Can bad fuel cause lingering performance problems?

[JAXRS6]

I'm rewriting this, trying to keep it short & simple, but it just isn't:

PHASE I -- Beast performs poorly, so I take to dealer. (Poorly = rough idle, lackluster acceleration, hesitation and surging.) Get back with new plugs, cleaned injectors, and recommendation to use 100 octane gas for a while because "bad gas" appeared to be the culprit. Diagnosis showed nothing wrong & CEL (check engine light) had not come on. Car performed no better when I left the dealer, but I went ahead with the plan, which includes adding Techron. One guy said wait til you're done with the 100 oct before adding Techron, but today the tech said, no, add it right away, it's a cleaner & not an octane booster. So I plan to add it now but it has no impact on the story so far because I have yet to use it.

PHASE II -- I filled up with 17 gal of 100 oct, meaning about 4 gal of the old (bad) gas was left. CEL came on for the first time at 73 mi of this new tankful! At 84 miles I experienced shuddering at low rpms for the first time, then again a couple of miles later. I was going to have the car hauled to the dealer (this was on a Sunday), but reconsidered when Audi Road Service said I would be OK if I drove the 10 miles home at 45 mph or less -- which I did. When I spoke to dealer Monday, they said I should continue driving, even accelerate hard occasionally when warmed up -- despite the shuddering. Then bring it by when I returned for more 100 oct, which is not available where I live.

PHASE III -- Late last night and today, from about 180 to 280 miles on the first 100 oct tankful, the beast was back to its old torquey self, running GREAT! CEL went off around 200 mi. I took to dealer to check on the computer memory re the CEL light, which showed that it came on due to sporadic misfiring of all eight cylinders -- a symptom of bad gas, I'm told. But since it had turned off and the car was running good, I thought things were definitely looking up -- hopefully fixed.

PHASE IV -- Bad symptoms returned soon after I left the dealer, at around 281 mi, so I went back & was told to proceed with the plan for another tankful of 100 oct. because it can take time to resolve bad gas problems. By the time I got to the pump a few miles later, car was shuddering again. Filled up at 285 mi, this time 19 gallons, so I couldn't go much lower to get rid of whatever might remain of the old bad gas from two fill-ups ago. Now I'm at 345 total miles on 100 oct. & car still runs poorly after that nice 100 mile break.

BTW tranny seems to fail along with engine. When engine runs good, tranny is smooth. When engine is rough, tranny becomes clunky. (I haven't mentioned this to dealer yet because I wasn't sure at first, but tonight's turn for the worse leaves little doubt. Does the simultaneous timing suggest a problem source besides bad gas?)

AoA has asked me to be patient and work with them on this, and I'm trying. But right now I'm seeking independent expertise on this issue: How long do or can the consequences of bad gas last? Should symptoms persist even after the bad gas is gone, plugs have been replaced (the old ones did have some carbon build-up after 12,700 miles) & injectors cleaned?

[sturs6]

Jax I am so sorry to hear about these problems that has to be driving you nuts and is probably getting expensive because 100 octane here is over 2.00 per gallon. I wish I had something to offer but I only have my condolences. :(
Please keep us up to date on the process and Beast status.

[JAXRS6]

Originally posted by sturs6
100 octane here is over 2.00 per gallon

I wish! It's $4 here.

[chewy496]

I've been having a similar problem to you on my (not so great) car. You explain it as it is but nobody can seem to point me in the direction to get it fixed. I've had new spark plugs and it made FA difference.

Recently the head gasket blew and I had that replaced, after that the car ran fine for a few weeks. Now it's back to the usual way of running, as it has been for 6 months or so now.

Only thing left for me to do is change spark leads I think, really not sure.

If you find out i'd be greatful if you could tell me what the problem was if you find out at all. My pockets arn't deep enough to keep going to the garage to find out.

Chewy

[rs6w]

I would think after two tanks it should be cleaned out.

I would have them check all the fuel filters. Cause if you had bad gas it could have fouled the filters.

[JP4]

IMHO....the only way to really rule out contaminated fuel is to completely clean out the fuel system. I.E. remove the fuel cells and completely flush them out. Flush out the fuel pumps. Flush out the fuel lines from the tank to the engine. Replace the fuel filter. Flush out the fuel rails at the engine and clean out the injectors again.

If Audi is so sure its the fuel problem I believe this is the only way to truely fix it based on your ongoing symptoms. If after that the problem doesn't go away I would start looking into ignition/electrical/computer problems.

