It appears to be virtually a choice for car makers between limp mode or cutting the engine entirely - an outcome of USA emissions laws. I guess an unintended consequence. Anyone got contacts with the appropriate law makers?

Going back many years cars weren't very reliable and would just quit. People were VERY unhappy and reliability improved hugely. Then to meet increasingly tough emissions laws we got cars with PCMs of stunning complexity - and limp mode.

Look round other forums and it's becoming an issue on more and more cars
(not always called limp home mode)

Better than uncontrolled acceleration, though!

 

Yup....The only computer controlled car I ever had that died was an 80's Chevy...Boy oh boy did I wish I had limp home mode back then.....

I know it is scary. I know it is frustrating. But the alternative is much worse, believe me....

 

I still don't think you guys are getting the point. We ALL understand that limp mode is a more viable option than the whole car shutting down, we get it, and it is obvious.

The point is, the car goes into limp mode when NO catastrophic damage has been done or is being done to the vehicle and its components. I have not heard of ONE single person on here that has had their car go into limp mode for a legitimate reason, or catostrophic failure which would necessitate it doing so as to prevent furthur damage from happening.

That being said, the sensors are WAY too sensitive, especially with this throttle body cluster f*ck we have to endure with the SType. This throttle body issue should have been a recall and at the VERY least a TSB.

Again, I get the idea behind limp home mode as opposed to complete power loss, however, Jag fails in proper implementation.

 

Would you prefer unintended acceleration to limp-home? I think that I prefer to cope with a reduced power issue as opposed to full trottle with no control!!!

 

Bull stated it perfectly. These S-Types seem to throw themselves into "limp home mode" for reasons that are far short of running risks of engine damage. You pull over, you let 'em sit for 15 minutes, and most of the time they crank right back up again and drive as if nothing happened. The sensitivity factor is apparently set at "hair-trigger" when it needs to be set at "something serious is wrong internally and it is very risky to keep the engine running at full power"....

 

Huh!? Full throttle with no control? Is that some kind of joke aimed at Toyota or something?

 

Stating my credentials first, I've been driving for around 45 years, and personally owned getting on for 100 cars, leaving out company cars.
This thread poses an interesting question: Are cars more reliable than they were, say, in the 1970s?
I'm not at all sure that they are! When a 1970s car went wrong, the problem was usually glaringly obvious, and often due to lack of basic maintenance. If you kept your tyres blown up, kept the contact-breaker points, condenser, plugs, filters, oils up to date, there were many reliable cars around.
Today, fault diagnosis has become a nightmare, with layer upon layer of electronics in the way. Electronics which in my opinion are unnecessary with a few exceptions. Nowadays, mechanics are relying on inbuilt fault diagnosis from a microprocessor's memory which are only a "best guess". I still think you can't beat an experienced mechanic's diagnostic brain. I'll give just one example:-- Nowadays, its common to find that an engine has a spark coil for each sparkplug, the theory being that individual coils get more time for the primary to charge up the flux and produce a bigger spark at high revs., partic. with 8-cyl. engines. But this problem was solved in the 1970s by what was called "capacitive discharge ignition" whereby there was no flux build-up in the coil's primary, instead a capacitor, charged up to 500volt or so, was discharged VERY quickly by a power transistor into the coil's primary. The only requirement for the 500volt power supply was that it was big enough, say approaching 100watt capability. The contact-breaker points were replaced by a pulse coil and magnet assy. on the distributor's shaft. Same single coil, same distributor, no cb. points, no capacitor. I know all this because I built one to modify my own car's ignition. The sparks produced by this system were enormous, about 1.5 inches long in free air. It was so good, you could gap the plugs at 60 thou. and reduce the idle richness (and emissions) considerably, indeed the idle speed increased by 50% or so immediately the 60thou gap was used.
I call the whole fiasco "microprocessor madness".
Leedsman.

 

You've missed the point: it's not for reliability, it's for emissions. Those 1970s cars had terrible emissions and as I recall too many people were dying.

It does SEEM like the settings are too "hair-trigger". As the S-Type's no longer made I can't see them being changed

 

The point has been posed, "it's not for reliability, it's for emissions".
Ok, so what is the single biggest improvement in emissions?
I say it's variable valve-timing technology -- nothing to do with electronics at all, because it can be done mechanically, and is indeed by the French.
Explanation #1:--
With fixed valve timing, the two (usually) valves are both open at the same short time during the cycle for efficient gas flow in practice. This is around 2000rpm for most engines. This means that, at idle of 700rpm., the inlet mixture is 'poisoned' by exhaust gasses, due to the 'sucking' effect of the manifold depression when throttle is almost closed. This will result in a bad lumpy erratic idle. To overcome this, the idle richness is increasd from stoichiometric, say, 15:1, down to 12:1 or less. This applies whether you are carbureting the petrol or injecting it. The upshot is partially burned petrol producing an amount of carbon monoxide at idle.
When valve timing is variable, this backflow of exhaust gasses into the inlet manifold can be largely stopped, making the idle richness requirement much less, AND THEREFORE CO POLLUTANT LESS.
EXPLANATION #2:--
I consider the second most effective way of reducing CO pollutant is by catalysis, the fixing of a device in the exhaust/muffler system usually of platinum on a ceramic substrate, which "after-burns" the carbon MONOXIDE to carbon DIOXIDE. (But only when it's properly warmed up). What has this to do with electronics? Nothing.
Explanation #3. The other great pollutant NOX? Again, it's nothing to do with electronics, it's the EGR idea (Exhaust Gas Recycling) an old american idea from the 1960s to reduce exhaust gas temperatures, and therefore NOX pollutants.
So then you might ask, what has electronics achieved in terms of pollution reduction?
Spark timing is more tightly controlled -- yes. Mixture control is better for all driving contingencies -- yes, (provided of course the lambda sensor is working). So what do the electronic controls add up to in the big picture?
Really, NOT MUCH.
And the future for petrol engines? I pin my faith on the GDI engine, an old idea that is being furiously pursued by the Japanese. GDI, Gasoline Direct Injection. It works by the direct injection of petrol into the combustion chamber under the so-called "stratified-charge" system, where the mixture strength around the spark plug is very rich, together with very lean eleswhere. But the main idea is to get rid of the THROTTLE as a means of controlling the engine power, controlling only the PETROL. This idea approaches diesel engine fuel-burning efficiency, but on the downside, having all the noise and knocking of the older diesels.
I hope this small contribution puts emission control into proper perspective.
Leedsman.

