cleared codes.
2. Replaced wires, cap and rotor. Read about these Bosch single platinum plugs not being great in the 4.0L after researching first misfire codes, so replaced again with Autolites, gapped to .035.
3. Distributor cap screws rusted and broke off in distributor housing, couldn't drill out successfully = new distributor. Replaced distributor, the Jeep ran and drove, but ran rough, was probably a spline or so off. Had a friend come over and we did the distributor replacement from scratch, marking housing, finding TDC etc. Fairly confident distributor is in correctly now, but still idles rough and has valve tapping noise when on the throttle. Repeatedly throws the Misfire Cylinder #4 code, even if taking it easy.
4. Cleaned throttle body, and removed/cleaned/replaced IAC. Still runs rough, meaning it idles like it's got a big cam in it. Exhaust pressure at tailpipe pulses. Still throws cylinder #4 misfire codes.
5. Hooked up a vac gauge to the brake booster line off the intake manifold and the needle stays in the middle of the green "good engine" range on the gauge at idle. It does however tic back and forth slightly, not a big fluctuation, imagine a hand on a clock ticking 1 second forward and backward off the dead center point of the green range on the gauge. The ticking matches the way the motor 'lopes' like it would with a big cam.


I've done a ton of searching on this and got a lot of "possibles", but no clear definites. The possibles include:

-bad #4 injector,
-bad #4 injector wires (look fine),
-bad coil (would expect more cylinders to misfire?),
-bad spedo gear sending crap signal to engine,
-valves with too much carbon buildup.
-valve and/or lifter not working correctly
-cam lobe bad leading to valve issues (per dealer service guy who helped with parts, per him the 4.0L engine is notorious for this)

I'm at a loss as to what to try next. I'd welcome some suggestions at this point before I start tearing the top off the engine (which I've never done before). Thanks in advance!

spdrcrpete is offline   Quote Quick Reply
Old 05-25-2008, 12:20 AM   #2
Jeeper
 
Rawkon's Avatar
 
Join Date: Apr 2005
Location: fullerton/big bear
Posts: 2,061
Send a message via AIM to Rawkon Send a message via MSN to Rawkon
give it a leak down compression test. swap injectors to see if the cylinder misfire changes.

Rawkon is offline   Quote Quick Reply
Old 05-25-2008, 03:18 PM   #3
Jeeper
 
Join Date: Jul 2007
Posts: 24
could it be the CPS?

still searching threads, saw a thread where the CPS was generating this type of effect and codes as well. Thoughts?
spdrcrpete is offline   Quote Quick Reply
Old 05-25-2008, 06:12 PM   #4
Jeeper
 
rthdtj's Avatar
 
Join Date: Aug 2007
Location: Tampa Florida
Posts: 270
Quote:
Originally Posted by Rawkon View Post
give it a leak down compression test. swap injectors to see if the cylinder misfire changes.
I was thinking of the Injector swap myself....

Carbon build up...dought it, you could try the SeaFoam/top end cleaning...

With that many miles it's funny how trying to help, makes for problems like this. From all I know, (which is not much ) go back and re-trace everything you've touched. I'd also replace as many vacuum hoses you can.
Double check the wires, sometimes when pulling on them $hit happens. Double check the Cap & Rotor, just because they're new, maybe a crack or something, sorry to ramble...but re-check & then re-check.
rthdtj is offline   Quote Quick Reply
Old 05-25-2008, 06:19 PM   #5
Jeeper
 
rthdtj's Avatar
 
Join Date: Aug 2007
Location: Tampa Florida
Posts: 270
I just re-read your post again, sorry missed the new wires, still worth a check though. Does it ping on accel under a load..?
just thinking timing & vacuum....
rthdtj is offline   Quote Quick Reply
Old 05-25-2008, 09:27 PM   #6
Jeeper
 
