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Discussion Starter #1
Have had my '00 E39 M5 for about 3 weeks now. When I first bought it it was lightning quick in lower gears with minimal throttle. In the past week or so the acceleration has gotten noticeably worse, to the point where in 1st and 2nd, especially, the car seems to just really be lagging. Coming off of stop lights w/ Sport Mode on I'm working hard to stay nose-and-nose w/ Grandmas in vans? No misfires, no SES lights, no other engine noises, just much slower. Idle seems fine, no rev-hunting. Wednesday night I took out the MAFs and sprayed them down thoroughly with some CRC MAF cleaner (per instructions on the can), and didn't notice much change. I have the instructions for testing MAFs, just haven't done it yet. I have an aftermarket warranty, supposedly covering everything but the wear items (brakes, clutch, wipers, etc), but for a $200 deductible, I was wondering if it's possibly anything I can check myself. Plan on checking MAFs today or Saturday... Any input appreciated, thanks.
 

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Do you have the maintenance records on the car and what all has been replaced over the years? If the MAF's have never been replaced on your '00 car then I would first do that.
 

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Discussion Starter #3
Do you have the maintenance records on the car and what all has been replaced over the years? If the MAF's have never been replaced on your '00 car then I would first do that.
I don't have them, and will have to get them. But I'm guessing that they probably are the original MAFs, or have just been cleaned.
 

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Get a code reader and pull the codes, even if there is not a SES light showing. The usual culprits in the absence of codes are:

1) MAFS
2) pre-cat O2 sensors

Strange, though, that everything was working well until now...the above items usually degrade performance slowly over time, such that the loss of performance is difficult to perceive until the items are changed out. So you may have a different issue.

Good luck!
 

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Discussion Starter #5
Get a code reader and pull the codes, even if there is not a SES light showing. The usual culprits in the absence of codes are:

1) MAFS
2) pre-cat O2 sensors

Strange, though, that everything was working well until now...the above items usually degrade performance slowly over time, such that the loss of performance is difficult to perceive until the items are changed out. So you may have a different issue.

Good luck!
I'm no expert, but that makes sense to me. Though I do remember reading a thread where somebody had MAFs go bad on them seemingly overnight, but still. It sucks not having the beast at full power. The worst is that now everybody wants me to drive them everywhere, and I'm having to make up creative reasons why I can't... Don't want to hear "I thought this thing was supposed to be fast!" come out of anybody's mouth.
 

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I'm no expert, but that makes sense to me. Though I do remember reading a thread where somebody had MAFs go bad on them seemingly overnight, but still. It sucks not having the beast at full power. The worst is that now everybody wants me to drive them everywhere, and I'm having to make up creative reasons why I can't... Don't want to hear "I thought this thing was supposed to be fast!" come out of anybody's mouth.




+1
 

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Get a code reader and pull the codes, even if there is not a SES light showing. The usual culprits in the absence of codes are:

1) MAFS
2) pre-cat O2 sensors

Strange, though, that everything was working well until now...the above items usually degrade performance slowly over time, such that the loss of performance is difficult to perceive until the items are changed out. So you may have a different issue.

Good luck!
Will the pre-cat O2 sensors degrade performance if they have gone bad but no SES light or code? How about the post-cat sensors?

Are these just plug-n-play sensors and easy to replace?
 

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Will the pre-cat O2 sensors degrade performance if they have gone bad but no SES light or code? How about the post-cat sensors?

Are these just plug-n-play sensors and easy to replace?
Yes, the pre-cat O2 sensors can degrade performance without throwing codes (from my reading on the board). The post-cat O2 sensors, I as understand it, should have no effect on performance.

The O2 sensors are plug and play. There are plenty of great write-ups on installation on the board - check the FAQ sticky first.
 

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Discussion Starter #9
Sluggish Beast Update

History:
- Beast started acting sluggish about a month ago, cleaned the MAFs and didn't see any improvement.
- Got progressively worse until I was almost afraid to drive it for fear of stalling in an intersection.
- Dealer (mistake #1) pulled codes and diagnosed as bad MAFs, replaced under service agreement, SES light went away, but still sluggish.
- A day later SES is back on, beast is still slower than usual.
- Take it back to dealer (last mistake) a few days later so they can fix it for sure this time. Pull 'Secondary Air System' codes... Hear "Remove engine heads"... "possible carbon buildup"... And I'm thinking, 1) I'm pretty sure that's not what's making my car go slowly, 2) there's *NO* way I'm letting a dealer disassemble my engine, and 3) If there's a problem I know of a chip solution thx to m5board.

From what I've read, the secondary air system won't make the Beast go slower, so I'm taking it to a trusted Indy on Friday. I think the $tealership is just chasing codes and hoping that I don't notice. In the meantime, my Peake reader is on the way so soon I won't have to have it diagnosed elsewhere anymore. I guess my question is, will carbon buildup, in either the SAS or heads, effect performance? My take on it was "no".
 

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History:
- Beast started acting sluggish about a month ago, cleaned the MAFs and didn't see any improvement.
- Got progressively worse until I was almost afraid to drive it for fear of stalling in an intersection.
- Dealer (mistake #1) pulled codes and diagnosed as bad MAFs, replaced under service agreement, SES light went away, but still sluggish.
- A day later SES is back on, beast is still slower than usual.
- Take it back to dealer (last mistake) a few days later so they can fix it for sure this time. Pull 'Secondary Air System' codes... Hear "Remove engine heads"... "possible carbon buildup"... And I'm thinking, 1) I'm pretty sure that's not what's making my car go slowly, 2) there's *NO* way I'm letting a dealer disassemble my engine, and 3) If there's a problem I know of a chip solution thx to m5board.

