Author Topic: Engine bogs unless given full throttle. (Read 6011 times)

JoeDellio · « **on:** February 07, 2011, 06:23:07 AM »

Ive read the other bogging threads. I have no CEL. Car bogs down unless I give it full pedal, this has gotten worse over the past couple weeks. I didnt think it was a fuel issue since it responds to full throttle, but I really dont know. Whats new is the fuel pump, fuel filter, plugs and wires, and a coil pack. I can unplug the AFM and it doesnt change anything, so I dont know whether to rule it out or anything. This problem sucks thanks to the absence of a CEL.

Janne · « **Reply #1 on:** February 07, 2011, 09:38:26 AM »

Quote from: JoeDellio;101220

Ive read the other bogging threads. I have no CEL. Car bogs down unless I give it full pedal, this has gotten worse over the past couple weeks. I didnt think it was a fuel issue since it responds to full throttle, but I really dont know. Whats new is the fuel pump, fuel filter, plugs and wires, and a coil pack. I can unplug the AFM and it doesnt change anything, so I dont know whether to rule it out or anything. This problem sucks thanks to the absence of a CEL.

Maybe it is bad THROTTLE VALVE SWITCH (part number 5.) :http://www.realoem.com/bmw/showparts.do?model=BE51&mospid=47425&btnr=13_0578&hg=13&fg=15

JoeDellio · « **Reply #2 on:** February 07, 2011, 01:00:13 PM »

Thats the TPS I was wondering about, I guess its worth a shot unplugging and investigating. Im torn between buying any new parts because I dont have a CEL, I guess the TPS is a cheap start, then Ill waste money on a rebulit AFM

B318M42W · « **Reply #3 on:** February 07, 2011, 04:50:00 PM »

you can test out the sensors using a multimetre... the e30 ETM has all the goodies! the tps has a linear continual voltage change.

I really dont think the AFM is the culprit since the car responds at full throttle. might also be ECU?

whats the idle like?

JoeDellio · « **Reply #4 on:** February 07, 2011, 11:58:08 PM »

I lost the link on how to test the TPS, I didnt know you could test the AFM, It idles fine 90% of the time, if I come to a stop after the cars starts bogging the idle is choppy but clears out if I give it gas and then will idle fine. So youre saying if the AFM was bad it wouldnt respond at full throttle?

JoeDellio · « **Reply #5 on:** February 09, 2011, 05:27:52 PM »

Well guys, got my new TPS today and problems seem to be solved. I didnt test the new one because I was so anxious to get it in. It fired right up and idled at 2k for a second and then idled smooth. It doesnt hesitate at all anymore even going up hills at 45mph in 5th gear. Sooo, my TPS was bad and didnt throw a code.

B318M42W · « **Reply #6 on:** February 09, 2011, 06:56:46 PM »

great to hear you fixed your problem!

JoeDellio · « **Reply #7 on:** February 11, 2011, 10:05:02 AM »

WTF, car ran fine for days after the TPS was replaced, but now it fell on its face in 1st once yesterday and its been fine since then. Its startin to do what it did before it was totally undrivable.

doitover · « **Reply #8 on:** February 11, 2011, 01:51:53 PM »

From a purely debugging things in the lab point of view,

If you still have the old TPS, test it. If it wasn't bad and the short term improvment was due to replacing the TPS, it would have to be the connection between the ECU and the TPS. Could be that the connector is corroded or there is an intermittent open or short in the wire.

Cars can be frustrating though, especially 16 year old ones. The improvement after changing the TPS may have been completely unrelated.

JoeDellio · « **Reply #9 on:** February 11, 2011, 03:45:11 PM »

Quote from: doitover;101364

From a purely debugging things in the lab point of view,

If you still have the old TPS, test it. If it wasn't bad and the short term improvment was due to replacing the TPS, it would have to be the connection between the ECU and the TPS. Could be that the connector is corroded or there is an intermittent open or short in the wire.

Cars can be frustrating though, especially 16 year old ones. The improvement after changing the TPS may have been completely unrelated.

The old ones numbers were really screwy, so thats why I bought a new one, though I didnt check the new one. I guess Ill take it out and check it out for the hell of it.

DesktopDave · « **Reply #10 on:** February 11, 2011, 04:19:10 PM »

How old is your O2 sensor? Does the trouble happen only when the car is cold, only warm or both? I'm asking because WOT disables the O2 sensor.

JoeDellio · « **Reply #11 on:** February 11, 2011, 05:00:14 PM »

Quote from: DesktopDave;101373

How old is your O2 sensor? Does the trouble happen only when the car is cold, only warm or both? I'm asking because WOT disables the O2 sensor.

Dave, oxygen sensor has 30k on it, took it out and it looks real good. The problem happens when the car is warm. Then when I shut it off for like a half hour it hiccups again real bad at start up, which makes no sense hot vs cold. Its got me stumped, I dont wanna pull a AFM out of my wallet if I dont have to.

JoeDellio · « **Reply #12 on:** February 16, 2011, 12:13:13 PM »

I have pinpointed the problem to only happen after I shut the car off after being warm. If it sits for say 20 minutes, it will then bog when I start to go, then I floor it and its fine. Weird.

colin86325 · « **Reply #13 on:** February 17, 2011, 09:05:45 AM »

You could have a lot of carbon build up. Try running some Techron through the tank when it's aout 1/4 full. You can also perform a "hot soak" with a produt called Sea Foam.

fiftytakedowns · « **Reply #14 on:** February 22, 2011, 02:11:45 AM »

Im having similar symptoms? any luck?