3.4 idle question...

[fallingat120mph]

So, my 86 3.2 was supposed to idle around 800. Newer years went to 880. With my 3.4 I am curious about my idle.

It was quite high early on and I tried to bring it down to 800-880 levels but it seemed too low.

Just wondering of the mechanics and if "bumping things up a bit (3.4/cams/twin plugging)" should my idle be different than fresh out of the factory.


Erik

[PeteKz]

If you changed the cam to a more aggressive one, then you probably need to set the idle a little higher to get it to idle smoothly, and to start off from a stop without causing the engine to stumble or stall. I would raise it a little and see how well that works, then a little more or less to get it where you want.

And if you twin-plugged it, you will need to reset your timing lower. Check with Steve Wong for an appropriate chip with revised timing curve.

[911MANN]

Erik: You ultimately went with an EFI setup, right? I think Pete's response is correct, and I think you (or someone) can customize your fuel supply and ignition timing program to idle where (or close to where) you want, provided you have enough supply of idle air. Hopefully, one of the EFI experts will chime in.

[fallingat120mph]

Originally Posted by PeteKz

If you changed the cam to a more aggressive one, then you probably need to set the idle a little higher to get it to idle smoothly, and to start off from a stop without causing the engine to stumble or stall. I would raise it a little and see how well that works, then a little more or less to get it where you want.

And if you twin-plugged it, you will need to reset your timing lower. Check with Steve Wong for an appropriate chip with revised timing curve.

Originally Posted by 911MANN

Erik: You ultimately went with an EFI setup, right? I think Pete's response is correct, and I think you (or someone) can customize your fuel supply and ignition timing program to idle where (or close to where) you want, provided you have enough supply of idle air. Hopefully, one of the EFI experts will chime in.

Thanks gents...

I will probably be taking it back to the shop as I feel it needs dialed in a bit. I am no MAF expert, nor twin plug guru...quick learner with engineering common sense but know my limits.

I had 20 years of 800rpm at idle and feel anything over 850-880 sounds odd. But it does run/sound better around 900-950/1000.

Big issue that towed it back home from out of state was a bad CHT sensor and after I replaced that it ran well.

Called Steve W and put an O2 sensor back on also.

Was just curious about the idle and feel 3.4 conversions are kind of a no man's land finding info other than specifics of physical items.

I will report back with outcomes, etc.


Erik

[Jeff Alton]

Not sure what cams you have, sounds like still running Motronic, single throttle intake.

Assuming a 964 or 993RS/SS type cam, we want them idling up near 1000rpm to be smooth. Say 900-1000rpm.

Cheers

[fallingat120mph]

Originally Posted by Jeff Alton

Not sure what cams you have, sounds like still running Motronic, single throttle intake.

Assuming a 964 or 993RS/SS type cam, we want them idling up near 1000rpm to be smooth. Say 900-1000rpm.

Cheers

Thanks...just online reading all I can.

993SS here and 900-1000 seems to work pretty well. Set base idle today to that and just a matter of the new feel of "new" engine and new idle.

I will keep close to 1000 and see how that works this week.


Thank you everyone...

Erik

[fallingat120mph]

Originally Posted by Jeff Alton

Not sure what cams you have, sounds like still running Motronic, single throttle intake.

Assuming a 964 or 993RS/SS type cam, we want them idling up near 1000rpm to be smooth. Say 900-1000rpm.

Cheers

Couldn't resist this morning and got the car out.

After warming the car, setting the idle to around 1000-1100 (per dash gauge as I wanted to just run it a bit higher for the quick warm up) drove some more and the car was running great. Only problem I was having was a bit of lurching around town which for me has always meant idle was a bit high.

Drove some more, highway and interstate, and car was running fantastic but around city streets was lurching a bit still in second gear, etc from street to street driving as I was downshifting, coasting a bit in second and trying to turn corners or coming to a stop(s)...

Came home and attempted to set the idle lower using the base idle method/wire method and trimmed it down to 1050-1100 just to see how that felt. As soon as I removed the wire from the ports the idle dropped to 900ish and I felt like I was right back to where I was earlier with the running issues.

I was surprised to see a 200-250rpm drop when I removed the wire from the ports.

My question is do I still need to use the proper 'base idle procedure' with a chipped, twin plugged 3.4 build or can this be done more by feel and finessing?

