I'm about to clean the MAF sensor and Throttle body. Any tips or tricks those of you with years of experience could pass on would be much appreciated. The model I'm working on is a 1995 XJ6. Runs fine just a loopy idle and need a 15-30 min warm up before driving in the morning (or whatever time of day I decide to drive it). I'll also be doing the spark plugs. Any tips or things to watch for here would be thankfully received as well.
Thanks in advance for any tips or advice.

 

First i would get two seperate cleaners, one for the MAF and one for the TB. Second i would take the entire intake elbow off and remove the maf to give it a thorough cleaning. then i would remove the entire TB off, being mindful of the cruise control connection that has a screw, washer and bolt that can easily be lost if you drop them. The TB doesnt use a gasket so no worries, take it out, get two hose clamps to clamp the coolant hoses located on the bottom side of the TB. Once the TB is out you can give it a thorough cleaning, i use a cotton towel and tb cleaner until it shines! then to put back, just do the reverse. Careful with the tps located on the bottom of the TB, you dont want cleaner getting there as this could be bad. others will chime in on this, hope that helps. Oh and be careful with the rubber boot that connects to the TB as this can easily rip.

 

Today I ordered plugs as they were out of stock. I did check a couple of them and they look very good and fairly new (it seems). I sprayed a cleaner in through the air intake and this seemed to help but I think your right a complete tear down and cleaning will help. After a couple of hrs running and a few short shut offs I shut the car down for about 10 mins. It then refused to start. After several attempts and checking all hoses and checking for a spark (good spark) I took stock of attempts. The plugs where all good but also dry. This lead me to believe that there was no fuel. I removed the gas cap and there was a loud sucking noise. left the cap off and it started right up. put cap on and it ran rougher, took off smoother. Has anyone else seen this on a Jag. I've seen it on bikes but never a car.
Summary. Checked voltage and it shows good even when cranking. Tried starting with big booster and made no difference. Sprayed 1/2 can of clean flo throttle body and MAF cleaner through intake with motor reved. Checked for spark and color of plugs, all good. checked all intake hoses for leaks (sprayed ether around connections and listened for reving). Tomorrow I will take MAF off and clean throughly (any suggestions for type and kind of cleaner?) and change plugs just because.

 

OK, your up there, and I am down here, and our cars are VERY different.

I believe you have an EGR (exhaust gas recirculating) system, we dont, and I read constantly of this system causing grief with idle, and/or starting. People in your area will discuss this waaaaay better than me.

The cap off situation is PURELY tank venting issues, and that is inside that huge ringed cap thingy on top of the tank, the one you can just see, but cannot get at without removing the tank.

I would also be changing the long forgotten fuel filter, basically coz its cheap, and FORGOTTEN in most cases. I change ALL mine every 2 years.

Inside the tank, your gonna luv this bit haha, is the fuel pump, and they do play up from time to time. Have someone place their head in the boot, near the LH side of the tank, and listen for a pump "whirr" as you turn the ignition ON. Also check the fuel pump relay, as it may be getting tired/lazy by now, and again, CHEAP.

The stumbling as it warms up may be O2 sensors a little out of range, old age again.

 

Well Sir your being down there is fine with me. 1/2 of my biker friends are down there on their russian motorcycles. I get my best advice from them and a couple of Englishmen on their Isle. I have been know to help them on occasion as well The EGR valvewas the first thing my Jag mechanic relative mentioned tonight. He claims there was afactory recall in the late 90'2 but alot of them got missed. Less than 6 months he had one in that had not been upgraded. Same issues, stall when cold and slight rough idle when warm. Claims EGR valve sticks open so acts like a vacuum leak. Claimed a 15 min. cleaning and working of stuck unit fixed problem and car ran like a new unit. Guess I'll do it first thing in the morning. I've done the fuel pump diagnosis and the pump whirrs and the relay clicks. I do plan on changing fuel filter as soon as I find it lol. The suction in the tank is a problem and I hope tomorrow when I start it I will be able to restart if it stalls.

 

SWEET.

Yep, I reckon the EGR IS your issue, and will sort most of the ills.

The venting will be exciting at least. Sometimes its just excessive moisture jamming the ball thingy inside that dome.

Fuel filter is accessable by removing the LHR wheel, and peering straight IN above the exhaust pipe and it will be seen. If you got accesss to a hoist it is easy to change, flat on the back under it is not so sweet, very doable, but vocabulay increase WILL occur.

