ilib11
07-25-2021, 06:04 PM
Hi All,
Got some issues after a dealership did a service and need your collective knowledge to understand what is going on.
Legacy (Liberty) GT, Auto, 2010, 100K miles . Went to the dealership for one of the typical service, got the car back with strange symptoms - engine is shaking on idle on added load like AC compressor turning on or a transmission set to reverse.
With AC compressor, each time when it starts when engine is idling, there is a vibration wave for a couple of seconds. It is quite significant - can be physically sensed by hands on the steering wheel, via the driver chair, hood is visibly shaking etc.
The engine looks like choked, rpm dropped for couple of seconds and then comes back to a normal idle work. No such issue on rpm higher than idle.
With transmission put in reverse and the vehicle is kept stationary with brakes or with very slow moving backwards, it is the engine rough idle and a high vibration. If AC starts at this moment, the vibration becomes worse.
Apart from this vibration, the car drives good, no problems with acceleration, no strange sounds, does not look like it has any misfiring. Real time data from ELM327 dongle & Torque and Rom rider logs look ok.
I tried to return the car back to the dealership but they unable to actually fix the issue. They increased idle by approx. 100 rpm, so the vibration become a bit less but the issue is still there. They mentioned an adaptation/relearn period after a battery disconnect but after a while the issue is still there. Plus I do not recall any previous battery disconnects did anything like that. Unable to get them to fix the issue.
I spend significant effort doing various tests and parts replacement while trying to find a root cause for the issue. The discussion is here in AU forum:
http://forum.liberty.asn.au/viewtopic.php?f=18&t=36648
I can now say what it is NOT:
- spark Plugs (new NGK)
- ignition coils (new OEM)
- MAF (new OEM)
- first O2sensor (new OEM)
- PSV valve (cleaned, checked)
- throttle body unit (cleaned, swapped to another one used OEM)
- air filter (new)
- battery (new)
- any rubber pipes etc I can touch without taking off the intake manifold
- electricity noise or problems (oscilloscope shows stable supply with no noise mostly at 14.2-14.4 v)
- oil cap
- no intake leaks are found by a reputable service and myself.
- petrol (used multiple stations, typically use 98, the symptoms is worse on 95 though)
Other checks I completed:
- Fuel
51 psi with vacuum disconnected
41 psi with vacuum connected and AC off
42 psi with vacuum connected and AC on
39 psi-> 40 psi -> 41 psi when engine is off
- Intake vacuum
20 mm Hg with A/C off
17 mm Hg with A/C on
(measured at brake buster pipe)
- Cylinder compression with open throttle (slightly warm engine):
1 cylinder - 9 bar (130 psi)
2 cylinder - 10 bar (145 psi)
3 cylinder - 9.5 bar (138 psi)
4 cylinder - 10 bar (145 psi)
I am practically out of ideas what else could be a reason for this issue and how to fix it, at the moment the only workaround I have is to increase Idle RPM settings as + 200/300 rpm via Rom Rider, but that only reduces the symptoms to some extent, not a fix.
I appreciate for any of your help and advise on that problem. I truly hope someone knows a solution for that.
Regards,
ilib11
Got some issues after a dealership did a service and need your collective knowledge to understand what is going on.
Legacy (Liberty) GT, Auto, 2010, 100K miles . Went to the dealership for one of the typical service, got the car back with strange symptoms - engine is shaking on idle on added load like AC compressor turning on or a transmission set to reverse.
With AC compressor, each time when it starts when engine is idling, there is a vibration wave for a couple of seconds. It is quite significant - can be physically sensed by hands on the steering wheel, via the driver chair, hood is visibly shaking etc.
The engine looks like choked, rpm dropped for couple of seconds and then comes back to a normal idle work. No such issue on rpm higher than idle.
With transmission put in reverse and the vehicle is kept stationary with brakes or with very slow moving backwards, it is the engine rough idle and a high vibration. If AC starts at this moment, the vibration becomes worse.
Apart from this vibration, the car drives good, no problems with acceleration, no strange sounds, does not look like it has any misfiring. Real time data from ELM327 dongle & Torque and Rom rider logs look ok.
I tried to return the car back to the dealership but they unable to actually fix the issue. They increased idle by approx. 100 rpm, so the vibration become a bit less but the issue is still there. They mentioned an adaptation/relearn period after a battery disconnect but after a while the issue is still there. Plus I do not recall any previous battery disconnects did anything like that. Unable to get them to fix the issue.
I spend significant effort doing various tests and parts replacement while trying to find a root cause for the issue. The discussion is here in AU forum:
http://forum.liberty.asn.au/viewtopic.php?f=18&t=36648
I can now say what it is NOT:
- spark Plugs (new NGK)
- ignition coils (new OEM)
- MAF (new OEM)
- first O2sensor (new OEM)
- PSV valve (cleaned, checked)
- throttle body unit (cleaned, swapped to another one used OEM)
- air filter (new)
- battery (new)
- any rubber pipes etc I can touch without taking off the intake manifold
- electricity noise or problems (oscilloscope shows stable supply with no noise mostly at 14.2-14.4 v)
- oil cap
- no intake leaks are found by a reputable service and myself.
- petrol (used multiple stations, typically use 98, the symptoms is worse on 95 though)
Other checks I completed:
- Fuel
51 psi with vacuum disconnected
41 psi with vacuum connected and AC off
42 psi with vacuum connected and AC on
39 psi-> 40 psi -> 41 psi when engine is off
- Intake vacuum
20 mm Hg with A/C off
17 mm Hg with A/C on
(measured at brake buster pipe)
- Cylinder compression with open throttle (slightly warm engine):
1 cylinder - 9 bar (130 psi)
2 cylinder - 10 bar (145 psi)
3 cylinder - 9.5 bar (138 psi)
4 cylinder - 10 bar (145 psi)
I am practically out of ideas what else could be a reason for this issue and how to fix it, at the moment the only workaround I have is to increase Idle RPM settings as + 200/300 rpm via Rom Rider, but that only reduces the symptoms to some extent, not a fix.
I appreciate for any of your help and advise on that problem. I truly hope someone knows a solution for that.
Regards,
ilib11