Decided to take my newly-bought 2000 XJ (58k original miles) for a camp trip up to Tahoe. I’m currently in Mammoth Lakes and having some real trouble with shifting. It’s losing power on hills pretty bad in 3rd, like it hits a wall, throttle doesn’t affect RPMs much (stays at 1800RPM or so until floored and it jumps up). ATF looks a little dark, doesnt smell awful. I want to drain/replace filter at the least, since no garage has time to do a flush. I adjusted the throttle valve cable, which had apparently popped loose at some point. I thought that was going to be the end of it because it seemed so obvious. Still struggling. I’m worried about driving too far ******* the throttle this way, but I have been turned away at every garage (a week or more worth of backlogged work) for any real help. What should my next step be? Should I test the throttle position sensor, and if that is good, move to maybe TCM? At least Mammoth is nice, looks like I may be forced to hang here for a second.

 

No need to replace the filter (it's a screen). Remove the drain pull on the pan and replace with 3.8qts of Dextron. Don't do a flush. See how it goes then.

 

Well having lived at Tahoe, lack of power is a common complaint. There is only half the air there as at sea level. So yes, expect loss of power. The only way to compensate is with a turbo charger or super charger. That is why the shops have turned you away

 

Was wondering about the altitude affect.

 

Thanks for the input here. The shops are turning me away because every single one of them is backed up till next week. I can understand the lack of power, but it certainly doesn’t feel like any normal thing. I am having a hard time hitting more than 50mph going up hills. Getting passed by every car on the road. And I’ve never had that issue with the throttle not translating to added RPMs.

 

I live over 5,200 feet and I'm fine with the power my XJ has with 220,xxx miles. Its a little sluggish sometimes, but thats when I'm doing 65mph and hitting a long incline, then you can tell the difference between an old 4.0 and my other cars....

 

I’ve adjusted the TV cable again, replaced TPS since it was easy enough to do, and drained/filled ATF 3x now. Still hitting that wall with the throttle.

 

Yep. I spent a few years at 6,000 feet. There is less power, certainly but not THAT much less. You have a problem, and I doubt it's the transmission. Not that you don't need to service it (replace the fluid. See my sig, #3).

But you have an engine problem. Any codes? Many auto parts stores will read them for free.

Yes, test the TPS. Testing is free, and the part isn't horribly expensive. Don't buy aftermarket. These things are very picky about sensors. Lots of horror stories about aftermarket sensors being bad out of the box, or failing in days or weeks.

 

I already replaced the TPS. I’ll continue to do the ATF drain/fill out of protocol. In the meantime, i’ll run OBD if i can. I just got it smogged in CA last week, so I would assume it was at least code-free then.

 

Well since we're talking altitude, what about fuel and timing with thinner air..??? Where do you normally live? Is it possible the computer doesn't know what to do and is trying to learn the air density and adjust accordingly?

 

Nah. It would figure that out in milliseconds. It adjusts on the fly according to input from the sensors. Vehicles do this kind of altitude change routinely. It's not the altitude.

This might be a vacuum leak, or maybe a sensor has failed.

 

How much does the motor rely on vacuum for acceleration? And where is the vacuum at?

 

Lucky for me, no shops here who will just run the OBD for free like an AutoZone. Might as well buy the scanner from NAPA.

I’ve read a couple other threads where the TCM fuse is mentioned. Anyone know which side the TCM is located in a 2000? The thread I was reading said it’s passenger side, but the youtube video I just watched clearly showed him replacing the TCM under the steering column. Thanks!

 

Just ran an OBD scanner. No codes. Still chipping away at the dirty old ATF, definitely look forward to more thoughts here.

 

That's not how it works. The motor develops vacuum because the intake stroke is pulling in air, and the throttle plate restricts the amount of air coming in. If you were to have a vacuum gauge installed permanently, and were to watch it as you drive, you'd see the vacuum suddenly drop when you floor it, and gradually increase as the RPMs come up, and you'd see it spike when you take your foot suddenly off the throttle while cruising along.

https://itstillruns.com/car-engine-c...-12193724.html

Diesels don't have a throttle plate, so they don't develop vacuum the way a gasser does. They adjust power by regulating the fuel flow. I have a 6.2 diesel that has a vacuum pump on it to provided the needed vacuum to shift the transmission (TH400). That's the only reason it's there. The brakes are hydroboost.