So I've got this Xede in my car, lovely piece....

I installed SMART not too long ago, I was one of the first people to get it and was unlucky enough to get a bad creader.

When I first installed everything my car would get an audible misfire whenever transitioning from a negative SMART timing cell to a positive SMART timing cell on the SMART timing table. I could reproduce the error at will, and the simple fix was to zero all of the positive cells. Problem solved, no more P0300. I was happy enough with the way the system was performing and I knew I had to send my creader back, but quite honestly wasn't that worried about it since all I kept reading about was Vishnu being out of creaders and I didn't want to deal with it at the time.

Fast Forward to about a month ago. I started getting P0300's again, random and low-occurance but they'd still happen on occasion. It was annoying enough for me to finally return my creader though, so last week I sent it out. Vishnu probably got it late last week or will be getting it soon. I took the car on a road trip to MD and back last wednesday-friday. The car had no driveability issues, although the CEL was on the whole way. When I got home friday I checked the code with my scanner, P0300 (no suprise), cleared it and went on my way. The next day it was back. I figured it was coming back with a vengeance due to the creader not being there. Maybe a bad creader was still doing something, maybe mine wasn't bad and my car has other issues?

I did the old diagnostic dance on my car, checked all the connectors, checked the plugs, check compression (185-175-185-185 btw), and all seemed good. Still, the code would come back rather quickly. I then took the car for a short trip yesterday up the parkway (~30mi each way) On the way up my car not only threw a P0300 again, but actually had an audible misfire. This occured at ~15-35% throttle at light highway cruise (~75MPH). Applying more throttle would result in the misfire getting louder, but not clearing it up, completely releasing the throttle and then reapplying would clear the misfire. A mile later, it's back again. This off/on throttle dance must have occured 30 times on the way to where I was going, and another 20 times on the way home. Changing gear had no effect, changing vehicle speed had no effect. At light throttle cruise, bam, misfire.

Needless to say it's a bit frustrating, I am waiting until I get a creader back (Read - Vishnu please rush shipment even if I have to pay for it) and see if that solves the problem.

Any other ideas people, something I might be missing?

- Steve

 

Seems weird that the missing reappears after a month of running fine. How are the sparkplug conditions? Gapping comes to mind. The missing occured after you did the diagnostics, perhaps something is loose or you may have missed something putting it back together?

 

Back when I used to upload and download maps into my Xede all the time from my laptop, I had a problem worse than yours.

I solved it by carefully downloading all my maps and viewing their 3D image (an Xede feature I thought was rather useless until this point). It turned out I had not tightly secured my serial cable and the map transfer data was corrupted. I reloaded my correct map, reset my ECU, and went on my way. It ran perfect after that.

So, you may have one or two cells with + values that should be -. This caused my car to go into limp-home mode until I reset the ECU. Just a thought.

If this doesn't help, put out this distress beacon: "Help us Shivey-wan-Kanobe, you're our only hope."

 

Spark plugs are fine, gap is fine. I'm running one-step-colder iridums, have changed them within the last 7k miles, and well I don't know. I can recheck everything, but this is the same type of misfire the car did when I still had the positive timing cells in my SMART timing map. That's what seems weird to me, like an old demon is here to revisit.

- Steve

 

I'll check it out smog, thanks.

 

smoggy, I hate blowing coffee through my nose... thanks...

 

Try what Smogrunner suggests. If that doesn't workout try uploading a generic smart map of the Vishnu site. Seems far fetched, but try a different map than the one that's been giving you problems since you installed Smart. Maybe even load a non-smart map and disable smart to see if that has an affect.

 

I got a similar occurance randomly around 3000-3500 rpms after I loaded the more aggresive timing/fuel maps on my car about 5 or so months ago.

Plugging in the creader seemed to have remedied the problem up until recently. I noticed/felt a misfire occuring just this past weekend on a few WOT runs close to 7K rpms. Just after that, I noticed (at another point) the 3K misfire cruising at highway speeds, partial throttle. The partial throttle procedure you described cleared that up only to have it come back later. Mind you I leave my creader plugged in everytime I drive which troubles me a little.

So I did a few more WOT and easy cruising runs after shutting the car down from being pulled over for "moving at an excessive rate of speed" to find the misfire had vanished. I also happened to keep an eye on the boost gauge before/after and believe I noticed that during the misfire WOT runs, it was holding around 21psi near 7K where as after the key cycle it was around 19.5psi.

I'm really lost as to what the problem could be at the moment and wonder if it could be realted to yours.

 

PO300 is a funny code. Hard to pin down especially when the car is modified.

 

^^^ Hence the C-Reader solution.

On a side note, we finally got our shipment of C-Readers in this morning. Give us a call if you want one ! There are a few that have been waiting for them. They'll ship out today or tomorrow...

Cheers,
shiv

 

First thing I'd do is change the spark plugs. My 03 Evo V390 went through plugs on regular basis.

 

I've experienced the same misfire problem while cruizing. I change my maps quite a bit, and I noticed it happens more frequently with agressive maps. I actually have this misfire datalogged, so I can post it later

 

i had it once and i switched my plugs and it went away.

 

Figured I'd do a followup...

The c-reader fixed the problem.

 

WOOT!!!

Welcome to the Dark Side.