engine issues at WOT

[emdoe]

Hey everyone,

This is my first post on this board. Earlier today I just picked up my first BMW, a 1997 318is coupe in white. My last car was a modified Mazda MazdaSpeed Protege. That thing was pretty fast when I was done with it(13.1 ets), but I just need that RWD Anyways, The car has about 110,000 miles on it, and as I was driving it back to my home today I noticed that there was an issue that is scaring me a bit. Whenever I go to wide open throttle, right as I am coming up to the 4500rpms mark the car just has this horrible stuttering and bucking sensation, and can't really produce more power. It has happened in all the gears, and is the same each time. It also seems like the electrical system gets weaker during these episodes cause the lights flicker a tad dimmer. I am hoping it is something simple like dirty duel system or sparks or something. I bought some seafoam and new plugs for now, will throw them in today or tomorrow and see if it helps. I searched around the board a little bit but couldnt find this problem anywhere else. Is there anyone out there who could help shed some light on the situation. Im hoping I dont need a new fuel pump and filter too......arrgh

 

[Kirby]

Other than dirty fuel filter, injectors, or bad pump, at that RPM range, it *might* be a problem with the DISA control. The 318 4 cylinder has a dual intake runner setup that changes the intake manifold porting at around 4800 RPM. Basically a vacuum solenoid moves a butterfly valve inside the intake, and changes from long runners to short runners.

 

[emdoe]

so any suggestions about how to resovle this problem without spending a lot of money taking it to a bmw tech?

 

[emdoe]

could anyone point out this solenoid to me so that I could make sure it is properly connected, and not cracked or leaking or stuck?

thanks

 

[Kirby]

Click Here

Part Number 6 is the DISA control unit.

 

[emdoe]

i found this thread somewhere else on the forum and I thought it might pertain to the problem im facing, any thoughts??
thanks

http://www.318ti.org/forum/showthread.php?t=5019

 

[Kirby]

Do you have a check engine light on? Have you checked for any stored codes?

 

[emdoe]

occasional cel for front o2 sensor, goes off and on, thats it

 

[Kirby]

The O2 sensor problem might cause the power problem, don't know to what extent though. It uses the O2 sensor to adjust air/fuel ratio. I would fix that first, see what happens then.

 

[emdoe]

i have now installed new spark plugs, belts, coolant, fuel filter, full seafoam cleaning of engine, fuel lines and intake, and im still hitting his wal at 4000 rpms, it just wont go past that mark, and just bounces off, even in nuetral

 

[epj3]

i have now installed new spark plugs, belts, coolant, fuel filter, full seafoam cleaning of engine, fuel lines and intake, and im still hitting his wal at 4000 rpms, it just wont go past that mark, and just bounces off, even in nuetral

You said you get occasional check engine lights for the O2 sensor, but that is the one thing you didn't replace?

It is most likely bad, and possibly the cause of the problem. I'm not sure if OBDII cars are different than OBDI when the O2 sensor fails, but in OBDI, the engine runs in an open loop mode where it uses a pre-determined amount of fuel. It will get bad gas mileage and the exhaust will be filled with pollutants from running rich. I have a feeling OBDII might be programmed to run in open loop but to limit to 4,000 rpm or whatever to keep from burning up the catalytic converter. Again - definitely could be wrong on that. Just becuase the CEL for the O2 sensor isn't constantly on, does NOT mean it isn't bad ALL the time. The O2 sensor sends a specific voltage range to the car's computer, and will only display the check engine light if the voltage reading is out of range. A sensor can fail but still be in range, so the computer assumes it is fine - but will still not send the correct information to the engine.

 

[emdoe]

im starting to think its my tach thats actually off and im hitting redline but only seeing 4500....has anyone encountered this at all with these cars? thanks

also, what does bank one o2 sensor mean...is that the first or second sensor, thats what is showing up on the scantool.

 

[emdoe]

any thoughts about the tach? it says it shows the idle at 300-400 which im pretty sure is impossible and if im correct then it is the tach that is messed up. I also noticed the mpg gauge seems farked and the speed reading seems about 2-3 mph slow.

 

[Kirby]

I can't speak specifically for a BMW tach, but I can tell you about other electronic tachs. The tach in my boat was reading high. My boat has a V8 in it. I removed the tach, and found that there was a switch on the back that was labeled 4/6/8 . This switch told the tach how many pulses from the ignition primary represented one revolution of the crank. The switch was dirty, turning it a few times cleared up the problem.

Again, I have no idea if there is a selection switch inside the panel for a BMW, or if this is determined by the ECU. I would actually think that the ECU would just send the proper voltage/pulses to the tach, since the ECU is specific to an engine.

It could just be a failure of the tach itself, but seems odd that all the gauges are affected. If you had a grounding problem, I would expect intermittent operation rather than odd readings...