My 4.0 just started to idle unevenly -- sort of like it's misfiring. It was doing this some months ago, but it went away by itself. Is this due to clogged fuel injectors? If so, would a bottle of fuel injector cleaner take care of this? Any suggestions?

 

First thing I would do would be to pour a bottle of Chevron's Techron fuel injector cleaner into my gas tank. It's great stuff. All of our vehicles get a bottle of it at every oil & filter change that I do....

 

I'm gonna say you have an ignition coil that was going bad and has now finally given up the ghost. You will probably start to get hesitation on acceleration, and then finally the check engine light will come on. Once that happens you can have the code read and possibly be able to pinpoint and replace the bad coil.

 

So, until the check engine light comes on, a diagnostic connector won't indicate anything?

 

A diagnostic may well provide data pointing to what's wrong. But it may not be in the form of a straightforward code (DTC). Instead, it may be either a pending code and/or a sensor (or other reading) that's out of range.

The issues then can be that not all diagnostic devices provide access to these data and also many people (and I include some garage "technicians") cannot interpret them.

In case there are pending codes, be aware they won't necessarily turn into actual codes but may instead clear (in the case where the cause was something temporary).

It's especially important to read but NOT clear codes when trying to diagnose a problem, since it can take a lot of driving to get the car to re-flag the problem in the diagnostic data.

Idle problems are often air leaks. Often, small ones. Try listening through a length of thin plastic tubing, moving the end around the engine bay WITH CARE (moving parts!).

However, for the 4.0 it's more likely you have one or more bad coils.

You may be able to see misfires by monitoring the O2 sensors (OBD or a 'scope) but if you're inclined to try this spend some time reading about it on the net. You can also monitor the coil pulses (more reading!).

John

 

Well, I started with the easiest first. I bought a bottle of Techron fuel system cleaner and poured it into a nearly empty tank of gas that I filled. I used almost half a tank today (about a month's worth of driving for me in one day), and I see no improvement. Looks like a trip to my local mechanic is in order. Thanks for the replies.

 

Part of your issue may be that you're not driving your car enough, especially highway miles. All cars' fuel systems do much better if they get enough uninterrupted highway driving to keep condensation on and in various parts (gas tank, fuel lines, exhaust system) to a minimum. Uninterrupted highway speeds also help to keep carbon deposits in your throttle body from building up too thickly. Frequent highway driving is often considered part of keeping a vehicle in good working order....

 

good advice, it also burns off contaminants in the oil, namely moisture accumulated while sitting and fuel accumulated at start up in and idling in heavy traffic.

Also run the car out to redline from a rolling start from ~30mph about once a week to keep the ring packs from getting gummed up.

 

my 3.0 V6 sport was doing the same thing but with the check engine light on......hooked it up to the computer and it showed up as lean banks.......opened the hood and heard an air leak on the small 3 inch plastic pipe just up from the MAF filter...replaced with a peice of garden hose and the car drives like new.....ordered a new pipe from jaguar for $3.50....

 

Did you buy these in the store or online? I looked and they are listing for like $107.99 each, at that price I will likely only be locating the bad one and replacing it.

 

what shop in long island do you go to?

 

Buy your coils on E-bay!! I got all 8 of my coils for my old 00 V8 for 225 plus shipping they are OEM from the OEM manufacturer, they just aren't in a Jaguar Box. Look for the one's that say Lincoln LS/Ford Thunderbird. Sometime they will list the Jaguar also, but they are all the same.

 

Deal of the century, why buy one at the dealer when you can buy all eight on Ebay!!

http://cgi.ebay.com/ebaymotors/2000-...ayphotohosting


I want to caveat and say that i am in know way affiliated with these people, but I did purchase replacement coils on ebay and they worked flawlessly.

 

So, that's $49 x 8 = almost $400 plus an hour of labor just for the ignition coils?