[tomtom11]

hey everybody. i have an 08 335i with about 63,000 miles on it. i have a jb4 and the car pulls really really hard once i get to about 4,500 rpm, but anything under that even with full throttle the car doesnt really pull very hard and then it just takes off at 4,500 rpm. I feel like the power used to be more linear and I had more power down low. I will do a log if it will help, but would like to know if anybody has any thoughts before I go into the engine bay and start taking things apart to do a log. I know it's not a boost leak because I use map 2 and when im flooring it at say 50mph in 4th gear all the way up to 4,500 rpm i'm getting 14.5psi but I still feel like I'm not accelerating like it used to. then at 4,500 rpm it is still at 14.5psi but the car takes off. I don't have a rough idle or any codes or anything. Thank you.

[BlackBB6]

If your plugs and coils are up to date you might need a walnut shell blasting. I got mine done around 65k. If you're 6MT maybe your clutch is going out.

[tomtom11]

I havent changed my coils because everybody seems to say that the coils eithe rare working or they are not, they dont degrade in power prior to them dying. I dont have any missfires or anything so I think my coils are ok. unless my understanding of changing the coils is incorrect which is entirely possible. I was leaning towards the plugs and the walnut blasting as well, but can the gunked up intake cause it to feel that slow, but then completly normal after 4,500rpm, is that a common symptom?

[BlackBB6]

Yeah, you'll definitely know when a coil is bad, I did all of mine at 80k just to be safe. Regarding the blasting, I was getting what felt like extra lag when I would go WOT, like a brief pause and then it would throw you back. After blasting there wasn't the 'extra lag' feeling and acceleration was very smooth compared to before.

[Cloud9blue]

did you monitor the timing? pulled timing will cause the most significant power loss, aside from a low boost.

if it is timing, check your gas quality, plugs, and carbon buildup. 14.5psi can be too high of a boost for the car to sustain a healthy ignition timing is you can only get crappy 91 gas, assuming you are not using methanol or mixing ethanol to the gas.

[tomtom11]

is timing something that shows up on the logs? I have downpipes and an intake and have only filled the car up with Shell 93 Vpower for the last 60,000 miles. how do i check the timing and what should it be? and will the timing be fixed with new plugs and a cleaned intake system?

[BlackBB6]

Yes, you can log cylinder timing and/or cylinder timing correction. The DME will pull timing for a number of reasons though, it might not be as simple as plugs and a blast. High intake temps will pull timing too.

[tomtom11]

will do, I am leaning towards a walnut blasting because the car has 62,000 miles on it and has never had it done. and i think i changed the plugs like 30,000 miles ago so probably a good idea to change them as well.

[Jeff@TopGearSolutions]

Post a log from 3rd gear at 2500 RPM to Red line at Wide Open Throttle on Datazap.

[Zach1328]

Originally Posted by tomtom11

will do, I am leaning towards a walnut blasting because the car has 62,000 miles on it and has never had it done. and i think i changed the plugs like 30,000 miles ago so probably a good idea to change them as well.

My '08 535i feels the same way. It is bone stock and just about to hit 60k miles and the intake valves have never been cleaned. The lack of low end power was hard to notice until I got a 335i because the power drops off gradually as the valves continue to get dirtier.

My 335i has 78k miles on it but has certainly had the valves cleaned as the lower end torque feels unbelievable compared to the 535i. I'll be cleaning the 535i intake valves soon and I'm very interested to see how dirty they are. I drive pretty spirited and down here in 100F, humid Houston weather I can only imagine how bad it is

[stanlalee]

Add backend pump flash. Wastegate setting? (not that I know anything about them but I've heard if they are adjusted open too much to eliminate wastegate rattle it effects low end power.

[BlackBB6]

Originally Posted by tomtom11

will do, I am leaning towards a walnut blasting because the car has 62,000 miles on it and has never had it done. and i think i changed the plugs like 30,000 miles ago so probably a good idea to change them as well.

Tuned plugs will last maybe 15k miles if you're lucky, I would start there.

[tomtom11]

alright so I have not had a chance to do a log yet, but i thought maybe it was just a bad tank of gas to i filled up with a fresh tank of shell 93 vpower today and then got on the highway to go to work and put it in 4th gear at around 3,000 rpm. when i got to about 4,200 rpm i got a cel and the car said it had reduced power. i immidetly turned the jb4 to map 0 so i hope it doesnt auto delete my code. i then pulled off to the shoulder and restarted the car and there was no cel. I hope the code did not autoclear, i will scan it tonight.

