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I finally got my car back on the road after having it stolen and crashed into a house!
The car is driving like it was before, however I have a strange issue I cannot resolve. The car is idling high. The TPS is at 18.8%, even after I reset it with a PDU. I reset the idle adaptations as well. I replaced the TPS with a brand new one about a year ago, finally solving my trim issues. I did try to force the throttle butterfly back by hand (from the top of the spindle), but I didn't get any movement on the TPS reading.
Here are two unusual clues:
1. While sitting in traffic, I shifted into neutral, the RPMs went up to about 3,200 and steadied. I then shifted back into drive and the RPMs went back to 900 but the TPS went down to about 14% then casually floated back up to 18-20%.
2. When I start the car cold, after about a minute, the car seems to want to lower it's idle RPM, but then goes up. Every 10-15 seconds or so, it tries to drop the idle, but then races back up to about 1,500. Admittedly, I wasn't watching the TPS through my OBD2 reader. Once I drive and the car gets hot, and it is what I reported above with no obvious attempts to lower idle.
Unplugging IACV had no effect. Unplugging MAF killed the engine.
Do you have traction control? I'm not familiar with that engine in XJS's, but I had an XJR where the throttle cable boot had broken where it went into the traction control modulator and the cable was randomly binding. Caused all sorts of weird idle behaviours until I snipped the zip tie holding the cable and routed it straight into the traction control modulator and it idled fine.
On the X300's there is also an in-cable adjuster for slack, not sure if the XJS has that. Maybe make sure it isn't adjusted a bit too tight? As a thought, try disconnecting the cable and see where the idle TPS position is.
At $1,200, I spent more than I should have getting the radiator support welded into the car. There weren’t too many shops interested in taking that project on.
I spent $1,600 in paint and another $1,200 in repairs at a Jag specialist I trust. They fixed a bent differential cage, found and repaired a coolant leak, replaced the AC belt the welder broke, replaced a rear muffler I provided, which included monkeying around with the attached exhaust pipes and mount I also supplied, replaced bent transmission mount and straightened some chassis mounting points.
Throw in another $1,000 in parts....which, frankly, I feel I got for free. A bumper cover, hood, fender and radiator support for $600! Then a bunch of odds and ends for the other $400. I’m not including the $450 I spent getting the radiator recored, because it was probably due, even though the core was destroyed. (Luckily, the radiator ends we’re still pristine.). Had I not found the parts so cheap, I would have found another XJS instead.
All told, it was a long two months of not having the car. Everything took longer than expected and I missed the fact that my hood had an extra pair of holes for a stupid leaper AND growler. WTF? I’m not gonna argue over which ONE is better, but for the love of God, please, let’s stick with ONE freaking hood ornament!
I’ve reset the TPS numerous times with a PDU. (I’ve also reset throttle adaptations, oxygen sensors reorientation and the throttle kickdown test) It starts off good, but then as I drive it, it seems to want to return to the 18.8-20% range!
I noticed that the ram intake assembly came apart. I owe it one large hose clamp to keep the plastic parts from pulling apart again. I don’t think that’s what’s causing it though.
While the car is running, I cannot seem to affect the idle by pushing on the throttle assembly, or the TPS. I can get the engine to rev using the throttle, but I can’t get it to slow down from its high idle, obviously caused by the higher TPS.
Is there anything that affects the TPS? Anything that can tell it to open up? No, right? It would have to be a bad TPS? Would unmetered air cause something like this? What about anything on the exhaust side? LTFT is 0. I would think that anything going on with unmetered air, etc, would cause fueling issues without causing the TPS to report anything different?
I’ll pull the throttle body off this weekend and take a look. I thought the TPS was simply reporting back what position the throttle plate is at based on my foot. There should be no way for the TPS to affect the position it’s reporting to the ECU, right?
If the TPS is reporting it’s at 18.8%, then it’s either busted, or the butterfly is getting stuck? There’s nothing else that can affect what the TPS is reporting back to the ECU, via OBD2, right?
A quick spray down down of some carb cleaner and a rag took out what was a barely perceptible buildup of oil blow by residue that was a direct result of having the car sit for a few months as it was stolen, and slowly repaired. I’ve attached pics of the before, and if you zoom in to the open butterfly pic, a ridge that starts about halfway up the TB intake. I suspect that was the cause. After cleaning it, I experienced a very high idle which was solved with a TPS reset.
I previously installed an oil catch can that, as you can see, has done a marvelous job at keeping the throttle body clean…to the naked eye. This issue that arose, I fear defeats the purpose of the oil catch can. I thought I may have found a way to keep the throttle body maintenance free…alas, there is no way around a good old fashioned throttle body cleaning.
Luckily it’s easy to get to, remove and replace. No gaskets, not much of anything. Once the throttle body is off, the costly TPS can be easily removed so that there is no fear of damaging it with carb cleaner. At that point, you can go to town with a bottle of cleaner and a rag or two.
02-19-2019, 04:53 PM
Facelift TPS at 18%, even after rest with PDU!