A buddy of mine picked up a bad load of gas once in his 911 Carrera with similar symptoms and it was fixed only after going through a clean out like I just described. This was a quite expensive proposition ~ $3000 US before it was all over. But since he was able to document exactly when it started and where he got the gas, the fuel dealer stood behind their fuel and wrote him a check for the repair bill.

So.....IMO the answer to your question is YES. If your fuel system was contaminated by a bad load of gas you will have lingering problems until ALL contaminated components have been completely clean/purged/replaced either by driving it out or manually intervening.

Please keep us posted and good luck finding the solution.

JP4

[JAXRS6]

First the good news: Performance came back during a run I just took on I-75 at mile 370 of my 100 oct. usage. Now the weird part: It happened after I noticed that the ESP light had come on -- by itself -- and it wouldn't switch off! As I kept pressing the switch while I approached a stop sign at the bottom of an exit ramp, the car shuddered briefly, almost stalled, and then voila -- the ESP light went out and torque returned along with smooth idle etc. (Later the ESP light went on again by itself, but only briefly before going out -- and there was no shuddering.) No Techron yet because product instructions say add only to a near-empty tank & then fill up, and I have a way to go for that.

I'm trying not to get too excited since this was followed by failure before, and the CEL remains on for now (it didn't go off last time until after 20 or so miles of good performance). But this does make me more curious than ever about how long performance issues can linger following bad fuel -- and I wonder: Whatever the answer might be for most cars, maybe it's longer for us because our beasts are somehow extra-sensitive to gas quality?!?

Meantime ...

Originally posted by chewy496
I'd be greatful if you could tell me what the problem was if you find out at all. My pockets arn't deep enough to keep going to the garage to find out.

Why do you need deep pockets, chewy? I know the UK warranty is only two years & the car has not been out that long, but I don't know the UK warranty mileage limit; have you run past it? If not, why are you paying to get it fixed?

Also wondering if your techs addressed the possibility of bad fuel.

Finally, to JP4 and rs6w: Thanks for your suggestions re cleaning/replacing fuel system components; I will pass on to dealer if problem persists.

[rs6w]

Originally posted by JAXRS6
F It happened after I noticed that the ESP light had come on -- by itself -- and it wouldn't switch off! As I kept pressing the switch while I approached a stop sign at the bottom of an exit ramp, the car shuddered briefly, almost stalled, and then voila -- the ESP light went out and torque returned along with smooth idle etc. (Later the ESP light went on again by itself, but only briefly before going off -- and there was no shuddering.)


Hmm.....

I wonder if you have a sensor failing if the ESP is engaging? (or perhaps some other electronics...)

You may have more than one thing going on....

[pterps]

I don't think this has something to do with the fuel. If a dealer/mechanic can't find the problem it's easy to blaim something else, in this case the fuel. (He doesn't blame them selves). With all the regulations here in Europe it is not possible to deliver Fuel of bad quality, I think it's the same where you live. By the way what has bad fuel to do with a flashing ESP light?

Peter

[JAXRS6]

pterps, you raise good points, and as rs6w also pointed out, the ESP light could indicate there's more than one problem.

As for fuel quality, I suspect it is fine when major brands are delivered. The problem here in Florida may be storage after delivery. It is almost always humid & also very hot in summer, which leads to widespread mold & mildew probelms. And as Joe Hoppen pointed out when we talked, it can be important to use a service station that gets a lot of traffic. Because if their gas remains in storage for long periods, without being sold & pumped out & replaced, contamination may be more likely.

I live in a small town, tho, and none of the gas stations I've seen seem particulary busy. Anyone out there have any ideas on how to find a busy station and/or one more likely to have fuel free of problems?

[TheBrit]

I'd be worried by the ESP coming on by itself - doesn't that indicate a fault? It couldn't be a general electrical problem could it? Have you noticed if the voltmeter does anything unusual when the problem occurs? Any interior lights dimming out or anything like that? Stereo/Nav glitches?

Good luck with resolving it.

[nene]

Really sorry to hear of your woes, and let's hope that the beast is back to her normal self very soon. More importantly, I hope you get to the bottom of it.

Is this anything that using a VAG in real time would catch?
The VAG has some logging capabilities, so all we'd need to know is which module to log.

Goo luck!

[chewy496]

Originally posted by JAXRS6





Why do you need deep pockets, chewy? I know the UK warranty is only two years & the car has not been out that long, but I don't know the UK warranty mileage limit; have you run past it? If not, why are you paying to get it fixed?

Also wondering if your techs addressed the possibility of bad fuel.






I drive my mums old fiat punto LOL :blush: , but am having similar problems with low rpms and shuddering, lagging etc.

Deep pockets? i'm a student :(

Nobody has suggested the possibility of bad fuel.


