AFR Goes Lean ..... Sometimes

[Dirty Howie]

go in to the scanner and insert them to the table. Just right click the table and insert, it is under engine diagnostics>misfire.

Mike

I know how to add PID's to the table and chart and histogram

But I didn't know where they were . I inserted all 8 cylinders and deleted a bunch of other crap from my config as I didn't know if resolution was important here. I will log this on way to work in morning.


DH

[WS6FirebirdTA00]

ok I thought you were having trouble finding them haha

[Dirty Howie]

Here is the log from today.

I logged all the missfires ..... I don't see any but someone else please check

My AFR seem not as lean today........?????


DH

[WS6FirebirdTA00]

I would be curious to see what the other bank is reading too, if the leanness is consistent.

[Dirty Howie]

I would be curious to see what the other bank is reading too, if the leanness is consistent.

Well if I didn't have a job. And I had better tools. I would have another bung and WB installed on the passenger side.

How about looking at O2 and or fuel trims on both sides .....

So there is no misfires right????

Look at these logs coming home from work.........barely lean and rich at times????? Does this make any sense????? But I didn't get on it hard for very long.


DH

[MCBRIZ]

Had this problem with a car I tuned a few months back everything would look great until the minute you went into pe mode and then it would go lean. car was supposed to have a new fuel pump finally got owner to hook up fuel pressure gauge after checking all my equipment wideband etc. The problem was the new pump it would hold 58 psi at all times until you went wide open and the pressure would drop badly. Changed pump everything was fine after that.

[WS6FirebirdTA00]

yeah right now that seems to be the first solution really, hard to tell without a pressure gauge though. Is your pump stock or upgraded?

No misfires in the log either.

[Dirty Howie]

Had this problem with a car I tuned a few months back everything would look great until the minute you went into pe mode and then it would go lean. car was supposed to have a new fuel pump finally got owner to hook up fuel pressure gauge after checking all my equipment wideband etc. The problem was the new pump it would hold 58 psi at all times until you went wide open and the pressure would drop badly. Changed pump everything was fine after that.

Thanks for the input!!!

Not saying its not the FP but it was lean every where if you look at the original logs. Now it seems to be rich sometimes at WOT as seen in the last log.........??????

I will be getting it checked.


DH

[Dirty Howie]

yeah right now that seems to be the first solution really, hard to tell without a pressure gauge though. Is your pump stock or upgraded?

No misfires in the log either.

Okay ..... I am deleting the misfire PID's

Anything else I can lot ?????

Its the stock fuel pump and fuel filter (which is located INSIDE the gas tank!!!)


DH

[EC_Tune]

Might be time for a 255 lph pump...

[Dirty Howie]

Might be time for a 255 lph pump...

Doug

Well I will be getting my Fuel Pressure checked for sure. You don't really think I need a fuel pump .... or do you??????


DH

[redhardsupra]

oh yea you do, stocker is barely good for stock setup, you're flowing twice the air of a stocker, so if you want to keep your AFR stay the same, you need more fuel too.

[Dirty Howie]

Well next monday I will have time to get some things checked.

PLEASE help me put together a check list.

Here is what I have so far:
1. Fuel pressure at idle and WOT
2. Check AFR against another WB
3. Air leaks ?? Where???
4. Sensor failure/shorting: MAF, IAT, MAP

Any advise on how to do these and other tests methodically and effeciently will be greatly appreciated!!!!!!!!!!!!!!!!!!!


DH

[Dirty Howie]

oh yea you do, stocker is barely good for stock setup, you're flowing twice the air of a stocker, so if you want to keep your AFR stay the same, you need more fuel too.

I am not resistant to adding a fuel pump if necessary !!!!!!!!!!!!!

But I don't understand why, as I have logs WOT at the track up to 143mph and WOT in 2nd gear to 6800 rpm which show 88-911 IDC and commanded AFR below 13.

Now if the pump is failing or filter is getting pluged I can understand it needing to be replaced. Replacing with upgraded fuel pump will certainly be considered.

Did you look at my list ?????? ...... Thanks!!!!


DH

[Russ K]

Hook up a fuel pressure gauge & tape it to the windshield. Then do a WOT run to redline, if the pressure drops below 50 psi, then you have a weak fuel pump.

Upgrading the fuel pump on the late 2003 & newer Corvettes is a big job. LPE charges $3300.00 to upgrade the fuel system on their twin turbo 530 RWHP packages (late 2003 & 2004 C5)

Russ Kemp

[Dirty Howie]

Hook up a fuel pressure gauge & tape it to the windshield. Then do a WOT run to redline, if the pressure drops below 50 psi, then you have a weak fuel pump.

Upgrading the fuel pump on the late 2003 & newer Corvettes is a big job. LPE charges $3300.00 to upgrade the fuel system on their twin turbo 530 RWHP packages (late 2003 & 2004 C5)

Russ Kemp

Thanks Russ. I will probably be able to do it on the dyno and check AFR out the tail pipe at the same time. But if not I will get them to do as you suggest.


DH

[Dirty Howie]

More Wierdness.......

I just moved back into my house which burnt down last year so I didn't get a chance to look at this short log I took coming home from work friday nite. It is from a cold start and it was cool and rainy outside. There is no WOT, just a little spot of PE but after warm up the WHOLE thing is RICH !!!!!!!!!

[redhardsupra]

But I don't understand why, as I have logs WOT at the track up to 143mph and WOT in 2nd gear to 6800 rpm which show 88-911 IDC and commanded AFR below 13.

Did you look at my list ?????? ...... Thanks!!!!

the list looks good, and it's a lot like my first list
I don't think it's the sensors as they're all acting normal (except for WB of course)
airleaks are out of the question as you keep constant MAP at all RPM's and airflows.

the pump might have been just stressed for a long time, and now it's its time to go to fuel pump heaven. think of a big fat slob that's suddenly forced to run a marathon, he'll be fine the first half a mile, and then his heart will just fail because it's not prepared for that sort of output for extended period of time.

[Dirty Howie]

the list looks good, and it's a lot like my first list
I don't think it's the sensors as they're all acting normal (except for WB of course)
airleaks are out of the question as you keep constant MAP at all RPM's and airflows.

the pump might have been just stressed for a long time, and now it's its time to go to fuel pump heaven. think of a big fat slob that's suddenly forced to run a marathon, he'll be fine the first half a mile, and then his heart will just fail because it's not prepared for that sort of output for extended period of time.

Okay

Didn't know you could determine air leaks by observing MAP. When you say it stays constant I assume you meann 96-100 at WOT is normal variation. What would I see as MAP to be diagnostic of air leaks.

I assume you saw the log for missfires you recommended......


DH

[Dirty Howie]

Well I guess my problems is fixed......and I didn't do ANYTHING !!!!!!!

Look at this log from today. Check out the AFR histo ..... not lean anywhere.

Check out WOT at 21400 (2nd gear), 24350, and 26550 (up to 115 mph)

My WOT afr is pegged to commanded as it was just a week ago


CAN SOMEONE PLEASE EXPLAIN THIS !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


DH