XJ40 ( XJ81 ) 1986 - 1994

Intermittent Stalling, Other Issues

 
  #21  
Old 03-11-2019, 02:03 PM
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Originally Posted by cooldood View Post
Just for 100% clarity, I would not say it re-displayed (suggesting some flicker or change) the mileage, just that the display never changed? Agree or disagree?
Cheers,
John
Hey John, I think you're ok regarding the VCM code etc., The earlier cars like yours have a smaller number of codes (8 I think?) and VCM fault codes are usually (if not always) flagged in combination with the check engine light. With my late model car, if I get the check engine light and press the VCM the code displays, otherwise just the mileage.

In my experience, there are exceptions to the above, one is when the display changes to PAD after a press (low brake pads) and another (IIRC) when it displays the word FAIL without a corresponding FF and a number - of course I can't remember what that means but it was a very long time ago I had that.

In both of those cases though, the check engine light didn't illuminate. In your case, I don't think you have any DTC's stored.

CPS sensors are pricey all right, at that price, you could pick up a running parts car!

The CPS does give trouble and it is good to have a spare but with a cold start ok and hot start not I think it wise to check out the coolant sensor circuitry first, certainly a more economical step if you're going to start replacing components.

This may not apply to your car directly but this ain't a bad article on the CTS ..

https://www.jaguarfuelinjectorservic...e%20Sensor.htm

Larry



 
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  #22  
Old 03-11-2019, 02:29 PM
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Thanks Larry. I think we can lay the VCM messages to bed, nothing to see here. :-) A used CPS might be something to try first, if warranted to have come off a running car.

The resistances in the linked article match well with what I see from my CTS. I do have a new NAPA supplied one, but have not fitted it as yet, due to the acceptable resistances. I noted that voltage supplied to the CTS without the engine running was only 4.2V, but it was 5V when the engine was running.

I have no idea if there is a fault in the CTS wire running back to the ECU. That sounds like a task for another day.

I can certainly try the paperclip trick next time, hopefully tonight, after removing the CPS and cleaning/replacing it
 
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  #23  
Old 03-11-2019, 03:15 PM
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I was having similar issues, that were all pertaining to fouling of my TPS. If that is not reading properly, it can go into limp mode and hesitate. Its attached to the underside of intake and it gets oil in it very fast.
 

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  #24  
Old 03-11-2019, 09:25 PM
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Tonight I got the bolt out (T30) that was holding in the CPS.

The CPS was quite cruddy, wiped it clean and it looked fine. Reinstalled it (noted that it looks like it is not oem, the cable running to it is white, and the red/blue/black wires from the connector disappear into some electrical tape and emerge as the white cable. Peeled off the tape to confirm this. No idea what effect that might have on the functionality of the CPS, but I guess I ran the last 1500 miles since we took ownership, and presumably prior to that - there is a used one on eBay for $50, I think I will grab that for now to at lest have oem one).

Car started, but was rough, then cleared, then wanted to idle at closer to 2000 rpm, black smoke from the exhausts. Switched it off fairly quickly and then it would not restart, even though it really could not have warmed up much at all.
Getting dark, time to stop.
Tomorrow I will change out the water temp sensor, and look for the TPS.
 
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  #25  
Old 03-13-2019, 12:44 PM
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Last night I swapped out the water temperature sensor with a replacement from NAPA. Car would not start afterwards.
Located the throttle position sensor, on the underside of the the throttle body. It did seem wet with oil.
Perhaps one of the tasks this weekend will be the removal of the throttle body and a more thorough cleaning of that. The replacement TPS is on its way, hoping that cures all.

Other upcoming tasks include the intercooler water pump on the X350 and an exhaust manifold gasket on the Grand (never has a word been so misused) Caravan.
 
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  #26  
Old 03-13-2019, 01:37 PM
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Located the throttle position sensor, on the underside of the the throttle body. It did seem wet with oil.
They can be carefully pried apart and cleaned with contact cleaner or as some prefer holes drilled in them to blast out and drain the gunk inside....

anyway you've got a new one on the way .. interesting that the car wouldn't start with the new temp sensor ...how 'crispy' is the harness I wonder?

