Fuel cut?

[zedekias]

I've had all my engine mods and tune for at least a year now and I've had no trouble until about a week ago. It hasn't happened in first gear and it primarily happens in second or third gear around the 2,500-4,000rpm range. I'll be casually driving, (no WOT), and my car will feel like it will stutter for a second.

Now I know logs are really what is needed to diagnose this, but every time I've logged it hasn't happened. Fuel pressures looked good. No KR. I've been constantly monitoring the fuel pressures in live mode, but it happens so quickly I can never tell if the pressure is actually dropping. This has all been on one tank of gas, so I'm guessing it may have just been a bad batch? I always get it from the same place though. I did however full up will all 93 octane tonight, instead of my e85 mix and went back to the stock tune just to see what would happen.

Any ideas?

[zedekias]

Well im on a new tank of gas and with the stock tune it still happened twice today. But it happened in fifth gear around 3k rpms and it lasted longer than it has before. It completely stutters. But every time I log it won't stutter! Is there anything I can look for under the hood?

Should I use the economy tune to stay out of boost in the mean time to be safe?

[JgamB]

What % corn were you running? Might want to take a look here first.

[cthomp]

I've seen bad upstream o2 cause similar symptoms.

[pwned]

Make sure you maf screen did not become detached. Take off your air filter and take a peak. I had this happen to me and had shuddering and 13afrs at wot.

[zedekias]

25-30% e85

Thanks for the link. If it doesn't clear up by Saturday that is what I'll be doing with my time. I didn't realize it could be a problem going from e85 mix back to 93 only.

Originally Posted by pwned Make sure you maf screen did not become detached. Take off your air filter and take a peak. I had this happen to me and had shuddering and 13afrs at wot.

Thank you. I'll try this before I clean the hpfp. How likely is it that it would need cleaning after a year of 25% e85 mix?

[JgamB]

Originally Posted by zedekias 25-30% e85 Thanks for the link. If it doesn't clear up by Saturday that is what I'll be doing with my time. I didn't realize it could be a problem going from e85 mix back to 93 only. Thank you. I'll try this before I clean the hpfp. How likely is it that it would need cleaning after a year of 25% e85 mix?

I think you're in a rather small minority of 1 year+ corn burners, so that's a tough question. If I were getting symptoms that felt like fuel cut or stumbling under partial throttle, I'd look at coils, plugs, then open up the HPFP, particularly if you aren't throwing any codes.

[mr.speedy3]

This shit has been happening to me too.. I currently run 3/10 e85 and it's been happening sporadically.. I'm in for an answer. I'll check what's been mentioned. I've been running this mix for... 8 months or so I'd guess. It's impossible to log and happens so sporadically. I know that when I added in Launch Control to my map, my car would stumble at the RPMs I set it to in casual driving in 2nd, sometimes 3rd gear. Not sure if that was normal but it annoyed me enough to the point where i took it off (put it back to 6700 I believe).

Edit --

It's been happening to me for a few weeks. It's very recent. I'm blaming the gas right now. I am going to run the car almost dry and get fresh gas this weekend and see how she responds. WOT shows no sign of knock, and my Fuel Pressure is nice and sturdy as it should be.

[zedekias]

So I just took the air filter off and took a picture. Everything seems to be in place to me, but i'm not really positive lol.



Everything else is going to have to wait until the weekend.

Whoooaa sorry for the mega picture

[kritz]

Disconnect your SWAS and see if issue is persistent. More likely to be load cut. Are you on an OTS tune? Self tuning or pro tuned? See if you can catch it on a log.

Sent from fastest ko4 Pu!

[zedekias]

Stratified tuned by lex. But I've been on stock tune all day and it still did it a couple times.

[jakk]

I am planning on getting an E85 25-30% tune after my 93 tune is done, so this interests me. It was my understanding that the spill valve issues and switching from E85 to only 93 were only an issue if you were running over 50% E85. I'm interested to see what the more knowledgeable people on here have to say.

[mr.speedy3]

Originally Posted by jakk I am planning on getting an E85 25-30% tune after my 93 tune is done, so this interests me. It was my understanding that the spill valve issues and switching from E85 to only 93 were only an issue if you were running over 50% E85. I'm interested to see what the more knowledgeable people on here have to say.

That's my understanding. However, when we first installed my autotechs, I had black gunk in my HFPF, but I know the car wasn't modified before me. I am not sure what to make of that..

[jakk]

Originally Posted by mr.speedy3 That's my understanding. However, when we first installed my autotechs, I had black gunk in my HFPF, but I know the car wasn't modified before me. I am not sure what to make of that..

I had some black build up in mine as well when my internals were put in (~11k miles after I got the car new). I think that is just normal carbon build up and not the same thing that clogs up the spill valve, but I am not sure.

[kritz]

Originally Posted by jakk I had some black build up in mine as well when my internals were put in (~11k miles after I got the car new). I think that is just normal carbon build up and not the same thing that clogs up the spill valve, but I am not sure.

