Engine Surge (VIDEO).
 

I completed a lot of work on the XJ today. Still though, my work continues as I have more issues to resolve, and projects I would like to do.

Today I swapped my motor mounts out in preperation for a new manifold swap. I also installed a new window regulator at the drivers side. Then had to turn my attention to the ladies Subaru.

Getting back to the XJ, I thought I'd document some issues.

Issue #1) A rattle... I'm glad the video actually picked it up rather loudly, because really it's quite faint.

Issue #2) My engine has been surging randomly. By that I mean... The RPMs will hop up very quickly, then die back down. Usually does this at idle, but it will do it while driving. This concerns me more so than the ticking. Truth be told... It's quite a healthy engine. You'll know that when you hear it.

http://www.youtube.com/watch?v=oczvf...ature=youtu.be

The engine jolting starts at 0:28 seconds during the video. You'll see it happen once or twice. Then you'll get a peak into the engine bay. I promise... my engine is never that dirty. You'll also notice the ticking happening. However you'll hear right around 2:11 into the video, the engine sounds quite healthy.

Known issues:

Manifold crack.
Power steering leak.

Thank you for watching.

P.S. Sorry for the poor video quality, it was taken on the phone. You may need to turn your volume up.

I'd also like to note that at 1:23... That's me giving it gas. Just as a comparison.

Bump.

Have you cleaned your IAC? i would start there for the surging. Other than that a vacuum leak.

I"m interested in #1 i have what seems to be the same noise. and I'm really hoping its not a cracked flex plate.

no1 is definitely noisy. have you tried tightening the flexplate bolts?

I did.

In what limited room I had, I couldn't get them to move with a box wrench.

Can I clean that with throttle body cleaner?

you can. just use it sparingly and brush it gently with a toothbrush. dont put much pressure on the pintle as it can break quite easily. there is a good writeup on this somewhere on here.

Not sure after watching the video again that it is the IAC. It's certainly worth cleaning but that change in revs is very quick. Not seen that before (in my limited experience lol)

When i cleaned my IAC, my revs went smoothly from 1000 to 2000 and back again, it was gentle, yours looks very erratic.

Start with the IAC and let us know. good luck.

It does go quick. I can't even rev it that quickly. It's like the XJ gets hiccups. I will take a look at the IAC... However when cleaning the TB, the TB itself wasn't even that dirty. The IAC is located on the side of the TB correct?

As for the knocking... I don't know. In person, it just doesn't sound like it's coming from the engine. If anything, from the very back.

i've heard similar knocking coming from a flex plate, really not sure what else it could be besides engine internals...

There are many more knowledgable people here than me though :)

jeepxj19 did the IAC clean writeup, full of useful pics etc. just found it under write ups. I would post the link but i'm using the android app.

Well I pulled the IAC. It wasn't really that dirty. I assumed as much because my TB wasn't that dirty when I cleaned it a few months ago. The socket it plugs into had a decent amount of build-up, but not enough to really rule anything out.

I ran the XJ for a bit and didn't notice a difference. The engine jolts to me, seem completely random. I didn't get any this time around... So I'll have to put a few more miles on her to tell.

As for the knock... I'm out of time for today, though I'll check the flexplate bolts again when I have the time. Maybe this weekend.

Any other opinions?

Hmm...

Throttle Position Sensor could be a potential suspect. Or it could be the manifold leak that's letting air into the system, causing a sharp correction via the O2 sensor...

Then again, I think the Moon Landing was real, and wrestling is faked. Take my thoughts as the Lunatic Fringe material they are.

:)

I'd say Throttle Position Sensor. I've changed this out twice on my Jeep, and thats what happens, sudden loss of power and it jumps back up. my vote = throttle position sensor