engine shaking at start up..

[ard]

Crazy threads... no wonder internet forums get a bad name...

First, people say "I have that problem"...No, you have that SYMPTOM. There may be 10 things- problems- that cause shaking engine at idle. The shaking is a symptom.

Second, there is spotty detail about what time window everyone is talking about... it is the first 15 seconds? OR until warm? or 3 seconds, 8 seconds....every start? only cold starts? How cold?

Third, they pathetic attempts to correlate other things (engine noise, fuel, what you had for lunch, coming back from lunch, other service tasks performed on the motor, you wife, etc, etc) with this symptom are, well, ...whatever.

Cold start is a funny time for the motor... a few things go on during that period that are generally not monitored by the DME. This period the engine is running 'open loop' and the motor is trying to warm up as quickly as possible... the motor runs rich, the O2 sensors are ignored, secondary air is circulating..... I would look at the intake and specifically any valves that are operative during the initial start. These can be dirty, faulty, leaky, and you will NEVER see a code.

When the engine revs are so low, and change back and forth, the engine will shake..this is a SYMPTOM, and a normal outcome when the rpms are low and fluctuating.

[solrac6262]

Originally Posted by ard

Crazy threads... no wonder internet forums get a bad name...

First, people say "I have that problem"...No, you have that SYMPTOM. There may be 10 things- problems- that cause shaking engine at idle. The shaking is a symptom.

Second, there is spotty detail about what time window everyone is talking about... it is the first 15 seconds? OR until warm? or 3 seconds, 8 seconds....every start? only cold starts? How cold?

Third, they pathetic attempts to correlate other things (engine noise, fuel, what you had for lunch, coming back from lunch, other service tasks performed on the motor, you wife, etc, etc) with this symptom are, well, ...whatever.

Cold start is a funny time for the motor... a few things go on during that period that are generally not monitored by the DME. This period the engine is running 'open loop' and the motor is trying to warm up as quickly as possible... the motor runs rich, the O2 sensors are ignored, secondary air is circulating..... I would look at the intake and specifically any valves that are operative during the initial start. These can be dirty, faulty, leaky, and you will NEVER see a code.

When the engine revs are so low, and change back and forth, the engine will shake..this is a SYMPTOM, and a normal outcome when the rpms are low and fluctuating.

thanks for explanation, this is something that occurs randomly, it can be when cold or the car warm.. if I turn the car it can shake when I change to D normally takes me 2 seconds to do it, then it will shake like 2 or 3 seconds.. or I can start the car just in P two 2 or 3 seconds after feel the shake for also for a few seconds, the revs stay always below 1000rpm but when the car is shaking the needle moves but always below 1000 rpm