85 Carrera Idle Question
 

HI
1) my car idles a little rough. it idles at about 600-700 rpm.

When i brige the socket to override the idle stab.unit ..the idle goes up to about 850 and is stable.
i have tried to up it but about 10 seconds after i take the bridge wire off it drops back again and idles lumpy.

- do you think it is the idle stab.unit?

2) i have done seaches about setting the co. as the unit is upside down does clockwise adjustment (turning screw out) make the mixture leaner?

your responses are appreciated:D

thanks

You have to drill it, and the factory won't support it for emissions. Best to leave it. Most problems can be solved by cleaning the injectors with something.
the 84 to 89 Carreras have a lot of reported problems that I never see or hear about except that they are reported, like rod bolts and valve guides, but the fact is, they have idle problems for sure.
I replaced the idle stabilizer for that reason, didn't help much. I think it was working OK.
The idle goes up when you bridge it. You bridge it, adjust it higher than you think you want it, then it settles, then 2 days later when your car is back to running normal, it's bouncing off at 1500. (I assume you're talking about the Haynes manual adjustment technique).
Once again, check your air box as per Bentley Manual, but mainly just change the fuel filter, air filter, run some techron through it, check the plugs and plug wires, the injector connectors etc and evaluate it from there. Chances are it's that and not a bad unit--coming from someone who changed all that stuff out for exactly that reason.
Also, you could have screwed up injectors...

Is your TPS adjusted correctly?

Jerry M
'78 SC

excuse my ignorance...what is a tps?

also i drove the car this morning...it really battles to rev clean while warming up..splutters a bit ...not undrivable though.

i remember from my sc that there was a auxillary air valve that aids cold running?

thanks:D

THANKS KURT

if i pull of the injectors ....how can i check the spray pattern or clean them other than running cleaner through the tank?

i suppose i could somehow bridge the fuel pump and get it to spray.

thanks:D

You can't easily test the electronic fuel injectors ('84-on). They are opened electrically. If you just apply a voltage across them you can get them to open - until the the selenoid burns out. (Translation: Don't do that.)
-Chris

Make sure your off idle switch is working. With the motor off, pull up on the throttle lever. You should hear a faint click - like a ballpoint pen. This little switch lets the DME know that it should switch to the idle mode. If the throttle linkage is too tight, the throttle may not be returning all the way. Try pushing the throttle lever closed by hand or try pulling the gas pedal up with your toe.
-Chris

I agree with Chris. I'd check the idle switch first...mine had fallen loose and the idle was hunting all over. It is on the drivers side back of the throttle body...tough to see.

As for what is being reffered to as the TPS (throttle position switch), that little black box switch on the passenger side of throttle body is actually a wide open throttle switch (looks like a modern day TPS). When the linkage is full open throttle, that switch rotates and engages a contact for full fuel enrichment. It is not a resistive type TPS like the later 911's have and what many cars are equipped with today.

-BG

TPS = "Throttle Position Sensor". If it's misadjusted it can cause an erratic idle (among other things). Rather than trying hit-or-miss adjustments (especially the fuel mixture, what you call CO) you should do the entire Motec check. It's not difficult once you have the procedure and all you need is a fuel pressure gauge and a volt\ohm meter. The procedure will discuss checking fuel pressure and delivery, the "TPS", the idle air valve, the mass air flow sensor, the air temp sensor, etc. These items must work together, adjusting one without checking the others may be part of the problem.

Jerry M
'78 SC

thanks for the replies

jmohn is correct on the TPS, my point was that an 85 Carrera doesn't have one. That function is controlled by the air vane meter, the much larger box right off the air filter box.

-BG

I can hear the click...i checked the tps on right hand side of the throttle body...it is the adjustable one.it has a plug with 3 connectors going into it although only 2 are wired. according to the bosch book i should have o resistance at idle and then again 0 at fully open.

i only get 0 at fully open......????
IS this ONLY A FULL THROTTLE SWITCH?
IS it supposed to be O AT IDLE?
i have tried to adjust it but it wont...

(1985 carrera 3.2)

THANKS
:)

Like I said in my post above, that IS NOT a tps (but it does look like one!!). It is a "wide open throttle" switch only, and has nothing to do with your idle problems. I thought the same things you did when I was having similar problems on my 84 Carrera, this is how I know with confidence. You should have no continuity through those 2 active pins until you pull the throttle lever all the way open (back towards you) and then your meter should sweep or beep or whatever. When you floor the car, that switch engages at the end of its rotation, and tells the DME computer to make the injectors go like nuts for max fuel flow. Your Bosch book is most likely giving you info for the '90 and on cars. Get a manual (like the Bentley sold on this site or find one at a bookstore) and start going through the fuel pressure checks. Could be you have fuel pressure bouncing around too and causing a fluctuation.

thanks BG.

