lag at WOT

[jrobie79]

driving down the highway in 5th gear tonight, and I noticed when I went to pass someone and pushed it, there was almost a hesitation, kinda stuttered for a bit...only at WOT tho, it would still accelerate if I let off even just a tad

was thinking maybe the fuel pump on its last legs?

[jlevie]

A weak pump, flaky FPR, or clogged injectors are possibilities. But also check the WOT switch in the TPS. If it is bad the engine will be down on power at high rpm.

[jrobie79]

new development....it happens in all gears, when I push it to get onto a highway and/or passing people, and sometimes its not even at WOT, just during 'spirited' acceleration and the check engine light pops on, but as soon as I lift my foot off the gas it goes out...definitely a huge loss of power and while the check engine light is on the car would barely accelerate if at all, kinda just stayed constant or even slowed down a little going uphill.

Thinking maybe one of the sensors or TPS? I dont think the fuel pump would cause the CEL to come on, no?

[IRON-E]

I'm on an aftermarket MAF system, and I have felt the same as OP. I've had this issue for quite some time (maybe a year or 2) but can't pin it down, though I have not checked my injectors lately., I'm willing to bet that it will be the actual MAF or in the OP's case AFM.
I've replaced the TPS, FPR, plugs, cap & rotor and still the same results.

[jrobie79]

I'm gonna clean out my AFM and take some resistance readings on my crank and cam sensors and see what happens (that is assuming I can make it home tonight)

[jrobie79]

it seems like I have code 1234 popping up, which would make sense b/c my speedometer doesnt work right now (wires are cut) but that shouldnt cause these problems right?

[jlevie]

I'm not sure what DME does with the speed signal on this car. I'd say to fix the speed signal problem and see what affect, if any, it has.

[jrobie79]

it hasnt been connected for over a month, dunno why it would suddenly create a problem now. I'm still gonna check the resistance of the sensors and use my sisters TPS to see if that helps.

Thanks tho! hopefully I can make it home tonight without AAA

[Xat1cZ]

I've had similar sounding stuff happen when the alternator was going bad..

but then you would notice other electronics go off .. it might not get enough air .

[jrobie79]

have to rescind my previous statement.....popped in a known working TPS, still have the same issue, although the check engine light didnt go on this time, will know more on my way to work tomorrow

[jrobie79]

so its getting a bit worse, I still drove an hour to work today, and everything seems fine for the first 20-25 minutes of my trip...it does seem to not have as much top end power when I am trying to really accelerate, but there is no stumbling or hesitation.

fast forward to about 25 minutes into my trip and the problem comes back, so bad that I had to pull over on the highway and get all frustrated, so I shut the car off, and start it bcak up and it seems the problem is gone again (at least to the extent previously explained)

I unplugged the o2 sensor as someone suggested this was the problem...no dice, I changed the TPS to a known working one....same problems.

I'm going to check the resistance of the sensors when I get back to my parents house this weekend, crank, cam, coolant temp, etc...

does this help at all with a possible diagnosis?

[Xat1cZ]

Have you had a computer hooked up to it for a diagnosis? does it seem like it could be that the alternator doesn't charge properly

[jrobie79]

No I havent, where/what kind of computer would be used for this?

[Xat1cZ]

I use Carsoft, it's a program that reads the ECU and can be used on a "normal" computer .. you just need correct plugs to be able to plug it into the connector in your engine bay ...

any BMW dealer could (should) do it for you tho'


that:
http://www.carsoftinternational.com/...oft_bmwv73.htm