Join Date: Jul 2007
Posts: 24
Quote:
Originally Posted by rthdtj View Post
I just re-read your post again, sorry missed the new wires, still worth a check though. Does it ping on accel under a load..?
just thinking timing & vacuum....
It does ping under load, and acceleration. The timing should be correct at this point, I wouldn't THINK I'd screw it up twice.... I did put a vac gauge on it and it's right in the green/normal range on my gauge.
spdrcrpete is offline   Quote Quick Reply
Old 05-26-2008, 08:02 PM   #7
Jeeper
 
Join Date: Jul 2007
Posts: 24
Quote:
Originally Posted by Rawkon View Post
give it a leak down compression test. swap injectors to see if the cylinder misfire changes.
I'm going to try your suggestion of switching the injectors around tonight or tomorrow night. That sounds like a good idea. I need to grab a Haynes manual for this Jeep first, I only have the one from my YJ. I'm not sure how similar the 4.0L is from YJ to '97 TJ.

I see that I do have a small 3/8" of so hole in the bottom of the header, all the way at the bottom right where both branches of the ehausst are fist above each other. THis of course makes all my valve noise seem MUCH louder. I'm going to get that welded up too ASAP.
spdrcrpete is offline   Quote Quick Reply
Old 05-29-2008, 07:55 AM   #8
Jeeper
 
Join Date: Jul 2007
Posts: 24
Update

Quote:
Originally Posted by spdrcrpete View Post
I'm going to try your suggestion of switching the injectors around tonight or tomorrow night. That sounds like a good idea. I need to grab a Haynes manual for this Jeep first, I only have the one from my YJ. I'm not sure how similar the 4.0L is from YJ to '97 TJ.

I see that I do have a small 3/8" of so hole in the bottom of the header, all the way at the bottom right where both branches of the ehausst are fist above each other. THis of course makes all my valve noise seem MUCH louder. I'm going to get that welded up too ASAP.
Update; Got the hole in the exhaust welded up. Changed the coil and the misfire is now showing up on cyl 6 and also threw the multiple misfires code. Also did the Seafoam bit before changing the coil and still no improvement. It still idles pretty rough, shakes the whole Jeep a bit, but runs around town fine. I drove it about 15 miles with the new coil, working it pretty hard to get it to throw a code and it was fine. Let it sit for a couple of hours and then about 200yrds into the drive home it threw the cyl 6 misfire code.

I'm at a loss here. I don't want to play 'throw parts at it until it's fixed", that just seems expensive and stupid. I'd certainly welcome further suggestions. I have not swapped the injectors around yet, but seeing that the misfire code isn't always the same cyl, I'm wondering if it's worth the effort.
spdrcrpete is offline   Quote Quick Reply
Old 05-29-2008, 08:15 AM   #9
Hacks off Parts while Lit
 
whitebuffalo's Avatar
 
Join Date: May 2005
Location: The Sandhills of South Texas
Posts: 2,290
are you sure you got your plug wires in the right order? when you crank it over, is it steady or does it chug (speed up and slow down)?
__________________
'90 YJ, ford 8.8, SOA, lincoln front, aussie rear, 4.88s, swampers.
whitebuffalo is offline   Quote Quick Reply
Old 05-29-2008, 09:01 AM   #10
Jeeper
 
Join Date: Jul 2007
Posts: 24
Quote:
Originally Posted by whitebuffalo View Post
are you sure you got your plug wires in the right order? when you crank it over, is it steady or does it chug (speed up and slow down)?
I'm 99% sure the wires are correct, but will recheck again. It's steady, but 'lopes' like it has a big cam in it, kinda like an old schoool modified big block motor.
spdrcrpete is offline   Quote Quick Reply
Old 06-02-2008, 09:02 AM   #11
Jeeper
 
Join Date: Jul 2007
Posts: 24
Update after the weekend: Put some miles on the Jeep this weekend. Noticed that after clearing codes, I can usually drive 1 trip before the CEL/misfire codes come back on. They come back on almost immediately after a warm start-up. Also, when accelerating slowly with very even throttle pressure, I can still feel it surging ever so slightly.

