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I bought a 2004 E55 AMG (111k miles) a month ago on auction and have noticed that it has HORRIBLE gas mileage. My average in city is about 7.5mpg (gotten as low as 4.5mpg) and the best I ever got on highway was 13mpg. I also noticed that it doesn't seem to have nearly the 469hp it should. It feels slower than my N/A C55 AMG. I can feel the S/C clutch engage when I step on it, but I've never heard the slightest S/C whine. It seems to have more power in 2nd gear than 1st too... Also, 0 abnormal indications or fault codes on my MB2.0 scanner.
So far I've changed the engine air filters, and pulled the S/C pulley spacers out to get it within spec (I think .35-.45mm spacing?)
I've done a bit of research, but I don't know what to start diagnosing and I'm not going to a dealer. I've heard potential I/C pump, boost leak, fuel pumps, etc. As far as the I/C pump, wouldn't I only see power loss after the engine was warmed up for awhile? The loss of power has always stayed constant for me...
For those more experienced than I, what do you recommend?
Get it scanned preferably with Xentry/STAR, then note all the codes. Clear them all, drive it some and scan again to see the actual fault codes. That will help you a lot to get started.
^+1. Scan the system. List the codes. Start with the lowest number. Fix that and it will remove most if not all of the higher numbered codes.
I Am thinking this may be a relatively easy fix.
Edit: If you do not want to mess with it I would be happy to offer you what you paid for it just to get it off your hands.
Probably IC pump. I'd clear codes and then drive and check. If there's no error code, check the IAT
My understanding is that if it's the intercooler pump, supercharger won't engage at all once it warms up, is this true? The supercharger always seems to engage just doesn't add any boost really
This isn't a Hellcat so you won't hear the blower like you would on the American cars. Maybe the gas mileage is you romping it to diagnose over a period of time?
Second, the IC Pump kicks in above 2K rpm, whether you engage the blower clutch or not. I'm willing to bet the pump is bad - has it been replaced ever?
Air temps can vary car to car. My prior M113K cars all had better air temp numbers, but ran noticeably slower than my current vehicle. That was around the time I began to believe in real world performance and not give a damn about numbers anymore.
Thx for the info! Ok so I'll check the I/C pump, but how do I confirm that it operates correctly? I heard someone say to hook it up to 12v power and see if it turns on? The pulley seems to be secured well and it engages good. I might get a belt wrap kit in the future in case it could be slipping. I'll check the IAT and report back to see if the numbers are not normal.
What current codes show up in the scan? Don't bother with hooking up 12 volts to the intercooler pump; just activate it using the diagnostic system, that is how one bleeds the circuit of air after working on the system. The diagnostic system allows one to individually test most everything attached to the motor electronics. The issue is most likely going to be simple *once you identify it*.
My bet is an air intake temperature sensor or a coolant temperature sensor indicating to the motor electronics the engine is in a cold start condition (like -20* F) so the computer is throwing massive amounts of fuel into the engine. I learned this one the hard way years ago with an intermittent connection on a coolant temperature sensor.
Diagnostic system will read all of the sensors.
Let us know what you find.
Just putting it out there. I had a similar issue to you, even had it in a workshop to check. They pointed to the sc belt tensioner not being up to par. However, by dumb luck, I diagnosed it as a crank pulley delamination, e.g. the sc drive 8 rib portion of the crank pulley was free spinning - essentially just a ring around the pulley body. It fooled us because at idle there was enough friction on the sc portion to drive the sc - to a point. It would stop driving the sc when you accelerated under load. It would make the chirp noise sometimes associated with a tired sc tensioner.
You've had the sc pulley off but so did I, several times until I slid the piece off the crank pulley as I was pulling forward on the belt while it was partially around the crank pulley, that's when the whole piece slid forward.
Just putting it out there. I had a similar issue to you, even had it in a workshop to check. They pointed to the sc belt tensioner not being up to par. However, by dumb luck, I diagnosed it as a crank pulley delamination, e.g. the sc drive 8 rib portion of the crank pulley was free spinning - essentially just a ring around the pulley body. It fooled us because at idle there was enough friction on the sc portion to drive the sc - to a point. It would stop driving the sc when you accelerated under load. It would make the chirp noise sometimes associated with a tired sc tensioner.
You've had the sc pulley off but so did I, several times until I slid the piece off the crank pulley as I was pulling forward on the belt while it was partially around the crank pulley, that's when the whole piece slid forward.
Are you referring to the bearing ring inside the pulley? Not 100% sure what the 8-rib portion means
The crank pulley has 2 parts, the inner ring (6 ribs) is for the serpentine belt and the outer part (8 ribs) is for the supercharger belt. This outer part should be not be loose or turning on its own.
The crank pulley has 2 parts, the inner ring (6 ribs) is for the serpentine belt and the outer part (8 ribs) is for the supercharger belt. This outer part should be not be loose or turning on its own.
I pulled off the belt and tried my best to twist the crank pully with my hands (not able to use alot of leverage) but it wouldn't budge. Unless there's a better way to diagnose it, I don't think this is the problem.
What current codes show up in the scan? Don't bother with hooking up 12 volts to the intercooler pump; just activate it using the diagnostic system, that is how one bleeds the circuit of air after working on the system. The diagnostic system allows one to individually test most everything attached to the motor electronics. The issue is most likely going to be simple *once you identify it*.
My bet is an air intake temperature sensor or a coolant temperature sensor indicating to the motor electronics the engine is in a cold start condition (like -20* F) so the computer is throwing massive amounts of fuel into the engine. I learned this one the hard way years ago with an intermittent connection on a coolant temperature sensor.
Diagnostic system will read all of the sensors.
Let us know what you find.
Car shows no codes on my MB2.0 scanner, but I don't really have access to a STAR system. Do you have recommendations for a STAR system that reads what I need without breaking the bank? I monitored the IAT on my scanner while driving and it stayed pretty consistent around 50 degrees F.
Last edited by ThunderSlug; 03-19-2024 at 06:04 PM.
You guys are making this way more complicated than it is. How did we end up at the crank pulley?
OP - did you test your IC pump? Hell, don't even test it just replace it. It's a cheap part (relative to what things cost for this car) and it's easy to do - you seem like you're mechanically inclined so this should be a cake walk. Has it ever been changed or OEM part? It's probably shot and your supercharger isn't making any boost, maybe even limp mode.
So turns out... After trying to diagnose everything and still coming inconclusive, and despite me not changing a single thing on the AMG, it miraculously started running perfectly normal yesterday. I've driven it 3 times over about 25 miles and it now flawlessly accelerates with what seems like all 500hp and the MPG is steadily increasing. Fingers crossed it stays this way... maybe it just needed an Italian tune up or it had bad gas :P
I'll report back if the problem comes back, but for now I'm just super happy for the free effortless fix.
You guys are making this way more complicated than it is. How did we end up at the crank pulley?
OP - did you test your IC pump? Hell, don't even test it just replace it. It's a cheap part (relative to what things cost for this car) and it's easy to do - you seem like you're mechanically inclined so this should be a cake walk. Has it ever been changed or OEM part? It's probably shot and your supercharger isn't making any boost, maybe even limp mode.
Um because I had the same mystery power loss and a broken crank pulley was what it turned out to be despite investigation by Mercedes mechanics. It's an uncommon, left field occurrence and is an easy check and not that complicated.
03-15-2024, 07:37 PM
E55 AMG Loss of Power and Horrible MPG
