I mentioned this issue several weeks ago.

Issue: Car starts easily and goes up to around 2800-2900 rpm and stays there.

Last summer I refreshed the entire engine with new belts, hoses, plugs, wires, etc...Engine ran really good but I was having a new issue with the transmission. It was not shifting into 3rd gear.
This spring I had the transmission re-done by a very reputable local shop. Drove the car home and was very happy. All seemed grand.
However, within a few days I started the car and this high idol issue emerged.
My previous post on this issue brought responses of a large vacuum leak somewhere. That made sense so I began methodically going thru all the hoses and connections.
I did find a crossover pipe hose with a big crack. I naturally thought that was the likely culprit. New hoses on the crossover pipe did not fix the issue. As the problem only emerged after coming back from the transmission shop it was suggested that one of the vacuum lines there had come off. Tracing the hose from the passenger side intake manifold back to the vacuum modulator on the trans indicated no issues. Connections and hose were all correct.
The only hose I have not physically seen is the one at about the 1 o'clock position on the bell housing running rearward. Not sure what it connects to. (I have a spare trans in my garage and this hose has a connection almost at where the trans connects to the drive shaft)

My last action was to get down to the AAV. I closed the screw down completely and then backed it out 4 turns. It has a total of 10 turns until it falls out. I figured this was probably close to the original factory setting but don't know for sure.
Air intakes have been checked for tightness. Butterfly valves were reset to .002mm.

Don't know what to check or where to look next. Any suggestions are welcomed. Thx

 

I hope you meant 0.002 inches. The 2 microns you have indicated is less than a human hair.

Have you checked the Throttle Position Sensor? They go out of adjustment with age.

 

Try putting a large stopper/plug in the air feed tube to the aux air valve.

There is probably an inlet pipe to it behind the filter on the driver (LH) side (if your car is the same as mine). if that brings the idle down, the AAV is probably the culprit.

Doug

 

The only two hoses that I can recall running aft under the the car would be the hose from the RH intake to the transmission modulator and the hose from the balance tube to the ECU. You'd know in a heartbeat if either of those was leaking or adrift.

What about the linkages? And throttle cable. Any binding? I had to replace my cable a few years ago because of a bind right before the throttles closed. Quick test: disconnect the linkages at the throttle bodies so there is zero chance of the throttle blades opening due to a linkage problem. If the idle is still high then the linkage isn't a problem.

Back to vacuum leaks: the air cleaner housing bolts, four per side, will create a huge vacuum leak if they are loose ....or if even one of them is missing.

Cheers
DD

 

Right.

With the AAV totally (and temporarily!) plugged-off the idle should be about 350-400 rpm.

Cheers
DD

 

Check the large spigot under the A bank thottle body that feeds the cruise control vacuum pipe.
Check inlet manifold nut tightness.
Did you say you verified that the vac line to the ECU is airtright? The one from the centre of the crosspipe down under the car to the ECU.

 

You could always use the brake clean method but be specific with it. If you spray small bursts in specific areas and listen for RPM increas it will get you in the ball park the vacuum system on these cars is nuts and goes all the way to the back of the car, even the heater matrix so tracking down vacuum leaks is no fun. By the sound of the RPM though it is pretty huge.

Check your intake manifold nuts - mine had a nasty habit of coming loose, the cruise bellows can crack too, but I'd be doing some probing with the brake clean to get me into the right place(s).

 

Update: No joy.
ECU hose that connects to the big cross over pipe is tight.
Blocked off port to the AAV inside the air intake. No effect on high idol.
All vacuum line hoses appear to be connected to their proper ports.
Cruise control hose and bellows are in good shape.

Tomorrow I will try swapping out one or more throttle sensors. I have a couple of spares and the other cars.

The car starts easily and runs smooth. This is one of the final four issues.

 

My findings over the years, and I know you have visited some, and maybe all.

AAV, you plugged it, good. Check the 90deg hose at top, particularly the underside, they crack and split.
Balance pipe hoses, I think you did them.
Blanking cap on the 3rd spigot at the rear of the A Bank Inlet manifold.
Brake booster plastic elbow in the bottom of said booster, they fall apart.
Over run valves, I dlelete them. Jag did the same, fitted, removed, fiited again, fair dinkum,
PCV bits and pieces. Again I No Got that junk.
Oil cap seal. They suck AIR via the PCV system if not in good shape.
Throttle discs are not closing as they should, Doug mentioned this. Loosen the 2 small screws CAREFULLY, and ensure the discs actually close central, then reset to .002:.
Injector lower seal, they see huge Vac, so work hard.
Emission valves etc, NO idea, we got none of it back then, clean engine.
Cruise control cable AT the throttle pedal, maybe holding the system mechanically open, fun job, NOT.

