Lumpy rough missing startup

[30ONA]

Lumpy rough missing startup

When my 07 350gt (stock and no recent work) starts, dead cold, the car stumbles for about 5 seconds before firing on all cylinders. Fine on a warm start and some days is ok.

It fires up on first crank but stumbles and misses. The revs are up at 1000 but it's not firing properly. I'm thinking iacv?

Edited January 1, 2017 by 30ONA

[Memm]

Had similar issues when I use to own my R33/BMW.. Some days ran rough and started hesitantly but cleared up once warm if I was lucky - Ended up being fuel pump on both cars

[30ONA]

51 minutes ago, Memm said:

Had similar issues when I use to own my R33/BMW.. Some days ran rough and started hesitantly but cleared up once warm if I was lucky - Ended up being fuel pump on both cars

It runs fine. It's just the first 5 secs.

What was wrong with the fuel pump?

[sonicii]

Does it seem to miss in a regular/repetitive pattern?  which would suggest an issue with an injector, spark plug or coil pack.

Or in a very random pattern?  which would suggest something common, like a fuel pump or other component.

[30ONA]

No pattern that I can determine.

This was a cold start video just now but the ambient is about 30. I am yet to get a video of the issue.

A theory. If I start the car straight up and have the issue compared to if I turn on the ignition and let the pump prime the line and then start up and there is no issue I could understand fuel pump. But neither seems to make a difference.

In my last tank I put in some injector cleaner and hasn't seen the issue since. I'll keep trying to get a video of the occurrence.

Are fuel pump issues intermittent? Wouldn't it also cause issues driving not just at start up?

VID_20170102_134918.mp4

VID_20170102_135013.mp4

[sonicii]

Seems unlikely symptoms for a fuel pump.  I would expect a bad fuel pump to show symptoms under load with a cold engine too.  but I  wouldn't  rule anything out at this stage.

Might be a bit of a stretch, but what is your battery like?  do you usually make short trips?  my wife's J31 maxima is usually only driven short distances, and if we don't take it for a decent drive on the weekend it will start to have some hesitation from a cold start after 2 weeks or so, usually only 1-2 seconds before running fine.

[30ONA]

The battery is quite new. About 6 months.

[X jap]

I would suggest changing your plugs if you havent done that in a while. Scotty Kilmer said some hesitation is caused by the fuel running rich which is what you get when the engine is cold. Bad spark plugs dont do well in igniting a rich fuel mixture.

Other than that please make sure your injectors are clean, and do the IAC learning properly. You will need 12.9V and all electricals turned off, including door lamps. Hooking up another idling car like jump starting may solve the 12.9V issue cause Its hard to get that value while the engine is not running.

[X jap]

Minor air leaks also cause the issue but I dont suspect because they are persistent and will occur each time you change your pedal position.

[30ONA]

11 minutes ago, X jap said:

I would suggest changing your plugs if you havent done that in a while. Scotty Kilmer said some hesitation is caused by the fuel running rich which is what you get when the engine is cold. Bad spark plugs dont do well in igniting a rich fuel mixture.

Other than that please make sure your injectors are clean, and do the IAC learning properly. You will need 12.9V and all electricals turned off, including door lamps. Hooking up another idling car like jump starting may solve the 12.9V issue cause Its hard to get that value while the engine is not running.

Yeah plugs might be getting long in the tooth. Iridiums with about 75000ks on them. Fuel economy is still fine though. I'll have a look at them.

Is IAC learn the same as IAV on data scan 3? Because it never works when I try it. I didn't know you need to up the voltage. Where can I find the procedure?

[sonicii]

if it is like the DE idle learn, there are prerequisites, like engine coolant at full working temp. And according to the FSM, there are a couple of throttle valve learn procedures that are supposed to be run first.

[30ONA]

Ok so here is the video. Its defiantly an issue with temperature. It was about 24 in the garage this morning compared to the other video at over 30. Next time I'll turn on the ignition and wait a few seconds for the pump to prime and see if that makes a difference. I wonder if it is possible with this really hot weather that parking up in the extreme heat then the car cools and loses the remaining static line pressure?

VID_20170105_055914.mp4

[30ONA]

Problem sorted. Bad batch(s) of fuel. Change supply and added some booster all good now.