rondocap

So yesterday I went to some gas station in NJ, and put in some gas. I always put 93, but in NJ they put it for you, so it is possible the guy put in 87 or 89, and not 93 if he misheard me.

Anyway, I'm driving a few hours later, and I'm accelerating here and there in the usual AMG fashion. ( )

So..after I accelerated on the highway from maybe 40mph to 65mph with the kickdown, I noticed something very odd. I had no more power from the accelerator pedal. It didn't stall and was still going, but wouldn't accelerate more. So I pull over at an exit, and turn the car off, put it in park, and start again. OK, so now it's accelerating again, but it's still a bit funny. So I give it a little push...and the check engine light comes on. The Throttle response is much worse.

I think to myself, hm - what could it be? Then I remember reading about bad gas and how it can cause bad performance or bad throttle response. I pull into a gas station that I know and put in some 93. The check engine light immediately turned off, and the car was back to normal throttle response.

That's strange - so was it really just bad gas that caused this? The check engine light went out immediately after I put 93 gas in, without me even driving it. Is it just bad gas, or could I have something that is failing, like the MAF sensor, or something like that?

Car has 124k miles for reference. Thanks!

Gondon

They prob mixed it with Water.

Jud Chapin

If the CEL went out upon immediately starting the car, it wouldn't be the gas I don't think because it wouldn't have had time to get to the engine. Perhaps the gas cap wasn't secured tightly by the attendant which will prompt the CEL but I don't know if that would cause the engine to run as you describe. If you're concerned about it, loosen the gas cap and see how she runs. Keep us posted.

tusabes

yeah much more likely a loose gas cap than bad gas. Bad gas would not react like that.

If you have continuing problems, its an electronic problem, not a gas problem

rondocap

I hope it was only the cap, I've never had power cut out like that while on the highway, I would press the pedal and nothing would happen. Felt like I was driving a BMW. (haha, Just kidding....)

I'll let you guys know if the problem returns and how it is running in the next few days. I did open the gas cap and close it again the first time I pulled over quickly, but the light stayed on, it only went off after I put some 93 gas in the car. Maybe it needed a little more "breathing" space for the vacuum or pressure to be released.

tusabes

You dont need to use 93. I use 87 just fine. Modern cars have knock sensors and compensate for low octane gas. You might lose a few hp but it does not result in drivability problems

rondocap

Ah, I've always used 93 - I figure it may be cleaner and help the engine last longer. Also I did notice a power decline anytime I accidentally put 87 in, especially being an S55 I pay attention to the smallest difference in power.

tusabes

the 87 and 93 is the same gas with a different additive package/octane enhancers. So the cleanliness of the gas is the same, since it comes from the same tank in the tanker truck.

If you ever notice a gas truck filling the underground barrels at a gas station, they fill from the same truck tank. They just (supposedly) pour an octane enhancer / additive package in the "high octane" storage tanks. (And I bet sometimes they dont even do that.)

Gondon

The ecu is tuned for 93, any less and yea you lose HP your engine cuts timing and in general that's not good. Why would you cheap out on gas

socalsounds

Tusabes- unfortunately, you're completely wrong on the one-truck issue; my dad co-owns several stations here in San Diego.

Every gas station has two tanks, and a mixing valve (sometimes connected to a third tank), to create midgrade (89 here in California). There are ALWAYS two trucks, and California weights and measures requires that 91 be trucked seperately from 87. Period- there are hellacious fines for unmetered mixing, and tests are conducted very often for octane rating of each tank, as well as the output of the mixed midgrade. I'm not saying one brand is better than another, but trust me, most states regulate the hell out of delivered gas, and there are a lot of different regulatory agencies that monitor octane, pump volumetric output, price multiplier factor and cash / credit discount schemes. You are very well protected in this arena.

I'm not going to weigh in on the "which gas to use", since the owners manual clearly requires 91+. But, it's your car. I HAD to put in half a tank at Lake Arrowhead once (its all they had), and the car ran like crap all the way to the basin. Filled up with El Cheapo Arco 91, and no more problems. I'm sold on 91.

As far as "adding additives"? Illegal- The gasoline that arrives by distributer is pre-additized, and only comes in two flavors- 91 and 87. Federal law requires that any additive, like MBTE be clearly disclosed (ands its illegal in California, now anyway...) on the pump.

Chris

tusabes

Thanks for the insiders info.