I did check the connector for the CPS (crankshaft position sensor) and at least the connector seems fine. The CPS seems to be functioning, at least basicly, since unplugging the harness makes it so the Jeep won't even start. I tried to check the resistance on it with a multimeter, since the Haynes manual says to check the resistance to see if it's 200 +/- 75 mil ohms, but I couldn't get a reading at all. I was probably just not doing it right. I'm tempted to spend the $40 to swap the CPS out as well just to rule it out, but really don't want to just throw parts at this thing without a clear reason or plan.

So, still at: recurring multiple misfires, worse on warm restart, rough idle, and feels like it's down on power some. I'd welcome any more insight on this.
spdrcrpete is offline   Quote Quick Reply
Old 06-02-2008, 12:40 PM   #12
Hacks off Parts while Lit
 
whitebuffalo's Avatar
 
Join Date: May 2005
Location: The Sandhills of South Texas
Posts: 2,290
I've seen on a hemi when the cps went out, it threw mulitple misfires, very low power, etc. guy thought it was his transmission crapping out. did you pull the sensor to check the impedence? (i.e. so you could get to it better?) pull it out and take it to the parts house with you with your multimeter....test yours, then theirs and see what you come up with.


if you mean its loping while cranking it, thats usually indicative of timing issues.....or compression problems....given your recent distributor swap etc, id suspect the former more than the latter.

if it runs fine for the first 90 seconds or so (on cold start), it almost has to be sensor related. i think its 90 seconds it runs in closed loop mode before o2 sensors etc. start being read. i could be mistaken though.......take it (all) for what its worth.



if it were me, id try the cps, just to rule it out. u could always resell/return it if it doesnt work.....$.02
__________________
'90 YJ, ford 8.8, SOA, lincoln front, aussie rear, 4.88s, swampers.
whitebuffalo is offline   Quote Quick Reply
Old 06-02-2008, 01:01 PM   #13
Jeeper
 
Join Date: Jul 2007
Posts: 24
OK, will check CPS.

Quick question: put my scan tool on and had it read TPS w/ engine off, it read 14% throttle open. Am I correct in assuming that this should be 0% when engine is off and that the TPS may be part of my problem?
spdrcrpete is offline   Quote Quick Reply
Old 06-02-2008, 01:32 PM   #14
Hacks off Parts while Lit
 
whitebuffalo's Avatar
 
Join Date: May 2005
Location: The Sandhills of South Texas
Posts: 2,290
i would assume it should be zero but i really dont know. i dont think tps would cause misfires, but anything is possible, especially when one sensor goes caput and makes everything else start acting crazy.....

__________________
'90 YJ, ford 8.8, SOA, lincoln front, aussie rear, 4.88s, swampers.
whitebuffalo is offline   Quote Quick Reply
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Jeep Wrangler Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
My Clutch Problems and How I Resolved Them linz TJ Tech Forum 6 05-10-2013 07:11 PM
4.2 rough idle and stalling problem truemainer150 YJ Tech Forum 9 04-12-2008 05:10 PM
rough idle spanky TJ Tech Forum 9 04-08-2008 04:25 PM
rough idle for 5 or 10 minutes... Jonny15 TJ Tech Forum 5 04-02-2008 07:34 PM
Very Sad I bought a Lemon... Jahaira_JeepYJ89_fan YJ General Discussion Forum 19 07-13-2007 03:01 PM


logo carid shop wrangler parts carid fender flares custom wheels store avs deflectors at carid
» Rates
Get low rates on auto insurance in Canada!

» Network Links
»Jeep Parts
» Featured Product

All times are GMT -5. The time now is 03:23 PM.



Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC.
Wranglerforum.com is not in any way associated with the Chrysler Motors LLC