Running Issues

[akeizm]

Hey all,

 

I need some help with my car. I just got my Z tuned on the dyno on Monday and she was running quite nicely on the dyno and on the drive home. But when I tried running it the next day it was playing up pretty badly. So I took it back to the dyno joint and they said it was running very lean (Now I know they tuned it properly because I had to help them, needed to show them the program and I could see my fuel ratio's etc when he was tuning).

 

On the way home it all of a sudden started running normally. But when I ran it later on that day it reverted back to its problematic state and has been that way until today.

 

When it plays up it bucks, coughs and really struggles to get up in the RPM's. When my dad and I were looking at the car today it looked to be running rich because it was blowing smoke, but at the shop we saw it was running lean. So I dont know whats happening, one minute its really lean and one minute it seems Rich. Now these are the details on my car:

 

L28e converted to an ET

GT30/40r Turbo

60mm 240sx Throttle Body

440cc Supra Injectors

Intercooled with 2.5" piping

3" from DP back

Z31 Narrowband O2 Sensor (3 wire)

Megasquirt and Spark Extra (u21, Tuned in MegaTune2.25b358. Started with Moby's map)

 

Now I have done some data logging. The logs I am putting up are of the car when I 1st got it on the road in May. 2nd is today when the Car is out of gear and the last one is a run today around the block:

 

Run In May (22nd May 2005)

Run today (Out of Gear)

2nd Run today (Drive around the Block)

 

Now I'm no expert but it seems like the O2 sensor is screwy. But looking at the last Log the MAP graph goes off the scale. Here is the copy of the file in my Megasquirt:

 

My Current Tune

 

The car is only tuned to 6psi at the moment for running in purposes. So can anyone shed any light on my problem? I am really REALLY getting sick of this car consistantly having problems. For my 1st go at an engine swap/conversion it really hasn't left me with too much confidence in working with motor's anymore.

 

Thanks for reading, Marc.

[Phyxius]

Don't give up just yet. This is a lot to jump into on your first swap. You'll get comfortable with it. I'm a firm believer that the simplest solution is the most likely. After nearly a year of dealing with my megasquirt, I've found that the problem rarely lies with the computer itself, but usually with the associated wiring or sensors. It sounds like you may be getting an intermittent contact somewhere, or your MAP sensor line may be leaking. You may also want to check your fuel pressure. Aslo, it looks like that even though you have an o2 sensor, you don't have MS configured to take it into account. Under "Fuel Tables 1+3: Exhaust Gas Settings", you have the o2 correction set to only occur above 6000rpm. A more reasonable setting is somewhere between 1300-1700 rpm.

I hope this helps!

[akeizm]

Ok cool, well that puts the O2 sensor out of the question. The MAP line is fine, the people who tuned my car checked the line, and my fuel pressure. They said it was running lean when it was at their shop because he blocked the return line only ran fine when the pressure raised up to 100psi.

[akeizm]

So no1 has a clue?

[Nismo280zEd]

100 psi? what fuel pump are your running? I thought the injectors siezed up around 70psi.