random lean spikes at cruise

[bacchus418]

Hello all,

I'm out of ideas and I'm here looking for some advice.

2003 RSX-S with:
Merc racing JRSC w 3" pulley
Stock crank pulley
GM IAT sensor after the blower
Hondata 4bar MAP
DW65c fuel pump with ID725 injectors
Kpro4

Logs show random lean spikes at cruise or very low TPS values, like lightly rolling onto the throttle. Problem manifested out of the blue, no mechanical changes took place within three weeks of the first occurrence.
I've been over the engine grounds and checked the injector wiring. I've been working with an experienced, reputable engine tuner for the last month and we're both scratching our heads on this one. Any theories that might explain this behavior?

Log is here:
https://www.dropbox.com/s/8r7cv206jyn8k ... o.kdl?dl=0

FYI I'm at 5300' above sea level so that will explain some of the data

[Spunkster]

At what point exactly are you seeing this in the datalog?

[bacchus418]

Hey Spunkster,

Thanks for your time. You can see the behavior at 0:23, 0:47-0:49, 0:53-0:55, 1:16, 2:24-2:25, 3:27, 4:20, 6:00-6:01, 6:42, 7:19, 8:14.5, 8:32.

Of course it's difficult to drive the vehicle and note the exact moments when it happens. When it occurs it feels like the car loses power and I can see the AF ratio spike on the display. I see it in the logs when the TPS is greater than 0, constant or rising, and the AF ratio spikes when it should not.

It would be great to hear your opinion.

[Spunkster]

Have you checked your fuel pressure?

[bacchus418]

Yes I have a gauge at the fuel rail. It shows 60 psi at idle. I do not have a means of checking fuel pressure while driving.

[Spunkster]

You may need to put this on the dyno to see what it is doing at other times.

[bacchus418]

ok, that's a possibility. Any other theories I can rule out before I take that step?

I guess I should mention that it runs fine in WOT up to redline. Is it possible that the fuel pressure stumbles when I roll onto the throttle?

[Spunkster]

Your injectors could be slightly clogged as well and only affected at low opening times.

[bacchus418]

Well, the injectors are practically new. See, I had a good tune on this same setup for a little over a year. Car ran great, no issues. Then I had a misfire condition and after going through all the troubleshooting, it turned out it was the previous injectors. I ran some Chevron Techron through the system and when that didn't work, I ran a bottle of 44K through, which didn't work either. At that time, I couldn't have the car down for more than a day, so instead of sending the injectors out to be cleaned, I swapped in the ID725s. That was around Thanksgiving. This issue we're discussing now, it came up during the course of re-tuning for the ID725s. So I'm having a hard time understanding how the new injectors could be clogged.

[Spunkster]

All the injector cleaner you put in the system can actually cause injectors to become clogged. There may have also been contaminants in your system before that cause the previous injectors to have issues.

You may also not have the correct dead times for the injectors you are now using.

[bacchus418]

Interesting. Could you tell me more about how injector cleaner can inadvertently clog injectors?

What sort of contaminants in the fuel system do you have in mind?

We are re-tuning injector dead times now to see if that solves it.

[Spunkster]

Injectors cleaners can cause stuff in the fuel system to partially dissolve and become trapped in the injectors if it is larger than the opening on the injector. I have seen this happen a number of times.

[bacchus418]

Well I have ruled out the clogged injector theory. I had them professionally flow tested and they checked out perfect.

If there are any other suggestions, please let me know. One of these days I will get it on a dyno to check fuel pressure.

[Jeremyg95]

This is the closest post I can find to fit my problem. So I just installed hondata and aem gauge for wide band. My gauge reads correctly but on s300 it’s jumping from 10 to 17af I can add fuel and the gauge af will change but not the s300 i datalog and saw the af just jumping like it’s losing connection. Is a obd2b car has obd2 to obd1 jumper. I’ve grounded it to obd2 connector B pin 2 and then grounded it to B Pin 20 as well as the thermostat. Power is obd2b Connector B pin 1. It’s a 4 wire aem red to power black to ground blue to obd2b connector C pin 16 and white wire is disconnected. Idk what else to do. All connections are solder together.

[Spunkster]

I would recommend that you take this to a tuner to help you diagnose the issue on the dyno.