Team, I had a no start situation 8 yrs ago when I purchased a 1998 XJ8 4.0. Throttle body had been updated via TSB from previous owner as well as timing chain tensioners. At that time, compression test showed low in 3 cylinders so added a bit of oil (more than a tsp) and it fired up fine ... aside from the smoke. Ran fine since.

Honestly though, I've had no issues since until recently. A short jaunt from garage to car pad back to garage, I believe, left engine flooded and broke the liquid oil seal. Checked the ignition system which is working fine (all spark with new plugs). CPS appears fine as I'm getting proof of engine rev on the dashboard. Fuel pressure is good. So back to forums where I remembered to check compression (all cylinders but one were low) and led me to add oil in the cylinders as I did 8 yrs ago. *crank crank crank* to no end (20 sec cycle/10 sec wait) for 10-15 min. Still no start ...but... Oddly, I was receiving a lot of belching coming from the intake manifold/TB almost as though I was receiving small combustions coming from inside intake manifold. Odd indeed. I put the plastic air intake tubing back on and attempted another bit of cranking with more oil. *bam* There was so much back pressure from the intake manifold, that the entire plastic assembly from the top of the TB to the air filter shot up to the roof ... the roof of my garage. Well, that sucks because now I need to duct tape until I have $150+ saved to replace.

Being persistent, I continued without the plastic air intake. It has run before without MAF plugged in on user tests, so I know the no-start wasn't caused by this. I noticed the compression continued to die quickly after putting in oil and attempting multiple cranks, so I added ungodly amounts of oil to each cylinder ... like, 5 tbsp (yes, I know, I'm destroying my O2, catalytics, etc, but I couldn't get compression with the normal 1-2 tsp). It actually started! *yay* But then died almost as though it wasn't getting fuel. *huh?* Not getting fuel made no sense since I know pressure was there and injectors were firing. Attempted a new start but sprayed in Ether as soon as it turned over itself at which point the engine continued to work a few seconds longer, but then died. We're talking 5 sec or less. Still a win since I couldn't even get 0.5 sec before.

I then tried starting but not using Ether and instead just depressing the pedal to keep the revs up. Oil fumes out the wazoo, but it kept running. *yay* Until you let the pedal off and it stalls again. Again.

Restarted and immediately applied pedal once engine turned over on its own and am able to keep the engine running for long periods (30-60 sec is long at this stage) but the pedal only keeps me @ 3000 rpm when it's depressed. If I let off too much, the engine will drop down near proper idle and will stall unless I apply the pedal again at which point it will go back up to 3000 even with slight fluctuations in the pedal (engine just keeps a stead 3000 rev).

At this stage, I'm either going to:

1. Shoot myself in the face
2. Replace the TPS
3. Replace the ECM

OBD shows P1224 - Throttle Control Position Error (hence #2 above) as well as a code for the MAF which would make sense since I, literally, blew it off my engine before.

It also shows P1336 which I didn't have on any of my prior cranks until the very last so I'm pretty sure my CKPS is fine (hence #3 above), but my head it telling me I just need to clear that code and move forward.

Dealer doesn't sell just the TPS, but I'm unsure how to test since I can't locate a pin diagram. JTIS is pretty crap on detail but is amazing on telling you what to trouble shoot. For example, where the h*ll is PI06. You get the point. Unable to locate a good replacement TPS other than used eBay or entire TB be it rebuilt (ASI) or new. That's not happening. I still need to get the metal cover off the TPS but need to locate the tool for those flipping star bolts with a hole in the middle before I can locate a part # and search for a replacement.

Yes, I know it's a Nikasil cylinder wall, but no I'm not going to replace my entire engine (for those who are about to post that). The issue now isn't compression; now my issue is idle but I wanted you to understand back story, since engine explosions are helpful when diagnosing.

ON TO YOUR HELP:

• Throttle body has been replaced from original TSB so should be good (prior to my explosion).
• I have compression now and engine will turn over fine.
• Ignition system is working fine.
• Fuel pump, relays and injectors are fine.
• Engine runs fine as long as I hold the accelerator from idle.
• Thoughts?
• Do you think it's just TPS?
• Anyone have a diagram that shows pin #s so I know which pins to jumper/test?
• Bless your heart for reading this entire thing.
• What other culprits even though I'm darned sure the CPS is fine?

