[335i Pal]

I have been having some issues with my car the last few months where I am not getting full boost and have checked the vacuum lines...nothing wrong there. I have yet to check the boost pressure, which is not the easiest thing. But I don't think that is the issue, wouldn't I keep losing boost the longer I have the issue? So far everything is staying steady. But doing some research I couldn't find out on the jb4 what the under/over boost on target function did or how to read it. Assuming if it is always in the middle I am good, under WOT I only get to about 1/4 range

I have checked codes and I have the fuel pump plausibility code and just last week I had a cylinder 5 misfire code. Thinking my fuel pump might be going out again, would this keep me from getting full boost?

2007 e90 335i
93 octane always
BMS DCI
JB4 G5 iso Map 5

[335i Pal]

Forgot to mention I can not get over 12psi....if I'm lucky.

[335i Pal]

No one have any info on the under/over boost feature?

[Jeff@TopGearSolutions]

We would need logs...

Move your coilpack to Cylinder 6, see if the misfire moves, that won't cause a boosting problem unless you go into limp mode.

The only way you can have a boost problem is if you have a leak. (assuming your tune is fine, which it should be).

There are several vac/boost lines on this car, including under the engine cover, near the intake manifold, near the boost canisters by the turbo's. Any could have hairline fracture or leaking under boost.

The car will throw an underboost code if you go wide open throttle for 4 seconds and underboost. (30FF underboost code). Charge pipe connection before and after the intercooler also need to be checked.

If you have any aftermarket FMIC or charge pipe they are usually the culprit 9/10 times.

[robc1976]

Check you selonoids, mine did exactly as you are stating...I will post before and after logs.

[WilliamS]

Originally Posted by robc1976

Check you selonoids, mine did exactly as you are stating...I will post before and after logs.

How do I do this. My car isnt getting over 7psi regardless of Map.

[robc1976]

Originally Posted by Goofyguy

How do I do this. My car isnt getting over 7psi regardless of Map.

if that is case you have a huge boost leak....check the following:

1. Charge pipe to throttle body "c clip" may not be seated
2. intercooler connections
3. Brake booster line is plugged in correctly
Check lines that go from break booster vacuum lines under the valve cover and go to vacuum canisters (I replaced mine with silicone vacuum lines.

[WilliamS]

Im thinking its intercooler connections. My front end was rearranged by a deer a month ago. I just got the car back yesterday. I can hear a ton of air movement but I dont know what to start with. The body shop did a great job on the car, but I just cant bring it back to them as they didnt know much about the car. So Im going to tackle this one. The paint matches, the lines are straight, no over spray anywhere. Just a huge boost leak somewhere.

[Jeff@TopGearSolutions]

All you need to then is get under the car and see if pipes are not attached.

One going in to intercooler and one going out.

The intercooler may have been damaged and they did not know, this would cause an excessive boost leak and would require you to replace it.

You will need to remove the under paneling on the bottom of the car to get a good look.

Otherwise you need to check the remainder of piping post intercooler to your charge pipe which leads to the intake manifold.

If this is out of your league I would suggest bringing it to a competent shop or dealer.

There are way too many areas to cause a boost leak and without any of us looking at the car we are just guessing.

[WilliamS]

Originally Posted by Jeff@TopGearSolutions

All you need to then is get under the car and see if pipes are not attached.

One going in to intercooler and one going out.

The intercooler may have been damaged and they did not know, this would cause an excessive boost leak and would require you to replace it.

You will need to remove the under paneling on the bottom of the car to get a good look.

Otherwise you need to check the remainder of piping post intercooler to your charge pipe which leads to the intake manifold.

If this is out of your league I would suggest bringing it to a competent shop or dealer.

There are way too many areas to cause a boost leak and without any of us looking at the car we are just guessing.

Brand new intercooler. I can get a few pounds so its got to be something in the system with a small tear I would assume. Im going to get it on a lift in about an hour. I was just looking for situations that people have run into.

Found it, hole about the 8mm in the charge pipe before the intercooler. Found it quick. Gave me good areas to start.

[335i Pal]

I have checked all the vacuum lines and they are good. Checked the boost tubes and everything seemed solid( did not do a pressure or smoke test). If it is the solenoids wouldn't the vacuum lines not hold pressure?

That's why I am thinking there may be a fuel pump issue.