I'm very much confused :confused:

[JAXRS6]

Just got back from another ride on I-75 & car is still running good. This is after it "got better" again last night, 55 miles ago, and after a total of 426 miles on 100 octane.

So I called the dealer with that news & some questions raised here:

Re the seeming weirdness of the ESP light coming on by itself: This did not surprise the dealer, who said it's an example of the bad fuel working itself through the system. (Also said ESP comes on automatically if the car loses power, which it may have been doing; I was slowing down for a stop sign anyway & didn't notice.)

Re tranny performance dropping off when engine performance does same: This, too, came as no surprise, since "everything is interconnected."

Re recommendation to thoroughly clean all fuel system components: Dealer agrees this is a next logical step if the 100 oct and Techron approach doesn't clear things up completely within a few days.

Bottom line is, there's no reason to return to the dealer right now, which is fine with me. I love my beast but have spent too much time on its problems lately. I was on the verge of listing "RS6 Owner" as my full-time occupation, but maybe I can hold off now!

[chewy496]

I don't know much/anything about fuel!

100 octane is like a really good fuel in USA then?

I've been having this problem with mine for like 6 or 7 months now and have probably done it some damage.

But if 100 octane helped you then that's real cool.

Is Shell Optimax (uk) the same or similar?

Again sorry for being off topic.


Real glad you got yours fixed up JAXRS6!

:D

[Bauer]

JAXRS6-

I can tell you from experience that a bad tank of gas can cause problems for a while, especially on turbo charged cars. The sensors and electronic watch dogs on the turbo cars are designed to protect the engine when something like this happens. The RS6 motor is a HIGH compression motor for a turbo car, so bad gas could cause engine damage easily if the sensors and brain did not cut the performance of the car. My 92 S4, which was modified got a bad tank of gas and the same thing happened with the performance. It took 3 to 4 tanks for the problem to go away compleatly, the system needs to be clear of the contaminates or the car will sense it and shut the engine down. Also, I would from time to time have the dealer check the fault codes and clear them over a period. It sucks for the time being but should clear its self. Good luck.:cheers:

[TheBrit]

Originally posted by chewy496
Is Shell Optimax (uk) the same or similar?
Optimax is 98 RON. If I remember rightly, US fuel grades are (RON + MON) / 2? The higher the octane rating, the less likely the fuel is to detonate or pre-ignite. Different thing from contamination, which can result from sloppy handling or storage.

As to your Punto problems, HT leads might be an option but I wouldn't go changing stuff around randomly - that's going to get expensive! How about this forum (http://www.fiatforum.com/forum/)?

Hope you get it sorted! :)

[BBGT2]

Jax,
Sorry to hear about the crappy running, I am in the auto repair field. My advice to you would have to be to take the car to Audi and tell them to call you when it is fixed, no reason you should have to struggle along with it. Is it bad gas very possibly Yes, should it have cleaned up by now after 3 tank full's, again YES.
The problem lies elsewhere possibly in the Mass Air Flow Sensor or even the O2 sensor(s). Turbocharged engines are very tempermental beasts. There is no reason for Audi to tell you to get 100 octane gas when the damn thing was designed to operate at 93 octane levels, if that is the case then there is something wrong with the "engine management unit" which regulates the optimum operating mixtures and timing for the fuel and air mixture's. I think you have been patient long enough, some of these dealers are suffering from a case of "their techs just do not know" these cars are too new????!!!!!!!!!!
Besides only one of the techs out of each dealer was "awarded" the techincal training for these beasts and if he leaves guess what, all the other techs can do is guess. Audi really drop the ball on the maintenance issue (what a suprise).
Hope you find the remedy to your problem ASAP, and I just wanted to offer you some pointer's and my .03 cents.

Bajo:addict:

[JAXRS6]

I don't know the conversion formulas but can tell you Brits & others that 100 octane is sold as racing fuel in the US and is hard to find. Normally we drive on premium fuel, i.e. the best offered at 99% of gas/petrol outlets, rated at 93 octane US -- except for California and some other states where the highest octane available is 91 US. I think I read somewhere that the US RS6 is designed to run on 91 but I'm not sure if it's nationwide or just in the relevant states -- with other US beasts designed for 93. Can anyone clarify/confirm?

And Bauer, thanks for a great post! I am in fact grateful to all of you for posting!

[Bauer]

JAXRS6-

anytime.....I just hope that is the only problem and that it clears up for you soon. I was getting a little pissed when my S4 took so long to start running right. So I know what your going through.

[TaTaPiRaTa]

I had something simillar.

