Daryl

My 88 S-4 Euro specs (no cat or O2 sensor) has good CO and hydrocarbon readings at idle but goes lean off idle. I checked the manual and thought I was following the proper steps to check the throttle switch out. I followed the procedures on pages 03-20 and 03-21 to test the idle contact at terminal 3 and terminal 5 at the LH control unit plug.Throttle closed R=0 and throttle open R= 10 ohms. My reading was about .3 ohms. I also checked the full throttle readings and followed instructions to test on the EZK plug as well. None of my readings showed any where near 10 ohms at the appropriate times. So I thought the switch was dead. I removed the manifold and installed a new switch. Still no change, all my readings remain the same! Upon further frustrated investigation I come across Page 24-115 Test for the idle switch and find different instructions, and low and behold my throttle switch checks out. Can anyone explain where I am going wrong? My switch is working but do I have other problems? Help Please!!

GoRideSno

Hey Daryl,
Can you describe the readings/colors the ARM 1 shows as you have the throttle at various positions include acceleration and idle descriptions if possible.
Off the top of my head it sounds at you have a breached vacuum connection the the regulator.

Come to think of it you may want to return the switch you just bought and get an 85-86 switch. That is the one you will be needing for the SC.



Andy K

John Speake

Hi Daryl,
Page 24-115 actually is for the Euro S2, but the checks are valid for the later S4 etc.

Page 03-20 is for your car, but the closed throttle switch is between pins 2 and 5 on the LH plug, not 3 and 5 as you state you checked.

Regards,

Daryl

Hello John,
Thank you for hanging in with me on this problem. Yes you are right but on page 03-21 it is on pins 3 and 5 to check full load on the LH control plug. Pin 2 and 5 checks closed throttle and off idle. Sorry for any misunderstanding. Where I am confused is the readings I should be seeing with my ohm meter. Checking on the LH plug as per instructions on page 24 -115 my readings check out exactly as the manual states. The readings are 0 ohms and inf. ohms.

On page 03-20 the manual states that the readings are 0 ohms and <10 ohms. I don't see 10 ohms on my multi meter. Am I misunderstanding what <10 ohms means?

John Speake

Hi Daryl,
OK, you have the pin # OK.

In my copy of the manual, it clearly gives infinity ohms (with the normal infinity symbol) , not <10ohm for switch open condition.

This may be because my manual is the European version, maybe there is a printing error in the US one.

Daryl

John
Thank you for verifying that for me. I am relieved but a little peeved to say the least that the "bible" has let me down. How can I be a true believer after an experience like this? It's fun removing the intake manifold for no reason whats so ever!
I will email you regarding the MAF. Any idea how long it would take to get to me by UPS? If I can't get it by the weekend I may pick it up in Phoenix next week.
Thanks for your help.

John Speake

Yes, it's good therapy to take off a 32v plenum !

I will have to check on delivery, do you have a public holiday this Friday ?

dr bob

I have been under the impression that the brain reads the throttle closed with that switch, and uses the signal to completely shut off fuel flow (no injector pulses) when the throttle is closed and the engine RPM's are above about 1500. I'm not aware of any off-idle enrichment function tied to that switch.

John, are you aware of any enrichment function for that closed-throttle switch?

John Speake

Dr Bob,
You are correct about the injector switch off at hihish rpm. Also, when the throttle switch closes, the idle stabilisier loop tries to "capture" the rpm.

No, there is no enrichment at idle, except what can be provided by adjustment of the idle mixture pot, for Daryl's non cat/O2 car.

The symptoms that Daryl has described appear to relate to a badly aged MAF.

He has already checked out posiible vacuum leaks.

The idea is for him to "borrow" a MAF from my US agent on a sale or return basis. I believe this will fix the problem, but it's difficult to diagnose from here :-) - so he has a no risk option to find what is the problem.

Daryl

Hi John,
Just to clarify. My understanding of the throttle switch was to enrich the mixture just off idle then enrich the mixture again just before full throttle. Is this correct or not correct. I checked with UPS and they need the zip code from where the part is coming from before confirming delivery date. Please email to daryllmiller@hotmail.com

John Speake

Hi Daryl,
No, there is an enrichment (instantaneous, not constant) when you snap open the throttle off idle, because the mixture tends to lean out, and the ECU compensates.

The closed throttle switch just signals to the ECU that the idle stabiliser loop should be activated. It also cuts off the injectors when you take your foot off, as reasonably high rpm, as Dr Bob stated.

The WOT switch does indeed give full power enrichment.

Under steady state running, from just off idle, until the WOT switch operates, your car should run pretty much at stoich, being a non cat car.

I will mail you off list for details you request

Daryl

Hello Andy,
I am getting green, yellow on idle. Under driving conditions it goes middle red. If I floor the car it goes off the red. The car feels a little off (sluggish) especially in the upper rpm ranges. Removing the air filter housing does make a big difference. NOTE: Not the air filter but the air filter housing. When I do this the car runs strong and the gauge moves between red, yellow, green. It looks like it is running properly. It has good power through the rpm range. I confirmed this with a repair shop reading the CO and hydrocarbons in the exhaust. With John Speaks help we suspected the MAF but one of the mechanics suggested the idle throttle switch. He thought that it richened the fuel mixture. I checked the switch as per the shop manual and you know the rest of the story. We checked for possible air leaks and wire connections with the air filter housing installed and found nothing. Its hard to believe that the housing can make such a difference but that is what is happening.

John Speake

Hi Daryl,

By removing the lower housing you are altering the flow and richening the mixture.

But the inlet/MAF system was originally mapped on the ECU with the complete system. With a good MAF, it should then revert to the correct running with the original setup.

Regards

WallyP

The resistance readings on page 03-21 are correct.

What it is telling you is that with the idle switch closed, you should see
R < 10 Ohms. This simply means that the reading on your Ohmmeter should be less than ten Ohms. They are allowing for gauge errors, a little resistance in all of the wire connections, and a little resistance in the switch contacts.

Bottom line, you should see infinite resistance off idle (open switch), and virtually no resistance at idle position (closed switch). The ECU treats this as a binary input, not an analog input - that is, it sees off/on, not a resistance reading.

Daryl

Well there you go! Another instalment towards my 982 education. Thank you.