Thanks for updating, look forward to next report!

cheers

Larry
 
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  #27  
Old 03-15-2019, 06:12 PM
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The new (used) CPS arrived today.
She lives again.
Idle is a little lumpy, but we got all the way around the block, and more importantly, back again. And we restarted when hot.
More testing tomorrow, when I am not so in need of getting home again without waiting for AAA.
​​​​​​​
 
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  #28  
Old 03-20-2019, 10:12 PM
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Back to the drawing board then.
Went out tonight, she ran fine for around 30 minutes, round town, bit of freeway, open road, then as we were pulling up at the house, there was the hesitancy. Went back round the block to confirm and got the major pause after pressing the throttle before there was power. Back to the house, switched off and she will not start again. Noises from the gas tank were noticeable (she has the external fuel pump, which is quite a different noise), released the cap and there was a small vacuum, but made no difference to the starting - assume it was the return pipe discharge I could hear.

I guess I need to work through more of the options then, or look for another CPS?
 
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  #29  
Old 03-21-2019, 03:41 PM
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TPS? Clean it and set it to spec
 
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  #30  
Old 03-24-2019, 04:07 PM
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She started fine today, but a bit rough on the idle, then a bit of blue smoke, then cleared and was fine. Drove her into the garage and took the throttle body off. Very oily. A small pool resting inside the inlet manifold behind the throttle body.
Off to clean everything and reset the TPS, but wondering if there is something more sinister going on that that much oil was inside the inlet manifold, seals leaking or a valve stuck in the wrong position?
 
  #31  
Old 03-24-2019, 04:58 PM
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Originally Posted by cooldood View Post
A small pool resting inside the inlet manifold behind the throttle body. Off to clean everything and reset the TPS, but wondering if there is something more sinister going on that that much oil was inside the inlet manifold, seals leaking or a valve stuck in the wrong position?
Hi John,

That pool of oil is typical. There is no oil separator in the crankcase breathing system, so it feeds oily fumes back into the air intake just ahead of the throttle body, and over time oil settles on the bottom of the TB and intake manifold and drips down into the TPS and the EGR port on the bottom of the intake manifold. If your car is equipped with EGR (and if it was originally delivered to California it probably is), it would be good to remove the port and clean it while you have the TB off. Be sure to also clean the smaller hose fitting on the left of the port where the carbon canister purge valve hose connects.

Larry is our leading advocate for periodically removing the air intake, TB and breather hoses to clean out all of that nasty residue, and he's right.

Cheers,

Don
 

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  #32  
Old 03-24-2019, 07:28 PM
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I have a feeling all of your troubles are in the intake. Good to see that youre on top of it. All of my issues were because of a dirty TPS. Drill 2 tiny holes on the bottom of it to allow the oil to drip out. Every once in a while, wipe the TPS in order to keep things clean and flowing.
 
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  #33  
Old 03-24-2019, 09:36 PM
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Ho hum. Still the same, maybe even worse. Had the throttle body off, cleaned off the residue on the body and throttle plate, took the TPS off and wiped the oil off of it, cleaned its grommet. Could not see anything on how to adjust/re-position it any differently, so just put it back roughly where it was before. mopped up the oil inside the intake manifold, but had not seen the replies and did nothing else there. Checked the throttle plate was 0.005" open at rest.
Reassembled everything, carefully making sure there were not leaks evident (noted that there was not gasket between throttle body and manifold?).
finished installing door speakers, which took the rest of the day, then reconnected battery and started the engine.
Idled a little rough, but then settled, so assumed that was relearning positions etc. Went for a drive, maybe she was trying to idle to fast here, and she died after 1/4 mile - worst yet! (note - this was as we pulled away from a stop line). Luckily it was uphill, so when repeated cranking gave the same result as before - almost starts if foot on the floor, but she would not run, we just free wheeled back down and parked outside the house.

