Kirk930

I've started having some hesitation problems with my new (to me) 930. Occurs when the car is warmed up, and under load. Car is hesitant to accelerate and stumbles under load, especially before boost comes on. Not a huge problem but noticeable.

Some background:

'87 930

-1 bar spring and adjustable boost control (set for 1.0 max)
-SC cams
-B&B muffler and exhaust
-Garrett hybrid turbo
-no cat
-37,000 miles on top-end rebuild
-have only had the car 3 weeks

Mixture was richened 1/4 turn after receiving the car to improve slightly rough warm idle, and after an emissions test showed VERY low CO level at idle. Idle did improve.

I just replaced the plugs (Bosch W3DPO) with NGK BP8ES as a first attempt at fixing the hesitation. Cap and rotor look ok. Wires are OEM.

Car starts up perfectly and idles very smoothly when cold. There is some roughness and "spitting" at idle when warm now.

Exhaust spits and pops alot when under engine braking or coasting with foot off the gas.

Car would pull very hard before this hesitation started, and ran perfect.

Where to begin? Bad gas? Ignition? Mixture?

Kirk

senna21

Hmmm..... I'd say you're running rich. But, you were running lean before and I would think your correction to that would have put you spot on. Maybe it got corrected too far?

Just a shot in the dark. Sounds like you've got a nice car there. Don't get discouraged by this little hick-up.

DonE

I agree with Senna21 - a 1/4 turn of the CO screw is A LOT. You really need to set the CO with a gas analyzer (3%).

diabolos88

Kirk,
I had exact same issues , Im 2 month old owner of a '88 930.
My mods are Andial IC, 1bar, EVO intake, euro exhaust/cat delete.
I was also trying to "find' the optimal CO/idle setting in my car but was not able to tune right on until I used a CO meter.
Get a Gunson or Heathkit CO meter, theyre on Ebay from time to time. The mixture should be like 3% to 4%, depending on your sea level altitude.

Not sure if your plugs are the right ones, might want to check that out.

Kirk930

I actually have a Gunson that I bought off of Ebay, but I'm not sure how accurate it is! I tried adjusting CO on my '82 SC and I'm not really sure if it worked correctly.

Elevation here is 650' ASL.

Did the CO adjustment fix your problem?

Kirk

diabolos88

my friend owns a shop and I used his. Not sure what brand his was, kinda looks like a washing machine,
the CO adjustment worked perfect for me, no hunting, bogging or hesitation. When warmed up, my RPMs once in a blue moon do jump up about 500rpm for just a few seconds , no idea why, just happens. Besides that it runs great.

Blaine Sellie

Old thread but.........Kirk 930......how did you resolve the hesitation issue?

I am having problems as well.

911rudy

A small vacuum leak can cause similar problems and it is easy to knock a small hose loose or crack an OEM hose while putting in new plugs.