 

Well I found that today with the gas cap off the stalling problem seemed cured. It still has a bit of rough idle but the new plugs will go in on Fri. I stopped at the local shop and had the codes checked. They used a small hand scanner that just displays codes. Below is a list, the only one that I think applies is the random misfire one.
P0430
P1775
P0300
P1316
P0118
P0420
P0727
P0125
If any of these codes mean anything to anyone let me know. I did get a list from an online site that told me what they meant but it might be wrong.

 

Never done this particular car, only my XJ40, but my only quick reply is to use MAF Cleaner (NOT Carb cleaner) for the MAF....

 

Ok the MAF is cleaner than my dishes and the egr valave is not seized or gummed up. Seem to start and go when cold better. Still doesnt always want to restart after a short shut off. Tomorrow is fuel filter and spark plugs day. After that I may be stumped. Im sure there are no vacuum leaks.

 

Ok today actually brought a positive result. New plugs were installed. This alone I don't think was the fix. 3 of the coil boots were ripped and each of them had burn marks indicating shorting to the cylinder head. As I didn't have new coild I repaired this with several wraps of black electrical tape. Upon restarting the car idles smoothly and shows no stall like symptoms or rough running when driven around town. I now have a smooth running car that pulls away with no hesitation. The remaining problem is that after shutting down it really doesn't want to restart cold. Most times it wont restart for a hr or more after it has been warmed up and shut off. Long and the short hot restarts are the problem. Suggestions are welcome and will be pursued as vigorously as they have been so far.

 

Ok I'm posting this in both of the threads I started, hope that doesn't offend anyone. Today we removed the entire throttle body and the EGR valve. The throttle body had very little black gunk and none around the airstepper valve. The egr was not seized or gummed up. The wrist full of hot coolant I got when removing the throttle body was annoying lol. The situation is thus now that I have experimented all day. Cold start every time, throttle fluctuation of about 200 rpm for first 10 min. Can be driven during this time but may stall. Restarts with pedal pressed to the floor. Once warmed up if shut off for more than 10 sec it requires a 10 min cool down period before restart and pedal must be held to floor. If you try to restart before 10 min cool down you will get turn over but no start. If you try with the pedal held down you will get restart and die before reaching 3000 rpm. At this point the car is perfect except for the hot restart 10 min. period. When the car is restarted with the pedal held down there is the smell of being flooded. Any suggestions would be great, I'm leaning toward leaky injectors causing the engine to flood and the 10 min cool down allows some of the raw fuel to evaporate. Thoughts anyone?

 

Not disagreeing with the injector leakage idea, although not a common issue with the Nippon system.

The fluctuating warm up is "usually" to do with the O2 sensor/s. Mine gets a 50rpm waver at idle during warm up, sometimes, and it will be the sensors, when I get all excited one day I will change both of them. Once warmed up, sweet as, and hot start is NOT an issue, ever.

The smell of fuel after your warm/hot start indicates a lack of spark, to fire the mixture??, confusing, yes, but my V12 did that and it took some finding. The crank angle sensor (front of the timing cover) may be having a moment, which is odd, coz they usually just go legs up, and you got nothing.

Inside the RH fuse box under the bonnet, is a blue relay. That is an ignition relay, and supplies power to the crank angle sensor among other things, and they do get lazy, well documented. Pull it apart and clean the contacts, or simple replace it.

The same laziness goes for the fuel pump relay.

The coolant temp sensor (in the thermo housing), is also a well documented issue, and I seem to recall an updated part number for this item??. If it gives "flaky" signals to the system, then fueling maps etc will be off.

Blocked. or blocking cat convertors can also cause similar issues.

Hope that helps a little bit.

 

That does make alot of sense. I have gotten alot of comments on the crank sensor and due to the fact I can get one for about 150-200 I may replace it in the new year just to be on safe side. The relay is the first thing I will check after tomorrows test drive. Might just swap it out first thing and see what happens. I've checked for spark and seem to be getting lots when I pull a plug. I've thought of investing in a scope but always end up buying a toy instead lol. Will the O2 sensor throw a code by any chance? That would be great if it did, make things much easier. The temp sensor was mentioned to me to night by a Chev mechanic, seems they were an issue. Thinking I might rig a switch to jump it to "hot" mode when I try a hot restart. Christmas weekend I will be with my 3 other brothers, Aircraft/Avionics specialist. diesel/gas qualified mechanic, diesel mechanic/fabricator. Between the 3 of them and myself I expect theories to be produced to rival NASA. My hope is to pinpoint problem by then and avoid a full on 4 man battle royal at Christmas
Cheers
PS I may not have mentioned that the car has 297000 kms on it

 

AHA, now we have progress.