[tomtom11]

alright so i scanned it and got the following codes:



the catalytic converter codes are probably just from turning the jb4 off and the catless downpipes throwing a code. i saw the fuel pump code, but i thought the HPFP symptoms were more like long crank starts and i dont have that at all.

[Jklad]

It's possible codes are from jb4hiwever I had both 29f4 and f5 and don't use jb. Replaced my low pressure sensor and codes never came back.

Not sure about your other codes - maybe a high pressure issue, or hp sensor, but someone with more knowledge should hopefully chime in. Both sensors easy to replace.

[tomtom11]

UPDATE: alright so this may add to the confusion or may help one of you solve my problem. I turned the jb4 to map 0 and it feels like it always did when it didnt have a tune. so i have none of the hesitation under 4500 rpm and it pulls harder than the jb4 has been at low rpm with moderate throttle. the jb4 obviously use to be way faster than stock, but now it doesnt feel as strong as stock, one of the settings must be messed up or something. does anyone have any idea what could cause the car to feel perfectly fine with it on map 0, and have no power until 4500 rpm with the tune on map 2 or 5? thanks

[tomtom11]

bump

[els_86]

Originally Posted by tomtom11

UPDATE: alright so this may add to the confusion or may help one of you solve my problem. I turned the jb4 to map 0 and it feels like it always did when it didnt have a tune. so i have none of the hesitation under 4500 rpm and it pulls harder than the jb4 has been at low rpm with moderate throttle. the jb4 obviously use to be way faster than stock, but now it doesnt feel as strong as stock, one of the settings must be messed up or something. does anyone have any idea what could cause the car to feel perfectly fine with it on map 0, and have no power until 4500 rpm with the tune on map 2 or 5? thanks

If turning the jb4 to map 0 fixed it then the only logical explanation would be timing right? If it was the intake valves you would feel it whatever map you are on. Did this just happen all of a sudden or has this been an issue for a while?

[tomtom11]

alright so the problem started about a week ago. i have been running the same jb4 setup for the past several months with no issues whatsoever. but last week it started hesitating on acceleration so i thought it was the intakes that needed to be walnut blasted. it wasnt until a few days ago that i tried turning off the jb4 and it fixed the problem. so i dont know why all of a sudden the jb4 doesnt like my car lol. does anyone have any idea why this would suddenly start happening?

[Jeff@TopGearSolutions]

As I said previously, post up a log, otherwise all we can do is have you blindly replace parts.

If your plugs have over 20,000 miles on them you should replace those anyway.

If you dont want to blindly replace parts I'd suggest logs and I'd also suggest pulling your plugs and looking at them and checking the gap.

You can also check the condition of your plugs for signs of fouling. Gotta get back to basics.

You can also reset adaptations on the car, clear all the codes and see what comes back.

Those are the things I would do if it was my car.

[tomtom11]

Originally Posted by Jeff@TopGearSolutions

As I said previously, post up a log, otherwise all we can do is have you blindly replace parts.

If your plugs have over 20,000 miles on them you should replace those anyway.

If you dont want to blindly replace parts I'd suggest logs and I'd also suggest pulling your plugs and looking at them and checking the gap.

You can also check the condition of your plugs for signs of fouling. Gotta get back to basics.

You can also reset adaptations on the car, clear all the codes and see what comes back.

Those are the things I would do if it was my car.

thank you very much for the reply. i will do a log when i get a chance soon, i just didnt know if these symptoms seemed common for a specific jb4 parameter that needs to be changed. thank you

[els_86]

Originally Posted by Jeff@TopGearSolutions

As I said previously, post up a log, otherwise all we can do is have you blindly replace parts.

If your plugs have over 20,000 miles on them you should replace those anyway.

If you dont want to blindly replace parts I'd suggest logs and I'd also suggest pulling your plugs and looking at them and checking the gap.

You can also check the condition of your plugs for signs of fouling. Gotta get back to basics.

You can also reset adaptations on the car, clear all the codes and see what comes back.

Those are the things I would do if it was my car.

I am tuned for 5k miles and with 35k miles on my car and plugs have never been changed Jeff. Would you suggest changing them? I was gonna wait til like 40k miles or a misfire because I figured if car was running nicely why spend money if I don't have to...