When I just adjusted the idle screw the damn thing ran great...temp was good, idle was good and steady just a bit high as stated. Have never had my rpms drop that much after removing the jumper.

Follow up question: If I set the idle with the jumper wire in the ports and it is at 1200 and then remove said jumper and things fall to 1000rpm. Should I let it have a couple of cycles of starts, and restarts to let things adjust???



Thanks!

Erik

[mikedsilva]

Just to confirm, you're running the stock Motronic Ecu and efi system right?
But you have a Steve Wong chip?

I always thought that the idle is dictated by the settings in the chip. And that using the jumper method to set idle is purely so you can dial in the ICV to target the idle setting as per the chip?

[fallingat120mph]

Originally Posted by mikedsilva

Just to confirm, you're running the stock Motronic Ecu and efi system right?
But you have a Steve Wong chip?

I always thought that the idle is dictated by the settings in the chip. And that using the jumper method to set idle is purely so you can dial in the ICV to target the idle setting as per the chip?

Yes sir...stock Motronic and EFI. Steve W. did my chip, correct.

I may have to call Steve again and get his take - although I am sure he is tired of me by now

I don't want the ECU or ICV, etc running overtime...everything seems fine maybe tomorrow I will get on the road for a bit.

Seems like I remember guys having issues and the ECU getting "Hot" to the touch vs. "warm" so it may be old school -- but it's something to check.


Erik

[Jeff Alton]

Erik,

Glad raising the idle worked for you. That is fantastic, it has been our experience for countless years as well with sort of combo.

The lurching you are feeling will be mixture related, not idle related. Find a shop that has a 5 gas analyzer so they can accurately set the mixture. You can get pretty close with a volt meter on your O2 sensor, or you can try tiny movements on the adjuster in the AFM either way and see if that improves. By tiny, I mean tiny. Rich or lean can cause the condition, so without a gas analyzer its a bit of back and forth, but you can likely get it really close.

Steve is a great resource and has incredible knowledge of how these systems work. Not going to speak for him, but doubt he is getting tired of you as a customer. We have used him for many years, and he even was able to create a tune for a 4.1 993 RS motor we built. He is a gem.

Cheers

[fallingat120mph]

Originally Posted by Jeff Alton

Erik,

Glad raising the idle worked for you. That is fantastic, it has been our experience for countless years as well with sort of combo.

The lurching you are feeling will be mixture related, not idle related. Find a shop that has a 5 gas analyzer so they can accurately set the mixture. You can get pretty close with a volt meter on your O2 sensor, or you can try tiny movements on the adjuster in the AFM either way and see if that improves. By tiny, I mean tiny. Rich or lean can cause the condition, so without a gas analyzer its a bit of back and forth, but you can likely get it really close.

Steve is a great resource and has incredible knowledge of how these systems work. Not going to speak for him, but doubt he is getting tired of you as a customer. We have used him for many years, and he even was able to create a tune for a 4.1 993 RS motor we built. He is a gem.

Cheers

Thanks for the positive note - much appreciated.

I will get with my shop this week. I wish I hadn't tried to refine the idle as the thing was running beautifully, but for a guy like me who has owned unmolested 3.2s for decades you go with what you know and I thought bringing it down a bit 'might' help.

I was nervous with the higher idle, but man did it run like a scalded dog on the back roads - so, I am going back to the higher idle and live with the uncomfortable feeling of not seeing 800rpms on the tach

I have never messed with an AFM, not afraid of trying per se, but have always been told don't remove the plug unless you really know what you are doing...can of worms sort of thing.

I will do what I can as an active owner of 2-3 decades and cross reference everything with my mechanic .

It was great to get it back on the road today in a spirited manner...worst feeling in the world driving these things hoping you aren't damaging or making things worse as you try and diagnose issues...


Thank you very much for your input!
Erik

[PeteKz]

I think you can fix that lurch with more throttle. Just sayin'.

[Jeff Alton]

Erik,

Let us know how you make out. Feel free to reach out to me offline if assistance is needed.

Cheers

[fallingat120mph]

Originally Posted by petekz

i think you can fix that lurch with more throttle. Just sayin'.

indeed!

[fallingat120mph]

Originally Posted by Jeff Alton

Erik,

Let us know how you make out. Feel free to reach out to me offline if assistance is needed.

Cheers

Yes, will do and thank you for the offer to assist. Much appreciated.


Erik