Yes, plumb it in correctly, NOT in reverse. I read over the same info.

TPS reset (not a new TPS, not a replacement TPS) is what you need to cure the high idle.

 

I read about somebody thinking the Rochester valve was supposed to be reversed, which is not necessary. It can really only go in one way anyhow, the hoses aren't long enough to flip it around.
I got the car back from the repair shop today and checked the gas tank, its no longer pressurized. I think the Rochester valve holds just 1~2psi which, which makes a very faint sound.

Anyway, while the car isn't totally fixed it is noticeably better. The shop did perform the TPS reset, as well as the proper throttle cable adjustment. The worst it got on the drive home was 2400 rpm, but usually it was trying to idle at about 1900. That's down from nearly 3500.

 

If the TPS reset did not cure the high idle, you have:
1. vacuum leak. Somewhere between the MAF Sensor and the oxygen sensors, you have air coming in. This includes the intake manifolds. You can perform a smoke test to see if there is a leak somewhere. The intake manifold is more difficult to spot, but at the RPMs you're seeing, it won't be that hard.
2. a bad TPS. That is not a cheap part? You may want to find a used one to see if it makes any difference, unfortunately, you'll need another TPS reset to find out if it works.
3. a bad MAF sensor.
4. a bad Coolant Temp Sensor. Cheap and easy to replace.
5. bad oxygen sensors.
6. a bad ECU.
7. dirty and/or loose butterfly on the throttle body. Or maybe someone adjusted the idle screw. You might need a TPS reset to address this.

If you're shop didn't know how to correct the high idle, and you don't have another shop that knows what to do, it might be best to let this car go. The Rochester valve and tranny mount won't have anything to do with your idle.

I'm out of ideas.

 

I'd start at the throttle body. Take it off the car. There are four 10mm bolts holding it in place. Theres also a small coolant line underneath. You'll need two golf tees to plug them.

Clean the throttle body AND check the gap at the butterfly. Should snap closed at .002".

Take note on how the TPS is attached to the car. I would suggest loosening the two bolts holding it in place and making a manual adjustment to the TPS, but I'm not sure how comfortable you will be doing that.

 

Just to run through quick
1: Could be a vacuum leak, I will be checking one of my homemade gaskets to see if maybe it has failed.
2: Shop said the TPS was working alright and performed the TPS reset and adjusted the throttle cables.
3: I've tried 2 MAFs already before I learned about the low flow reading glitch OBD2 live readers do. I believe both are fully functional.
4: Checked the OHM's on the coolant temp sensor and it was ok. 2200 ohms, very slightly warm engine.
5: Could be bad O2's although they kind of look newish? They aren't as dirty as everything else. But if they're aftermarket they may just suck.
6: I visually checked the ECU and there was no sign of water damage, but that doesn't necessarily mean its working.
7: Im definitely going to take the throttle body off again, and re-clean it. Its kind of sticking closed.

Is it possible its the idle air control valve? Can those get stuck open? I did clean it but obviously somethings not right. I don't know that live scanners can typically read one of those so it would be easy to miss, even for the repair shop.

 

The IAC valve would probably not give you the 3500 RPM but some

The MAF on the center wire of te MAF connector will read 1.7 volts DC at the proper idle speed < connector remains on

The TPS will read 0.60 voltls DC on the center wire of the connector with it still connected throttle twisted closed idle position with engine not neded to run

If you never removed the TPS do not do so at this time and leave it installed / the TPS reset also says to not remove the TPS if the shop did their adjustment / orientation correctly

The O2 sensors are titanium technoligy different then the more common , can you read the part #

The O2 sensors do not come into play until the coolant temp reaches 88 degree C ( closed loop mode regulation )

There is a fuse for the O2 sensor heaters so they will read properly

Fuse right engine bay fuse box # 14 / 10 amp red

 

Its amazing how many garages don't know what they are doing when it comes to idle and TPS but then I suppose its very Jag thing to mess up and a specialist might be needed.
First thing anyone touching the TB should do is to read the idle TPS voltage from the OBD. If you had that value you could then mess with everything else and you'd know what it should be at the end of the day. Since you didn't and then proceeded with cleaning, adjusting linkages, etc you should start from scratch now and do a reset although there is a small chance that you have overtightened the throttle linkage. Simply loosen it up temporarily, start the car and manually and fully close the throttle with your hand, see if the idle goes down to what it should be. If it does then next thing you wanna do is to plug in the OBD and check the TPS voltage - whatever you do next, that value needs to stay there and not change. If it doesn't start from scratch.

