FF 39 cured, now high idle
 

The children are continuing their misbehaving this season. The 92 had a ff39 code come up. I looked at getting a sensor, and instead decided to try a deep clean. I found that the egr tube coming into the bottom of the intake was completely plugged as were the ports for the temp sensor there. I cleaned it all out- including the TPS after I filled it with cleaner, and put it all back together slowly and deliberately. I seem to have cured the code but now I have 1200 rpm idle (no codes at all). I was careful to set the TPS back at the marks that the bolts had made previously and I cant find an obvious hose left off or even loose. Is it as simple as loosening the TPS bolts and letting the idle settle? I did notice that on reassembly aligning the flats pulled the throttle open just a bit but assumed (!) that this was normal. The only other thing I can imagine is that I put the gaskets at the intake tube in reversed top to bottom. I plan to try the old shots-of-carb-cleaner around the affected area. As always, thanks!

As an addition, I came out here and started the car, it ran normally at about 800 rpm and I thought it was fixed. But as it warmed the idle rose back to 1200. Putting it in gear causes a drop to about 500 with an unnerving stumble and then a rise back to about 800. I have been spraying vacuum connections with no effect and the egr valve is functional. Oy!

You can set the TPS with a VOLT METER.

The TPS needs to be between 350ma and 730ma (.350-.730 milliamps).

Measure between Pin #3 (GY wire) and ground on the TPS connector. The reading should be around .5 to .6 volts.

All this info can be found in the document I uploaded to this site (S91_AJ6 4.0 Engine Management.pdf) and Gus also has it on his site.

I cannot attach it here as the file is about 14mb in size. Limit here is about 5mb.

bob

Thanks Bob. I have that file downloaded but can never think to refer to it. In any case, I hooked up my meter and found it to be .68v. I loosened the bolts on the TPS and turned it to where my meter said .6v but idle remained at 1100. I turned it as far as it would go, meter said .53v and idle thumbed its nose at me staying at 1100 and adding a transmission light for better flavor. I believe the file said the computer could "learn" the conditions. Is there a procedure (maybe simply driving it) that will cause the "learning" to proceed better? After this test I took it all back apart again just to make sure there was noting visually amiss. Upon reassembly I got same results again. I need to step away now before I do some damage beyond whatever I already did.... Thanks!

Ok then, let me pose another two questions- is it possible that the computer is simply "confused" by the sudden open port where it had obviously not had much flow for a long time? Is the port into the intake plenum from the egr crossover tube Supposed to be completely clear?- that is, is there supposed to be some sort of filter or Venturi in that tin piece (have I ruined my tin pipe thing?)? The only actual photograph I have found is Larrys in his "mucking out" thread. His has a second smaller tube located over the vapor canister port, but in any case I don't see anything in there....
Thoughts, ideas, or potshots are always appreciated.

You need to make sure the IACV is operating. When you turn the ign key to OFF it sets the opening for the next startup. You can remove the IACV and watch it operate when the key is turned OFF. The pintle will extend so you should use your fingers to stop it coming all the way OUT. It is supposed to bottom-out on the seat and retract a set amount.

If the IACV is inop, you need to find out why.

You also need to have the throttle plate set correctly. I forget the gap setting. It should be set with a feeler gauge.

bob

Hey Jerry, the pipe is just that; a pipe - no venturi or filter so you've probably not wrecked it.

High idle can be caused by a few things - don't think it's the egr as AFAIK the egr isn't active at idle.

Bob's points about the IACV and the throttle plate gap are on the money, I think that throttle gap is 3 thou or so, not much for sure.

On my car the high idle issue was from a tiny vacuum leak due to my re-using a broken gasket sans goop.

Well worth trying setting up that IACV again though before messing with anything else - the instructions for a 94 are from my old notes swiped from the forum long ago:

You can also try a hard reset, which (I believe:icon_cold::icon_fryingpan:) causes the saved fuel map to clear and set up the ecu for re-education :icon_stooge:


Instructions for the hard reset in the archive!

HTH

Larry

Yes that procedure. Thank you Bob and Larry both. I didn't think there was supposed to be anything in that pipe as the "stuff" in it all just looked like carbon. But one never knows really. The IACV turned out to be the problem. Running through the procedure that Larry has copied out was what I did. I also needed to do the set screw adjust, but it worked and also turned the trans light off-(or prevented it coming back on since I left the battery unhooked overnight.) I guess having the EGR tube go from completely blocked to completely clear is a bit of a shock.
As an hilarious aside, while I was poking around looking for vacuum leaks, I found one in the form of a defective Smog pump diverter valve dashpot. I had a good one in my stash attached to the bad smog pump I just removed from the Moneyfunnel. That assembly was rescued from my local favorite junkyard from a Red 92 xj6. So, that car has donated to both my white 92 and my red 94. Go figure.
Roger runs much better now what with the clog cleared and the vacuum leak fixed making the EGR system work better. Thank you for your input.

Alright, I'll bite!

WTF is a
Maybe mine's gone too ..you never know!! :icon_confused:

Larry

That valve is on a short hose stuck on the back of the smog pump. The valve is vacuum driven off of that solenoid at the top front of the motor. As I recall the tube then goes up into the air filter box.

I'll have a look for it later on Jerry - BTW, how did you figure out it was defective?

Larry

I was simply looking for vacuum pots and using oral suction to check. Almost literally grasping at straws. That one is a lot easier to see with the intake removed.

Hi Jerry,

The large photos at Jag-Lovers are still in the process of being migrated to a new server, but I'm curious to know if the part you are describing is the same as in this thumbnail:

Welcome to Jag-lovers - Members Photo Viewing Page

Cheers,

Don

It Seems to be. At least it's right there where the arrow is pointing. Delay does make more sense than divert too. Color me corrected. But I have to ask- did you use a trapeze to get that pic? I don't think I've seen mine from that angle. 🤔

I think I must have leaned over the engine from the passenger side!

I think I took that photo to help someone who was looking for the delay valve hose - I didn't know what it was or where it was either. I had to look it up!

Ok, so when and why does the "delay" take place?

Larry

That's a fine question. I only know I have one less vacuum leak now.

:icon_razz:

Larry