No, that's why I ask, I've replaced the clockspring. Don't want to muddy the original topic if its completely unrelated circuitry.

 

Looks like I'm in luck my dad had some very old Auto read OBD2 scanner but it deletes the code so we're good to go there.

 

That will make things quicker

...but back to the idle RPM problem, a misfire at idle is usually random @ idle, but manifests itself under load

you describe "flutter" at idle..and no evident misfire under load..that does not sound like a "misfire"..but something else.

imo, you need to establish the fluctuation & regularity of RPM at idle..something amiss there is likely to set a code ( once again, only imo )

I assume you have changed all spark plugs

 

its a bit anectdotal, but I must commend your determination here, as you have probably gone beyond what the "economic" repair situation

I have had this happen to me once, but seen it happen to a lot of people

The Service manager will say "how far do you want to go with this?..at $100+ an hour for labor...and they will fire the parts cannon (with your permission)

I recently had a chat about an XJ12 Jaguar, the guy has run up a $3K bill trying to get it fixed, and now wants to sell at $4k to cover the bill..but it still isnt going

It apparently has a blown ECU

upon me making enquires thru experts...no new or remans are available, the only guy that fixes them is late 70s, and not taking on any new customers

The only way to get the parts is off other enthusiasts who own the same model and have hoarded them from wrecks

 

I'll get a video of idle, cold/ hot doesn't matter. When I was first getting the engine going we replaced the NEWapp985 plugs and a new upstream o2. We suspected the plugs as not igniting well. I bought them based on a review of them running well with 4.0s. I think the o2 was the culprit though.

 

Watch "Jeep xj Slight idle fluctuations" on YouTube

 

I cant tell with the idle, sounds steady, only a digital or laser tacho will tell, I have both of these

It did not sound completely right to me when held at 1800-2000rpm ?, can I detect an off-beat sound ?...however, even the slightest exhaust leak would explain that

having the airbag light come on like it did must be exasperating...I cant even speculate on whether that might be an issue

you also mentioned an earlier cam sensor replacement..I would be examining the cam & crank sensor connector pins..forensically

 

Is related tho.

Did you replace the alternator post hydrolock?

 

Replaced one month ago

 

So you replaced everything EXCEPT the flexplate?

Doing any testing today?

 

a few questions from me

is it, or not, easy to remove the lower cover, crank it around and check for truth and also examine the notched area that passes the crank sensor ?

I know this will not be "easy", but can the trans be slid back, or engine forward a bit, and another flexplate bolted in without need to R&R trans or motor ?

what are others thoughts on that engine sound at 2000rpm ?


this is high level diagnostic work, I am fortunate to know a genius electronics engineer who is in our Jaguar club, an auto fanatic, he has all the diagnostic equipment to fix anything

As he is a contractor, when he was not working, he would charge $100ph to fix club members cars, they used to moan it was too much, however the dealer rate was $160ph, a 30yr Jag mechanic $130ph, and he was better, now he is working full time, rarely has time, we fixed some weird electrical issues on some later models recently

The Jeep dealer charges $130ph+ for labor

 

I can get more video of anything that helps. Lately it's been hot out so driving has been hell with no ac.

Ive noticed the hotter weather has the rpm dancing a tad more.

Does cam or crank sensor control rpm?

Are both susceptible to heat issues?

I'm not ruling flex plate out, but I looked at this thing close before installing the stock, obviously if there were visible cracks it would have been the time to replace it.

My gut says wiring or sensors but that's with no experience and my testing a handful if times turning out ok, and a diagnostic scope turning out ok.

Pin inspection tomorrow, I'll pull plugs and look at female side. Ive already tried cleaning them.

This has been such a goose chase. It's it safe to crack open the donor pcm? It's not installed because it didn't change CEL.

 

Maybe you should start at the beginning.

We're looking for bent, but yeah, you should've noticed that.

That's why you should bypass them en masse.

Absolutely! The issue is usually broken solder joints or fried capacitors. I've got some 220/35s you can have.

Except why are you taking it apart if that's not the problem?

 

I was just thinking it's worth a peak. I'll try jumping terminals again. And visually inspect the flexplate, Windows.

 

Just try to bes clear I'm goinng about this right.