From what I've read, the secondary air system won't make the Beast go slower, so I'm taking it to a trusted Indy on Friday. I think the $tealership is just chasing codes and hoping that I don't notice. In the meantime, my Peake reader is on the way so soon I won't have to have it diagnosed elsewhere anymore. I guess my question is, will carbon buildup, in either the SAS or heads, effect performance? My take on it was "no".
how many miles on the beast??
 

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Have your mech do an old fashioned analysis. Cars need fuel and spark and then need to get the spent gases out. Rare that there is a spark issue (dying battery, but no indication of starting problems, correct?)

So he should check things like fuel pump (and pressure), fuel filter, and possibly clogged cats (rare, but it happens occassionally). Symptoms sound like lack of fuel since this is degrading over time and you can't get any revs, but it is pretty tough to diagnos over the internet.
G/L.
Regards,
Jerry
 

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sluggish beast

all, I have been monitoring this forum for some time now, but this is my first post, so be patient.
I have a very similar issue with my 00' 125K miles. It seems that the car wants to run, but something is holding it back. It is somewhat sluggish, and I can't figure out what it could be. I have already replaced the plugs (100K miles), brand new air filters, and new MAFS (about 8k miles). In reading some posts, it seems it could be caused the the pre-cat O2 sensors, but I have not gotten any codes. On a side note, not sure if it is related, but I am also getting an audible noise which seems to be linked to engine speed. It is very noticeble @ 2200k RPM, but then gets drowned out by the higher engine sound above that. It is like a constant Huum, Huum noise in that RPM range, regardless if the car is moving or not. Clutch in, or out... I have ruled out the fan clutch, and I am pretty certain it is not related to the vibartions associated with the power steering and engine oil canisters (although the hum seems to be comig from that area of the engine compartment). Again, I am a first poster, but do appreciate all the info I have gotten off this forum.

TIA
 

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Discussion Starter #14
all, I have been monitoring this forum for some time now, but this is my first post, so be patient.
I have a very similar issue with my 00' 125K miles. It seems that the car wants to run, but something is holding it back. It is somewhat sluggish, and I can't figure out what it could be. I have already replaced the plugs (100K miles), brand new air filters, and new MAFS (about 8k miles). In reading some posts, it seems it could be caused the the pre-cat O2 sensors, but I have not gotten any codes. On a side note, not sure if it is related, but I am also getting an audible noise which seems to be linked to engine speed. It is very noticeble @ 2200k RPM, but then gets drowned out by the higher engine sound above that. It is like a constant Huum, Huum noise in that RPM range, regardless if the car is moving or not. Clutch in, or out... I have ruled out the fan clutch, and I am pretty certain it is not related to the vibartions associated with the power steering and engine oil canisters (although the hum seems to be comig from that area of the engine compartment). Again, I am a first poster, but do appreciate all the info I have gotten off this forum.

TIA
I know what you're talking about. As far as I can tell the engine is running ok - Revs fine, no noises, no hesitation, no stutter... just slow? My Peake reader is on the way so I'll report what I see when I get it. For the noise, I guess the VANOS is supposed to make some noise?
 

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Discussion Starter #15
Have your mech do an old fashioned analysis. Cars need fuel and spark and then need to get the spent gases out. Rare that there is a spark issue (dying battery, but no indication of starting problems, correct?)

So he should check things like fuel pump (and pressure), fuel filter, and possibly clogged cats (rare, but it happens occassionally). Symptoms sound like lack of fuel since this is degrading over time and you can't get any revs, but it is pretty tough to diagnos over the internet.
G/L.
Regards,
Jerry
Thanks for the feedback, Jerry.
 

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Matty747, I would be very interested about what you finally find regarding the sluggish factor. In the meantime, I have a scheduled appointment with an INDY for the noise. I just can't take it anymore, and it is driving me crazy. I have resorted to leaving the beast at home and driving my trusty (and rusty) E34 with 170K miles, but still running like a champ
 

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Discussion Starter #18
Could any of these unknown power issues be caused by slight clutch slippage? The effects are usually greater in lower gears, just a thought.
I have thought about it, it's a possibility. Would that yield an SES light? I still have SES lit... Before I had the MAFs replaced the car was becoming really hard to drive (i.e., sputtering, strange idle behavior), but now that it has new MAFs it is at least running smoothly, albeit more slowly.
 

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I've read on other posts that the car could be running too rich as a result of the pre-cat O2 sensors going bad. Would this make it feel sluggish. I did notice that my tailpipes have some black sut on the inside. Another post mentioned that cleaning out the Oil Separator Canisters will help. Not sure what that would do...
 

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My money would either be on the precat 02's or fuel filter...

I need to do both of those items this summer just as preventative maint.

If it was your MAFS i think you'd notice the car running a bit rough/choppy when cold. same is true (i think) with the precat 02's. it could also be a combination of said components.. if none of them have been renewed, just start running through the list. most are easy DIY.

- Tim
 
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