wstrohm

As mentioned in my second thread, our '94's idle just will not come down even after all the troubleshooting I've done. Probably the last item in the factory manual's list of possible causes of high idle (except for some unknown vacuum leak) is a fault with the Electrical Load ("EL" Unit), or with one of the inputs to it. So tomorrow I will warm up the car, let it idle, and disconnect the E/L unit connector to see if the idle drops down to the right value. If nothing is wrong with the unit, the idle will stay high. If it drops down, I will have to determine whether the problem is in the unit itself or whether one of the inputs it monitors is wrong.

Dudemaaanownsanrx7

iTrader: (23)

have you sprayed carb cleaner around the intake manifold and throttle body rats nest etc to determine if its a vacuum leak??

You could also get a boost tester or make one to pressurize the intake tract and check for leaks. they are very easy to make with a tire valve and either exhaust tubing or probably somthing from a hardware store.

GreatShamanGT

iTrader: (9)

How high does it rev to? And does it rev straight to that when you start up the car?

arghx

iTrader: (3)

you're sure it's not a thermal wax/fast idle cam issue?

wstrohm

Just proved it's not a thermowax/fast idle cam problem by pushing down on the throttle flange that bears against the thermowax rod to manually drop the linkage off the fast idle cam when the engine is warm. No change in the high idle.

As I've written in the two previous threads, the idle is at 1500 rpm or so when warm sometimes, and right where I set it at 720 rpm sometimes. But unfortunately it is usually at the higher of the two values.

Also as I wrote previously, I had the UIM off and checked all the rats nest hoses with my MityVac... no leaks. Also bought and installed new (metal) OEM gaskets for the LIM/UIM interface and the throttle body/UIM interface. New IAC gasket, AWS blocked off. If there is a vacuum leak, I can't find it at the top of the engine. And a vacuum leak doesn't explain the steady 1500 rpm changing to a steady 720 rpm and back again at the next stoplight.

Dudemaaanownsanrx7

iTrader: (23)

Does having the clutch in or out effect anythiing? Or a/c on or off.. You should still pressurize the intake or use carb cleaner to see if there are any leaks found. For instance my injectors were leaking air past them and replacing gaskets wouldn't help me there. Somehow your engine is injesting more air at certain times. Does disconnecting the ics do anything to the idle?

GreatShamanGT

iTrader: (9)

Make sure the screw that's stick straight out from the throttle body plate isn't screwed in too much. Try adjusting it. You might have accidentally screwed it in or something. It should be right near the throttle cable. That also adjusts how much the throttle plates open or close.

wstrohm

I ran the E/L functional test (i.e. turning on headlights, rear window defroster, and HVAC **** to positions 3 & 4) to see if the idle increased as it should. In all three cases it decreased from its too-high value of 1500 rpm. So I think maybe the E/L (Electrical Load) Unit behind the PCME is bad. If its output voltage is varying with time (even though all those loads are off), that would account for the two stable idle speed states. Retail price of that unit is $209.45, so I'm going to disconnect it and see what happens. I would have done that sooner, except I have to unbolt the PCME to get at it, and wifey has been busy running around town doing Xmas stuff. Maybe I can fix it (I hope).

Has anyone had a bad experience with the E/L unit?

Sgtblue

iTrader: (16)

Been following your thread just out of curiousity. IF that ends up being your problem I gotta think that fritz flynn or somebody might be able to come up with a replacement. I've never heard of them going bad before, but then maybe some owners gave up before you did and it went undiagnosed.
FWIW.....