I misread your earlier post. i thought that it did not have the micro switch!

i found it behind the linkage on the left as i traced the wire from smaller black plug from front?
yip you are right the one is full throttle only and the other plug is for micro switch.... ONLY works for idling.
that seems to work ok.

i am trying new plugs tonight as precaution. i pulled one and it seems old. no harm dto do it.
thanks ;)

question about idle positioner?

i read prev. post that resistance should be 40 with 2 outside pins (mine is 58) and 20 between middle and outside pins (mine is 25 and 30)

is this o.k?

i did plugs last night...not real improvement...checked resistance between plug wire ends and cap end. the highest was 309 and lowest was 288. (not sure how to use meter... but it was ohms)
is there a book to learn these analysers?

what should they be?

(btw: i have ordered WAYNES book and also service manual by bentley)

your replies are appreciated..
thanks.:D

My '85 idles on the low side of 600 too.

But, mine doesn't idle rough.

Perhaps you have an intake leak?
I hear this is common on these cars to become hard and sometimes crack causing leaks.

I keep checking mine, and found I had to retighten them about every other year.

Good luck.

if it leaks air won't it idle higher?

Hmm I am not sure, I know it would on a GM TBI car. :D

But when I take off my oil cap (air leak) it stumbles and drops the RPMs for a moment. Then the Idle circuit does it thing and brings RPMS back up. I can't really tell if it's idling roughly at that point or not.

Good luck.

Hopefully someone else who is more familiar with the 3.2 will respond.

yip i think you are right.
i will check again for air leaks.

ANYBODY with comments about the values i posted earlier....:)

Plug wires usually run around 2K ohms I thought.
Does the idle stabilizer vibrate when the key is on?
Idle stabilizers do wear out. The one on my '86 wore out long ago.
-Chris

I found some gunk in my stabilizer valve once, and shot some carb cleaner in there to swish the junk out. I suppose maybe a good German malt might do the trick too...

Obvious (or maybe not) stuff:

Last time the fuel filter was changed?
Last time the cap and rotor was changed?
Last time you put in fresh gas?
How many miles?
Original injectors?

do you think the wires are bad if higher resitance?

the idle stabilizer vibrates and twitches every 2 seconds.

the car idles at 750-800 stumbles to 650 and then "something" catches it and rpm goes back to 750-800.

could be in sync with twitch in idler....or is it normal
should it run/vibrate consistent all the time when it is in your hand and connected?

i want everyone to check theirs now:D :D :D only kidding

thanks CHRIS:)

Your wires are probably OK. The idle stablizer should hum. You won't be able to hear it but you can feel it. It shouldn't click really.
The ISV is basically a valve on a little electric motor. The motor doesn't spin 360 degrees, it goes back and forth. The part the brushes rub on or the motor brushes wear out (can't remember). Spraying them valve with brakekleen or carb cleaner will sometime makes them work a little longer.
-Chris

You may have an intake air leak. Disconnect each injector one
at a time to find a weak or misfiring cylinder. Use carb cleaner
to help find an air leak.

Check out this web site, systemsc.com. It may have some
helpful info.

Good luck
Loren
'88 3.2

One of my old posts showed some possible 3.2 vacuum leak locations. Hunting down Motronic vacume leaks
-Chris

I'm still tracking down an erratic idle. Mine idles right for 25 seconds or so, then falls to 600-650.

I squirted some carb fluid and found an intake leak on #1 manifold that was causing the cylinder to misfire. I'm replacing the gaskets soon (I had tightened them earlier with no effect).

Also richened to mixture as I found it was .38(!) rather than .8 at a smog inspection.

Look for intake leaks, and if you still have trouble, then you may have to work on the air flapper or CO mixture (3mm hex nut - have to drill to get at it).

thanks for all replies and threads....my printer is going mad printing all the stuff:D

i will be back in my garage playing later....i wonder what the wife and kid looks like:D :D

off topic: years ago i had my first porsche a 1974 911 2.7...my wife and dogs use to run away when they saw me backing the car into the garage as they knew i would call for help to pull the motor....the good old days....

One nifty trick I tried when I did my Carrera intake gaskets this winter was to coat the gaskets on each side with some of that copper spray gasket stuff. Once it gets tacky it helps hold the gaskets in place and fill any little voids when you place the intakes back into position. If you can use a little torque wrench too this helps keep you from torquing things down out of whack (I'm probably stating the obvious again...)

Sounds like the ISV is working so i'm gonna jump on the intake leak bandwagon too.

