I've been having a problem where my AFR's going extremely lean under boost for some reason. I actually had these problems before, but they went away once I got rid of my stock cats, however now they're back....

Comes and goes too so I have no idea what's going on. I've been told maybe its my fuel pump so far... My AFR's are typically solid around 11.2-11.5 under boost, but sometimes goes.. to 25+ right when I get on it. I thought it was my fuel setup (similar to AAM's basic setup) so I took it out but even without it, it still does this...

My car is running greddy tt's, rods/pistons, 650cc inj, crawford plenum, utec, TN ecu reflash, stock fuel system with walboro. Any ideas? I've tried to throw fuel at it and mess with timing, checked for fuel leaks, checked that the injectors duty cycles are good....

 

seems like it's either the ECU (seeing you're tuned on UTEC) or fuel pump or maybe a fuel injector going bad. Have you checked your fuel pressure during the times it goes lean? That might help to eliminate the fuel pump. Do you have an upgraded fuel pump?

 

Does the lean condition happen immediately after the initial throttle tip-in? As in, you stab the throttle, you get an immediate lean spike followed by the AFRs going to where they should be? Please post more details info on how exactly this happens.

 

It only ocassional, I don't have a fuel pressure gauge in right now, but when I had my fuel return in, it was around 50 psi and rising, never lost fp. I just swapped out my whole injector harness and all my injectors....

The lean condition comes on right as the utec jumps into the mapping threshold. The weird part is it only happens sometimes, could this be because of the TN reflash?? The better part of the time my afr's are fine, but its just maybe 2 or 3 times out of say 10 times that I try flooring it this happens, the rest of the time I hold a solid lower 11's.

Oh, and one thing I noticed that was weird is that when the lean condition occurs, right before that my injector ms column starts to jump all over the place.

 

Where is your UTEC grounded at? The UTEC has a 'known' ground issue with the injectors. You might want to check the ground to make sure it is solid.

 

^^^ This is totally correct. This sounds 100% like a ground problem.

 

Its grounded to the stock ecu location, is there a better place to ground it? Its weird I never had this problem with the TN kit....

 

TurboXS recomends grounding the black wire in the supplied molex connector to a factory bolt. I grounded mine in the passenger kick with a self drilling screw.

 

I'd like to know why the ground for the injectors is not tied directly to the metal casing (as it is for the stock ECU). That tiny little wire just doesn't look like it'd be that great of a grounding source. I know that the stock ECU does NOT like NOT having it's casing properly grounded.

EDIT: After reading KP's note I took the UTEC (on my desk till the replacement comes in Mon), and tested continuity to several points on the chassis and pin 1 of the Molex connector. Depending on the spot/bolt/port the resistance was anywhere from 0 - 5 ohms. Not sure that is significant or not, but not sure why not all 0 (could be my ohm meter I suppose). But the UTEC chassis IS grounded - not sure why it didn't register when I checked it while it was in the car.

 

I would like to know how the effects of grounding the UTEC to several differint places. Typically, that is frowned upon with car electronics as it can lead to ground loops and extra noise being introduced in to the system.

The UTEC obviously is using the OEM ground for operation. It would be interesting to see a circuit board layout for this, and how adding another ground (when one ground is already present) is fixing the situation.

I think I remember reading TurboXS saying that the OEM ground gets noisey under high load, so it seems to me like it would be a good idea to unhook the OEM ground and only use one 'good' ground.

 

From my experience with tuning with a WBO2, sudden spikes in the AFRs registered by the sensor during tip-in are normal. I believe a sudden change in exhaust gas pressures and especially temps can sometimes introduce error in the sensor. I've seen these lean spikes consistantly in the past and they rarely induced detonation which is really what you should be worried about. Are you seeing detonation during this brief lean condition?

