Just throwing parts on by guessing (without even testing the voltage?) is flying blind.

 

Hey, I took it to Tires Plus the day I wrote the original post. It's the only shop I could limp to unfortunately and I needed that car repaired asap since I need it to get to work.

They looked at it a while and the next day they told me it needed a new throttle body. The throttle position sensor is not sold separately by Jaguar. Jaguar also wants ~$3500 for the sensor. Tires Plus wants another $3500 for labor which is ridiculous because replacing a throttle body is not even that many hours of labor. $3500 is what, 23 shop hours? Ridiculous. A throttle body can be replaced in 1 or 2 hours tops on this vehicle. It's easily accessible and since this vehicle is drive by wire, you don't even have to unhook a bunch of throttle cables. The sensor by itself can be bought for $60 special order from various car part shops but I guess tires plus only wants to buy from jaguar.

I got the car working again by just flipping the throttle butterfly around a bunch. The sensor is just a potentiometer. I've used old stereos with staticy volume knobs and you can clear up the problem temporarily by just turning the knob around a whole bunch. The problem always comes back.

I'm gonna rebuild the throttle sensor this weekend when I have some time like this guy did:

 

Junk yards (wreckers) will have them if it's actually faulty.

 

The P1121 is nothing new to us on this forum we see it all the time along with P0121. You can have that throttle body rebuilt by ASI at a fraction of the cost.

Link http://www.autoecu.com/index.php?p=1

 

zephyprime, OK , you got my attention on the fix.
Let us know if that is a possibility. I just didn't like the fact he said at the end "it shouldn't buck as much at low RPM's".
Thanks anyway and good luck.


Wayne

 

In park the RPM limiter might be kicking in or it could be in restricted performance in either situation the engine RPM will not go over 2500 to 3000 RPM’s. With the code he has it is a good possibility.

 

If it plays up at idle it's often an air leak - watch fuel trims.

At high revs it's liable to be the rev limiter as Gus says.

 

Well, I replaced the old sensor with another one I bought on ebay.

First though, I will tell you what happened with the old sensor. I took it apart but I found that it was not a potentiometer type sensor like the one in the video was. It is some type of contactless sensor. It's got a little circuitboard encased with gel in it. It could be manetic or a hall sensor or something according to wikipedia. I am unable to do anything to fix this sort of sensor. The sensor itself looked fine. There was nothing obviously wrong with it.

I put the new sensor on and everything seemed fine at first but them I developed the problem again while I was driving. The problem has been getting progressively worse.

I found that I can temporarily get the car running if I disconnect the battery. At first, when I found this out, disconnecting the battery was very effective. As the problem has gotten worse, I have had to leave the battery disconnect for longer periods of time and sometimes I have to clear all the obd codes too. None of this makes any sense to me. I said before the moving the throttle butterfly got the car running again but I was wrong. The battery had probably been disconnected by Tires Plus as part of their diagnostics and doing that restored the car temporarily.

The duration I can drive after a reset has been getting shorter and shorter. At first, I could drive several days after a reset. Now I have to perform the reset nearly everytime I drive.

Today, before I replaced the sensor, I became throttle limited on the highway and then the car stalled out on the off ramp.

I tried replacing the battery too since I was getting desperate. I got a new battery but this did nothing to affect the problem.

Anyone have any ideas? Is the ECU bad? Does a problem in the throttle body cause problems like this?

 

From the start all you had was a pending code that wanted ignoring and a poor idle for which I suggested something you appear not to have done anything about.

So far it sounds like you made things worse......

Maybe go back to what you had and try what was suggested.

 

I already said that I swapped in a new battery which didn't work.

I'm not making it worse. What's happening is very common - a problem initially appears and is borderline. It's just on the threshold of being a problem rather than being working. As time progresses, the problem gets worse and worse and the bad part moves from merely being borderline to being totally broken. I also already stated that it was getting worse even before replacing any parts.

 

Post #27 is not about battery

 

What does "play up at idle" mean?

The car isn't always like this at idle. Sometimes it will be fine after I reset it. I've already checked fuel trim as I mentioned in a previous post and it's between 0-5%.

It's definitely the rev limiter as Gus says. That was never in doubt. The car is only like it is because the computer is deciding to put it in limp mode. The question is why is the computer putting it into limp mode?

Could it be the throttle actuator is not moving correctly sometimes and after the computer senses that the pedal position sensor is not agreeing with the throttle position sensor because the throttle actuator is broken the computer puts the car into limp mode?

 

When you reset it and also whenever it's just been started you may as well ignore fuel trims as in the former case it has to do a full relearn and in the latter needs to wait till the cats are hot.

There's no point trying to rev past the limiter. It's there to stop engine damage.

 

The fuel trim readers were taken before I reset it.

 

Some people and also tires plus have mentioned that the TPS might need to be programmed after a new one is installed. Is this true for the 2001 S type? I wonder a new TPS was installed previously already but the mechanic didn't know to program the tps?

 

I say replace the TB do a hard reset and drive the car.

You are spending a lot of time spinning your wheels the code is directing you to the problem. I must assume that you have checked and cleaned the plug contacts so move on and No you do not need to reprogram the TB.

Also Do not ask the question if you do not want to hear the answer!

Gus
www.jagrepair.com

 

Are you still running the eBay sensor? If so, I'd say that made the problem worse.

Rather than trying another sensor, I'd suggest replacing the entire throttle body. About a year ago, my '02 V6 kept setting a P1584 code. I picked up a guaranteed used throttle body (with sensor) on eBay. I think it was only around $60 or so. That took care of the problem. The code has never returned. The entire throttle body, complete with sensor, was about the same price as just the sensor.

As Gus mentioned, the throttle body was plug and play. No programming was required. Piece of cake to replace on my car.

JagV8, in his spare time from running an international diplomacy school , has also suggested strongly checking for vacuum leaks. That is very important, but might be tricky to do if the car won't behave itself long enough to get out of relearn mode after a reset. Hopefully you can undo whatever has made the problem worse (the eBay sensor?) and then check the fuel trims.

I have another idea, but you'll have to first promise you'll wait until somebody more knowledgeable than me can confirm it will work. If I remember correctly, if you disconnect the plug at the MAF sensor, the ECU will compensate with stored values based on other readings. The idea is a failed MAF sensor won't leave you stranded. You will get new codes, of course, and probably failsafe mode, too. In theory, though, if the MAF sensor was bad or there was a bad vacuum leak, the engine should run a little smoother. I mention this because of your original code pointing to a discrepancy between the MAF sensor reading and throttle body position. Remember, you've gotta wait in case I was in left field...

 

The complete throttle body is a little more han twice as expensive as just the sensor.

Yeah, checking for intake leaks is a good idea since it has a little excess fuel trim. But an intake doesn't cause problems like I have. The engine runs smooth when it runs and the fuel trim is only a little off.

I can just unplug the TPS and get the car to go into restricted performance mode.

Oh man, now that you mentioned it, the problem is probably he MAF! MAF's are generally unrealible. I was thinking that P1121 meant there was a disagreement between the TPS and the pedal position sensor but I just read the 2001 s stype trouble shooting manual and it's actually the MAF that is implicated.

I already took the car to the dealer though. We'll see what they have to say.

 

Ugh. And if it were the MAF, that would explain why the problem has been getting worse in the cold. MAF sensors usually work on the basis of heat.

 

You can try cleaning a MAF - MAF cleaner is cheap

Do not touch the thin wires with anything.

It's the moving air past the wire that gives the reading so any dirt makes it wrong.