You will end up with a an aircraft powered, diesel fuel Jaguar, capable of blistering speeds and use bugger all fuel, damn I want one in RHD HAHAHAHA. Dont forget the consumption of Johnny Walker PRIOR to any actaul mechanical activity.

At that kms I would seriously be doubting that crank angle sensor, about 160k ish is the average failure area.

The code throw for the sensors is apparently supposed to happen, but many report "no code", and mine certainly has no codes of any sort. My opinion is they do throw a code, once they go legs up.

Those CTS units are cheap, about $35 here, so I would just replace it and be done with it.

The other thing I did think of whilst doing some TLC on a 1959 Wolseley, was that the TPS may be giving issues. Apparently they require synchronising via a dealer operation once they are disturbed, such as removal for cleaning, or replacing with a new unit, which I find rather silly. I had mine off for cleaning and simply refitted it, BUT, mine is a 3.2ltr with a 3 wire TPS, and no electronic transmission section, and I "believe" the 4ltr units are different, but I may be wrong??. Again at the kms you have on the car, that TPS would also be high on my list of suspect items.

 

Ok this is good stuff. I have to find these cheap CPSensors as they run around 200 here. I've been instructed to check to temp sensor from an old sage type chev mechanic and a member on here in another thread. Do remember that this car does not run real good at cold temp. It starts lovely but there is at least a 200 rpm fluctuation and it will stall if you try to drive and apply power. It may idle away on its own but lord help the application of throttle while driving in the first 10-15 min. A full throttle "flood clear" will start it again cold if it stalls same as when it has a 10 min wait when hot. It starts great cold, runs good warm. 2 0utta 4 not bad but does leave room for improvement. As to the aircraft powered diesel burning low fuel consuming Jag, I expect more of a pedal powered whiskey drinking jag pushing brotherhood that smokes heavily.
Merry Christmas

 

Have found with more experimentation that the car will always start if a flood clear is done first. Do flood clear, then start normally. If the car has set for more than 10 or 15 min it will start while doing flood clear. Seems I have learned her evil ways when it comes to starting. Can't wait till tomorrow when all my theories and methods go out the window.

 

Mmmmmm.

That CTS is part No LHE1600AA.

I would try some of the suppliers via this forum, or XK's Unlimited in San Louis Obispo, they have been quite helpful to me over the years and their pricing is usually pretty sharp.

As you have said and been advised, that TPS is now a very suspect item.

The air temp sensor in the intake elbow is primarily a "trimmer" and I dont believe is having any input on these issues.

Have you done a compression test??, especially at this higher kms, it may be just fine, but it would be good to eliminate that factor from the diagnosis.

The cam angle sensor (that wizzy thingy where a distributor used to live in an earlier life) may be giving some injector firing issues. They are deemed very trouble free, BUT, a few have appeared on here of late that were giving issues.

Also that cam angle thingy needs to be timed CORRECTLY, as it controls the injector firing sequence, or starting can be a mongrel. The Nippon system works it out eventually, but some serious cranking is required for that to happen, and as soon as the engine is switched OFF, the memory is gone, and the whole thing needs to re-learn again.

 

Today has brought interesting results. Little bit warmer here today +2 rather than -4. Today I went and had all codes cleared. I also soldered connections I made yesterday to fix my 2 lights that were out. Since having codes erased the car starts every time. Still has throttle surge at idle but as you mentioned could well be O2 sensors. Tomorrow she goes for inspection then a road trip planned over the holidays to work the injector cleaner through. will keep posted, I would rather no code and no problem, I expect no code and problem, more fun that way.
I expect Captain Morgan will have something to say on the subject.

 

Well with no codes the car is running like a top. Slight idle fluctuation but other than that it goes right off the start warm or cold. Clearing the codes was best thing I ever did. All done the inspection and she passed with flying colors. The signal light I fixed seemed to have died but That can be fixed. I'm a happy Jag owner!
Merry Christmas Everyone

 

Good for you , thanks for your feedback
Happy driving