Normally the PCM will detect and flag codes for misfires long before you can feel them, so at least look for pending codes.

Check battery is good - so far the alternator looks OK but that's all we know. Volts after standing unused overnight and don't start the engine / do a load test.

Another cause of RP is SC coolant pump failure if this engine has that pump (as mine does).

An easy (& cheap) check is fuel trims in case they're odd.

 

yep have done that...still wont show a code

 

thanks for all the help, I'm still struggling with this problem though. battery checks fine and yes it should show pending codes and I hate to start just throwing parts at it.
it dose seem to have a miss small as it is and it doesn't show a pending code but you can feel it and if you watch the tac real close you can see it

 

Not trying to rub your nose in it but from the panic of "how am I going to get back from Belgium" I calmed down and did some proper work. So, running the engine I could hear a strange whoosh noise and sure enough there was a break in a hose.

A load of masking tape later, no restricted performance light, no bumpy idle, and a happy relieved me!

 

ok think I found my problem got code off a newer snap on scanner P2601
think its my inter cooler that would be abought right for it to drive 30 miles before restricted performance came on.... but still no cel??? next I need to understand difference between the sc pump and aux pump and where they are and how to test them. also with the car sitting for a while could the system just need to be bleed?
thanks for all your help!!

 

The IC pump is on the RHS of the radiator half way down. The auxiliary pump, for the heater, is at the bottom of the radiator RHS.

The IC pump is on when the ignition is on. If the aux pump is not working then you would be getting little if any heat with your heat on inside the car.

Some say you can feel the coolant flowing when you pinch a pipe in the IC hose cicruit. You dont need the engine running just the ignition on.

I could not feel coolant flowing however coolant flowed out of the reservoir when I was changing coolant recently.

 

ok sure I did this Wong but I couldn't tell if pump was on so I pulled the hoses on sc off 1 by 1 to see if there was flow....there was antifreeze in it but not much flow maybe a dribbling - but I put it back together and no code

 

If the ignition was on and no coolant flowing out of any IC hose then the IC pump is not working.

Check the fuse which I think is #14. If thats ok check the connection on bottom of pump.

If you need a new pump you can get an upgraded Bosch pump on Ebay new for around $100. Which is what I did.

You have to modify the pump holder since it has a larger diameter than the OEM Jag one.

You know NOT to mix coolant types. It should have OATS compatible coolant. Dextron from Walmart is good.

 

thanks I just got one from orileys was 64.99 new, I have a shop so I get discount. any way I traced the hoses from my intercooler and mine is the opposite of what you said. the pump to my intercooler is on the bottom and my heater pump is mid way
but I think your right about it being my problem. the 20 to 35 miles befor it comes on would make sence because it takes that long to over heat the inter cooler. my thinking any way.

any way ill keep you posted and thanks much for all the help!!!

 

What car do you have?

 

2005 late xjr

 

Well it will be interesting to see when you replace the bottom pump whether that corrects the problem.

On my 2005 XJR the coolant reservoir feeds in to the top of the pump half way down the radiator. Thats where it drains when the ignition is on without the engine running.

 

I believe you really, I don't know if mine being a late 2005 makes a difference I found this out with the ballast a 05 uses a 12 pin a late 05 uses 4 pin.
any way I traced the hose from the intercooler down to the bottom pump the other end of pump go's into the radiator. I would take pics but you cant see it. looks like bumper cover has to come off, I'm thinking I may relocate it.
give me your thoughts.

 

lets see if I'm right... the inter cooler are the 2 boxes on either side of the air tube
they have 2 hoses coming from either one, the passenger side and comes in from the pump then go's over to the drivers side then out to radiator...... one big loop

thanks again jackra-1 if ever by Branson mo yell ill buy you a dr pepper

 

The intercoolers are where you said they are. Correct about the loop.

The bottom pump can be seen if you take off the plastic clip on cover adjacent to the fog lite.

If you take of the front under body plastic shield you may be able to access the pump? also if you take out everything above the pump including the pump half way down along with hoses you may be able to get to it.

You have to drain the coolant anyway.

I had to make use of several different tools to get at hose clips several of which were a PITA to get off. This was when I was renewing hoses including the valley hose.

 

that's what I thought, well I have to replace a ballast any way and want to pull both headlights to split so I can clean inside and might install halos while I have them split any way.
thanks again for all your help wish you were closer...lol

 

People in this forum say they find it easy to remove the bumper. I always have trouble!

I did upgrade all my bulbs including the driving lights with led bulbs except the fogs which I intend to do later with modified inserts which is wip.

 

yes I did my fog with hid had to make inserts for them - my low beams are stock hid I don't know if I'm going to convert my highs yet I already have a set of hids to do them with but haven't decided yet

 

might be a dumb question - but here go's.
are the ball joints in a 2005 xk8 or xjr the same as a 2005 xjr v-8 super charged?
wanting to change upper ball joints with out doing whole control arm. I do know that thay were made by ford and a lot of the 2000 Lincoln ls parts fit the jxr.
thanks for your help, and I got a lot from here so far. learned a lot to!!

 

That would have shown up big time in the fuel trims!