Not carbon as there is no combustion in the pump. Dirty fuel, and most likely some oil residues from whatever makes it passed the o-rings. I ran 50/50 for 40k on a pump and now it is in a friends car who is still running e with no issues. But do check and clean the spill valve. @silvapain; has a fantastic how to on it.

Sent from fastest ko4 Pu!

[mr.speedy3]

Originally Posted by kritz Not carbon as there is no combustion in the pump. Dirty fuel, and most likely some oil residues from whatever makes it passed the o-rings. I ran 50/50 for 40k on a pump and now it is in a friends car who is still running e with no issues. But do check and clean the spill valve. @silvapain; has a fantastic how to on it. Sent from fastest ko4 Pu!

How often did you clean it running 50/50?

[cthomp]

Disconnect upstream o2 sensor connectors and drive it unplugged see if it stops. Seen these symptoms multiple times on our cars. Very common on cx7 I change them often. Don't over look it.

[zedekias]

Where exactly are the o2 upstream sensors?

And sometimes it takes a while for the stutter to happen. Having it unplugged for a day or two wouldn't be bad??

I'm taking some logs tonight on the way home from work here in a minute. Even if it doesn't stutter during the log, maybe it'll still show something

[kritz]

Originally Posted by mr.speedy3 How often did you clean it running 50/50?

Once at 20k and it was fine.

Sent from fastest ko4 Pu!

[zedekias]

So here are a couple logs. I'd appreciate if anyone can take a look and tell me what you think.

Of course the stutter didn't happen while logging, but it did happen once on the drive home.

And if it matters, this is on my stock tune.

[zedekias]

Originally Posted by kritz Once at 20k and it was fine. Sent from fastest ko4 Pu!

And that's exactly how many miles I have on mine. Which is why I am kind of confused.

[kritz]

Yes, I see but not showing IDC, and Pulse rate. Put back your tune because that stock map is pig rich man! Copy paste your fuel table and Throttle req load tables.

[zedekias]

Originally Posted by cthomp Disconnect upstream o2 sensor connectors and drive it unplugged see if it stops. Seen these symptoms multiple times on our cars. Very common on cx7 I change them often. Don't over look it.

So I'm beginning to think this is the culprit. I checked the coils and plugs and they looked fine.

I didn't check the spill valve yet, but my symptoms have happened at really low speeds and low rpms. I feel like if my hpfp were working great on WOT pulls, it'd be fine at cruising in my parking garage. (Where it stuttered tonight).

So I can disconnect the upstream o2 sensor for a day or two and be ok to test it? Is that something that'd possibly be covered under warranty? Or am I shit out of luck with my mods?

I'm changing jobs, going on a cruise, and moving to Colorado all within the next 3 weeks. I'd really like to not spend $300+ on something right now.

[zedekias]

Can anyone help me with the location of the upstream o2 sensor?

[RLam]

It is going to be right on top of the Downpipe bellmouth. The wires should run either behind or close to the firewall heatshield and connect into the harness under the battery box/TIP area. It's expensive. I replaced my sensor, and Mazda wanted $400 for the sensor, lol fuck you Mazda. It's made by Denso and branded by Mazda. You can get it straight from Denso for ~205 on Rock Auto

More Information for DENSO 2345042

[zedekias]

Originally Posted by RLam It is going to be right on top of the Downpipe bellmouth. The wires should run either behind or close to the firewall heatshield and connect into the harness under the battery box/TIP area. It's expensive. I replaced my sensor, and Mazda wanted $400 for the sensor, lol fuck you Mazda. It's made by Denso and branded by Mazda. You can get it straight from Denso for ~205 on Rock Auto More Information for DENSO 2345042

Were you having the same symptoms? And replacing it fixed them?

Was there any visible damage? I've heard you can just clean it and it may fix the problem if there isn't any visible damage.

[RLam]

Originally Posted by zedekias Were you having the same symptoms? And replacing it fixed them? Was there any visible damage? I've heard you can just clean it and it may fix the problem if there isn't any visible damage.

My sensor was stuck in my DP, and I broke it trying to get it out. It was still good otherwise. If you get electronics cleaner, that might work. spray it and let it dry.

CRC/Mass air flow sensor cleaner (05110) | Electrical Parts Cleaner | AutoZone.com

[cthomp]

Don't try and take it out they do like to seize in the cat. Only disconnect the electrical connectors to see if it goes away. If u go from underneath u don't have to take anything out.

[zedekias]

So it connects right under the battery? Does it have anything to easily identify it as an o2 connector? I apologize for all the retarded questions. I'm on call at the hospital a lot for the next two weeks and can't really have a non working car for anything longer than 5-10 min.

[cthomp]

Just follow the wire from the sensor in the cat. Upstream is the top sensor.

[mr.speedy3]

Update:

My issue went away almost completely after running the girl dry and filling her back up with some fresh gas.