When you stab the throttle, you all over sudden have a rush of air coming into play. The ECU usually has a tip-in enrichment table to handle situations like this to account for sudden throttle modulation changes. It's usually a 2D table where for a given tip-in value, so much extra fuel is dumped to account for this scenario. You have to remember that injectors have an inherent latency too so even if the ECU sends a pulse down to them, it will take some time before they can respond to the command and deliver the fuel. The ECU cannot predict what you're going to do so it tries its best to account for the latency but it's not perfect. Not sure if UTEC has the ability to alter tip-in enrichment since my experience with UTEC is limited. Just something else to consider.

Grounding could be a problem but honestly, that would not be the first thing on my list to check. How is your UTEC threshold set up? Is it based on throttle delta? Overall throttle %? Certain RPM? If you have multiple points of entry, you can easily determine if the tranistion is the problem or if it realted to the tune. I'd start there first.

 

I have a 10 wire 4 gauge ground wire set AND I have a 6 gauge wire connecting the rear and front chassis (I went a little crazy when setting up my audio system). I also have a carPC. I wonder if there is "noise" on the ground system that is giving my UTEC problems. I hope the new unit fixes things, cause if it doesn't I don't know what I'll do (can't have one bank of injectors stuck wide open).

And the OEM ground is connected to the chassis - so I don't know why multiple grounds should cause a problem as long as each is "good". I also don't understand how ground (negative terminal at battery) can be "noisy".

 

http://en.wikipedia.org/wiki/Ground_loop_(electricity)

Basically, you're connecting one piece of equipment to two seperate ground sources. Theoretically, they are the exact same point (the (-) of the battery) but in reality the different metals in the car will all offer some sort of resistance to the flow of current from the ground.

 

But if you connect many points with heavy gauge copper wire, then a ground loop should not be possible...

 

I'm going to try this tomorrow, one of the ic right off the compressor popped off today, what a b!tch!

So is running a wire straight from the neg. terminal on the battery better than just grounding to the chassis?

 

bring it to me man, i will take care of it...

 

You would have to connect all points with the wire. I'm not sure why they sell 'heavy guage' copper wire, as the wire carries no current. Sure, it has less resistance then a thinner wire, but it can't be a measurable amount.

To this day I still have never seen any data that shows added ground wires does anything to the operation of a car. But, possibly, it can help if you hav a UTEC!!!!!!

 

The general rule of thumb is to keep all ground wires as short as possible, so running a wire directly to the battery is unnecesarry.

 

So Update...

I grounded the molex plug, and grounded the utec tuner to chassis, so that shouldn't be an issue anymore. I just recently installed a TXS BCS, and I get it up to 10lbs regularly. But I'm real nervous because it started doing the lean thing again. I wanna go to the track!!! but I'm

So things I've checked...
Injectors are good,
ground is good,
no leaks anywhere,
fuel pressure is good,
map sensor is getting good reading,
my threshold crossover point starts at -1psi and 50% throttle.
I've reflashed the utec,
reflashed the throttle control,
and made sure all connections are good.

Couple of points to note:

I get a good idle, 14.7 +- .1, good crusing 14.5 +- .1.

Under boost 1/5 of the time, my afr's go like this... 11.5, 11.4, 11.3, 11.4, 12.5, 16.7, 25+ otherwise it stay's solid 11.3ish. So its not exactly a lean spike, it just goes lean and stays.

1st gear never has the lean problem, 2nd-6th it will be about 1/5 of the time (meaning when I floor it).

3/4 throttle going into boost lean issues will happen more often...

At 10psi my injector duty cycle is around 65% and stays so even during the lean reading (is my O2 sensor fudged??)

My injector ms column jumps anywhere from 02 to 98 when the lean issue happens, otherwise when normal it is gradually increasing...

Hellllppp...

 

Post up a log. My UTEC goes lean on WOT then rich, then levels out. I've just learned to live with it, as long as it doesn't stay lean.

I wasted a bunch of time trying to 'tune' it out, but it killed the drivability of the vehicle (too much fuel) and never fixed the problem!