Like many on here my car has idle issues. (96 x300)
Started with violent intermittent miss with eventual stall.
I searched and read relevant threads.
I tried one fix at a time to determine what actually worked for me.
-Swapped the NGKs for Champions--ran perfect about 240 miles that weekend with mostly inner city stop and go traffic.
Issue returned.
-Checked coil values; all above 9.0, boots looked fine.
Ran fuel inj cleaner through several tanks of fuel and car idled perfectly for a few miles. Intermittent idle returned with occasional stalling. Transmission light on, 2nd gear start. (Pulled over for a few seconds, restarted and was fine- no light)
Changed 2 prong temp sensor, seemed to help at first, then returned to missing idle.
-Cleaned MAF, TB( heavy soot) and intake opening.
Perfect idle for a few extended traffic stops; then returned.
Swapped out clean used TB complete and Maf. 2000 rpm idle.
Installed original TB, again idles perfect for a few stops.
Check engine light finally lit, many codes as I had unplugged everything at one time or another to see the result. Cleared the codes and light and it relit later. Codes were slow responding O2 post cat and #5 miss.
Checked coil, was okay, swapped with another. Plug was fine.
Cleared codes/light. Idle still screwed, now drops to 500 rpm and stalling as I slowly feed throttle to get under way.
If I put it in neutral and rev it a couple times to about 2000 rpm or so, it usually settles to a steady idle as long as the stop isn't too long.
Swapped out IAC with used. Plunger moved normally, I suppose.
No change.
This weekend I installed a new egr, cleaned the passages, cleaned everything again. Idled perfectly on a test run, next day same problem.
RPMs no longer drop quickly as I begin to brake, but want to settle to a 500 RPM idle and stall.
I drove in a heavy traffic jam with 2 feet keeping the idle around 1000 rpm. 35 minutes of stress and frustration!
It seems that everytime I fix something, the car runs perfectly... for a bit.
I would commit to tps reorientation but I have trust issues with local dealerships. Can anyone recommend a reputable Jag specialist in the South Jersey/Philadelphia are? Classic Jaguar in Cherry Hill are close but will they pull my eyeballs out of their sockets? And not fix the car anyway.
I work and have worked for new car dealerships and all they do is replace parts. Hell, that's what I can do!
Having said all that I enjoy driving the car. I put over 3000 miles on it in the last 2 months.
Can anyone help. Thanks in advance.

 

Could it be the crankshaft position sensor?

 

Been there...a couple times





Oddly, my latest go-round with the issue was fixed by replacing Champions with NGKs, which was a totally whimsical move on my part.



Yup! That's the pattern. I've been fooled a few times as well. Only recently have I felt confident in calling mine "fixed". For *weeks* I assumed the car was only fooling me again.





"All above 9.0...". What does that mean?

Are they the original coils? Or replacements?

The ignition coils on these cars are a problem. A problem that is magnified by varying quality replacements.

The only test in the manual is to check primary resistance. The spec is .75 ohm. I've found that being "in spec" with respect to primary resistance does nothing to ensure the coil is good.

My theory, which I have no technical/scientific explanation for, is that *some* coils reject *some* spark plugs. If there's a shred of merit to this notion then someone else will have to come along and explain it to me. The only thing I can think of is some sort of resistance problem.



What about the O2 sensor?




I experienced the same situation where a short duration idle was fine but, if left at idle, the engine behavior would deteriorate. If dirivng conditions allowed for stop signs rather than l-o-n-g traffic lights, a person might never have known there was a problem with my car! Also, in my case, the symptom never developed at all unless the car had been driven 20-30 minutes.



I faced the same reluctance, but for different reasons, mostly logisitics. Still, you might have to take the plunge for a reorientation. Just don't let them replace any parts.


I'll add that 2-3 years ago I had a idle-misfire-stall that was fixed by replacing the crank sensor, as mentioned above. In *that* case I was lucky. It was a cut-n-dry fix.....quite unlike my recent experiences.

Good luck.

Cheers
DD

 

goose:
You are fortunate enough to have Doug's advice coming your way. I would bet he is the world's consummate authority on X-300 Idle miss issues!
I suspect both you and Doug's problems and extended repair process is a result of two or more contibuting causes. In my experience, thats what causes problems troubleshooting in any control system.

I did not see any indication you had tested or replaced the TPS. Using either a meter (analog is best), or using your scanner, reading the TPS position, slowly move the tps from idle and measue that the voltage steadily increases. Also, make sure the TPS returns to the same value each time the throttle closes.

The reason I suggest looking into the TPS is that it is involved in allowing the Idle control circuit to operate, and it affects idle mixture.

It is interesting that in both your and Dougs case, you got improvment several times after doing things not seemingly related, then having the problem come back. Were both of you carefule and pulled the battery cable, resulting in a reset? And... I suspect the problem might change from time to time due to the various adaptions that go on in the ECU systems.

In my case,I did not experience of the problems coming and going. The idle just hunted up and down,and I noticed no missing. I THINK that among the things I worked on, replacement and recalibration of the TPS is what fixed it.

Good luck and keep us posted!

 

HA! Thanks Ross, but I think you meant to say ".....most consumate sufferer...."

The word "authority" suggests an understanding of the problem and the fix. In reality, I am as mystified as ever.



I agree, but what were they? I still don't know!

Being unable to identify a conrete fault is frustrating. Some faults are apparently too subtle for me to discern. And sorting cause-vs-effect with OBD II systems...especially a cantankerous one, as mine appears to be....can be flummoxing.