Might do some more thorough checking of the fuel supply next time, or is the some hoodoo I missed on TPS setting?
I am still struggling with the concept that she will drive for 30 mins, hit 65 on the freeway, and then have issues - must be getting enough fuel for that.
 
  #34  
Old 03-24-2019, 10:12 PM
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Hi John,

For future reference, you don't need to disconnect the TPS from the throttle body in order to clean it, but you really do need to either pry off the bottom cover if possible, or drill holes of 3/32 to 1/8 inch diameter in the two lower corners of the cover and flush it out with zero-residue electronic cleaner until the fluid that emerges is clear. Leave the holes open when you reinstall the TB so the TPS can drain future oil that drips down the throttle shaft.

The position of the TPS relative to the TB is very important, so if you have to disconnect the TPS, alignment marks should first be made on both the TPS and TB so you can reinstall it in the same position.

All of that said, you can recalibrate the TPS by backprobing its electrical connector and measuring the voltage it returns at WOT and when the throttle valve is closed. The procedure is in the Jaguar Workshop manual, available from the Jaguar Daimler Heritage Trust, but I think it may also be in the Haynes Manual. You can download a pdf version of the U.K.edition (missing a couple of chapters) here:

Haynes Jaguar XJ40 Repair Manual

I have photos showing how I drilled holes in the cover of my TPS - unfortunately the large images are still down at Jag-Lovers but you can see the thumbnails and descriptions:

Jaguar XJ40 TPS Drain Holes

Cheers,

Don
 

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  #35  
Old 03-24-2019, 11:37 PM
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Oh well, it is in pretty much the same place now and the car seemed to behave alright initially, idled and accelerated, we can fine tune later.
I assume your photos are from a different model?
Mine looked more like this
 
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Old 03-25-2019, 09:18 AM
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Originally Posted by cooldood View Post
I assume your photos are from a different model?
Yes, a '93, but the principle is the same.

 
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  #37  
Old 03-26-2019, 05:58 PM
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Should I be drilling holes in my red end cap then, or trying to pry it off?
Worried that it is not cleaned well enough, but also leery of destroying it!
 
  #38  
Old 03-26-2019, 07:10 PM
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Pry it off and clean it out if you can, less destructive.

If it won't come off, then go for the drillzies.

Larry
 
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  #39  
Old 03-26-2019, 09:40 PM
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Tonight, she started fine from cold, as always. A little rough, missing a beat now and then. Used a stethoscope to check for clicking at each injector, all seemed well, Shoogled a few wires, but nothing made much difference.
By this time she was starting to warm up and was idling fairly fast, around 1300 rpm. I disconnected the two wire temp sensor and idle dropped down quite a bit. Switched off and swapped back to the original temp sensor and she seemed a little happier. A quick drive round the block and all felt well. Switched off and she started up easily, and again, off and then back on. This is better than normal.
Went for a longer drive, some wide open throttle and all was not perfect, pulled well, drove fine, but wanted to idle at 1500-2000 and was making stopping a little harder. Did a U turn to come back and she stalled trying to pull away again. Cranking produced the familiar almost starting if foot is on the floor, but not quite. I got out and disconnected the two wire temp sensor and she started right up. Drove home fine with it disconnected, although still wanting to idle a little fast and hunting for the right idle.
Reconnected the temp sensor and she idled faster.
I am thinking the fast idle could be due to cleaning the throttle body. Although the plate was at the right gap, 0.05", it presumably flows more air now at idle/closed position with the gunk removed, and the throttle position sensor is no where near optimized,
But should I be looking to try a third temp sensor, is the original bad, and the NAPA replacement not appropriate?
At least I seem to know how to get her to start when hot.
 
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  #40  
Old 03-27-2019, 09:28 PM
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Hmmm... these cars have an air fuel mixture hex screw at the top of intake. It could be cranked up up to far. I cant remember which way to turn but give it a quarter of a turn and you will know which way to go in order to bring the revs down at idle. Just make sure your TPS is properly set or youre working against it all.
 
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