My
987.2
base m/t has a odd issue.
It has a very slight surge at 2200 RPM. It is more pronounced when cold and mostly goes away when upto temp but not fully. The problem has been present since I purchased the car last summer.
I have no check engine light or pending codes.
I've recently replaced the
AOS
, Coils, Sparkplugs, & Air Filter.
The MAF has been cleaned and I've checked for vacuum leaks and replaced any questinable intake o-rings/seals
Modifications are Long Tube Catless Headers, Carnewal Exhaust, Softonic tuned,
Numeric Shifter
and Cables.
My camshaft deviation at idle is -2.013 on bank 1 & -4.171 on bank 2
My fuel trims at in the upper load range B1 is 1.054, upper load range B2 1.060 and at the lower load range B1 .997, lower load range B2 is 1.042.
Fuel trim at idle B1 -.188 & B2 -1.5
Idle Loss adaptation is at 1.88
I'm fairly new to the 9a1 engine and I am desperate for more information regarding the motor. Including the allowable specs for cam deviation and fuel trims.
Could my cam deviation or fuel trim be the cause of my light surging issue or am I chasing my tail?
Also can anyone point me in the proper direction for more information on the 9a1 motor. I.E. service manuals, ect.
Any help is deeply appreciated. Thank you.
Thanks for the reply Kinsman.
I'll clean the throttle body out today and report back. Do you happen to know what the acceptable range is for cam deviation and fuel trims?
Just cleaned the throttle body and intake plenum. There was a decent coating of oil. The surging is still there. No changes. Where to
next
team? Could it be fuel injectors maybe?
I don't know what the acceptable cam deviation is - but mine (same engine) with 80,000 miles on it has 0.1, 0.2 degrees.. enough to say dead on. The Variocam+ should be able to bring the numbers very close to zero.. And I noticed: Fuel trim at idle B1 -.188 & B2 -1.5 - one is 10x the other. That might indicate injectors. Have you run any injector cleaner through the system? I've found
Techron
to be quite effective on this engine. Add one bottle to 11 gallons of fuel (or so, doesn't have to be exact) then go drive it fairly hard through that tank of fuel.
As
@Kinsman890
noted - the surge could be related to the tune, exhaust and particularly the long tube catless headers. Have you checked with Softronic if the tune your car has took all of those changes into account, and if they have anyone else running the same setup. It might be a tweak of the mixture at around where you feel the surge might clear it right up, and the tuner is the guy who can do that.
As far as technical info on the 9A1 engine - I would have to look ad make sure - but in general - AllDataDIY is a source for accurate info, gotten from the factory manual, and organized so it's useable (unlike the factory PDF manual..) It's worth looking at - they offer a 1 month subscription, which would be long enough to determine if it was useful for you. I use it quite frequently, often to answer questions here..
Update:
Spoke to Scott at Softronic.
Cam deviation throws a code @7%. However Scott advises that anything above 3% is abnormal. I will be investigating the VVT Solenoids and Primary and Secondary o2 sensors. He advised that the solenoids can be faulty and not throw codes as the voltage will still be in spec but the screens can be clogged or solenoids can have the spring broken. The fuel trim at idle being at a negative also points to a slight timing issue not a vacuum leak as a leak would show as a positive. Also I will need to confirm that the primary o2 sensors are fully in the exhaust stream after the 3-1 merge. If they are not I'll have to swap them to the secondary o2 location and the secondary o2's to the primary location. We also discussed ensuring the throttle body is properly calibrated. (battery disconnected, then reconnected with the key in the ignition for 60 seconds at the on position, you will hear the throttle body cycle).
I will update this further as I get further down the rabbit hole.
I have swapped the DS solenoid, no change.
I'm still hunting the issue down.
Are you experiencing any issues?
