Rough Idle
-rough idle when idling or stopped (in gear)
-still rough idle in neutral but significantly less
-drives normally when pressing gas
-uses more fuel now

Changed
-spark plugs and wires
-Distributor rotor
-cleaned connections inside distributor cap
-Button inside cap still has spring

Next Step - Change Distributor? Can anyone help me out here?

This started after a heavy jaunt on the HWY where I was giving it pretty hard for a prolonged period 120-140kms. Feels great flying past new BWMs in a 1992 Jag!

The changes I made really haven't made a difference.

Thanks for any help!

Dan

 

Hi Dan

Re-post in the 'Xj40' section for best results

Cheers
DD

 

Only 120-140?

Cheers,Jim.

 

Check your gearbox fluid level.

120-140 is not that fast to be honest. Unless you are talking about Mph?

 

Welcome to the forum Dan,

I've moved your question from XJ6 & XJ12 Series I, II & III to XJ40 forum. Members here with the same model will be able to help.

Graham

 

Hi Dan,

There are a number of possible causes of rough idle, and in my experience it can be the result of more than one issue. The first thing I would recommend is that you check the Vehicle Condition Monitor for any stored Diagnostic Trouble Codes that may help narrow down the diagnosis.

With the car in Park and your foot off the accelerator pedal, turn the key to Position II (Run or On), but do not start the engine.

Press the VCM button on the trip computer to the right of the steering wheel.

Observe the small display window below the speedometer. If any faults are stored, they will show up in the form of "Fuel Fault 24," "FF69," etc. An asterisk indicates more than one fault is stored.

Off the top of my head, some of the possible causes of idle issues include:

Distributor cap terminals eroded
Fuel filter obstructed
Contaminated fuel
Fuel Pressure Regulator (FPR) not holding sufficient pressure in fuel rail
FPR diaphragm failed allowing unmetered fuel to enter intake manifold via the FPR vacuum hose
Air filter obstructed
MAF sensor problem - may just need the hot wire or electrical connector cleaned
EGR valve or system malfunction
Leak in intake air plumbing or vaccum line between the MAF and intake manifold gasket
Coolant Temperature Sensor (CTS) malfunction or problem with its wiring harness or electrical connector causing incorrect fueling enrichment by the ECM
O2 sensor lazy or voltage not swinging
Exhaust leak between manifold gaskets and O2 sensor
Ignition coil or ignition amplifier failing or loose or corroded electrical connectors
Fuel injector gummed up or obstructed or problem with electrical connector
Idle Air Control Valve (IACV) gasket leak or carbon buildup on stepper motor plunger
Compression low in one or more cylinders
Throttle butterfly valve gummed up
Valve clearances need to be adjusted
Burnt valve

There are probably several other possibilities, so any stored fault codes will be helpful in narrowing things down.

Cheers,

Don

 

Don thanks man.

you provided me with a ton of info.

I really appreciate it.

Ill let you know how it goes!

This site kicks A$$!!

DS

 

KMS.

Not that fast or as fast as she'll go.

But as fast as I am willing to go without risking my license