After a long story with damaged shipping on my original TB and a denial of insurance by Fedex, ASI was kind enough to swap my damaged TB for a good rebuildable core they had received, rebuilt it and sent it to me. I installed it, calibrated the PPS before starting and then started it up with everything reconnected (so all the lines and wires on the TB, air intake, etc). Immediately went to 3k rpm and sat there for a short time before slowing to 1400rpm. I figured it was doing a throttle relearn since the battery has been disconnected for a few weeks now, so I let it run and went to get a drink. Came back, fully warmed up and still running at 1400rpm. Shut it down, readjusted the PPS cable a few times, few more hard resets and still presenting the same high idle. Was thinking vacuum leak since I broke the brake booster line and had to replace it, but after re-examining it and even applying some black RTV around the line where it enters the manifold, I am reasonably confident that it is not leaking.

Called ASI this morning and found out they recommend a TPS manual adjustment to set the idle as the TB is factory spec and the car is now 23 years old and they sent me their writeup that was supposed to be in the box (quoted below). Anyone know apart from starting it cold and then adjusting from there, if there is a way to use the live data reading on my scan tool to try to at least roughly set the TPS in the right ballpark so I'm not running the hell out of a cold engine? Like, with the intake tube off, can I use a feeler gauge on the butterfly opening perhaps? Or maybe just eyeball the opening with key on, engine off and gently twist the TPS back a hair on its set screws so the initial startup isn't so dramatic?

I did not replace the throttle body gasket in this process, ASI's note does recommend this and I was able to order a new one from a local Jag dealer, but it won't be here for a day or two...if my old gasket has no obvious tears or holes in it, is it safe to consider it good and proceed or is it likely to be introducing a vacuum leak through the base of the TB and maybe thats my problem?

Can I eliminate a vacuum leak by comparing intake manifold absolute pressure vs rpm or some other reading? If it matters, as of my last check, I was seeing 43.0 kPa @ 1409 rpm. I tried misting water from a spritzer bottle all around the brake booster line from end to end and around the TB, at no time did I notice the mist getting sucked in anywhere and the idle never changed a bit.

Seems like I've got nothing to lose by trying the TPS adjustment tonight with the old gasket in place, right? I've seen a few toher threads here that all seem to come back to don't adjust the TPS, a hard reset should do that, but this doesn't seem to be what's happening here. I'll mark its location prior to adjustment and see I guess?

Thanks for any advice!

 

It's not a Torx T20 unless ASI have changed it - A2Boost clarified it a while ago on here it's a TS 20H with the security hole a 5 lobe bit. Make sure you check as it's easy to bust them.

I read through your thread update and did think the same thing about adjustment, but a new gasket would make certain of no unmetered air leaks, they're a crush seal.
I've done enough posts on this and live adjustment if you have time to search.

Gingerly! tiny movement of the TPS body has a big impact on RPM, I've done it and its scary if you go higher revs.
Good luck and let us know when you get the burble back!

 

Thanks Sean.

TPS adjustment was completed last night and seems to have fully resolved the issue for me. Car is running great, drove it to work this morning.

I'll be contacting ASI one more time though, the screws on the TPS were indeed T20's...or at least they seem like they used to be before someone gutted them, wondering if they used to be S20 and someone decided to drill out the security pin or something...though the closer I get to the photo attached, the more it looks like a 5 point start, not 6, Either way, they were mangled and nearly unusable. I was very fortunate that my T20 had sharp teeth and that the screws weren't set in very tightly. I'm genuinely surprised because the TPS is new, and had to have been put on my them since there's a big sticker on it with their name, no way this wasn't something the tech would have not seen. Hopefully they'll send me a couple screws and I can replace these with the right ones at a later date.

One thing bugs me though, I was completely unable to get the engine to start and run without the air intake on, which makes it nearly impossible to get at the TPS screws. I did remember to unplug the MAF, but all it would do was cough and die. Foro future reference, am I missing something here? Maybe the TPS was just way too far off when I tried this as it started flopping around after I loosened the screws.

I eventually eyeballed the TPS, put the intake back on and started it and son of a gun did I ever get lucky, 640rpm warm idle on my first try. Tightened everything up and put my tools away and went to go buy a lottery ticket.

 

Glad you got it adjusted! It is quite tricky to get it right.
Also, the car will not run with the air intake not fitted over the throttle body. I suppose the MAF sensor is not sensing air movement so the car cannot operate correctly. Everything is controlled by the ECU!

 

Mayhem, if you have ACE hardware up where you live, they have a wonderful selection of hard to find fasteners. It might be easier to go there and get a comparable replacement rather than ASI sending you some. Just saying.

 

So its been about 400-500 miles since I got the TPS sorted. Hopped in this morning to go to work, driving just fine and then the thing goes into failsafe mode, about a 1/4 mile before the thruway entrance. I pulled into a parking lot, shut it off, restarted it and it was ok, but failed before I got out of the lot, MIL now illuminated. Turned around and drove home, work from home day today! It went into failsafe mode probably 5 more times on the 3 mile or so drive home. Got home, in the garage, safe. Connected my OBD reader, I see the P1121 code is back.

Now this is on a freshly remanufactured throttle body from ASI...and its a different one than I sent in, which went in for the same code and (presumably) a worn PPS, which I'm under the impression ASI addresses in their rebuild process, will be reaching out to them in awhile when they open. Question for the group here is, are there other things I should be looking at when diagnosing this issue? It ran amazingly well after I got the new TB dialed in, smoother than it has since I bought it. I'm inclined to think I just got a bum PPS in my repaired throttle body, but its pretty odd to me that I'd be having the exact same issue with a second throttle body assembly, so I want to be thorough.

- Battery is good. Fully charged, never given me a lick of trouble or hesitated to crank and start the car.
- Alternator is good.
- I saw no nicks in the wiring when I reconnected the throttle body electrical connections, but I wasn't scouring them either. I'll try to do a more thorough examination to see if any wires might be questionable.
- Pedal cable was not replaced during this procedure. I'm sure its a bit stretched, but no kinks, corrosion or anything like that.
- Pedal cable was set so that when off and gas pedal is untouched, the PPS rotating assy is not being pulled at all, but also there is almost no deflection in the cable.
- Throttle opening in my reader says 86.7% at full pedal press, but not engaging the kickdown switch. When I press the kickdown switch with the pedal floored I saw it vary a bit between 99.2 and 89.9%, which makes me suspect the PPS is perhaps faulty in this throttle body as well as the one I sent in. I need to do a more careful measurement of this later today to confirm this.

Any suggestions?

 

ASI recommended a hard reset, which I did. Car drove fine, but I assume its just a matter of time before this pops up again. While clearing the code i noticed the PPS makes noise (key on, engine off). Video attached, can anyone confirm this is normal or not?

Thanks!

 

That whining is normal.

 

Thanks Sean. Wasn't sure and want to eliminate red herrings.