whats up folks,

So for a while now I have been struggling with with a nagging issue. When I first start up the car in the AM or after it has fully cooled to ambient temperature, it idles lean and rough (16.5:1 to 17:1) while the O2 feedback trim is 0. Once the O2 feedback trim kicks in, the afr cleans up 10 14.5:1 to 15.1:1 as the O2 feedback trim climbs to around +10. This typically takes around 60 seconds or so.

Once the car is fully warmed up and driven a bit, the 02 feedback trims settle down. My long term trims are currently hovering around -2 low and -4 middle regardless of when I log them (am during the warm up cyle, or after the car is fully warm and has been driven for a while).

After a good drive the O2 feedback trims will float between 0 and +4 ish, so I don't think the injector scaling is off by much. Battery voltage is always right at 14.5 volts at idle and during warm up.

Any thoughts on what to look at?

 

So i guess I'm the only one who has run into this...

So far, I have tried lowering the ISCV settings by 10 and noticed things got worse, idle got leaner and rougher. Today I will be raising iscv setting by 10 over stock settings.

Based on the logging I have done, lowering the ISCV causes the mixture to get leaner, so I hope raising it will move the mixture richer.

 

could be your thermal switch....this relates open loop to closed loop operation. In other words richening up mixture at start up...Just a guess.

 

That is exactly the kind of feedback I'm looking for. I was figuring it to be related to cold start enrichment. Any idea on a service manual section or a part number??

 

happens to me a lot of times. couple blips on throttle solves it. maybe o2 sensor needs time to warm up to operating temp.

 

I have the same issue with cold idle. Is there a way to alter a coolant temp enrichment map?

 

exact same issue and symptoms here. Been living with it for about a year. Started when I put bigger injectors in.

 

mad_VIII

If you just let your car idle for 10 minutes, what does your LTFT Lo (request 0C) and STFT (request 0F) go to? Does the LTFT Lo hover around -2 like you said, with the STFT around 0?

If so, then it's not the injector scaling. If your LTFT Lo settles around +10, though, it is you injector scaling.

The reason is because when you start your car from a cooldown, the car starts in open loop and will stay there for a set period of time (coolant temps, etc). So, during this brief period, you don't get any O2 feedback or fuel trim correction and you are running solely from your injector scaling and I think even your open loop fuel map.

So, what I would do to rule out your injector scaling as a possible issue is to go for a drive to make sure you are up to operating temps, then just sit in your driveway and idle for a good 10 minutes. Watch your LTFT Low (request 0C) and tell us what it settles to then. If it settles around 0, then at least you can rule out any injector issues and look elsewhere.

Eric

 

This isn't a O2 issue because the sensor hasn't warmed up yet.

Post up your Hi Octane Fuel Map (because thats the map the car should be using when cold)

 

Eric, since it is a cold start problem only, that suggests his issue is not trim related.

if it were a general problem the fact that his non closed loop idle is bad, I ask if you would adjust the open loop map. Or is there another feature that controls cold idle

 

probably lots of other things that control cold idle

I think Eric meant that if his injectors were scaled incorrectly then the AFR would be incorrect. He was telling the OP how to ensure his injectors are correct...

 

Right. I wasn't stating it was a trim issue, since the trims aren't used during a cold start. I was merely stating that if his injectors were in fact scaled wrong, then the open loop AFR would be off. The trims are what would tell us if his injectors were scaled correctly or not.


Eric

 

you have a good point, sometimes I should think before I write

 

Raise your hi-oct fuel map values 0-1500 RPM and 0-50% load to about 141-145 (Sorry, I do not use the AFR numbers). This puts my cold idle at 13.0-13.7 depending on air temperature.

This does not affect your trims since the map since the closed loop map is used at operating temperatures ( 128 using 8 bit).

Try it like Mikey....I know you will like it

HiVolt

 

Man you guys brought this one back from the dead

Anyway, once the engine is warmed up the trims are fine long term low normally around 0 (+ / - 2) O2 feedback around + / - 2. Problem only occurs during cold start. I suspect is has to do with a out of scale maf reading at the cold start rpm. Reason I say this is the only time the engine sits at 1,300 - 1,500 rpm is during cold start. I'm going to scale the maf at that Hz reading and see what happens from there.

Also to support the maf theory, I recently changed from the ebay BR knock off filter to an AFE filter and the cold start lean spot has gone from 18:1 to 16.5:1. Prior to the filters, I was just running the banks box mod but still had the issue.

Like Eric was mentioning, during the initial warm up, the trims are not active so I think this is either related to a cold start enrichment map (that does not like re scaled injectors) or a wacky spot in the maf output that only occurs at the cold start rpm range.