greetings one and all, I am a Newbie to posting but a Jag owner of various models over the last 15 years. My current Jag is a 98 X308 , bought with a blown engine ( didnt tear it down but looks like peices of piston came out of exhaust port as I was swapping manifolds over). I bought a low mile used but already reman engine with the Blue temp stickers on the heads. Pulled the eng and trans as a unit. I did the A drum replacement as a precaution (it had begun cracking...good call you guys!) while the trans was out. More on that later as I was able to buy all the needed parts inc Orings, gaskets, updated A drum, filter etc for under around $200. anyway, I did check the tensioners, and found them to be Gen 2 but not cracked anywhere. I left them alone pending how the whole thing ran, and would return to them later.
I put on a new waterpump, water outlet and new aluminum thermo housing, and the hard-to-get-at-later heater hoses under the intake manifold.
Ok, put her all together very slowly and carefully. cleaned the bore of the throttle body, checked the partial breather hose and holes in valve cover. On first start attempt only cranked, eventually started...has "stability control failure" but cruise switch light wprks on/off normally no apparent affect on system warning , also "Engine Fail safe" with both amber and red lights always on. I have pulled P1220 with orig throttle body and P1224 with a used but updated TB. Engine starts and runs, "learned" after several hard resets with Batt cables (battery is a new one BTW), system warnings on, OBD will recode the P1220 Throttle Position. Here is the weirdest thing: when I put trans into gear, forward or reverse, the engine rpm goes up like I am doing a torque converter stall test and the car want to "go". If I pop it out of gear, the rpms go to about 2000 before then settling to around the current 1000 rpm idle..also when not running the brakes seem to work normally, but when I put into gear, the rear brakes become inop no matter how hard I push the pedal, and so it is ridiculous to even try and stop this runaway even on a short test drive. I have inspected and found no problem mechanically, even bled the brakes. also took out the ABS control module as discussed in the forum and resoldered the heavy contact pins and some relay ones for good measure ( no change in this weird brake problem or stab failure indicator). I cant smog this thing to complete my California transfer of ownership, and cant drive it because it is so unsafe to stop. I am a now-retired Master auto mechanic with 30 years mostly import experience, but this has me ready to sell it off and I would much rather keep and drive her, especially after most of the known issues have just been "handled"....any suggestion? Oh yeah, one more thing, after engine has run about 15 minutes, the alternator light comes on, sometimes will go off for a second if throttle is "blipped". could just be the brushes, didnt check yet ,, thanks fellas/ and or ladies

 

"the rpms go to about 2000 before then settling to around the current 1000 rpm idle"

Here I think is where I would begin troubleshooting: WHY is your idle so high?

1. Vacuum leak- Load breather? Cracked intake tube?
2. TPS- throttle position sensor misadjusted (I would check this one last)
3. Is the throttle cable too tight? (longshot)
4. Is everything put back? (belts, sensors, etc.)

Find the idle issue and I think you will be well on your way to resolution- I would connect an obd2 reader and look at the tps% while moving the throttle pedal to eliminate some possibilities.

Keep us posted, it'll get resolved.

 

Look into the electrical system earlier rather than later as the control systems are dependent on clean power at the correct voltage. Nothing will work right if the control systems aren't working right.

 

Put a multimeter directly across the battery with the engine idling & check that the system voltage is around 14v. It will typically be between 13.5-14.5v depending on electrical load & outside temperature.

The system voltage needs to be established as alright before doing any further fault-finding, otherwise you'll end up just chasing your tail...

 

thanks d, cant locate a vacuum leak. doesnt sound of run like one. I think the ECM is learning at this point but I am not sure. Idle is smooth when I can keep the check engine light off. throttle cable not holding the throttle "on", not sure how to adjust the TPS. my scanner doesnt read the TPS voltage, may need to back probe the connector. code says out of range TPS, Po1220. tried a diff Throtle body, got repeated Po1224 codes. All wiring, connectors et are back on. did not have any problems there, far as I know. gonna check all the cables and connections from the Battery forward. I would love a schematic of all the pin on the ECM connectors..I would like to check all voltages and/ or resistances there.....

 

Ok, I am not usually a fan of messing with the TPS setting BUT you may as well give it a shot- it worked for me helping another member when his car wouldn't idle below 1500 rpm after a rebuilt TB where they mis-adjusted the TPS on assembly. Once you get the idle at a reasonable level you can start chipping off the other issues. Are you SURE you do not have a vacuum leak somewhere?

My .02

 

On a side note, the ECM "learns" within a minute or so and settles down to an idle (just went through this today)so if it is still high after that you have other issues. Also, a video would definitely help us diagnose. (startup, idle, rev)

 

The full set of circuit diagrams is contained in the JTIS & that is accessable as a download on this forum if you have a look around...

 

Thank you again D and Red. I have been working a bunch. Ruby awaits testing....I get spurts of time to devote, then none...In the currently none until next week time frame. I will check the system voltages first, reading what I can at the major junctions as well as battery. I will post a fresh report at that time. Thanks again. I can't connect in my head how any voltage problems would make the rear brakes become inop though. The only way this could be is if the ABS unit is on bypass for the rear wheels as if they were skidding. Remember the brakes work fine with the eng running and trans in Park, but put in gear and no amount of pedal pressure will apply rears, jacked up, you can watch the wheels spin while mashing the pedal. There has to be a connection to all my problems here....

 

I replaced the engine on my 98 XJ8 with one from a 97 XK8. I was told that a 99 or newer would not work due to computer issues. The guys at Coventry West kept me
out of trouble. Might be good to check with them.

 

Thanks Guys. should get some time this week to test out some of the suggestions. Mahalo!