Looking for some help on e36

[zohaibrose]

Hello everyone I have a 98 m52 e36. I've owned it since this February and ever since the first day I got it it just doesn't feel the same I remember when I took it for test drive I would floor it and it would respond asap and feel like from factory and when I would rev it up it would come back to normal idle quickly. Now that im dailying it in fourth gear I floor it and car doesn't rev past 3k rpms. Idk if it's my bad cats or maybe that stupid muffler delete. I really don't have any fuel or air related air leaks. So was wondering what kind of issues you guys could think of

I sometimes rev the car in neutral and when the rpm needle comes down it doesn't maintain a proper idle. Like it will come back down to 800 revs then in a couple seconds eventually fall back down to my normal 600 revs it just doesn't feel smooth when flooring it or maintain proper idle. I get bad mpg too and isn't smooth as from February. I've cleaned icv,replaced maf,vcg all types of things and I do have a sucking sound when removing the oil filler cap wonder what that's for I just put in a new ccv and hoses. Replaced all vaccum lines too any ideas. No shop is helping me out because they say car is too old.

[323i E30]

Does the idle change when removing the oil filler cap (with engine at operating temp)?
It should, as you're creating a vacuum leak when doing so. If it doesn't, you might want to have it doublechecked for vacuum leaks.

[Pelican Parts]

Try pulling the codes. Did the car come with the straight pipe/muffler delete or is this something you did after purchasing it? If the latter, that's probably what is causing your less than ideal gas mileage. How are your injectors looking?

[zohaibrose]

Does the idle change when removing the oil filler cap (with engine at operating temp)?
It should, as you're creating a vacuum leak when doing so. If it doesn't, you might want to have it doublechecked for vacuum leaks.

yeah it starts to freak out and run rough, also has a suction noise.

- - - Updated - - -

Try pulling the codes. Did the car come with the straight pipe/muffler delete or is this something you did after purchasing it? If the latter, that's probably what is causing your less than ideal gas mileage. How are your injectors looking?

no i did the muffler delete. only codes are a evap code of P0446 which is prob why my gas tank hard to fill past 7 gallons but yeah no other helpful codes. i took fuel injectors out they dont seem to have any broken o rings and i did a ressistance test on them they were all very equal to each other.

[MarcoZandrini]

Is the fuel pump original? When was the fuel filter last changed? The engine refusing to rev passed 3000rpm could be a fuel delivery problem.

[328 Power 04]

or clogged cats

[zohaibrose]

Is the fuel pump original? When was the fuel filter last changed? The engine refusing to rev passed 3000rpm could be a fuel delivery problem.

Yes new filter and air and not necessarily refuse but it will go past it in a long time so basically I feel a loss of power

[MarcoZandrini]

Unfortunately the you engine doesn’t have a fuel pressure test valve on the fuel rail like the M54 engine does. Did you scan the computer for codes?

[bmwdirtracer]

or clogged cats

this.

[zohaibrose]

Unfortunately the you engine doesn’t have a fuel pressure test valve on the fuel rail like the M54 engine does. Did you scan the computer for codes?

M52 does have test valve, well at least mine does