mpguino acted up today, lost mpg during fuel cut
 

After changing my fuel injectors awhile back and getting a few tanks of data, I readjusted the usec/gal and since then has been almost dead on. This week hasn't been so great with all the wind and ice-scraping mornings, but today was a very nice warm day, like 70F.

I keep it on the first screen which shows instant mpg, current mpg, speed, and distance. It acted normal the first leg of the trip, 36 current mpg was a little better than usual, fitting well with being so warm out. Then I lost 3 mpg climbing the hill, normal. Gained back to just about 34 current mpg before the long downhill, normal. Then I went down the hill for at least 1/2 mile, which is one of the few locations where my car will perform a fuel cut every time. And I usually gain about 1/2 mpg during the cut. Instant mpg went to 999999 when it cut, like normal, and the car acted normal. But after coming out of the fuel cut, I noticed current was only at about 31.5 mpg. I was like wtf??? Did I go through one of those alien wormholes? From there home is about 4 1/2 miles and it is a beat up side road and I can creep along at 45 and usually gain another 3/4 mpg or so. Which I did, it acted totally normal after the fuel cut. I checked distance after getting home, which was accurate at about 25.6. I was on the way to an easy 35 mpg home today, yet the guino said 32 something when I got home. I also noticed my tank mpg was in line with the loss, since I was very close to 33 mpg for the tank (all around here with ice cold mornings and wind) and after the current mpg loss the tank mpg dropped to like 32.7.

Has anyone ever experienced this before, losing mpg during a fuel cut? It never flashed, blanked, frose, reset, anything. It acted totally normal other than the calculation during fuel cut.

Ok yesterday I got to see what it was doing. A rare set of conditions has to be met for my car to fuel cut, and for about 1/8 mile yesterday I got a fuel cut and I got to watch it the whole time. The IM went to 999999, but then there was a split second where it said about 3 mpg. And I watched the CM count down FAST. 20 miles into the trip I lost 2 mpg during that fuel cut. If I was sitting a light getting 0 mpg after 20 miles, it would tick down very slowly.

I filled the tank and it was still very close, seemed to be only off as much as it screwed up the other day. Other than during fuel cut, it is dead on.

Something's not right. I wonder if something happened with it being the warmest day of the year, maybe it got too hot. First thing I think I should do is reflash it tonight. If not, then maybe I need a different board or chip.

Or does anyone any other ideas?

what did GH say during cutout?
Also double check that speed is correct (for good measure).

I might also watch the current screen to see if gallons is climbing rapidly, maybe it thinks the injector is stuck open or something.

But a reflash shouldn't hurt either.

Speed and distance are still dead nuts. I'll check again today to make sure.

I don't have the g/h display, since I am still using v.70 which has been rock solid stable since you helped me get the display transistor issue worked out last year. But since I pretty much have to force a fuel cut, I can switch to the screen that includes current gallons before doing it.

I should have written down what it said for gallons the other day coming home from work. I know it said .7 something. If it said .73 then it would be the 35 mpg or so I planned on. But it could have said .78 which would be the 32.7 or so that I ended up with. I'll force a fuel cut on the hill and see what it says on the way home today.

Ok well on the way home I changed the display over to gallons before the fuel cut. Gallons stayed the same, and mpg went up. Same mpg when I changed back to the main screen. So today it worked just like it should. Not sure why. I'll have to keep an eye on it.

Still no problems and I had a few fuel cuts this weekend. All I can figure is maybe it got too hot and temporarily made the chip act up. Don't know. The warm day got me by surprise but from now on I'll take measures to keep it cooler like I did last summer.

It doesn't seem like it could be the car, since if the injectors really were dumping fuel like the guino implied, I would either be gaining speed on the downhill, or I would end up with a backfire, or at least something odd in engine behavior.

It finally did it again on the way home yesterday, same exact thing. One of the warmest days of the season, 70F-80F in the sun. Therefore I think it might be heat related. I'll drill some holes in the top cover plate and hopefully that will help.

FYI, I put a post together with some heat related thoughts here:
http://ecomodder.com/forum/showthrea...-etc-8684.html

I had some freezing issues with my guino about two weeks ago. Since then, it has cooled off and I haven't had any issues. Mine isn't even in an enclosure. It is mounted on the steering column and does get hit by the sun a bit though.

Ahh, lockup issues. I had to think a few times to understand just what you meant. Mornings were below freezing here 2 weeks ago.

Thanks for the tips, dcb. I normally crack the window just a bit when parked when it will be warm out. I also keep a piece of cardboard from a cereal box over the guino to keep the sun off it, and to keep prying eyes away. The enclosure is white so it should help with sun.

I like the dash light integration idea. Wouldn't work with the Celeb guino with its off-brand display, but it would be handy for the ones in the van and wagon. Those I commonly have to turn to full brightness in the day then dim at night.

8 volt regulator... I thought I remembered reading somewhere that the regulator needed at least 9 volts to regulate the 5v supply correctly? Or not?