1. Check TPS voltage and let us know what it is, it should be around 11% or 0.53V-0.65V.
2. Now disassemble everything and make sure that:
-you dont have leaks and you somehow didn't damage your intake gasket when replacing it
-throttle gap is at 0.002" when closed, this can be adjusted with the little screw on the side of the TB
-the iacv operates and closes fully. Can be done with TB or IACV in your hand and cycling ignition.
-that the TPS idle voltage is at around 11.5% or 0.6V(depending how your OBD reads it, but you can change % to V by multiplying your % value by 5V, which is max TPS operating value)
3. With the above and TB attached you only now can adjust the throttle linkages. You do it by monitoring the TPS voltage at idle that should always stay at its base value of around 0.6V(key in ignition, position 2) with the foot OFF the pedal and as close to 5V with the foot fully down. If you overdo linkage adjustment you'll basically loose your 0.002" TB gap and TPS idle voltage will go high causing high idle so its very important to monitor your TPS voltage while adjusting throttle linkage.
4. Now you put everything back together and start the car, if it settles to normal idle - you're lucky and can have a cold snack to celebrate. If it still high - you need a TPS reset. Do it yourself with a clone cable mentioned by Vee or take it to someone with correct cable that can do it for you.

 

Alrighty, so I think I've got it sorted. I took the throttle body out again and cleaned the heck out of it (again). Cleaned the throttle plate with brake clean and a small pick for the "corners" by the pivot axley bit. More aggressive than I like but I tried all my safer cleaning methods first. Cleaned the spring assemblies as well, especially between the end plates. Repeated this cleaning about 3 more times. I took out the IAC valve and scrubbed the carbon away with a bristle brush. (Checked for bristles before reassembly!!) Soaked the IAC valve plunger in isopropyl alcohol and cleaned the heck out of it. The idle grub screw had been wound so far out the throttle stopper wasn't hitting it, so I adjusted that to the 0.002" clearance throttle plate to barrel. This also was a good way to gauge how close I was to having the thing properly clean. If I couldn't get to 0.002" without binding or gumming up, I cleaned more. Also cleaned and re-lubricated the cruise control slider plates/arms/things.

I tried a slightly stiffer extension throttle return spring too. So far I've only tested it up on the jackstands, but it's idling about 800~900 and the revs come back down after I press the gas! The first time I turned it on it was running a little rough but after 2 or 3 minutes it settled in fine.

 

I went for a drive last night to set my OBD2 codes now that its running right. Did a bit of city driving and used the J-gate a bunch, everything is all good. Go to do a bit of highway, all good at first. It starts to smell funny; smells like a mushroom house. Then the transmission suddenly shifts out of 4th gear, and the transmission light comes on. At that point I was close to home so I just went back. All the other gears were working, but the shifts were getting kinda chunky. First thing I do is try to scan the car, but the light is gone. No record of any code. Transmission fixed itself?

This afternoon I go out to try and trigger the code again, but the car starts and idles over 2000rpm again. Now I'm really not happy. I just had this sorted out, it was working just last night. I drive around the block and its still idling too high, but now my transmission is shifting smooth as butter and there's no lights. So I go get some ramps to lift the car and look underneath again. As I'm driving up the ramps I suddenly realize at some point the idle magically fixed itself. What on earth.

So I have a missing 4th gear sometimes and the idle is fixed unless maybe it decides not to be.

 

Have you checked the connections to your ECU for dampness / corrosion?
I’m not sure about the smell you mention, but wonder if it is perhaps dampness drying out as you drive?

 

Have you checked the level of transmission fluid? If they overfilled it at the last shop, it could have been gurgling out as you drove.

 

I did do a small trans drain and fill to check out the fluid. Its very dark, so I'll be getting a fluid/filter change in the near future. There was no metal flake in it though.

Car drove fine today, no idle problem or transmission problem.

 

Do a drain and fill of your transmission three times, or take it to a shop and get it flushed.

Make sure you have it filled correctly either way. Wait till the car is hot, preferably after a drive, and then before turning the car off, set it in park and check the dipstick....while the engine is still running.

(Might as well check the oil level after you turn the car off)