A good coupla days work there.

 

Also check the throttle springs are good.

 

Thanks All,

Throttle spring: check. Good.
Brake booster hose and connection. Check. Good
Oil cap. Check. Good
PCV hose and connection. Check. Good
Injector retainer plates. Checked. Good
AAV elbow hose. Check. Good
Big hose under 'A' intake manifold. Check. Good
Blanking cap 3rd port rear of A bank intake. Check. Good
Swapped out throttle sensor mechanism. Check. No change
Cruise control hose. Check. Good
Linkages. No binding. Check. Good

LH airbox bolts. Gasket to butterfly housing. Good. 3 are very tight. 4th bolt is snug but doesn't fully tighten. Used some 'Form a Gasket' with a washer. Also put some Form a Gasket on the heads of the recessed bolts that connect the butterfly valve housing to the manifold.

Next step is try the spray brake cleaner test method mentioned above.
Am considering replacing butterfly valve and/or intake manifold on drivers side (the side with the snug air box bolt).

 

Brad
I think you might try duct tape over the air intake trumpets and LISTEN. This might also help identify the area.

 

Hmmmm .......

I'll try it. Nothing to lose.

 

Update:

Blocked off trumpet air intakes with spray can tops and duct tape.
Sprayed PB Blaster down both the cruise control and throttle cables and worked them back and forth. No issues. Checked for binding on the accelerator pedal and there is none.
Blocked off cruise control bellows hose.
Started car. Rpms are dramatically lower, around 1100.
Sprayed carb cleaner around air intake housings but no appreciable change in rpms. Could not hear any sources of suction with my ear down close.
With the throttle rods disconnected the throttle capstan does not go all the way back to the STOP post. Stops about 3/16" from the post even with the throttle cable adjusted all the way out. It has room to adjust from the underside on the three retaining screws.

Car starts easily and runs smooth.

 

That sounds like a dodgy capstan or an out of position TPS holding it open - it should go all the way to the stop at rest with nothing connected.

Like this




is the spring under the capstan broken - how does the throttle capstan feel when it thinks it is closed, there needs to be a full half turn of the capstan after the spring contacts the base plate to pre tension the spring underneath it before it is fastened down

This spring (the ones on the throttle body are only to help keep the throttle butterflys from 'bouncing'

 

This is the swapped out one. The original one had the same issue. Both are very 'springy.'

I'll adjust it from below and report back. Undoubtedly I'll have to adjust the throttle rods again but not the butterfly valves.

 

Butterly's should be set with the rods off you must ensure the only thing keeping the butterflys closed is the spring from the throttle linkage to the head - the gap must not be set on the rods or the capstan.

The rod adjustment is to take up the slack between the capstan and the throttle body nothing more.

 

Brad

1. With rods and throttle cable removed, the capstan should smartly close from being opened (which should be noticeably effortful to do) with a real CLICK. If yours does not, then the capstan is faulty as Ben suggested.
2. I think the trumpet test proves the butteflies are not closing properly. The airboxes are not airtight, so some air will get to the butterflies. As you hear no other hissing I think the butterflies are not closing; you can prove this theory by removing the part of the airbox that has the trumpet on it, removing the filters and taping over the butterflies. I think you will find the car will not start.

 

Both throttle capstans close with a distinctive thunk with nothing connected, i.e. rods and cable.
I did just go out and disconnect the cable from the capstan and pulled on it with some pliers. I was able to extract that extra 3/16' from it so now the capstan does hit the STOP.
I think the cable may have been sticking in the 'kickdown' housing just after the second micro switch. I put liberal lubricant on it.

I am now almost certain the issue is with the drivers side air intake box not fully seating. Either the butterfly housing bolts and/or the airbox bolts are not all fully seating. I know I have one air box bolt that does not fully cinch down.

I have a spare intake that I can swap out but that will have to wait for another day. It's pushing 100 degrees here with humidity in the 90's. Virginia in the summer.

 

10 out of 10 even moving ... that climate would have me moving North - I cannot function in the low 90's let alone that -

You sure the cable isn't breaking up internally ? though I don't recommend pulling it out to find out.