XJ Cherokee Shudder

[-JC-]

Hello,
I've done a few searches but can't find anything on this problem, and hoping someone can point me in the right direction.
I've got a '97 (pre-update) 4.0 Jeep Cherokee Limited Auto
It seems to drive great except I get an occasional shudder which is becoming more frequent over time. . . it's a very noticeable jerk.
I can't work out what triggers the shudder, sometimes it doesn't happen at all . . . sometimes it will shudder a lot in a short distance . . . it's shuddered when the engine is cold, when it's hot . . . it's shuddered when I'm accelerating hard or soft and even when I'm holding a constant speed . . . when I'm going fast or slow, etc.
I've replaced the CPS (twice), spark plugs, HT leads, ignition coil, catalytic converter, fuel filter, and probably a few other bits that I've forgotten. Had the Jeep mechanic read the error codes (which resulted in the CPS being changed a second time) but this problem seems to keep persisting.
Other than that the Jeep seems to run pretty good, smoothly and with decent power/torque, nice gear changes and no slipping auto.
Any ideas would be great, I started the work DIY, went to a mechanic then a Jeep mechanic but still not getting it sorted.
Ta

[xjdavid]

Re: XJ Cherokee Shudder

What codes is it displaying.

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[darksidecustoms]

XJ Cherokee Shudder

Welcome JC

Being a Pre-update you should be able to read the codes without a diagnostic tool. See if you have anything stored, even if you don't currently have a check engine light.

http://www.go.jeep-xj.info/HowtoECUcodes.htm

When you say CPS replaced twice, was this the crank position sensor (on the bell housing) or the cam position sensor (on the distributor)? Both can cause issues, but the one for the crank is more common, probably because of heat near the exhaust.

[ApacheResistance]

When you say "shudder" do you mean like a loss of power type of shudder, or like the jeep is actually shaking shudder?

Or is this "shudder" you describe kind of feel like the jeep is rolling backwards on the unibody yet the jeep is going forward? If it feels like a transmission slippage or something along those lines, i'd personally start looking at the TPS as the culprit.

Also, read this;

http://www.cherokeeforum.com/f2/free-quick-fix-41821/

That shows an adjustment you can make on the throttle body, and it appears that everybody is benefiting from it. However, skip to page (7) and read post #93. That's the one you want to follow!

[-JC-]

What codes is it displaying.

Sent from my Desire HD using Tapatalk 2

Not sure I couldn't get the OBDII diagnostic to work at home and when the jeep mechanic did the diagnostic I didn't see the codes was just told it needed a new Crank Position Sensor, had some battery warning (probably due to me trying prolonged starting due to CPS failure) and new catalytic converter. They cleared codes and new CPS fitted but I needed to go to exhaust shop for cat and haven't run a diagnostic since then.

Welcome JC

Being a Pre-update you should be able to read the codes without a diagnostic tool. See if you have anything stored, even if you don't currently have a check engine light.

http://www.go.jeep-xj.info/HowtoECUcodes.htm

When you say CPS replaced twice, was this the crank position sensor (on the bell housing) or the cam position sensor (on the distributor)? Both can cause issues, but the one for the crank is more common, probably because of heat near the exhaust.

Cool, I'll give that a try.

Replaced the Crank Position Sensor / Crank Angle Sensor on the bell housing. I did the first one myself using the step by step stuff on this site. (I'm chasing a warranty claim on the first CPS which was a different supplier). When the original CPS went it just wouldn't do hot starts after a decent drive but never failed when driving, the replacement CPS failed whilst driving and left me on the side of the Freeway waiting for it to cool down. With the new CPS I have neither of these problems.

I did find a few posts on the forum about the cam position sensor but the symptoms don't seem to match my current problem.

When you say "shudder" do you mean like a loss of power type of shudder, or like the jeep is actually shaking shudder?

Or is this "shudder" you describe kind of feel like the jeep is rolling backwards on the unibody yet the jeep is going forward? If it feels like a transmission slippage or something along those lines, i'd personally start looking at the TPS as the culprit.

Also, read this;

http://www.cherokeeforum.com/f2/free-quick-fix-41821/

That shows an adjustment you can make on the throttle body, and it appears that everybody is benefiting from it. However, skip to page (7) and read post #93. That's the one you want to follow!

At freeway/highway speeds the shudder feels more dramatic than than a misfire or a power loss. At lower speeds it's less dramatic, and there seems to be an increasing vagueness in the gear changes. I'm not sure if this is what you were describing with the unibody thing.

Unless the error codes tell me something different I'll start to focus on the TPS. . . and also have a look at the throttle body adjustment.

Thanks for all the helpful stuff . . . looks like I'll be busy over the Easter break

[darksidecustoms]

XJ Cherokee Shudder

TPS can cause all manner of issues. Mine was acting like a rev limiter at 3000rpm and bucking the whole jeep, sounds like it may be similar. Mine was most pronounced around 80Km/h.

[rainman]

I got a shudder like you describe when my MSD coil developed a thermal fail after 12 months .
however you have stated it happens when cold.
where are you?

[-JC-]

Being a Pre-update you should be able to read the codes without a diagnostic tool. See if you have anything stored, even if you don't currently have a check engine light.

http://www.go.jeep-xj.info/HowtoECUcodes.htm

Thanks for the link, followed the instructions and worked. . . great stuff! My error codes are:

12 - Battery Disconnected "Battery of power to ECM disconnected in last 50 key cycles." I'm guessing that this may have been done in the workshop when replacing the CPS, cat or ignition coil.

17 - Engine running too cold "Wrong of faulty thermostat"

44 - Battery temp sensor "Needs Specialist Diagnostics"

55 - End of Code

I know that 44 was one of the codes that the Jeep mechanic read before he reset the codes and the CPS & cat were replaced.

Not sure if any of these will account for the way that the Jeep currently runs?

It seems to be getting worse, the Jeep is now missing on idle. This morning is the first time I've had a miss on idle, before that it idled smooth as. This morning started, idled smoothly then a single miss, then smooth as and about 10 sec's later another miss and repeated 4 times.

Will look at the TB reset and cleaning TPS contacts next unless anyone's got any other ideas?