Lumpy Idle After Hot Engine Start

[Rekin]

Hey,

Noticed a slight problem with my r32 gtst.

What happens is;

if i take the car for a drive (20-30min peak hour drive etc)

Then park it and turn off the engine.

Then start the car after 5-10 minutes.

And let the car idle stationary in traffic.

The idles drop below 500rpm and the idle starts going up and down and sounds like its missfiring.

Once i get some space to move forward, the car is real hesitant (feels like ignition timing drops to 7~ or not building any boost in first gear.) Once i shift into 2nd gear everything is back to normal...

I noticed this problem after replacing my O2 sensor with a new NGK sensor, but i have my doubts its related to that?

Also, ive noticed on cold morning startups/drives, the ignition timing tends to drop to 7 whilst driving and you can feel the hesitation. After the car is warmed up, this doesnt happen, so im assuming its just the ecu running on cold start mode, but it has never been this obvious in the past 2 years..

At one point, i had an ecu error of faulty knock sensors appear, but cannot seem to get the same outcome again.

Car has new splitfire coilpacks, ignition module, new battery & new alternator. So im sure it aint an electrical issue.

Im thinking its either the o2 sensor or the ecu?

Cheers

Patrick

[Rekin]

update;

during the dodgy idling, my igntion timing fluctuates from 13-15 degrees.

Each time it drops to 13/14 is when the car starts acting all funny, and then goes back up to 15 where it calms down..

Is this a faulty CAS?

[cuppas]

could it be a fueling issue?

[Rekin]

could it be a fueling issue?

Ive got a GTR fuel pump, and dyno runs show there are no signs of any leaning out etc.

Would a faulty cas make the ignition timing fluctuate which then affects the idle?

This only happens once ive started the car after 5mins of turning it off.

Then, once i hit the first set of traffic lights and idle, the rpm's start fluctuating.. After i move off and continue driving, the problem doesn't occur again..

[julz2bit]

Hi there Rekin,

I have a r34 gtt and have a similar problem i can drive my car to work in the morning ok but on the way home and by the time im home the car is missfiring realy bad and when getting on boost the engine just breaks down , the other night i had to use the wifes car it was that bad. So have found out what the problem is yet ?

Im putting new plugs in friday and i have ox sensor coming somtime this week.