I agree




Yes, interesting. How euphemistic



Yes!





I would agree. And the lack of convenient access/abilty to reset/reorient parameters is, I think, a big contributing factor in these situations

Cheers
DD

 

I have two bits of advice that I have used myself many times. First I would start the car and while it is running unplug the MAF, if the idle evens out, misfires go away and she sounds better the MAF is bad. If no difference then I would remove the coil cover and take a look at them at night, if any are bad you will see them lighting up in the dark. Checking the ohms on the coils is not the most reliable way to check them. you can also test coils with a HEI Ignition tester, costs under 20.00 . just my two cents

 

Excellent tip but, to clarify,a coil that lights up is clearly bad....but lack of "lighting up" doesn't prove that a coil is good!


Cheers
DD

 

Many thanks for all your imput.

The reason that I cleaned/replaced MAF was that when disconnected, it did smooth out. Same for the temp sensor. No difference now.

The lopey idle persists intermittently, but the issue of the RPM dropping until stalling is relatively new. Maybe the crank sensor is failing.
I only found a rebuild kit as the OE is discontinued.

Also, after sitting overnight it general behaves properly. When I leave work in the evening it usually shakes its brains out immediately when I start it.
It feels like it's loading up; I rev it a couple times to 2000 RPM and it smooths out for a few minutes only to act up again a couple traffic lights later.

The O2 sensor code only surfaced a couple times in the last 5 weeks, so that is intermittent as well.

The coils: 4 Lucas 2 shady brand. Lucas are consistent at .90 to 1.00 and the aftermarket ones higher up to 1.20 ohms.

I have not hard booted the car in fear of loosing the radio code. Im looking into a gizmo that plugs in the lighter receptacle with a 9V battery that claims to save the radio settings. Will that save ECU data as well?

I will retrace my steps this weekend and try to find a suitable shop as well. All of the advice mentioned in this thread will be considered and
looked at.

Lastly, I have not explored the possibility of a vaccum drop... nothing apparent at the moment but I'll think about it some more.

Again, thank you all.

Ernie

 

Ernie:
If you have a US radio, there is no code. And, YES, if you keep the voltage up on the main bus, you will keep the ecu ip as well.
The check for the crank sensor is see if you get a tach reading while cranking. If it cranks up right after a shutdown, I would find it hard to blame the CKPS, but you never know!

 

Due to complicated family issues I've had little time to devote to my Temperamental Mistress. She's older, very classy, and knows how to move me... but every day gets on my damn nerves!
Also having issues with my Soulless Servant (Saab Turbo).
If it weren't for my Australian Crossdresser (Monaro GTO), I would'nt have any fun! I may as well surrender to a Volt that drives like a forward moving elevator.
Anyway... I hard booted the Mistress, replaced the silver EGR with a new one, tested and again swapped the IAC. Can't detect any vacuum leaks.
No change. In fact it seems to be getting worse. I adjusted the throttle cable to the point where it was hanging up a bit, and back.
Fearing a perpetual stall, I replaced the crank sensor as well. Bought an O2 sensor but no time to install yet.
Sometimes it will be idling PERFECTLY for a bit and completely shuts off for a moment, drops to 2/300 rpm, dash lights flash and regains its composure.
Akin to the TV going black, no picture, no sound and coming right back on.
Sometimes upon shake shake stall, the trans lamp will light, trans starts under way in second gear and P1775 and P0727 gets stored.
Pull over , restart like nothing happened.
I have a 60 mile daily comute and enjoy driving the car immensely, but toss in a traffic jam, and she'll begin the shake shake cha cha cha.
I suppose when I replace the oxygen sensor I will have to reorient the TPS. I'm tempted to replace all the coils as well but I'd be seriously pissed if it didn't fix the problem. Maybe I'll part it out.
Thanks to all your responses and to all those other posted threads I have been I have been drawing insight from.
Ernie

 

The flashing dash lights suggest a coil problem

Cheers
DD

 

I have many years experience in the manufacture and testing of wound components (coils). A resistance test will tell you very little other than the coil is not completely open circuit or completely short circuit. The biggest reason for failure in ignition coils is the breakdown of insulation paticularly in the harsh environment of an engine bay where they are subjected to rapid temperature changes, high operating temperatures and moisture. Initially this will cause intermittent problems but once the insulation is initially degraded it will only get worse leading either to complete failure or consistently poor operation. The insulation breakdown may be completely internal so there will be nothing to see. You can't properly test coil operation and insulation without specialist equipment. If you know a mechanic that has picoscope or something similar and who knows how to use it it may be worthwhile to get him to look at the coil waveforms when the fault is present as any intermittent or poor performance problems should be apparent. Other than that I am afraid it's down to replacement with known good coils.

 

V126MAN:
All true, but the replacement need not be all the coils. Simply buy one and rotate it through positions.

 

Okay, short story long...
I had the faulty O2 sensor replaced and noticed a considerable improvement.
Still did the idle dance and stalled a couple times but it would hold a steady idle during a long traffic light most of the time.
Now I noticed a stumble/ misfire when lightly accelerating on a couple occasions.
So I bought another Jag for parts. Runs really well and I drove it home some 50 miles. Swapped out the coils and...VOILA!!!
All of you that predicted the coils as the culprit were right. The parts car still had the Lucas units.
Big thanks to everyone that assisted me in curing the shakes.

Now... anyone need a parts car?