Car Jerks When Accelerated Hard -UPDATE-

[Nathan]

This just showed up and it is seeming to get worse. It started that when I pushed down far on thethe accelerator the car would jerk a little bit and the revs would not increese. I found that if I slowly accelerated it would not do it. After driving for a little bit, it seemed to have gotten worse. When I finally got home, I put it in neutral and then the idle starts going wierd. Going up to 1500 then dropping to like 500 back and forth. Could somone please help me track down this issue? I've got suspicions against the ECU but it is supposed to be the one with improoved idle control? Anyway, all help will be greatly apreciated.

Thanks,

-Nathan

[Nathan]

New Info:

Just went out and tried it. The idle problem seems to be gone... I didn't mention before but my low beems have randomly stopped working, not sure when the car was out of my possession for awhile. When I turn the high's on (which do work) the Idle RPM's drop like 3-4 thousand. When I start the car it cranks fast so i'm sure my battery is fine. Maybe there is a short involving my headlights cuaseing issues? Anyway, just another piece to the puzzle.

-Nathan

[kowalski]

could be a short but it also could be a vacume leak... check your running voltage

[Nathan]

Another update - It is still doing it... The idle seems high at about 1200 rpm's and the jerking only happens when the throttle is romped BELOW 2000 rpm's. I really need some help on this guys, If you know anything please help!

Thanks,

-Nathan

[Nathan]

I am going to check out the connection on the AFM inside. Jordan had a similar problem with a bad connection in the AFM. Modified it so that the connection was better.

[nando]

did that fix it?

otherwise I would check your two reference sensors, if they go bad your timing will be all wonky.

[Nathan]

My reference sensors are fine, just went through fixing a problem where the car would crank but never start. I will probably check the AFM tomorrow and post an update, but i'm still excepting idea's on what other kinds of things cuase these symptoms.

[Nathan]

AFM looks great, so I don't think it is that... I'm going to try switching back to my original ECU this weekend and see if the problem persists.

[Nathan]

So, now it has stoped starting altogether. At first I could start it by popping the clutch, which was wierd becuase that should not have worked. The ignition still cranks when I turn the key just fine but will not start; very similar to just a week ago when it wasn't starting, in fact exactly like it. I've checked and or changed all of my relay's in the fuse box. Headlights still don't work (low beams, may or may not be related). I'm without a Bentley manual so if anyone has any links to pdf wireing diagrams and such for my car that would help immensly. If I can't get this car started it will have to sit for 2 weeks without my attention, not to mention I will be without a car for 2 weeks...

[Nathan]

Well, Now it is starting again. The terminals on the Igniton Coil were loose(?) for some reason so I tightened them and it started right up. Now the only problems are that my headlights still don't work and my idle is unsteady when the car is warmed up. The idle varies between 1300 and 700 RPM. It moves up till it hits 1300 then drops to 700 and up to 1300 as long as it idles. If I pull toward me on the turn signal stock (flashes all of my lights) the Idle returns to normal. I think the light problem and idle are related. I know somthing is wrong between the headlight switch and fuse box. The lights and relay and fuses are all in working order. So still need any help anyone can provide.

Thanks

[bichmgnt]

What model car? Idle issue sounds like Idle Control Valve if it has one or idle computer. Check it by pulling the plug off the ICV. If nothing changes it might be the problem. That's for the 325e or es. Otherwise check for an air leak on the intake boot or other places. Lights - check the low beam relay - I think its the one in the fuse box closest to the rear middle of the car, i.e., the one it would be easiest for the passenger to touch if he could reach through the dash to touch it. Pull it, tap on it, check it with a multimeter if you can. As for why it all seems related your guess is as good as mine.

Good luck.

Steve

[Bryson]

I was about to tell you to check your damn distributor/wires/plugs/coil, but it looks like you figured that one out for yourself. Your coil could be bad, does the engine still buck? Try replacing the coil if it does ($50 new)

[Nathan]

I plan on getting a new Ignition Coil. All of the relays are good. I can get the low beams to turn on when I pull the turn signal stock towards me with the lights on (I know they are on becuase when I turn the headlight switch off the Low beam housings dim a bit, like one of the dual filiments goes out i.e. the lowbeam or highbeam one.) The car is not bucking anymore (thank god!). But there is definetly an idle problem, but only after the car is warmed up. It isn't time based but actually heat. However, when I intitially start the car, whether or not he engine is warm it doesn't have the issue untill after I start moving.

PS: I had the car model in the post, must of deleted it... 325e 1985

[Nathan]

OK, Just checked the ICV, and the idle fluctuation sped up when I pulled it. I'd say it about doubled in speed. What does this mean? Is it fine? Thanks for the suggestion.

[BMWE30]

o2 sensor

I can almost guarentee it from what you described.

Your ICV sounds fine if it sped up unplugged, and came back down when you plugged it back in. Try cleaning that too.