I had ESP and Brakes control lights on after driving few hundred meters from cold start. Then when I restarted the engine, it cleared and comes on after some time. After few tries (I thought when the engine is realy hot) everything come to normal.

While the ESP light was on I had very bad performance - when accelerated slowly everthing was ok, but when pushed hard it was like no turbo at all, drove like 4 cilinder car, then when I eased the pedal and pushed more slowly it accelerated normally.

We discovered at the workshop that the brake pedal switch which tells the stop lights to go on was unstable and cumputer recognized this as brake problem. After changing the switch everthing is fine.
The non accelerating stuff was happening while the computer was in error mode, maybe this was a precaution not to accelerate to fast when computer thought the brakes have a problem.

Hpe this helps somebody.

[JAXRS6]

My beast seems much better but I can't test to be sure (yet).

I used 100 oct for 600 miles and ran smoothly for the last 175 of those miles. Then I filled up with Chevron 93 oct, Techron and an octane booster; have run 275 miles so far on that, mostly Interstate, & lately feeling like its old, wonderful, torquey self.

So: That's a total of 450 smooth miles -- much better, and more encouraging, than the 100 smooth miles I spoke of before, which ended with resumption of rough running engine.

Lately it seems as if even the tranny is better at launch, so I'm hopeful that a new 0-60 time will be below my prior best of 5.6. (It may have performed faster before the bad fuel issue came up, but I wasn't timing it then.) Right now, however, I'm in a heavily developed area & won't be back to potential 0-60 territory until Monday night or Tuesday. Will post more then, or after the Christmas if I don't have time or good conditions to do a run before. Meantime things are looking up!

[JAXRS6]

My beast seems much better but I can't test to be sure (yet).

I used 100 oct for 600 miles and ran smoothly for the last 175 of those miles. Then I filled up with Chevron 93 oct, Techron and an octane booster; have run 275 miles so far on that, mostly Interstate, & lately feeling like its old, wonderful, torquey self.

So: That's a total of 450 smooth miles -- much better, and more encouraging, than the 100 smooth miles I spoke of before, which ended with resumption of rough running engine.

Lately it seems as if even the tranny is better at launch, so I'm hopeful that a new 0-60 time will be below my prior best of 5.6. (It may have performed faster before the bad fuel issue came up, but I wasn't timing it then.) Right now, however, I'm in a heavily developed area & won't be back to potential 0-60 territory until Monday night or Tuesday. Will post more then, or after Christmas if I don't have time or good conditions to do a run before. Meantime things are looking up!

[JAXRS6]

After 590 smooth miles my beast crapped out again.

I filled up on Amoco 93 oct, adding Techron and octane booster per dealer recommendations, last night at a busy station in Deerfield Beach, FL. Added 12 gal to nearly empty tank, per Techron instructions. Still running good at this point.

About 140 miles later, after crossing most of Alligator Alley at just the sort of steady high speed cruising that was recommended, my ESP light went on by itself again as I decelerated down an exit ramp. It turned off after a couple of seconds (coming on signaled a temporary power loss I think), but at the bottom of the ramp the idle was very rough. I cooled the car down for a few minutes, ate at a restaurant, and upon re-starting the idle was rougher than ever -- so bad it almost stalled while standing still in neutral, with the tach needle hitting 300-400 rpm before bouncing back up, then down, etc. That lasted about 2 minutes; then idle became rough but not as bad. Other symptoms: hesitation, surging, loss of power (as usual).

I called dealer, have an appointment Monday, and they are waiting to hear from AoA as to what's recommended next. As for me, I'm not sure what to do except urge that they re-examine for boost leak and MAF problems. Any other suggestions?

[JP4]

Originally posted by JAXRS6
After 590 smooth miles my beast crapped out again.

I filled up on Amoco 93 oct, adding Techron and octane booster per dealer recommendations, last night at a busy station in Deerfield Beach, FL.

I called dealer, have an appointment Monday, and they are waiting to hear from AoA as to what's recommended next. As for me, I'm not sure what to do except urge that they re-examine for boost leak and MAF problems. Any other suggestions?

Well JaxRS6...I'm going to have to recommend my original suggestion again. The fact that the 93 oct WITH the Techron and octane booster seems to have aggravated the situation again tells me that there may very well be some contamination STILL in your fuel system somewhere. The Techron more than likely worked more of it loose causing the bad running problems. I have heard of this before. IMHO the only reason Techron would cause an engine to run rough is by doing what it's designed to do...clean the "crap" out of the fuel system and the upper part of your engine. The fact that the problem is still occuring might suggest that the contamination is bad enough that the Techron can't get it ALL by itself. Again....manual intervention by be indicated here.

