I know there are a lot of threads regarding rough idles, but I've read most of them and still haven't fully narrowed down the problem yet, so im seeking help here. I've taken plenty of measurements to determine if components are working or not. At the moment, my guess is that its either a clogged injector, or its getting too much fuel when idling.

Coils: 0.17ohms for all (measured at 200ohm setting)
All Lucas "made in japan" LHE 1510 AB except for a jaguar LHE 1510 AB on cylinder 2. Disconnecting each coil causes increased rough running, all identical, so ive ruled out the ignition coils for now.

Spark plugs: just put a new set of champions in, with correct code of RC9YCC. old set was the same If I recall.

Injectors: all measure 16.7-16.9 ohms (measured at 200ohm setting).

Coolant temperature sensor (2 pin) measures 1066ohms at ambient and 237ohms at full warm up (measured at 2000ohm setting)

Coolant temperature sender (1 pin) measures 885ohms at ambient and 85ohms at full warm up ( measured at 2000ohm setting)

The rough running idle can be described as an inconsistent shaking of the engine, which can be felt when sat in the car. Exhaust makes an inconsistent thudding, which im attributing to a poor combustion (clogged injector?).

Another thing ive noticed is a delay when revving the engine under the hood. Also doesn't drop revs quickly, and has a tendency to hold the revs briefly when when the throttle is removed, which suggests to me its getting excess fuel from somewhere. When I unplug the coolant temperature sensor the hesitation becomes a near stall when large bursts of throttle are given.

If anyone has any other suggestions, things to measure, that would be great. Would just like to see the old girl running smooth.

 

I'm assuming you have some car with the AJ16 engine, BeCause of the coils description. Can you identify your car in a signature so you never have to tell anyone what kind of car you drive again? You won't regret it,I promise.

You could have a vacuum leak.

Did you clean them the throttle body? I mean like take the thing off and give it a thorough cleaning, both sides?

Replace IACV o-ring helped me. That thing was flat.

After that, blow some smoke back up through the camcover bypass hose, and see what happens.

oh, and I believe your engine is due for RC12YCC spark plugs for the AJ16 engine. There was a TSB for that.

 

Check the crankshaft sensor! when they are defective they either dont work at all, or gives a bad signal to ecu when the car is warmed up, resulting in rough idle

 

I did the carb cleaner test, sprayed it around the vacuum hoses and nothing. Is there a more definitive test? Like testing for a specific vacuum value at warm idle?

I did suspect that, gave it a clean and put it back on. I know you are supposed to see 200 rpm when cranking for a healthy one. I sometimes get that, other times not. Il record the next five or ten starts and see what the dials show.

 

Every Jag I've owned...until now.... has made me suffer with rough idle woes to one degree or another. Each of them has been improved, to one degree or another, by having injectors professionally cleaned. My present Jag has a great idle...possibly because I had the injectors cleaned before I even put it on the road, while it was still in the 'project car' stage?

Question:

Is your idle quality good in "D" and choppy in "P"? My X300, and a few others, suffered this weird condition years ago. In a nutshell, when idling in "P" the injector pulse width is at the very lowest and there are a few cases (like mine) where a couple of injectors were lazy...not responding to low pulse width commands from the ECU.

Cheers
DD

 

My suspicions pointed to bad combustion from an injector or incorrect mixture, but not enough to pay £20 per injector on a hunch. A try first with new fuel filter and injector cleaner wouldn't hurt right?

Yep, did notice this but didn't think to mention it. whats the cure for lazy injectors?

 

Same thing happened to my car, cranks at 200 rpm and perfectly fine at cold start but once car is warm idle is rough and eventually stalls when put into drive. The sensor either fails or it produces a bad signal so the ecm tries to compensate for it resulting in a rough idle, i would change the sensor first, they do fail anf they will fail on every jag sooner or later

 

Can't hurt.


I sent all six out to Jaguar Fuel Injector Service. Dave, the guy who runs the place, had no way of emulating exact pulse width commands that would come from the ECU. But he was able to identify two injectors that, even after servicing, were clearly sub-par in terms of flow and spray pattern and which seemed less responsive using whatever method he has....I can't remember exactly. He had a supply of known-good injectors on hand which responded well to refurbishing

Cheers
DD

 

Block off the air filter with some plastic. Then pull the hose off of the camcover, light a cigar/pipe/etc and blow smoke into the hose. Wherever you see smoke, there's a leak. That method helped me spot a leak at the IACV and EGR. Replaced an o-ring at the IACV and had to timesert the screws for the EGR to get the right torque on them. (Also replacing the EGR gasket)

Even then you might not spot it. The toughest one to spot is the vacuum leak at the intake manifold.

