'01 XJR has developed a periodic but persistent stumble during initial run after cold start - disappears after 4 or 5 minutes when the engine is up to temp. No codes. Feels like a fuel starvation issue, but heavier throttle eliminates the stumble. Wondering if this could be a faulty temp sensor that the ecu is reading?

On another note I'm getting an occasional cluster of dash warnings (Restricted Performance, ASC & Trac Unavailable, etc) - engine tends to run at high idle with little or no throttle response. The problem clears by cycling the ignition on and off a few times. The only code I'm getting in this instance is Throttle Position Sensor - is it time for a new one and could this be related to the first issue?

Appreciate any thoughts out there.

 

You might see if the TSB was performed.

 

Contact cleaner all around throttle body fixed mine at least for now

 

Thanks. No splices on the TPS harness so that TSB was never performed. Will try cleaner on the terminals as suggested to see if that resolves anything. Not sure that explains the cold running stumble, however. Any thoughts on that one?

 

The TB posted by motorcarman makes a lot of sense to me - so: Contact-corrosion due to material-mismatch as reason for your TPS issue.

As for your initial stumble:
I'd swap your fuel filter: This COULD BE the issue, it does not cost much, it's not difficult to do. Plus, if that really is the issue (early onset of a blocked filter) it could soon be blocked totally and you may find yourself stranded somewhere in need for a tow-truck to pick you up. Also: Swapping the fuel filter is always a good idea, if you have not done that for a long time...

 

Hard to guess on stumble, hang the obd reader and look for culprits, coolant temp, o2 sensors behavior, check for air leaks around etc

 

On all of the XJ engines I have owned, usually cleaning the throttle bore and plate fixed this issue (barring other codes).

 

Good news - I cleaned the connector terminals on the throttle position sensor and those running issues and codes have not returned (fingers crossed it stays that way). Jim, I cleaned the inside of the throttle body on the off chance that you were right about the cold run stumble - very minor carbon deposits on a rag sprayed with carb cleaner - and the stumble has disappeared. Makes no sense to me that so little carbon can upset running that way - the throttle plate must be virtually closed at low speed and low load? Also baffles me why the stumble disappeared once things warmed up. Anyway, my thanks to the folks who helped me resolve these issues - your input is much appreciated.

 

Don't quit, quiet yet. Sometimes a stuck temperature sensor in the crossover pipe will stick. The ECU then gets a signal that it needs to enrich for a cold start (or the opposite signal, the engine is hot, lean start). You might also clean the MAF sensor, including the socket that connects it to the sensors.

 

I'll order a temp sensor to have on hand should the stumble return. MAF sensor was cleaned last year so we're good there. Thanks again.

 

Unfortunately the beast ('01 XJR) continues to lose throttle authority periodically - probably a half dozen times in the past 2 months - to the point it's just not reliable enough to drive. As noted above I get a cluster of dash warnings (Restricted Performance, ASC and Trac Unavailable, etc.) -usually fires right up after a few start attempts. I thought cleaning the TPS connector did the trick only to have the problem return. I don't see any replacement TPS available for this model on line. I do see a throttle body rebuild service from Autoecu ASI in TN for $389 - this includes rebuilding the TPS and PPS (wherever that is). Is this my next step or is there something else to consider? Thanks.

 

Maybe not related to your stumble but the other bit where the throttle stops working and ABS/TC/STAB warnings come up.

I had that for a while on mine with just a TPS code as a clue. Problem is there's two TPS & one code. What fixed mine was a replacement throttle body as the other TPS is contained in that & can't be swapped. I had also worked out (after it was suggested on here) that if I left cruise control turned off (no red light by the gearstick) the error didn't occur. It seems that if the TPS on the cable & the TPS measuring the butterfly position read too far apart the car disables the throttle for safety (image the car thinking you want full throttle as you lift off etc). I'm not sure why the cruise being armed makes it worse but it did.

If you do consider that, then all TBs are fittable, my replacement came off a NA car. There's just a plate on the back with 4 allen screws & the throttle cable bracket to swap on them to fit a XJR (or visa versa).

I could imagine that TPS causing the engine to stumble, I think I recall mine seemed to stumble for a sec or two before it threw up all the warning lights. But I won't claim to know it's your issue.

 

This one is a correct two track tps with offset

 

Hooli, the stumble was a separate issue resolved by a simple TB cleaning - hopefully a new TPS will do the trick. Xjack, I did see that item on Amazon and eBay, but the listings did not show the XJR - just the normally aspirated 4.0L. If they use the same component I'll order one up to see if that's the problem before sending the thing off for a rebuild. Thank you both.

 

I believe they didn't change and would work on either old and new throttle bodies but if you wanna be sure have a look at the number on the back yours and compare
Just be careful with the price, those that cost few $ have a single track and won't work, good ones start at 25$+

 

Ya gotta love internet shopping and parts made in China - a dozen brands with the same PN and prices ranging from $12 to $90. Thanks again.

 

I would almost...rather acquire my part from the salvage yard than trust
something produced in China. I'm sure there are probably some quality
parts made in China....I just have not had that experience.

 

China went long journey from solely manufacturing junk to today, today they manufacture both junk and really nice stuff, now the problem is the buyers choice who would rather risk the failure than spend extra
The link i posted is one i've purchased myself, it was tested and keeps spec perfectly

 

I am very glad you have had that experience. It seems you are indicating
that if it has a high price...it should be good?

 

Yeah i know china shopping have bad rap and it is no surprise, to be honest buying on ali is quite an adventure, and don't get me wrong, many times i was fukin angry on them for selling me ****, but if you do your homework it will work. some may not have time or will to play detective and will purchase from someone who does at x3 price, nothing wrong with that either.
In case of those tps there are those sold for few $ with blank backside, they are single track, won't work and have plenty of bad reviews all around, and those sold above 25$ usually have a sticker on the back with part number, those are fine, there was graph somewhere on the forum showing correct tps values and tiny offset between tracks, those tps adhere strictly to those spec.