My e30 Keeps BUCKING! PLEASE HELP!

[derty30]

Mine does the same ill be driving fine then brapapabraaaaapapa and my girlfriend gets whiplash lol. I haven't changed the plugs yet I plan on doing that tomorrow, so hopefully that's the problem! It is like the fuel cuts in and out.

[7pilot]

OP. What are the gauges doing when it is bucking?
The Tach and the water temp gauges specifically.

m

[jlevie]

The behavior of the tach and econometer can provide a clue as to the cause of cut outs. The tach signal is generated by the DME. So if the tach takes a big drop when an event occurs while the car is moving, the DME is loosing timing data or loosing power/ground, or hanging. If the tach doesn't react but the econometer drives towards zero there is a problem with fuel delivery.

Really sudden cutouts, as if you switched off the key, are almost always a problem with timing data or with the DME. Most of the time a fuel problem is more gradual. The exception to that, on late production 325's, would be bad connections through C191.

[derty30]

i have a 89 and i tried to watch the tach and econmeter today and it seems like the tach does move. I After i changed the spark plugs it seems to have gotten worse, I didnt take a long trip but once I reach around 3k rpms it was baaad. changed my plugs, i have them gaped at .028. The hose coming off my valve cover is cracked pretty bad so might be a vacuum leak. I havent had a chance to check the tps and cps. How would I go about checking the c191. I am also strapped on cash being that i drove from New Jersey to CA and now living here.

Im dieing trying to figure this thing out.

[derty30]

oh and i did change my radiator to a e36 one if that make any difference.

[derty30]

http://www.youtube.com/watch?v=UKZweh2dk0M&feature=plcp

this is what my car does sounds like I hit redline + but im not.

https://lh5.googleusercontent.com/-AZ9JsRI1Sqo/T-qS6OO3mxE/AAAAAAAAAAw/OTjo2kjPiaU/s160-c/June26201202.jpg

I am pretty sure this is my tps, and it had oil in the connector so i think this could def be a issue. My cps had alot of crud on it so i cleaned it just but its late here so im going to finish everything up tomorrow.

[Bimmerista]

My eta did the same thing a few years back...turned out to be the TPS.

[jreddleman87]

I'm having the same problem with my '87 325is. When I rev to 5k, it seems as if the rev limiter engages. Along with that issue, the engine will intermittently 'misfire' anywhere from 1500 to 3500. When the 'misfire' occurs, the tach with drop a few hundred rpm and sometimes the temperature gauge with flutter. It only happens when the engine is at operating temperature. The fp relay, in tank pump, inline pump, and fuel filter have been replaced at my local shop at their recommendation and the problem persists. I have replaced the plug wires, cap and rotor, coil, and ground wire. I am running platinum plugs that are only a year old and look to be in good shape. I broke down on my way home from Vancouver to California and have to make the trip back this coming saturday so, any additional thoughts are greatly appreciated.

[bmxmett318]

OP or any contributors to this thread with similar symptoms ever get to bottom of this?

My e30 M20 over the past 2 years randomly exhibits a similar behavior every so often, sometimes months in between. The car "bucks" in the sense that it immediately loses momentum because the motor will suddenly "redline" at the RPM it is at. If I take foot off gas pedal and reapply then the motor will "redline" at the new RPM it's at. Sometimes this occurs while driving over a pothole, rough road or even just driving around a bend at a docile speed. Throughout the ordeal I usually downshift and upshift in between gears and rev the motor trying to give it some life. While revving the motor I hear it sputtering and struggling to reach a higher RPM….then magically power is restored. Perhaps by driving over more crap condition streets or continuing to rev/downshift/upshift etc.

It happens so infrequently I haven't addressed it, but similar experiences and their solutions would be awesome.

[tytypetersen]

Had the same problem in 2 of the e30s I've owned. New tps and new main relay fixed it.

[cabriodster87]

Intermittent symptoms? Maybe Harness or Connection..


EDIT: Once had a 318 that would reach Opp temp then shut off and restart magically, it was scwewy temp sensor/ wire

[IRON-E]

Tldr but it's your cps trust me.

[custom e30]

im having the exact issue, ive done a tune of research with a close friend, coming to the conclusion that the crank position sensor is the issue, that controls timing....my car not only cuts out but it also back fires very bad...

[E30NJ]

Afm?

[G-Man the Visionary]

Afm?

or cracks in intake/ bad motor mounts causing cracks to open... happened in my 318... seems like these guys know it's CPS, but other things to consider checking..