Hi there,

after finishing all the chains and starting like a dream, I'm experiencing a few little idle niggles... Well, mainly when going from D to N, R or P. The revs will drop to around 500 rpm and then creep up to 650 rpm again but rather very rough.

It does that only when going OUT of D. When putting it in D, it stays nice and stable.

When I for example then rev the car in N or P and let off the gas, the revs drop again and then take a couple of seconds to return to a stable idle.

The timing is spot on. Nothing electrical was damaged. The only thing I can think of, but doubt it has something to do with this, is that the transmission fluid isn't at a "full" level (about 300 ml fluid are missing). I didn't have time to do that...

So, there are no fault codes saved in the ECU/car diagnostics. The engine runs, when running, smooth. Idles otherwise after the "wobble" as if nothing happend...

What could it be?

Help and tips are greatly appreciated!

Cheers

Damien

 

Hot engine, watch fuel trims. May be a small air leak or something else but see what the trims show. At idle then about 2500rpm.

 

Have you checked the plastic brake booster vacuum line going into the intake sweep on the passenger side under the throttle body? The plastic collar hardens and cracks as does the o-ring inside the insert. If its not broke and just letting air in intermittently from the hardened pieces, ...saying when the engine torques..., that may be your issue?

 

Mine was doing that for a while after the spell with fuel pump failure. I think the ECU just needs to re-adapt to your new engine "tune". You can force it by resetting the ECU : disconnect the battery ground cable FROM THE BATTERY, and touch it to the live terminal for a few seconds. Or just keep driving. Mine took a few trips to figure things out.

 

I did my timing chains and the car would idle ok but going from park to reverse it would bog down and even stall. The stall was worst because it would have trouble then restarting. I did straighten out after a while but the other problem I had then was one of the cover gaskets dropped when I flipped the cover over and I had a leak into the valley that I could not see under the plenum. Not sure if fixing that helped or the computer just got happy with the new timing. Likely will get better. The other thing is check the small load breather tube and the orifice in the Left valve cover and make sure you have vacuum and that the hole into the valve cover is open. There are a few things to check. May or may not help.

 

Sorted!

A software hard reset worked wwll. The lack of power above 4000 rpm has gone too...

The tranny also is now more responsive than before...

Cheers for the reset tip! Worked wonders!

 

Keep an eye on it.

You've made it forget the fuel trims etc - and made it start to relearn. Fingers crossed it will be fine.

It'll also have unset all the OBD monitors (you may need them set to pass state inspection - read with OBD in a few days time).

 

-> Germany... No OBD emissionstests here with a 97 XJ8

I'll keep an eye on it. I doubt it'll cause issues now... But I'll still watch it

 

How lucky not to have those!

Still, you want it running right (or nearly so). Fuel trims are worth a look.

 

What it needs now is a good blast up the autobahn ;o))
And it will all settle back into place.

 

Well..... not if it's an air leak. Or if it's a part-blocked cat. Or...

 

Done... Was a struggle getting it up to 200 kph (125 mph) but that is a thing of the past.

What I did notice was that the economy was dreadful at first. Now though 10l/100km. That at a normal 120 kph pace tops with heavy traffic around the autobahns. Can't complain about that...

 

Good job ;o))
10litrs/100klm is normal, that's what mine does all the time at same speed.
I have had mine up to 260kph....but only once, never again ;o))
I use 95 octane fuel with the occasional bottle of octane booster just for fun ;o))