wcs

iTrader: (2)

Specs: 2005 GT - NA, Cobb AP, MM Tuned, BHR Coils, new plugs, Seafoamed last month.
As luck would have it these things happen on the way to an RX8 meet at MOSPORT International Speedway <sigh>

Situation:
- Cruise control set to 103 km, RPM's around 3100
- Engine starts running rough, holds speed. This continues for a few minutes, never gets a lot better but doesn't get worse.
- Approaching traffic light, I put car in neutral and it stalls, I re-engage clutch to start engine again.
- Pull over and car seems to idle fine
- Now I plug in the AP to monitor the situation
- Cruising down the highway AFR's are around 14.7 (good)
- After a minute or so the AFR pegs at 11.2, I can add some throttle and the AFR's respond and settle back to 14.7 at cruise. Rinse repeat.
- I get tired of this game and pull over at a coffee shop with a well light parking lot (it's 6am in morning)
- Engine idles for a minute and stalls.
- Starts back up <phew> Idles but is hunting/surging for a smooth level rpm. It almost stalls several times.
- During this I get out to try and inspect hoses and look/listen for whatever else. Check fittings etc. I find nothing.
- After a few minutes (maybe 5) the car finally settles down and idles fine.
- I say to myself "Self I still have a 2 hour drive ahead of me or a 40 minute drive home. Right home it is." Besides no use bringing a broken car to the track.
- On the way home the car runs perfect, better than perfect even. I thought that this was it, the last hooraw the engine is going to blow.
- No AFR pegging on the way back.

Impacting variables and items worth noting:
- Car has been running great lately, no issues
- Filled up with fuel yesterday, not at one of my regular gasoline stations (mmmmm misfire)
- Updated Cobb AP Software (maybe bug in software???? Pegging issue)
- No Cels generated
- Checked plugs yesterday to make sure they were in tight enough.
Ummmm yes, once in all my years of replacing plugs the last set I guess I didn't put in tight enough. So I'm a bit paranoid. I did get 1/8 - 1/4 turn out of all the plugs without really using a lot of muscle.

What could it be?
- I've been running this same tune for quite sometime and I've not lost power to the vechicle so I don't think ECU learning is an issue.
- Bad gas or vacuum leak?
- Cobb AP bug that happen to show at the same time as bad gasoline?
You guys got anything else please?

Kane

iTrader: (1)

Wierd....was your AP logging during this by chance? That would make the troubleshooting easier.

wcs

iTrader: (2)

^^^ Nah unfortunately I wasn't that smart .... hindsight 20/20

I did get some logs of the rough idle in the parking lot.

DarkBrew

Bad gas messing with front O2 sensor?
Your premix oil was contaminated?
You picked up something on the highway?
Run through the standard checks....

wcs

iTrader: (2)

The whole thing reminded me of a story Jeff told us about the engine misfire codes and how useless they are as they don't show up when the car does misfire but do when it isn't.

wcs

iTrader: (2)

I hate saying bad gasoline, I can't ever recall having bad gasoline before. I guess there is always a first.
Premix .... funny I wasn't running premix in this fill up.

I'm heading out shortly to the garage to do all the checks.
Why don't you get your *** up here and help me out and pick up or RB Gauge Pod kit.

DarkBrew

Is your car addicted to premix?
I'm going to try to stop by today...

wcs

iTrader: (2)

Meh for what it's worth, here the idle log while it was surging.

DarkBrew

The fuel trims are really hunting around

9krpmrx8

iTrader: (46)

Kind of compared it to my logs and other than being slightly leaner and the sporadic idle I don't see anything.

How did you do that Dark ?

DarkBrew

I could tell you but then I'd have to kill you

I created a chart in Open Office (free )
Alt+PrtScn
Paste in Paint
Save as jpg
Post as attachment

So, what threw the fuel trims so far out of whack?

9krpmrx8

iTrader: (46)

Ah open office, I knew it wasn't excel that's why I asked. Funny I post my logs the same way, haha except I load them to flickr after saving as a JPG.

wcs

iTrader: (2)

Update:
Can't find anything wrong.

I'm going to go with bad gasoline or a failing front O2 sensor.
I've not been able to reproduce the problem yet.

So I'll go out in a bit and refuel from one of my usual fueling stations, and/or wait for the O2 sensor to catastrophically fail.

dannobre

iTrader: (3)

There are a few other things that could make it go into spaz mode like that.....sensors...MAF, ECT, IAT...they should throw cel's..but stranger things have happenned

Bad gas is definitely one...I would throw some methanol into the tank to suck up the water and drive it.....was it raining a lot the few days before you left?

ECU glitch is another...sometimes they get a mind of there own....reset it and see what happens

Kane

iTrader: (1)

Check the MAF to make sure nothing weird happened, like the o-ring being torn.

It looks like my logs when I messed with my MAF housing and got turbulent air.

wcs

iTrader: (2)

Interesting Dannobre ..... you know, I have had quite a few Com Bus cels. I just thought it was the Cobb AP polling the ECU to frequently and causing the com error. Oh and it's been raining here since last week, I'm looking for Noah as we speak.


Ok guys, I've poured myself a vodka .... I'm ready to go out and start taking stuff apart.
First thing MAF.

BTW I just came back from a nice cruise (haven't refueled yet) and I could not reproduce the problem and I hate to say it .... but the car seems to the butt dyno .... stronger.

Some logs for your perusal

wcs

iTrader: (2)

MAF looks fine.
MAF Screen is fine.
MAF Oring is fine....

The hunt continus

dannobre

iTrader: (3)

I`d put in about 250 ml of methanol and fill it up with new gas...and forget about it unless it comes back

VashGS

How many miles on this engine? Test vac & compression..

REV-illusions

iTrader: (3)

you didn't disconnect the power or anything yesterday did you? What you describe is the kinda symptoms I normally get when power's been cut and the ECU tries to re-figure itself out... runs like **** for 30 minutes and threatens to stall all the time... then it finds it's way and everything's fine.

DarkBrew

Just got back from visiting my daughter in Barrie
I was going to drop in @ your place to see how things are going...
Got no answer so I'm sitting home drinking instead!

wcs

iTrader: (2)

Yaaa ... ummm I've not done a compression test ... some things you don't wanna know ... if you know what I mean ...
That being said I pulled a 196 HP on the dyno 2 month ago, I hope things haven't degraded that much since then.

17 hg vacuum on a heat soaked motor at idle.

Absolutely positive I've not lost power .... well in the sense that I didn't disconnect the batter and the car started no issue ....
But I hear you .....

I'm going with the water in the gasoline theory which has never happened EVER before to me .... with any car.


I'll report tomorrow and Monday on my progress....

Thanks everyone!

wcs

iTrader: (2)

Dude, I'm sooo sorry ... My phone was up in the office and I was sitting out in the garage watching the live feed from SevenStock ... broad casted by BHR

DarkBrew

No worries!
You guys will have to come over for dinner and drinks

wcs

iTrader: (2)

Kewl sounds like a plan.
I'll talk to Rach about doing something this week.

MMMMmmm food ... MMMMMMMMMMMMMMMMM DRINKS