All hail the forum,
Matt
'98 XJ8
'10 Triumph T100

 

Mine ran like yours when I failed to plug in the MAF. Once got sloppy putting the air intake back on the throttle body; air leak made it hard to start, too (can't believe duct tape would be air tight!). These crates hate air leaks.

Wonder what else got damaged when it backfired through the throttle . . . . ? Maybe intake manifold gaskets . . ?

But, what caused it to backfire? Next time, hold the gas pedal all the way to the floor (this shuts off the fuel supply, and crank it in short bursts, while allowing oil pressure to build in the cylinder walls), once you hear it trying to start, let up the gas pedal to allow fuel delivery, then wait for the idle to smooth.

 

I've started and run it before without the entire air intake assembly on the car, so I'm pretty sure this isn't the issue for the no-idle/3k rpm option.

I'm with on you this one, but it was a free-flow out of the throttle body, so shouldn't have damaged the gaskets. As well, the temp was cool on the intake manifold, so I don't believe excess heat was present.

Did this (pedal to the floor) but there was still fuel shooting out. How do I know? I could see it spraying when I took out the plugs. Coul have been built up fuel line pressure, but it was pretty consistent on each cylinder. Definitely petrol smell as well. Regardless, what you mention was my process nearly every time without progress.

I suppose I'm more concerned now about the "rough" idle. Hope this provided a more clear picture to my predicament. I'm on Kleenex box #4, so all good here. I do appreciate the troubleshooting suggestions though. Greatly.

 

Matt,

Welcome to the Jaguar Forums! It's great to have you with us.

I'm sorry you're having difficulty with your Jag, but I'm sure Jim and our other knowledgeable X308 owners will continue to try to help.

When you get a chance, please visit the New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum and post an introduction so we can learn something about you and your Jaguar and give you a proper welcome.

Cheers,

Don

 

Even though the engine will fire and run SOMETIMES with the MAF disconnected, I believe it depends on which of several backup strategies are being employed. I say this due to some experiments I ran when my XJR was having fuel trim problems, and as I recall, sometimes it would act like yours without the MAF. o, I would put the thing back together as best you can, clear the codes, crank, fire and run the engine if it will.

As to "replaced the TPS", GOOD LUCK. If you find a way to replace both of them please post the part numbers since none of us have determined where to get them. The two TPS pots are integral to the TB.

**Edit: Code P1224 is apparently not the throttle position feedback, but the throttle plate feedback, which is NOT the same. I would certainly check the connectors at the TB and clean them good. I would do a hard boot, reset the codes and give it another go. After that, I think you are looking at rebuilding the TB, but that is just my guess, worth what you paid for it.

 

How odd. Every time I've replaced my air filter, I've started it without the entire, plastic air intake and no issue or rough idle or bark or stubbing of the toe. I'll definitely take the advice, though.

Both? JTIS clearly shows only one for my vehicle to the RH side of the throttle body on a LHD. I was able to get off the metal cover for part# (192300-1003) with the TSB upgrade, but the blasted internet appears to be loads of suck today. Sadly, replacement appears to be "used". I'll check to see if I can find comparable (e.g. Lincoln LS replacement).

Quite odd as I got that from JTIS. Based on your feedback, I'll be sure to clean the connectors (I need a reason to head to purchase extra spray can fluid) and follow up with you folks.

Based on crap wiring diagrams in workshop manual, I believe I've diagnosed the TPS and have no issues based on Pinpoint Test D & K. I've no wiring issue which leads me to believe ECM is bad. *waaaaaaah* Just doesn't make sense though. I'm going to give it a couple days before I reassess.

 

Have a look at the lower right hand corner of the diagram: Aj26 engine, right? Two throttle positions sensors and a throttle plate position sensor.

I have not got a good way to capture the P 1224 Diagnostics, but they all point to the throttle stepper motor and it's feedback controls, not the throttle. I wonder what you are looking at?

** Edit:
OK, now I realize that you are using the correct nomenclature and I was wrong! The TB has two PEDAL position sensors, and one THROTTLE plate position feedback. So, I assume you are pinpointing the Throttle Plate feedback and it is tracking the throttle plate position smoothly?

 

Ok, finally located a wiring diagram for my vehicle so I could complete all pinpoint tests. From what I gather, it does appear to be my TPS which is not working (P# 192300-1003) or at least needs to be replaced.

