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-   -   Runing rough, idle rough, cylinder #4 misfire (http://www.wranglerforum.com/f282/runing-rough-idle-rough-cylinder-4-misfire-18772.html)

spdrcrpete 05-24-2008 09:31 PM

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!

Rawkon 05-25-2008 12:20 AM

give it a leak down compression test. swap injectors to see if the cylinder misfire changes.

spdrcrpete 05-25-2008 03:18 PM

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?

rthdtj 05-25-2008 06:12 PM

Quote:

Originally Posted by Rawkon (Post 232064)
give it a leak down compression test. swap injectors to see if the cylinder misfire changes.

I was thinking of the Injector swap myself....:confused:

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

With that many miles it's funny how trying to help, makes for problems like this. From all I know, (which is not much :D) 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 05-25-2008 06:19 PM

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....

spdrcrpete 05-25-2008 09:27 PM

Quote:

Originally Posted by rthdtj (Post 232218)
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 05-26-2008 08:02 PM

Quote:

Originally Posted by Rawkon (Post 232064)
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 05-29-2008 07:55 AM

Update
 
Quote:

Originally Posted by spdrcrpete (Post 232530)
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.

whitebuffalo 05-29-2008 08:15 AM

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)?

spdrcrpete 05-29-2008 09:01 AM

Quote:

Originally Posted by whitebuffalo (Post 233140)
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 06-02-2008 09:02 AM

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.

whitebuffalo 06-02-2008 12:40 PM

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

spdrcrpete 06-02-2008 01:01 PM

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?

whitebuffalo 06-02-2008 01:32 PM

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.....


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