 

Electronics are needed to get accurate fuelling. Without that the cats melt and they are way too costly to keep replacing (and besides think of the emissions). The O2 (lambda if you like) sensors are essential to this and are part of the electronics.

You partially describe internal EGR. That, with (external) EGR also needs electronics to be accurate. EVAP is another requirement and again needs electronics. And so on.

I think I already mentioned GDI but maybe not in this thread. Already used in the newer jag engines for a few years now.

VVT is not especially effective at getting emissions down but does help. Note that the STR did not need or have VVT to successfully pass the tough emissions regulations for years.

 

I have an 04 XJ that is doing the same things. Will someone post a photo of where I should check for moisture/corrosion so I can reseal it to see if I can solve the periodic limp mode without a costly throttle body replacement?

Thanks.

 

Well I have driven my car twice since it was at the dealer last so 2 months about and driven twice...now it pops codes before I can leave my neighborhood.. Whats frusterating is that the codes are all different each time. I disconnected many connectors around the throttle body and made sure they were clean and dry. I also disconnect the Maf sensor and cleaned it, was covered in a black soot material. Still came codes, and now some new ones. Ones I usually get are: P1111, 1107, 1240, 1241 new codes..1344*,1122,1215, 0222*, 0122*(these aren't on the jaguar list of OBD codes)..I Its like as soon as I accelerate..boom shuts downs. I am going to call AAA and get it towed once again..and see what happens. Its within business hours this time so that should make Alpine happy...Just took the car out, took about 5 mins this time for a code to pop up and it did..new codes above.

 

Soot on MAF is a disaster. You sure you have a clean OE filter and it's properly fitted?

Post the codes when you have them. I've posted about P1111 before - it's a status not a fault.

The others look to be about short circuits so you probably have a bad wiring harness somewhere. Usual places are behind front bumper and the wheel arch (left, I think) - oh, wheel well behind the liner (I'm a Brit lol). Some searches here and the .co.uk forum will find you posts about corrosion in the wiring.

 

Thanks JagV8, I called triple A and thier on the way. Going back to Alpine, I have a 3rd party extended warrenty so it should cover the problem, I don't have time to track down the harness, but if I didn't have the warrenty then I would be out there doing it..lol. Paper Filter is clean and replaced reguarly not sure why there was so much soot on it.

 

With so many codes, I'd make a note of the codes each day for a few days, clearing them each time. Then inform the warranty people of that diary of codes and ask for a fix (I guess: authority to arrange one). And I'd hope I knew a competent jag tech to turn loose on the problem

 

Here's a thought (not a promise!) for fixing those ramdom errorcodes. Try strapping another battery across the existing one with booster cables, leaving it on permanently while driving. See if it stops those pesky codes! Easy to do, costs nothing.
Leedsman.

 

My S type R went into nasty limp mode 3 times after I went to the car wash about a month ago. By the next day it was perfectly fine and haven't had any issues since. I'm going to seal up the throttle body very soon as recommended here in an attempt to prevent any further occurences.

 

Well the Jaguar dealer called and said they think theres a wiring problem in the steering column, they tore it apart and moved the harness below the steering wheel or out of the way where it was factory installed and its not acting up, so they feel theres a "chaved" wire in there somewhere. What really sucks is my warrenty doesn't cover wiring...so im screwed, last amount they were up to was $425...what I don't understand is its factory and never been touched. I hope I can talk my warrenty company into covering it since its a factory defect at this point. I'll give more updates when I get em.

 

Warrantys, warrantys warrantys. When push comes to shove and you want to make a legitimate claim, totally reasonable in anyone's view, the message is "Oh dear, the warranty doesn't cover that", or "it's your fault, you did XYZ, or you didn't do XYZ when you should have" or any of the blarney used to wriggle out of warranty obligations.
In UK no-one believes warrantys anymore, most people think they aren't worth the paper they're written on. BBC tv's "Watchdog" program exposed warranty scams to do with white goods/domestic appliances, when the buyer was ALREADY covered under the sale of goods act and the provision of goods and services act. (Note I'm only discussing UK law here). There are laws passed since those, covering mis-selling and mis-representation during negotiation of purchase. There are also statutory "cooling-off" periods for many transactions now.
Stand your ground Matey, insist your reasonable warranty claim is met, or you will take it further. Check up your law, read your warranty contract carefully, know what you're talking about. Be polite but firm. Insist you get what you have paid for.
Leedsman.

 

Aloha to all you Jag enthusiests! I had the same issues as many of you have experienced concerning going into 'limp mode' and getting erroneous error messages on the dash. I fully expected to find out that my throttle body sensor had issues after reading all your threads but happily, my jag mechanic read the codes and discovered that code P2135 (throttle pedal position sensor range/performance), was at fault. they reconfiquered the ECM (re-flashed the computer) and all is now well. So, when the idiot light says; engine system fault, park brake fault & dsc not avilable, it means none of those are true and you must still take it to Jag for assistance!
Drive safe and have fun....