1998 XJ8 Electrical Guide
https://dl.dropboxusercontent.com/u/...ricalGuide.pdf

1998 XJ8 Workshop Manual
https://dl.dropboxusercontent.com/u/...hop_Manual.pdf

For the life of me, I cannot locate a new part aside from ordering the entire TB assembly from the dealer. Even local, ex-Jaguar mechanics say "send it off to ASI or BBA Reman but they just fix your part instead of replacing it". That's 300 USD more than what my conscience is allowing me for a "fixed" TPS.

I can locate used on eBay but don't really want to pay money to keep myself in the same situation. Anyone aware of a swappable part for P# 192300-1003?

Since ASI & BBA Reman simply take the TPS apart and, I'm assuming, resolder, has anyone done this themselves? Or does anyone have a wiring diagram for the TPS? As it is all plastic housing, I'm concerned my clumsy hands will "accidentally" smash it trying to get it open. I'm good like that.

 

As I mentioned before, although many of us have tried to find a source, none of us have been successful. I even considered trying a retrofit of another part, but realized that the cost would probably be higher than the rework charge. On the other hand, the guys re-manufacturing the TBs are apparently getting their parts from somewhere.

 

I don't know if any of this will be the least bit helpful, but here goes:

There are a few eBay listings of a TPS that looks like a clone of a Denso part. The auction listing says it will fit a 99-03 XJ but not a 98 (or UK 97):

Throttle Position Sensor for 99 02 Jaguar XK8 99 03 Jaguar XJ8 New | eBay


There have been reports that an X-Type TPS clone will work on an S-Type or X350. I'm not positive this is the part claimed to work, but the price is low enough that it might be worth buying one to experiment on those models as well as an X308. I don't know if there are differences in the TPS specs for each model such as mounting screw spacing, engagement, maximum resistance or direction of rotation (CW or CCW) for a rise in resistance. Maybe you can tell some of these details from the photos and descriptions:

New Throttle Position Sensor for 2002 2004 Jaguar x Type 2 5L 3 0L 198500 3300 | eBay


Here's the X350 thread:

https://www.jaguarforums.com/forum/x...-3300-a-82398/


I've searched the Denso part finders for 198500 3250 and 198500 3300 with no success. Unfortunately some of the parts they supplied as part of OEM assemblies are not available through their aftermarket division.

Cheers,

Don

 

Thank you so much for the research and suggestions. From pics, the later TPS (what was posted) appears to be mechanical with electrics; whereas 192300-1003 ('98 XJ8) is strictly electrics based on electric field resistance reference from the mounting plate in the TB itself. BTW, appears to be the same P# for SC as for N/A for those who care.

Inside my "special" TPS (1998 XJ8 N/A):
https://dl.dropboxusercontent.com/u/436312/TPS.jpg

I've purchased a couple of used "less expensive" TPSs for troubleshooting prior to the 300 USD route. The amount still gives me goose pimples. Should come in 1-3 September, so I'll post an update at that time.

 

Hi Matt,

So does that look like a Hall Effect sensor to you? If so, is there a magnet attached to a moving part in the TB? Or is there a rotating part on the TPS itself that covers the circuit board shown in your photo?

I just did a quick search of eBay and there are a couple of listings for the 98 XK8 TPS that looks like it may be the same part number. I wonder if anyone in the XK8 forum has had any luck with sourcing a replacement?

Don

 

You've got it. It's a non-contact style (so basically) hall effect sensor as opposed to the potentiometric style used on later models. The pic I posted had nothing done to it other than simply pulling it away from the TB (after removing the 2 screws). What you see in the middle appear to be 2 inductive sensors which I imagine measure change in magnetic field as the butterfly opens and closes.

Side note, I believe I have a way of testing the TPS! From the Pinpoint tests in the Electrical Guide, they don't tell you how to test the TPS but how to troubleshoot everything but that. As there are 4 pins:

• One is constant ground
• One is 5V
• Two should be signal starting at ~1V with the butterfly closed and increase as it opens

With key to "On" but not "Start", I should be able to paper clip my 2 signal wires against a multimeter to check for voltage. As I manually open the butterfly, the voltage should gradually increase and visa versa as I close the butterfly. Haven't done this yet as I'm away from the vehicle.

Good thought. I completed quite a search through X100 forums but they all appear to be potentiometric style TPS with relatively high quantity for new. Sadly, not suitable in this case.

Waiting for used parts to come in, so I'll pop back here in a few days. Thanks!