JP4

[JAXRS6]

Sorry, JP4, that I didn't mention your earlier recommendation to flush all fuel system components. I did, and do, intend to ask for that; just forgot to mention in my latest post. Hopefully it won't be a problem to get it done, since the dealer service writer agreed that that would be a logical next step.

[JP4]

Originally posted by JAXRS6
Sorry, JP4, that I didn't mention your earlier recommendation to flush all fuel system components. I did, and do, intend to ask for that; just forgot to mention in my latest post. Hopefully it won't be a problem to get it done, since the dealer service writer agreed that that would be a logical next step.

Let us know the results. Hope you find the solution to your problem soon, regardless of what it actually turns out to be.

JP4 :0:

[JAXRS6]

Service writer said if my car's performance problems were caused by bad gas, it's not covered under warranty! I guess that makes sense, since Audi can't be held responsible for bad gas, but I'm constantly getting feedback from here & elsewhere that boost, the MAF filter, or (new idea) a bad coolant sensor is causing the problem. Dealer advises, however, that they are awaiting factory recommendations on what to do next (last time they replaced plugs & cleaned injectors) but they do not abide by web site recommendations. Keep in mind the only malfunction shown by codes so far at the dealer is sporadic misfiring of all eight cylinders.

I'm no tech but am considering two approaches:

1. I find someone with a VAG COM & get readouts/printouts before my dealer appointment at 11 eastern Monday (this helped me identify an S4 problem the dealer couldn't find); and/or

2. While at the dealer, I get a friend on the phone who has a master's in automotive engineering & is very familiar with Audis in general, the S4 & VAG COM -- but not, unfortunately, the RS6. (He's the one who added bad coolant sensor as a potential problem & he agrees boost leak/bad MAF filter are other candidates.)

Whaddya think? Any other suggestions? Anyone near Sarasota or Fort Myers with a VAG COM available that I could use at your site?

[gjg]

JAX,

check with "http://www.ross-tech.com/" if his product will read RS6 or not. Laptop install, works fine on all other VW/Audi products. He's been around for a while and the product support is unbeatable - and so is the price.

IMHO if the problem persits as long (and as many miles as you put on since this threat started) as yours I find hard to believe this is only related to a tank of "bad" gas - the dealer response starts to be similar to the standard bs (bullshit for Europeans) excuse some of us on the list are quite familiar with.

Translated - "we do not know what the problem is so it is your fault and it is no covered under warranty". No matter what, the service dept of any dealer will, at the end, look for their own interest first.

If that be my car I'd leave it in service dept (with appropriate loaner on hand) and let them figure out the problem. No more talks of bad gas - this is too easy way out for them.

Being in Sarasota I'd talk to Mike Hoppen to get his feeling on where to look for a problem. He's got the experience and, once you get him on the phone, he'd try to help.

gg

[gjg]

done some "mouse clicking" - check this one:

http://www.ross-tech.com/vag-com/interfaces.html#Chart

so it looks like there is interface cable for rs6

[JAXRS6]

Originally posted by gjg
it looks like there is interface cable for rs6

Yup -- and since I have a dealer appt. Monday, I'm trying to locate someone who has the VAG COM nearby & I can pay a reasonable amount to get a readout before the appt. Someone at audiworld linked me to a vag com availability list by location (all US at present, except one listed as Yugoslavia):

http://www.steve-hall.com/cgi-bin/VAG-Locator.pl

I've already used it to email three possible sources in Tampa, FL, which is 100 miles north of here but the closest I could find. No replies yet but it's only been a couple of hours & it's kind of a weird weekend, between holidays, so I'm not sure what to expect.

[got turbos?]

I Believe that my Beast is suffering from similar problems. Mine cold start below about 30 degrees is terrible. Jerking, hesitation, unburned fuel smell ect. Dealer has it now, they are replacing the MAF sensors but I'm not convinced it will fix it. the car runs fine after it is warmed up, It only takes about a few tenths of a mile to clear it up. But it can barely stay running the first few minutes. I started it on monday to take it into the dealer in the late afternoon (about 44 deg F) and no problem. I think the post about the coolant temp sensor makes the most sense for my problem but he dealer hasn't mentioned that yet. I have a Vag-com and have been able to hook it up and read the RS6 engine codes, it threw an 'over rich code' once on a hard acceleration. I don't know enough about how to monitor the measuring blocks and do data recording to document the cold start problem. I wish I did but the it doesn't seem to be obvious how to do it.
Has any one else experienced the cold start over rich problems, and gotten it resolved.
Thanks WWIV