Possible fuel problem?

[JasonHutter]

I would be interested in what people found out about any fuel that made their engines miss in the past. We still have fuel (110 octane) in our truck from Mexico and it is missing pretty bad. We have been talking about all the electrical things we need to look at to find the miss along with the compression test and leak-down test to make sure it isn't internal. We haven't done much yet, took a little break after the 1000 but will be tackling it soon! All we have done is pull the plugs and make sure the inside of the intake past the filter wasn't full of dirt and silt. It seems we need to add to the list, empty tank and put new fuel in it and run it as well after hearing some stories from peoples experiences in the past. Any thoughts, and did anyone have any problems this year? Was this miss issue a long time ago?

Jason Hutter
Fire Guys Racing

[sandking]

I dont know what motor your running, but have checked the fuel filter(s) and injectors?

[JasonHutter]

Not yet, haven't done much like I said. Both are on the list of to do's though. I just had heard a couple of stories pertaining to fuel issues and thought I would ask before getting into it on our truck and possibly have some extra knowledge of something to look for. We are running a 2.7ltr fuel injected 3rzfe. The other reason I was asking is the truck had a miss early on in the race after the San Matias pit while doing about 95mph on Diablo. We stopped to see if we had a loose plug wire or something. Couldn't find anything, when we got back in the truck ran fine until way down the peninsula when Paul was driving. Not sure when it came back, I'll have to ask Paul.

Jason

[John F2000]

Typically type of fuel or having it in the car for a month doesnt cause a miss. Usuallly when fuel goes bad it will cause the car to detonate. Except for the obvious, water, dirt, etc...

Is it backfiring out the intake/exhaust or missing?

Is it detonating?

Backfiring out the intake is usually electrical related, assuming the car is jetted properly and not lean popping. The spark can jump to a diff cylinder if a plug wire, plug, carbon in the dist cap, etc... are failing

Detonating, well that speaks for itself.

[JasonHutter]

It started missing during the race, so not from sitting around. It misses with the occasional pop out the tail pipe. The ignition is run by the computer and sparks two of the four cyliders at the same time. One is on the compression stroke and the other cylinder is on the exhaust stroke. I think most computer systems do that. The ones we work with at the Aspen Racing and Sports Car Club on the cars we have out there do the same. We have to drive 2 hours to go work on our truck and I think I am going down there to work on it next week sometime. I will let you know what I come up with and get some of the unknowns out of the way. I suppose because I haven't really started on much there is too many unknowns.

Jason

[22REKid]

I have a question for you. Are you running any type of stand alone fuel system or are you running the stock MAF? If you are still running the stock MAF than that might be the problem.

[JasonHutter]

The injectors and the fuel rail are stock, it has a stand alone computer telling it what to do.

Jason

[richard cretsinger]

just pull it out and put a v8 in it. it will fix all your problems, mostly the gutless problem!!!! show me the money. jk

[amr126]

If all of the electrical system has checked out, and you've made sure your timing or something simple isn't way off, I would possibly check into a possible air/fuel meter and something to monitor timing. If you have a new enough fuel injection that is OBDII compatible then you could get something like the predator hand held scanner to look into whats going on.

[EdSharkyCruz]

definitley sounds like an a/f problem.........:)

[JasonHutter]

Already proved we don't need a V-8 to run faster than them. Don't worry, we'll give you a chance to run as fast as a 4 banger one day!

I have an a/f meter but a stock O2 sensor. Need to buy the $300 O2 sensor that works instantaniously.

Unless the computer reprogramed itself the timing shouldn't have changed since we programed it on the dyno.

Was down there to work on it yesterday but got side tracked with seeing how much we were going to have to change to fit the 35" tires on it to fly through the silt next time we come across some! We got really good at digging ourselves out down in Mexico this year with the 33 X 10.50's!

Jason

[drtdevil93]

jason: i'm assuming you have the crank triggered distributor-less setup? i had similar problems on mine and it turned out to be steel dust built up on the crank magnet that was distorting the signal apparently. as soon as i saw it and wiped it off, problem gone.

erik

[richard cretsinger]

jason, im just kidding, i know how fast you run, its scary fast for a truck that is basically stock suspension. wondering what lc enineering says i know that you had them do alot of your engine work?

[JasonHutter]

Yeah, I know you were kidding but had to say something!

Cleaning the magnets off is a good idea and totally forgot about that. When we got the system they said to always start there. How easily we forget! I will give it a try when I am down there next week. The engine is coming out and going in for a refresher but would like to find the problem before sending it in so when it is back we still don't have a problem!

Jason

[Moss2]

Some high lead race fuels will foul the plugs after it cools off or run slow for a long period. Maybe try a fresh set of plugs and hook it up to a scope before you tear into it to deep..

This is probably worse to if you are not running really high compression and are using such a high octane race fuel.

[JasonHutter]

Good call, this was the first time we ran straight 110. The first time it was missing was just after coming off the goat trail down on Diablo. Then way down the peninsula after Lareto after some slow going through the silt. When I pulled the plugs, all were running a bit rich. I thought that was a little strange with the fuel injection and all. I checked to be sure the map sensor was plugged in and the vacuum line was on. I'll have to either empty the tank or cut it with some pump gas to see what happens. We are running just 10:1 compression and have been running a 50/50 mix of 110 and 91 octane fuel till Mexico. Will have to get about 100 octane next time!

Thanks for everyones info.

Jason