3.6 idle issue

Synchromesh · 12-03-2021, 10:52 PM

I have an '87 coupe with a '90 3.6 engine. It's been sitting for sometime before I bought it 2 months ago so I've been fiddling with it to get it to work properly. It's running a full 3.2 exhaust.

Things I've done so far:
1. clean out the ICV - seems to click ok
2. regap the flywheel position sensor to about .8mm. I have a lighter flywheel so .8mm was correct from what I gathered on the forums rather than 1mm
3. replace the old O2 sensor with a brand new Bosch one
4. readjust idle micro switch so it actually gets engaged when arm drops
5. readjust idle screw to crank up the rpms a tad as it was a bit low - hovering around 800 right now

The car is running a stock '90 ECU with a basic SW chip.

So the issue is this. When I get off gas and let it pop down to idle speeds it dips to something like 400rpm sometimes times starting to cough slightly then it readjusts itself to the proper 800rpm. This seems to be more pronounced when engine is cold. As it gets hotter it maybe dips to 500-600 and then quickly corrects itself. What could this be?

911obgyn · 911obgyn's Garage

The later chips are supposed to run at an idle of 880. Have you cleaned the injectors?

Synchromesh · 12-05-2021, 07:56 PM

Quote:

Originally Posted by 911obgyn

The later chips are supposed to run at an idle of 880. Have you cleaned the injectors?

Negative. Is it difficult to do? The engine has about 700 miles on a top end rebuild so I'm not sure it's necessary as everything seems to work fine otherwise.

walt · walt's Garage

Lightweight Flywheel will cause the rpm's to dip below normal. I have a SW chip and with the
AC on I have a similar problem and will on occasion cut-off. What flywheel do you have?

Synchromesh · 12-06-2021, 07:22 PM

Quote:

Originally Posted by walt

Lightweight Flywheel will cause the rpm's to dip below normal. I have a SW chip and with the
AC on I have a similar problem and will on occasion cut-off. What flywheel do you have?

No idea, I'll ask the previous owner. According to SW the current 964 chip includes a lwf fix so this *shouldn't* be it.

Jaskas · 12-09-2021, 02:37 AM

I was chasing idle issues for a long time in my 3.6 ( Varioram). Changed lot of parts, before founding out that i was a tiny vacuumleak. Try to retighten all the clamps one more time