Jaybatl911

I have a 1999 C2 that was bought with a rebuilt engine. The original owners modified the original engine and blew it and couldn't afford the work. The Porsche indy mechanic installed a rebuilt engine and sold it. I've had it for 3 years and the car is a champ - except for one minor issue. It only runs on non ethanol gas. Any time I try regular 10% ethanol fuel is runs like there's water in the line. It sputters and coughs at slow RMPs and stalls in turns or at a stop.

I've changed the fuel pump and filters and still nothing. It was in a Porsche dealer for a week and they couldn't figure it out. The indy mechanic doesn't know either. But today I was talking to my brother's mechanic - who has never worked on a Porsche - who said to check the fuel mix. That if the air/fuel mix isn't right that that could be the result. Not knowing what to think, I thought I'd pass this by you guys. Is there something else that both the dealer and the indy mechanic missed? Is there a regulator somewhere that can be reset to mix the fuel differently?

Thanks for any ideas you might have to offer.

dan_189

Why not just run non ethanol fuel? Is there a specific reason you want to run ethanol fuel?

The way the M96 is temperamental and so highly strung I'd be running the best fuel you can get.

jhbrennan

Can't always or easily find non-ethanol gas in the states.

dan_189

I see, I see, perhaps a custom tuner with a dyno etc. might be able to customise some fuel maps to allow you to run a particular type of fuel? That's only a guess though!

Porschetech3

Yea, your brothers mechanic is right. I can't believe it was at a Porsche dealership for a week and they could not figure it out? You must of had them working on something else for a week , if they didn't even check the fuel mix working on it, for a week. Didn't even check for codes?

Anyway yea sounds like the fuel mix is not right at times, should have some codes or CEL (if it works). Also sounds like the 02sensors are ageing, they get a bit lazy and don't control the mix properly at times and are probably not to happy when you swap fuels. When you swap fuels the system has to re-adjust, and if the 02 sensors are old and slow, it may run sh*ty for a while as it slowly slowly tries to adjust to correct mix.

It's a 99 so the 02 sensors are probably 19 years old, just replace all 4 and reset the DME, and it will re-adapt much faster.

MoeMonney

thats a great answer!

Jaybatl911

Thanks for the great answers. I run the non ethanol whenever I'm driving in town but when I go on a road trip I can't always fine it. Just this weekend I drove 7 hours to New Orleans and put in premium gas along the way and it knocked, coughed and sputtered at low speeds and even stalled in a turn. I found a station with non ethanol 87 octane and tanked up and it purred like a kitten. But on the way back to Atlanta yesterday I had to put premium ethanol in it again. Yep, coughing and sputtering this morning. I'll fill it with the 90 octane non ethanol once it's low and I'll ask the indy mechanic to recheck the o2 sensors. I know he replaced one but I didn't know there were FOUR!

porschedog

I have been running E10 in my cars, boat, motorcycle, generator, etc for 12+ years as that is all that is readily available in the part of South Florida where I reside. Zero issues.
I do use an enzyme fuel treatment every few tanks which seems to be keeping everything happily spinning.
I only use Top Tier fuels and never get gas if the tanker truck is there making a delivery (and thus stirring up all the crud in the underground tanks)

joe-1972

I can say that my 996 dose not have any issues with the gas in Illinois. We have E10 in almost every pump out here... you can find non ethanol gas now and again... but rare.
I have filled up with some race fuel once or twice just to kick it in the @ss and she liked it!
Something is really off with your ignition / fueling parameters if she is acting like you are describing.

Paging Jake Raby for the answer here?

Splitting Atoms

Sounds like you are running 87 and 90 octane no ethanol. The octane rating may be too low. There is only one station in my area of upstate SC that has 93 octane no ethanol. Why can't you run 93 octane E10? Usually the only reason for running no ethanol is if you have certain rubber or plastic parts in the fuel delivery system that degrade in the presence of alcohol. I would rather run 93 E10 and risk an eventual leak than run the engine too lean on a lower octane gas.

Splitting Atoms

I should add that if it doesn't run right on 93 E10, then I agree with Porschetech3 that new O2 sensors and a DME reset is the way to go. It should run well on 93 E10, better than 87 or 90 octane.

Flat6 Innovations

Mr. Raby doesn't post on forums these days :-)

That said, the original poster likely has a knock sensor issue, or the injectors need attention. Ethanol is doing a number on the fuel injectors, and we see this mostly from the mid- west regions where Ethanol use is greatest.

Splitting Atoms

Interesting. Are the o-rings that seal the injectors in the fuel rail degrading causing fuel leaks, or is the damage to the injectors themselves?

Quadcammer

Care to explain why you think running the car on lower octane would lean out the a/f ratio?

stever996

Can't help with a fix, but.....pure-gas.org for 'real gas' nationwide.