Rough idle - loss of power.
 

Hi All.

I've recently had a problem with rough idle and loss of power. I cleaned the connections to ign. Amp, idle valve, distr. cap, coil. It was Ok for a couple of weeks - but now it's back, and happened from one day to another.
Cleaned the same parts with no result. During engine load it looses power, gives a jerky ride and just about to stall, but it getting better when engine picks up revs. At stand still, there is no indication that engine will stall, just under load when drving, especially after stopping for red lights e.a. The engine starts from cold with no prob, but gets worse as engine gets warm.

With hourly rates at $250-300, it would be nice if someone could guide me to a self-fix, rather then spending thousand(s) for a diagnose at my local Ford garage. (no jag-dealers close)

I have a small leak at front exhaust manifold that will be fixed when parts arrive. Can it be related? (I have drven for weeks with the leak without trouble.)

Any suggestions for what to look for?

Rough idle - loss of power
 

Oddman.

You're symptoms sound real familiar to an issue I had a few years back. I won't go into high detail (conditions similar to what your experiencing), other than the condition would be erratic, meaning okay for a few days, then show up again.

In my case it was a faulty oxygen sensor. I had everything else checked, as you have, with all other components and could find nothing. You may be able to meter the sensor for ohms or resistance, not exactly sure, but I do know a new oxygen sensor cured the problem and have had no re-occurrence since.

Good luck.

Thanks a lot, Rob.

I see a oxygen sensor wouldn' break the bank. I' ll order on at once. Thanks again.

Hi

Changed O2 sensor and Fuel filter. I think one (or both) of those were the culprit. Changed Ditributor cap, rotor, plugs and leads while I was at it.

All fine again and drives lovely...

Norway huh? I hope you have a warm place to work. Do you have tools? You need to do a compression test on that vehicle. My initial response is a head gasket. Do you know how to do a compression test? We need to start there. If you have the desire to fix your own car, willing to learn and get dirty, you won't be paying that 250+ an hour any more.

Hi MrTalkRadio.

No prob with the car at the moment. Recently changed parts as described above - all Ok. Main culprit was the O2 sensor, but I also had a suspicion to the fuel filter... All changed and all Ok again.

Yes, 5 below 0 in Norway right now, the Jag starts with no hesitation :-) next issue is a transm and diff service - but i am no mechanic so I have no option than to spend some $$ from time to time. Of course, simpler maintenance I do myself...

rough idle
 

Oddman,

That's good news, glad it worked out. In regard to the transmission and differential, are you talking about rebuilding them, or just maintenance?

Changing the fluids is no big deal, other than putting the car up on jack stands, fluid, filter and gaskets is it.

Then again, it is cold out isn't it? I grew up in North Dakota, I know all about cold. Also, I'm half Norwegian, the other half is Irish. My grandfather came directly from Norway in the 1880's. You probably didn't want to know any of this, but too late now :))

Good luck

Hi MrTalkRadio.

You have good genes then :-) nice to know a little about you.

Yes, it's definately winter in Norway, but I enjoy my Cat even when weather is cold. Nice then with heated mirrors and door handles :-)

And, as we speak, I've planned a gear and diff service, for maintenace purposes. Today, at my way home from work I had some problems. If you have a look at my latest post, maybe you have a comment?

Sorry.. Rob! :-) my bad calling you Mrtalkradio..

Loss of power XK S3
 

Have a similar problem with the car lacking power after some time in the garage. It runs OK on idle and gearbox works fine but it feels tired lacking power to reach 50 mph. Just like the motor its weared down but oil, oil preassure and the compression is OK. Could it be the AFM that needs cleaning or replacement after a long standstill:icon_question: