The car has been running pretty well of late, since I resolved the MAF problems that were boning Jeff's tunes, and got an updated tune from him that leaned out the upper regions which were pig rich from the base map. The car has been totally drivable up to higher ranges of boost where it starts choking on excess fuel. I've been driving the car regularly just shifting early before that point. While it definitely needed some tweaking its been very safe, AFRs have been if anything richer than necessary and I've done some very hard mountain runs successfully.

I was headed to work the other day and got a touchless car wash because the car was filthy. Water on the intercooler or intake cone gave me the infamous CEL for MAF voltage. When the car had sufficiently dried I reset the ECU to clear the codes knowing this would reset my trims. I made no other changes.

The car is now running too lean, especially in boost. Idle is hunting a little bit, still hanging out around 5-6 g/s with AFRs rolling from stoich to 15.3 at most and back. The most noticeable place it is running lean is in cruise. Normally if I have any throttle in cruise I'm almost dead on 14.7/1 but I've seen high 16s at light throttle in cruise. If I press down on the throttle it commands more fuel and it goes back to 14s. In boost, especially the lower gears I've seeing much leaner values now, low 13s in 1st and 2nd under partial boost with mid/high 12s in 3rd. I'm scared to try a WOT run in 1st or 2nd right now. Before I cleared the ECU I was getting mid/high 11s in 3rd. The upper gears still have enough fuel, but its clearly leaner than before. With this same tune when I originally flashed the car (ie fresh trims) I was not seeing these numbers, so something has definitely changed.

I'm sure there are a couple possibilities, but my vacuum looks fine, as its at the same place it has always been, and my idle isn't really choppy or turbulent. This doesn't rule out a vacuum leak, but I don't see anything really noticeable. I did do a really rough downhill mountain drive last week that could have knocked a coupler loose, but its nothing in the top part of the bay or its too small to see/hear at idle.

Any suggestions?

 

has it started setting the long term trims?
I have noticed that the initial A/F tends to be very different from what happens once the new trims start to develop.

 

Well, its hard to say; the LTFT was trimming in +6% at idle, but only 1% while driving. 1% is what it was showing before I reset. There wasn't a huge red flag either way. I'm definitely leaning towards a mechanical issue because the tune is exactly the same and at no point did the tune behave like this before.

 

It will take 3-4 drive cycles to settle . Don't worry about it -just be careful boosting .

Do you have the AEM intake ? I have a suggestion to stop water getting into it at the car wash .

 

Yeah, I know the trims take a bit to settle, but its had several drive cycles now. I reset the ECU on Wednesday morning on the way to work. The last couple of days its been running lean. I've never seen quite this behavior from the car so I don't think its a simple issue of wait for the trims to sort themselves. I'm going to try and get a closer look at the intercooler piping and UIM this weekend just to see if I have a small leak somewhere. If it isn't raining (which it probably will be) that is.

 

Oh and yes, I have the AEM intake, whats your suggestion?

 

Water comes in from above through the gap between hood and bumper then drops straight onto the filter.
I just took the plastic shield off,ran a bead of silicone along the edge of the steel part underneath adjacent to the filter so as to divert the water away . Then put the plastic bit back on once the silicone has dried.

 

Yeah, something is definitely screwed up... its running way too lean in boost. I took some datalogs on the way home, I'll post em up in a bit. I was seeing mid/high 13s in boost at partial throttle at 3rd and its never been even close to that lean before. 4th and higher are fine in boost still although leaner than normal.

 

Make sure the MAF sensor is completely dry...

Also you can try reflashing the map.

I disconnect my battery almost everytime I'm done driving since my car isn't my DD and it stays parked for a weeks at a time. So I can connect the battery, let her warm up, and it runs just fine.

 

Well, I've looked over the logs a bit and something is definitely up. I'm going to try reflashing the car tomorrow. Here is a sample of the logs:

Seconds (sec) Equiv. Ratio (AFR) RPM (RPM) Engine Load (%) Mass Airflow (g/s) Short Term FT1 (%) Rel. Thrott. Pos. (%) Vehicle Speed (mph)
96.79,20.29,3403,15.68,10.99,-0.16,2.34,49.09
96.96,20.29,3283,10.98,8.22,-0.16,1.95,49.09
97.11,20.29,2996,9.8,8.35,-0.16,1.95,49.09
97.28,20.29,2748,11.76,8.31,-0.16,1.95,49.09
97.42,20.29,2497,12.54,8.49,-0.16,1.95,49.09
97.6,20.29,2282,13.72,8.13,-0.16,1.95,49.09
97.75,20.29,2014,14.5,13.87,-0.16,7.41,49.09
97.92,20.29,2088,54.88,44.62,-0.16,13.65,49.09
98.11,20.29,2995,60.76,48.12,-0.16,12.87,48.47
98.27,20.29,4261,51.74,63.43,13.88,14.04,47.85
98.46,16.61,4874,50.96,62.24,19.34,12.09,49.09
98.63,13.82,4660,49.39,63.24,17,13.65,49.09
98.79,12.79,4727,58.02,82.61,13.88,16.77,49.71
98.94,12.94,4829,71.34,95.24,13.1,18.33,50.33
99.1,13.23,4842,82.32,96.32,6.08,18.72,50.95
99.27,12.79,4910,81.54,109.73,2.96,18.72,51.57
99.44,13.08,4985,81.54,112.98,2.96,18.72,52.2
99.56,13.52,5068,87.02,116.24,-2.5,18.33,53.44
99.71,13.96,5123,93.69,137.58,-2.5,18.72,54.06
99.88,14.11,5194,102.31,123.47,-0.16,20.67,54.68
100.04,14.41,5278,115.25,165.3,-0.16,26.52,55.92
100.23,13.52,5375,119.17,185.91,-0.16,26.52,57.17
100.4,13.23,5504,125.05,196.7,-0.16,30.42,58.41
100.54,13.67,5650,130.93,208.26,-0.16,36.27,59.65
100.69,13.82,5735,141.51,220.62,-0.16,39.39,60.27
100.87,13.67,5878,141.12,228.83,-0.16,40.17,62.14
101,13.82,5986,150.53,232.28,-0.16,39.78,63.38
101.17,14.41,6128,154.06,264.51,-0.16,39.39,64
101.33,14.11,6122,158.76,95.33,-0.16,5.07,64
101.48,13.67,6092,58.02,43.46,-0.16,2.34,64.62
101.64,13.23,5771,25.09,56.88,-0.16,1.95,64
101.83,11.91,5428,20.38,21.7,-0.16,1.95,64
102,11.76,5033,14.11,10.22,-0.16,1.95,64
102.16,12.35,4729,11.37,13.4,-0.16,3.9,63.38
102.33,11.17,4435,25.09,77.32,-0.16,14.04,63.38
102.5,12.05,4694,62.33,79.77,-2.5,14.04,63.38
102.62,12.94,4567,64.29,81.55,-0.94,14.04,64
102.81,13.08,4415,67.82,89.82,-2.5,16.38,64
102.97,13.38,4429,80.75,98.81,-7.18,15.21,64.62
103.16,13.52,4433,80.75,92.48,-11.86,14.82,64.62
103.33,13.67,4458,76.05,87.15,-13.42,14.43,64.62
103.49,13.96,4480,76.83,91.15,-11.86,14.04,65.24
103.67,13.08,4480,72.52,54.5,-15.76,8.58,65.24
103.82,12.05,4464,37.24,26.83,-0.16,4.68,64.62
103.98,11.17,4376,21.56,22.53,-0.16,4.68,64.62
104.15,12.05,4390,19.21,23.16,-0.16,4.68,64
104.31,13.23,4391,18.42,23.71,-0.16,4.68,63.38
104.5,14.41,4368,19.21,22.03,-0.16,4.68,63.38
104.67,17.93,4339,18.82,19.81,-0.16,4.68,62.76
104.83,20.29,4306,17.25,17.71,-0.16,4.68,62.14
105.01,20.29,4293,16.86,17.93,-0.16,4.68,62.14
105.16,20.29,4256,16.46,18.38,-0.16,4.68,61.52
105.29,20.29,4235,16.86,18.01,-0.16,4.68,61.52

 

I can't imagine the MAF sensor being wet really. It's been dry all day and the car was taken through the car wash 2 days ago so its not still wet from that. The snippet of datalog above is a partial throttle from a roll in 3rd. I start hitting the throttle at about 49 mph, AFRs are solidly in the 13s even hitting 14.4 while flowing 264 g/s... I don't know, maybe reflashing the tune will sort it out, but it's normally in the 11s so something is drastically changed.

 

Try reflashing the car again with the map and then let it sit for at least 10 minutes. I noticed sometimes the tune isn't right if I reflash the ECU then fire the car right up and go into boost (after the engine is warm, obviously).

So now whenever I reflash I always take the key out and let the car sit for at least 5-10 minutes. Never had the problem again.

 

Cool, I'll give it a shot.

 

Thanks for the advice chicken... that did the trick. I don't know why it did the trick, but it did. I reset the ECU, waited 20+ min and then drove it... drives like a freaking champ. Any idea why in the world this would be the case??

 

I'm not sure, maybe someone else can shed light on it, but it's happened to me as well. That's why after reflashing I always pull the key and let the car sit for a few minuets. It may have something to do with the flash memory of the PCM and the file getting corrupted or something screwy.

 

I've never had that & iv'e done over 120 flashes .
Must be an AP thing

 

The car is driving fantastic now... god I love driving an FI RX-8.

 

/\ heh - kinda hard to stay off the throttle isn't it

 

Yeah, I'm amazed I haven't been nailed with a huge ticket... thank god for radar detectors I guess.

 

relying on a radar detector is how you get sloppy and end up getting a ticket. Making sure someone is 200 foot in front of you is usually much better - just watch for brake light out of the blue

 

Yeah, thats true enough. I normally drive pretty sedately when I'm commuting... but its hard to resist going into boost, and the speed goes up really fast that way. I'm a pretty attentive driver and I've lived in MD my whole life, so I'm familiar with our horrific cops. I use the radar detector as an extra safety blanket, and it has saved my bacon more times than I can count. I do find that my speed is actually lower since I've been turbocharged, I just hit that speed a lot faster. Fast acceleration and loud exhaust do make me a target though.

I can't wait until I get my tune fully sorted out, and make a few tweaks to my boost controller. I am really happy with were the car is so far, but it has a long way to go still. I can't imagine how much better its going to drive when I get it fully sorted. On that note... Jeff! Tune me bro!