I only see one truck come at a time, so the other truck with the different grade must come at another time if they must be trucked separately. I have never seen two trucks at a gas station, ever.

rondocap

Update: Actually I was wrong, I test drove the car more and here is what I am getting:

Check engine light is off, but something is really strange. When on park, the car revs higher pitched than normal, like it's strained. When you turn it on, it's the same thing..higher pitched whine that wasn't there before.

When driving, low rpms it is OK, but there is no power really, like if I accelerate. I checked with a scanner, and I got these codes:

P0700 - (Transmission control module, says TCM has detected emissions related fault)
P0120 - Throttle position sensor
P0500 Vehicle speed sensor - I recently had the ABS speed sensor for the right wheel changed, is this possibly it and the code was just not reset? So this code probably isn't it.

So is the throttle position sensor the most likely cause? It's really strange, anyone had these problems before?

socalsounds

Well, the high-pitched whine is usually an alternator that's starting to get strained (have you changed your serpentine belt lately? A tight new belt on an old alternator can stress the bushing and make it whine)... POssible electrical nexus to these issues? I would test your battery charge hold and alternator output first (Autozone does it free), and then move to other areas... JMO

Chris

rondocap

Yeah I did change the serpentine belt about 2 months ago. The problem started just now though, along with the loss of power and check engine light with those codes.

I'm hoping it's just the throttle sensor, that seems like a fairly cheap fix.

socalsounds

Hmmmm. Get that alternator checked, both unloaded and for any drop as well- Your new belt may have dumped the bearing, which over time will hurt output big time from overheating. Check it out- good luck!

tusabes

belt may have loosened up.

Seems the root issue is always electrical or some sensor in these cars.

rondocap

So a loose belt would cause power loss, and a check engine light? The codes were the ones I posted above.

When I put it in park, it's really funny - like it is an unstable rev. It goes up a little and down, doesn't stay still.

Anyway I'm going to get it to a shop soon to get it completely figured out, but thank you guys - keep the ideas coming as I like to know what may be going on! I
ll keep you guys updated.

tusabes

A loose belt wouldnt cause it directly, but the low electrical supply resultant from a loose belt can cause all kinds of electrical and drivabiility issues.

I have never seen any car so dependent and so senstive on a fully charged battery to run properly than a w220. Other cars you can have a completely dead battery, jump it and drive off. These w220 cars get damaged if you jump them, get all kinds of errors if the battery is just low, etc.

Corsa9000

As to "tusabes" comment on using 87 octane gas, the difference in price per gal. is $0.20 for 87 vs. 91 octane in California OR $3.40 per week for me( 17 gallons a week for me). For that much, it is not wise to using a lower octane and risk damage to your engine.

Just my two cents.

rondocap

I took it in to my local shop, but I'll have to bring it back - he just took a quick look, and pulled these codes, similar to the ones I pulled:

Pedal Value Sensor, short circuit at signal path 1

Component n15/3 (ETC control module) memory is fault)

No CAN message vehicle speed signal left rear wheel from control module


So maybe it just looks like it may be the throttle sensor or something to do with the pedal. The car is sounding a bit different, a bit more strained - especially when I put it in park the idle is not consistent as before. I've been driving it at low rpms and it drives fine, but I don't want to do the kickdown as that caused the loss of power and check engine light before, so I figure it will do it again.

I'll keep you guys updated - hopefully it's not an expensive fix.

rondocap

So I figured out it, got it fixed. It was the accelerator pedal that went bad - so the throttle position sensor. Getting it changed fix the problem, car runs great now.

tusabes

in CA the spread between regular and premium is only 4 octane points (87 to 91) and I use regular in all of my cars that recommend premium fuel, without any issues whatsoever.

Its not about the price difference, all modern cars compensate for lower octane gas. They dont start running badly. I just cant believe all these tall tales of using regular gas and actually experiencing a noticeable effect in how the car runs.

goliver

I am having the same problem with my 2002 S430. I was driving yesterday and the accelarator started responding very slow. I am experiencing the simptoms as "RONDOCAP". I plan to take it to the shop today, I'm curiuos to see what they find. I'll keep you guys posted.m

mz3bo

Any Update.. ?

gikky1

Hey rondo, I have the exact same symptoms on my 03 s55 amg but when I called in about the throttle position sensor the guy said these cars don't have them and what I needed was a electronic gas actuator... That part is 1270 bucks... Please help me lol