These inhex nuts seem to come loose rather easily. I'd recommend anyone doing this job to replace the plain washers that are underneath the nuts with lockwashers. Good insurance in my opinion.

Problem is, the inhex nuts are hard to get at with the motor in place. You just can't get a hex key socket, ball end hex key, or any other combination of universal joints, extensions and whatnot to get at all the nuts. When I R&R'd my intake (thankfully with the motor out of the car) I used a long 8mm ball-end hex key with the bend cut off of it to get at some of the nuts. I didn't know of any other way. This allowed me to somewhat evenly torque all of the nuts.

I recall others mentioning in previous topics that even with new gaskets the intake still leaked a bit. The recommendation of using the copper gasket sealant is a good one. I remember another person recommended some type of GM non-hardnening sealant in past topics. I also think those plastic spacers that are sandwiched between the two gaskets tend to shrink and/or crack with age and add to the leakage problem?

Sounds like you're narrowing the problem down. Good luck!

I think your idle is the cold start enrichment...

Your mixture at smog time was most likely .38 AFTER the CATalytic converter. While the .8 setting is supposed to be measure BEFORE the CAT. Look before the CAT there is a little bolt there. That gets removed and a CO adapter plugs in it.

There's a Snap-On ball hex head for a ratchet that works well for the manifolds. With a little work you can use a regular torque wrench with it.

About the CO - I thought 3.2's were supposed to get the .8 measurement at the tailpipe after the cat?? Is this not so?

The CO before the CAT S/B about 1.5% and less than 1% after.
The CO setting is not the problem unless way out.

Too many darts are being thrown at the problem.

Good luck
Lorenfb@systemsc.com
'88 3.2

ok this is what i have done...

checked all vacuum lines..
tightened all intake srews..sprayed carb cleaner and no difference.

put all together...DISCONNECTED CO SENSOR 1 plug with 2 wires and push on plug with 1 wire.
disconnected idle stabilizer.

idled car and set mixture ....when it got close to closed position
( rich) the car idled ultra smooth. connected idle and set idle...no problem ...still smooth.

connected co sensor AND BACK TO BAD LUMPY IDLE.....:mad:

what gives...:D

what does the co sensor do to affect it...
anyway to check the wires going to sensor?

am i digging in the right place..?

thanks

Completely unscientific anecdotal advice here. I recently posted about a stalling problem with a/c on, accompanied by an idle that dropped when throttle was closed then returned to normal, a/c on or off. Solved the problem by opening the air bypass screw with idle stabilizer disconnected until idle was nice and stable at around 900 rpm or so-at idle, the bypass seems to work like an old fashioned mixture control-turn it cc until rpm is maxxed, then as you go beyond that idle deteriorates - it was easy to find a sweet spot. Now, I'm sure someone will point out the error in my ways, but it fixed the problem. Could just be a band aid, dunno.

I did take my ISV apart, and while it works, its clearly on its way to failure. The commutator has a large divot where the brushes ride, probably as a result of its limited range of motion?

Greglepore's approach works fine, which is how I set the idle at
many shops I work with and on my car. Simple methods are usually
the best.

Good luck
Lorenfb@systemsc.com
'88 3.2

thanks greg.

i have done the adjustment on idle screw and the enrichment screw.

---- did the enrichment first....with o2 sensor and idle stabilizer disconnected.

1) adjusted enrichment and close to fully closed (about 4) full turns from closed position the car was smooth.

2) i then adlusted idle to about 900 rpm.

3) connected the idle stabilizer and the idle dropped slightly and idle not as smooth.

4) connected o2 sensor......idle starts stumbling at about 700rpm and rough.

have i isulated it to o2 sensor...??.
how can i test it?
how can i test the wires going to the sensor?

thanks:)

Oxygen sensor info here: http://forums.pelicanparts.com/showthread.php?s=&threadid=112120&highlight=oxygen +sensor

One of two things is happening, I suspect. Either your O2 sensor is bad, or your mixture is off far enough that the hunt is caused by the DME trying to correct it. I'd never mess with a mixture screw on a DME car without either a voltmeter on the O2 sensor (gets you ballpark) or an analyzer in the proper bung-not a tailpipe sniffer.

No offense, but I'm wondering what screw you're adjusting. You say "enrichment" screw-are you talking about the mixture screw that you have to drill to get to and use an allen wrench on? Or are you talking about the air bypass screw that takes a 7mm socket?

thanks greg

the enrichment is the allen key i am adjusting.
i also adjusted the idle (7mm) screw.
i was naughty as when i got the car it felt too lean and i felt that if i enrichen it a bit via allen key i would get the idling smooth:o

any neg. affects if i undo the o2 sensor? we don't have emmision controls in florida.

btw. thanks for the link. will look at that now.