Okay I've been putting it off long enough and now I'm tired of the limp light on. So before that lamp burns out I will try to first fix the TPS. So my question is this, is there a gasket between the throttle body and intake that will need replacing? Haven't seen any mention of one in any manual or discussion on any forum, seems like a logical place for one and would like to have it on hand before I start.Thanks for any input.

Charlie

 

I'm going to join you on this. I may do it tomorrow, Wednesday the latest. There is no gasket. I going to pull the whole throttle body out. Flip it over and its sitting right there. I'm just going to clean mine out, but its time I can tell. Keep us posted on your progress. Are you replacing yours?

 

Not replacing it yet if I can clean/repair and adjust it. Just cleared FF14 and 37, now working on FF11 need to see if I have the right MAF installed. The PO was not too mechanically inclined, seems as though anything touched is broken, I just look for signs of tampering and check the area myself. The FF11 is causing my limp mode right now and I will need to troubleshoot and repair that before I needlesly tamper with the TPS.
Good luck with your project, and thanks for the gasket info. I'll post after I find the source of the trouble. I need to get MAF part #'s for my 91 VP 4.0 to see if the MAF is correct.

Charlie

 

the correct part number is dbc12517 but I believe they are for the most part interchangable

 

Okay the MAF is the correct one, haven't thoroughly tested it yet need to drive it too often to put her down for a few hours.I'll get to it this weekend, will check the MAF specs, maybe fiddle with the idle adjustment screw see if there's any improvement. After that if I'm not satisfied it's on to the TB and TPS .

Charlie

 

I changed the TPS on my car. I highly recomend taking the throttle body off to replace the TPS for obvious reasons. It can be done with the tb still on if you are decent with your fingers. I used a 1/4 drive socket with a short extension and possibly a knuckle buster to get the bolts in place. You can use the old stuff a tissue in the socket trick to hold those tiny bolts in place while you line them up.

To check the tps I found a high quality voltmeter with lonk prongs worked well. I could loosen the connector just enough to stick the long prong through where the clip for the connector is and make contact with the signal lead.

I got a cel for my tps and measured it. It would read properly at wide open throttle and was not far off for idle. This can be misleading as one might think if those two readings are good the tps is good. This is false, the throttle must be opened from closed to wide open and back down again in a slow smooth motion. The voltage should increase/decrease smoothly as well. My tps would start to jump around and unsteady at around 3v indicating a bad tps. I assume because of contact issues caused by an oil filled device.

I reinstalled a new tps and followed Haynes specs for the correct idle setting. I think it said between .2v and .5v, this did not work! I get a cel for the tps with any of those values. The guys over at AJ6 Engineering have it pointed out on their webste that the correct idle setting is actually .6v for the 4.0l engine. I emailed them to confirm it was not in error and they kindly replied back that they were certain it was .6v. I set it to .6v and has been running great since.

Apparently some (or all?) xj40's did not come stock with a gasket around the throttle body. Mine had what looked like a factory permatex job on it however. I would recomend using the-right-stuff on it, don't want to risk any air leaks past that MAF.

This was all on a early 1990my

 

Thanks Gunner, yes I believe it is my TPS, even with no TPS code. I just want to check the MAF specs because of the engine behavior while driving. I was thinking of adjusting the TPS while the TB was off with the connectors on rather than struggle with it on, I think it should be possible. I'll find out for sure though.

Charlie

 

which pins on the TPS do you check with a voltmeter?
*edit*....nevermind

but remember set to .6 volts not .5

 

The range at idle for the TPS is actually 350mv to 730mv but the nominal setting is 600mv. (page 25 of the S91_AJ6 OBD Diagnostic Guide)

bob gauff

 

Okay, had the TB off this weekend, filthy as well as the TPS full of oil. Cleaned both, set TB to specs, tested TPS it works as designed, set it to specs. Cleaned the general area of oil and soot, cleaned all contacts tested all resistances and voltages all dead on except for the IACV. Seems as though my MY is a late release and the voltages spec out as 11.8/11.8 0.4/0.4. Put it all back together still crappy idle, limp mode and FF11.
I need to do further testing of the stepper motor, right now it's not connected and running ok (not great) but connect it and it goes to hell.
I did reset it according to the book on JL. and also pulled the motor off and watched the plunger move with ign on then off. It moves but not sure if it works properly, need the resistance specs for that coil. Going to check the harness for tampering, found splices from PO in the past that caused other probs. Will update when I get new info/results.

Charlie