Dudemaaanownsanrx7

iTrader: (23)

seems you could disable the ISC to get your idle to at least settle down. ANd if you still have a problem then you know its not the ISC or the E/L thing your referring to, as it would have to control the ISC in order to adjust the idle. The stock computer uses a combination of the ISC, Ignition timing, and fuel to adjust the idle speed. I'm running the PFC and datalogit and disabled the idle contro systeml and now run manual idle.

wstrohm

Today I disconnected the E/L unit connector and drove the car. Exact same symptoms... no change. I did find out that without the E/L unit connected, turning on the headlights, or the rear window defroster, or the heater fan to positions 3 or 4 did NOT reduce the idle speed, which was still at 1500 rpm. One side effect of the disconnect was loss of the MIL indicator, i.e. when I checked for stored faults with the "TEN" terminal in the Diagnostic Connector jumpered to the "GND" terminal, the lamp stayed off... no 2-3 second light-up and then going out as it usually does.

So the idle problem is still there.

Thanks for all your replies!

jd to rescue

iTrader: (3)

Along Dudemaaan's line, you may have the ISC hung open. Sometimes debris will get in there and actually lodge it open. It will affect the idle like a vacuum leak.

Ottoman

are your throttle bodies fully closing?

u might want to take off the elbow and check...

as suggested by JD.. your ISC may require cleaning..

if all else fails.. u can do a boost leak test

wstrohm

jd, I had the throttle body off, had removed the ISC valve, and cleaned it very thoroughly with WD-40. I also tested it with a variable power supply and it worked fine with no stickiness. When I re-installed it, I used a new OEM gasket. The throttle butterflies are completely closed, both the primary and secondary. The AWS valve is removed and blocked, also with a new gasket. The EGR manifold tap is blind-capped.

If there truly is a vacuum leak, it is randomly sealing and then opening, and it would have to be below the LIM, since I just put new OEM gaskets between the LIM and the UIM, and also between the throttle body and the UIM. Maybe a leak in the brake booster diaphragm? But why open and then sealed from stoplight to stoplight?

Dudemaaanownsanrx7

iTrader: (23)

Extra air is getting in somehow. Thats what creates a higher idle. I still suggest you either pressure test or use carb cleaner to find where the extra air is getting in

Ottoman

Thermal expansion is sealing it perhaps?
it could be the gasket between your LIM and block..(if it a gasket)


it could be a leak in a vacuume hose,

it could be a worn/cracked coupler..

Dudemaaanownsanrx7

iTrader: (23)

A cracked coupler wouldn't effect the idle since the car is map based. It has to be something from the throttle body back. To the op go buy some carb cleaner, start the car and start spraying all around the uim, throttle body etc. The carb cleaner will cause the car to bog down when you find the leak. You have air leaking into your engine from somewhere and its best to pin point it instead of blindly replacing things.

arghx

iTrader: (3)

he has already sprayed carb cleaner.

I have recommended it before and I'll recommend it again: physically pressurize the entire system with an air compressor:

this one for a 300zx might work, the "dual pop" one on www.boostpro.net/prodtester.html . I have never used one on a car with twins but I'm sure you can make it work.

wstrohm

I'd like to believe I haven't been "blindly replacing things." I have meticulously gone through the "high idle" row of the 1994 FWM's "Troubleshooting Guide" on pages 178 and 179, and have now addressed every one of the circled causes except "air conditioning sensor," and "intake air leakage" (since I cannot see anything below the top of the LIM without tearing the entire engine apart). There is also an alternate cause... something is telling the PCME to increase the idle speed, or there is a fault in the PCME itself. Although I tend to agree the problem is air leakage, I cannot see how that explains the varying idle speed while the engine is warm, in a random pattern that changes so slowly.

I will be gone until 12/18, but would still appreciate any other ideas you folks might have. As for now, I have reconnected the E/L unit, since that wasn't the source of the problem.

gracer7-rx7

iTrader: (16)

At times, my car's idle would tend to remain at a higher idle at the 1300 or 1500 RPMs that the Power FC is set to regulate the idle to when revs drop. I only noticed this when I was stuck in traffic for extended periods of time going light to light (or bumper to bumper). In this scenario, the car was quite warm from a coolant and air temp perspective. In some instances, the idle would remain at the elevated 1300 RPM level for the duration of the stop light - in other words it would take longer than a few seconds to normalize back to the standard idle (850 RPM as configured in my PFC).

