997 hesitation from cold
Discussion
Over the last couple of months I've noticed that when I use the car for the first time for the day it hesitates when accellerating?
After a mile or about 5 minutes it disappears and starts accelerating smoothly again...
I've just replaced the battery in anticipation of the coming winter months and the previous owner said the HT leads and coil were replaced within the last year.
It's not related to weather as it's done it on warm sunny days and cold damp days...
Has anyone had experience of this and resoled the issue?
I'm starting to think it may be the MAF
but hey I'm no expert!
All help and info gladly accepted
Oh it's a 2006 C4S
Cheers
G.
After a mile or about 5 minutes it disappears and starts accelerating smoothly again...
I've just replaced the battery in anticipation of the coming winter months and the previous owner said the HT leads and coil were replaced within the last year.
It's not related to weather as it's done it on warm sunny days and cold damp days...
Has anyone had experience of this and resoled the issue?
I'm starting to think it may be the MAF
but hey I'm no expert!All help and info gladly accepted
Oh it's a 2006 C4S
Cheers
G.
HT leads and single coil are 993 era (albeit a twin system except on turbo) - 9x6 on have Direct Ignition, one-coil-per-plug ignition systems with no 'High Tension' leads.
+1 above, the MAF and/or Coils could be at fault but usually once faulty the problems occur irrespective of temperature.
The timeline of the problem you describe suggests it occurs during the 'warm-up' phase (this lasts approx 2 minutes from cold start at 15-20 degrees C ambient). During this initial phase before the engine warms through, the cam and ignition timing are manipulated to heat the Catalysts as quickly as possible. At the same time the Variocam Plus system runs the inlet tappets locked in 'Large Lift' for the same reason. If the tappets stick - either in the 'Small Lift' (therefore not switching) at warm-up or 'Large Lift' (not releasing) after warm-up, misfires or rough running can occur.
Try a quick test:
Start engine from cold, leave it idling and stand at the rear of the car, at start you should hear the secondary air pump running (this blows air into the exhaust tract which along with the large valve lift and retarded ignition creates post cylinder combustion to additionally heat the Catalysts to get them to their efficient working temperature: 300-400 degrees C - and the snarly crackly noise which sounds good
). After approx 120 seconds the system will switch to its normal running phase, the air pump will shut down, the tappets will split to small lift setting and the ignition timing will be adjusted to suit. If you get any misfires or check engine lights at this point the inlet tappets are likely to be the culprit.
In Variocam Plus faults, because the engine is usually already being revved as the switch-over occurs problems are not logged or felt; the idle test can be helpful in showing up problems in this area.
+1 above, the MAF and/or Coils could be at fault but usually once faulty the problems occur irrespective of temperature.
The timeline of the problem you describe suggests it occurs during the 'warm-up' phase (this lasts approx 2 minutes from cold start at 15-20 degrees C ambient). During this initial phase before the engine warms through, the cam and ignition timing are manipulated to heat the Catalysts as quickly as possible. At the same time the Variocam Plus system runs the inlet tappets locked in 'Large Lift' for the same reason. If the tappets stick - either in the 'Small Lift' (therefore not switching) at warm-up or 'Large Lift' (not releasing) after warm-up, misfires or rough running can occur.
Try a quick test:
Start engine from cold, leave it idling and stand at the rear of the car, at start you should hear the secondary air pump running (this blows air into the exhaust tract which along with the large valve lift and retarded ignition creates post cylinder combustion to additionally heat the Catalysts to get them to their efficient working temperature: 300-400 degrees C - and the snarly crackly noise which sounds good
). After approx 120 seconds the system will switch to its normal running phase, the air pump will shut down, the tappets will split to small lift setting and the ignition timing will be adjusted to suit. If you get any misfires or check engine lights at this point the inlet tappets are likely to be the culprit.In Variocam Plus faults, because the engine is usually already being revved as the switch-over occurs problems are not logged or felt; the idle test can be helpful in showing up problems in this area.
Thanks for the responses chaps.
Tried the quick test, Engine idles at around 1000 rpm and sounds like the secondary air pump is running, sort of blowing noise from the drivers side of the engine.
After a couple of minutes it goes off and the engine revs drop to about 800 rpm.
I'm not getting a CEL or misfires and the exhaust pipes are not overly sooted...
If I then drive off I get no hesitation
I'm using the car everyday this week so I'm going to check it each morning and see how it goes
Tried the quick test, Engine idles at around 1000 rpm and sounds like the secondary air pump is running, sort of blowing noise from the drivers side of the engine.
After a couple of minutes it goes off and the engine revs drop to about 800 rpm.
I'm not getting a CEL or misfires and the exhaust pipes are not overly sooted...
If I then drive off I get no hesitation
I'm using the car everyday this week so I'm going to check it each morning and see how it goes
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