 

[QUOTE][QUOTE]Block off the air filter with some plastic. Then pull the hose off of the camcover, light a cigar/pipe/etc and blow smoke into the hose. Wherever you see smoke, there's a leak. That method helped me spot a leak at the IACV and EGR. Replaced an o-ring at the IACV and had to timesert the screws for the EGR to get the right torque on them. (Also replacing the EGR gasket)

Even then you might not spot it. The toughest one to spot is the vacuum leak at the intake manifold.

I'm not catching on how this would work without stalling the engine , although it looks to be very helpful and in all due respect I don't understand fully . I plan on using the method and useful information you provided for I have the same engine uneven idle below throttle up .

Thanks , Parker

 

Yep , I can be pretty stupid at times , figured it out , engine off .

 

Had a proper look at this, and the difference is very noticeable. P tends to idle at 800 rpm with the intermittent shaking, D idles at slightly more than 600rpm, maybe 620, and the engine is nice and smooth.

 

Unrelated question, but I didnt want to start a new thread just to get an answer. I notice that there is an unused white 6 pin plug in the boot, and I got to thinking whether the wiring for an amplifier is already there, even though I dont have the HK amplifier on my car, so by that I mean is the wiring for the speakers already installed in the boot? I can find info that the heated seat wiring and similar options are installed on all cars, but I cant find anything with regard to amplifier wiring on a non HK car.

If so then it makes for a very easy job of upgrading to a premium amp.

 

Referencing Wiring Schematic fig. 18.1 and 18.2 the speaker wiring on the non - premium system comes out of the Alpine AJ9500A head unit and with the premium amplifier option the speaker wires come out of the trunk with the amplifier using the same AJ9500A head unit . Unless the factory put in that premium speaker wire harness in the trunk you would have to tap into the speaker wires up front with the head unit . The 6 wire connector you have in hand may be the premium amplifier input . To improve the sound of the speakers that you have ( the foam cones surrounds rot to dust giving poor sound ) there is a cone surround replacement kit ( $ 24 dollars for all 4 ) non - premium speaker size kit # SWK525 for the factory original Philips / Jaguar # LNA4140BA speakers . I have the non - premium sound system and the premium system has different main door speakers with different speaker part #'s and size ( ? ) hence the Harmon Kardon reference I believe. Order the optional better suited glue for outside applications . See the video on their website as to how to do the repair . Don't forget to put new mounting foam on the speaker frame ( from the hardware store ). The tweeters should be fine . You can put in a crossover network and place a woofer box on the back seat with quick disconnects to reconnect in trunk . You can modify yourself the AJ9500A with an auxiliary input jack for smartphones or MP3 players . Any questions just ask . Good music should always be played loud . I designed and am handcrafting a 4 x KT88 2 channel push - pull vacuum tube valve final amplifier hiding the transformers to set on my dash to give my Lady P some class . Bypassing the Toshiba TA8221 solid state final amplifiers in the Alpine AJ9500A .

5 1/4" Speaker Repair Kit For Replacing Foam Surrounds - Advent, Altec, AR, Boston Acoustics, Infinity, JBL, Paradigm

Auxiliary Input via Radio / Cassette

http://www.alldatasheet.com/datashee...BA/TA8221.html

Thanks , Parker

 

Sounds like youve put a lot of thought into your future system Lady P, same for me. Was going to go for some Hertz 5.25 components front and rear, with hertz amp. On top of that, some soundproofing in the doors, and some custom enclosures for the speakers, as the jags over here at least, have quite a large cutout from the factory thats large enough for a custom MDF speaker enclosure.


I was also going to put twin 8" subwoofers under the rear bench, but I didnt realise how shallow the compartment actually is, which is a shame as I had planned to do the enclosure in matching carpet material with just a vent at the bottom, as in a bandpass style enclosure, so you wouldnt even notice.

 

As it should , as it should . If you want to run speaker wires from the back to tap into the front connector you can run them under the plastic on the edges of the headliner . Protect against the sharp edges . That is where I ran the subwoofer wires after the bandpass filters which is up front after the final vacuum tube amplifier . You may want to shield the wires from each other by spinning around them strips of aluminum foil which is grounded at one end . I didn't have to in my setup as the subwoofer wires were alone , one leg on each side , and not possible to interfere with any other wires . To put a single factory location subwoofer in requires removing the hat shelf and rear seat to do that . Besides it does not make sense to put it above the fuel tank that has a small resonance dimension as the reason for the relocatable subwoofer box . The speaker frame dimension is 6.25 inches ( 6.5 will mount ? ) with the cone being 5.25 inches with a 3 hole bolt pattern .

Now back to that engine , is yours running rich spitting raw fuel out the exhaust or have a short term fuel trim above 0.0 ? Read with a ELM327 not a code reader . I just made a smoke pump machine out of a 12 volt tire pump to check mine for vacuum leaks for I have the same rough idle with a STFT of 24.2 spitting fuel and goes toward 0 at throttle up . Veteran Member
poster Vee suggested that I have a classic vacuum leak . Something I thought of was the 2 D shaped parts of the valve cover gasket on the back side can easily be out of place and not see it . I caught myself once before . Off to the 25 cent cigar shop , I'm sure Lady P is not picky on which flavor .