While I am not as adept as you with electronics, I did clean the idle control valve at the rear of the UIM and readjusted the throttle body mechanical settings. I remember readjusting the throttle body mechanical settings decreased the issue for me - meaning the car would drop down from the higher idle sooner. Its been ages since I've been stuck in extreme traffic and the temps got as hot as they did when I was having the problem so I can't offer any other input at this point.

I'd be interested in seeing a video of your scenario to better view timing of the events and how they manifest themselves.

arghx

iTrader: (3)

What is the air bleed screw under the TB set at currently? Have you tried the 1/4 - 1/2 turn that most people run with a power FC? I know in your very first thread you mentioned jumpering one of the diagnostic connectors and adjusting it that way. Try just setting it to 1/4 turn and see what it does.

wstrohm

Still looking for vacuum leaks, I used the MityVac to pull a vacuum on the brake booster line. Odd result... although the MityVac is capable of about 25 in. Hg vacuum, I could only pull about 18 in. on the brake booster. It did not leak down at all, but could not get it to pass 18 no matter how fast I pumped the MityVac. Same sort of thing under pressure... the MityVac will do about 18 psi, but on the brake booster it wouldn't go over 15. Again, no leak down at all.

Is this normal behavior of the brake booster?

I'm pretty much committed to setting idle speed per the manual, i.e. so that jumper in vs. jumper out gives no change in idle speed with no electrical accessories on and engine fully warm. That occurs at around 720 rpm. Any adjustment "offset" would restrict the ability of the IAC system to control idle speed over the full range of the PCME's voltage capability.

Once again I re-confirmed that the E/L - PCME idle speed compensation system is not working. Neither turning on the rear defroster, nor setting blower fan speed to #3 or #4, nor turning on the headlights speeds up the idle, as it should per the manual. However, disconnecting the E/L unit doesn't cause the idle speed to fall, either. It's like the E/L unit just isn't there, or the PCME is not recognizing its signals. The CEL, which is powered by the E/L unit, does work, however, so at least the E/L unit is doing something.

wstrohm

Just visually inspected the PCME PC boards. All 4 sides looked good; no leaking or bulging electrolytic capacitors. (Maybe idle doesn't rise in response to E/L unit inputs because the idle speed is already higher than the correct value.)

wstrohm

Yesterday I replaced the air filter element (35000 miles old), and now the idle speed is permanently high at about 1400 rpm either with jumper between "TEN" and "GND" or jumper out, no change. I backed off both the primary and secondary throttle butterfly adjust screws until they weren't touching anything, AND screwed in the Air Bypass screw fully CW. No effect. Pressed down on the fast idle butterfly flange... no effect. I have never checked the timing... looks like it is set by the Crankshaft Angle Sensor locations, which are fixed. The idle has a lot of putt...putts in it, which sounds like a piston engine's idle if ignition timing is advanced too far, but I cannot see how the timing could ever have been changed on this car since new. Is there a way to adjust it? The FWM does not address it other than to say essentially "don't do it." I guess I could measure it... have never done so.

What elements or units below the UIM/LIM interface could be leaking air into the intake manifold volume besides the LIM-to-housing gasket?

wstrohm

Wife is gone to visit grandkids, and took the Fusion, so I used this opportunity to remove our '94's Air Adjust Screw and clean it and its passageway. Had to extract it using my Mityvac in vacuum mode with a klugey adapter setup, but it finally popped out. The tapered cone area was really oily, not surprising since the intake air track is oily too, no doubt from the turbos. I got everything clean, turned the screw back in until it was about 1/2 turn out from fully CW. Then I discovered wife had taken all the RX-7 keys with her, and she won't be back until tomorrow. So whether the cleaning operation has changed anything, I don't yet know.