Thanks , Parker

 

My jag isnt too friendly with these ELM readers, im thinking because its 1995 and therefore possibly not OBDII. I will have a peek around the cam cover gasket.

Only thing thats certain with mine so far is that Doug was spot on with the lazy injector theory, as mine idles fine In D, but terrible in P. Im generally thinking fuelling issues as when revving the engine using the butterfly itself, large doses of throttle almost stall the engine out before it revs, and then when you let the throttle go, it hangs briefly. Really need to give the gearbox a flush too, as it shifts pretty harsh. Fluid is red, correct level and not smelly or burnt.

 

With the ELM327 the free sofeware on the internet will only show you the screen but no values , codes ,or graphs until you buy the authorization key . What a rip off . The other issue is that the cheap ones on Ebay are Chinese counterfeits other then the original Canadian developer so you have to correct the device driver ( or firmware ) . The 02 sensors on the X300 or Titanium oxide vs. the more common Zicronia oxide type . The difference is the Titanium generate a changing resistance that as a reference voltage that comes out of the ECU is changed before it returns . The Zircronia generate their own voltage from ground and gives that value to the ECU . The PID's on the ELM327 have to be modified to take this into account . If you Private Mail me I will land mail you only a Operation software program that works fully . The OBD 2 was not mandated in the US until the 1996 models but the engineers may have been ahead of that date as the 1994.5 was the first production X300 model . Europe was not mandated until 2001 I believe but for simplicity it may have already been compliant . If you had a OBD 2 read no codes that may be a false reading and I would suggest reading it again and and pulling beforehand the coolant temp sensor to see if you have a valid test configuration . You may have to revert to the OBD 1.5 or 1.0 pin jumper procedure and you my see a code of interest .

As to the injectors , fuel porting surfaces could be fouled causing lag or laziness and a flush with MEK ( Methel Ethel Keytone ) may resolved this and it would be a cheap and proactive try . The connectors in the trunk lights are the same and if you wire 2 of them in parallel with a 4 inch piece of rubber hose with clamps and 2 of the injectors you can pulse some MEK through them . Drill a small hole in the rubber tube and epoxy the small red nozzle tube in place . Just pulse the injectors with a battery but don't leave in the spray position too long for it may burn out the injector coils . MEK is very explosive and can be absorbed through the skin and kill a liver or kidneys so take safety precautions . The injectors have a basket filter on the inlet side that can be removed threading in a screw and pulling with pliers . As a cheap option you can clean the baskets up with the same MEK with a fine soft brass brush . A toothbrush will melt plus the residue will migrate to the valve seats and you would have the same issues of laziness and contaminated spray pattern passages . Reusing the O - rings is up to you as a on condition inspection . EBC8492 . This may or may not resolve your engine regulation issue but is a cheap try and from a routine high mileage maintenance item it can't hurt . You can bring the recommended by Jaguar RC12YCC spark plugs gap back down to .035 from the .040 addressed by a Jaguar TSB as that would give you a better spark but reduces the service life of the coils . You may have a weak coils and a smaller gap would compensate for it , but that also means that the coils are dying and on the way out .

https://www.jaguarclassicparts.com/uk/part/EBC8492

Thanks , Parker

 

Took a video of this, as it is bugging me, and now I can see it clear as day. Play the video frame by frame in vlc player, I can count the frames before it starts to rev, its pretty obvious when I stamp on the throttle. But you can actually count about 9 frames of the revs dropping after I press the pedal before it revs. When comparing to the reference video, I count 40 frames from idle to 2000 rpm, whilst the reference does it in 21 frames, and no initial rev drop. I know mine is the 4.0 and the one in the video is a 3.2, but the difference shouldn't be that significant. My car is the one with the walnut dials.

https://www.dropbox.com/s/bn2mmdr60a...14402.mp4?dl=0

 

Main irritation at the moment (besides the fact my ac has all leaked out during our UK heatwave), is that my fuel gauge simply never seems to work for any period of time. Its much more reliable on 1/2 a tank or more, but once it get below half it will usually fall to empty within a few miles. Wide open throttle also seems to encourage the gauge to stop reading. Ive already replaced the old sender with one from british parts, and its giving resistance readings from 900 to 90 or so ohms when tested. Not really sure what to try next, although id like to check the obvious, and that you install it with the float to the right of the assembly?

Ive had situations where ive been sat still, and the fuel gauge starts at 1/3 or something like that, and I can watch every 15 sec or so it drops a pinch, so in two minutes its now reading empty, really weird.