Well, here I was thinking "no problems and 30K this must be a good one off the line". This will teach me to not even think those thoughts.

I noticed a while ago ~April that very occassionally I would get a bucking when exiting from my work car park onto Castlereagh St and crossing Liverpool St. At the time I thought it was me as the road is pretty second hand along there with recessed pit lids, bumps, etc., and I thought it was just my foot bouncing on the throttle.

Well I have now had it occur regularly on exiting the toll collection at the end of the M2 while coming into work at about 6:30 in the morning. So it is not me and even my neighbour who is a regular passenger commented that it wasn't my driving (he needs the lift so has to be nice...).

I looked at all the threads on this and unfortunately there was never a conclusion on the real culprit, either the AIT or the MAP Sensor.

Firstly has anyone else had this occur, and secondly if yes what was the final fix?

 

Well that is weird. I was thinking about this problem on the way home tonight. I was thinking if I start a new post saying my car bucks like my old EH Holden used to when I was learning to drive and didn't have the clutch thing happening properly that you guys out there would think "this guy just doesn't know how to drive a manual car".

Now that you mention it, I have been experiencing this phenomenen for some time. My car is at about 17k now. The way home at night for me takes me to a roundabout where you usually have to wait in a line of traffic for your turn to go around the roundabout. Sometimes you have to crawl along in first gear pushing the clutch down, slipping out of gear sometimes and sometimes leaving the clutch down and then crawling a little more.

Anyway after a few minutes of this my stook gets pissed off and wants to get up and go I guess. It is then that she bucks even after I have changed into 2nd gear. The only way to calm it down is to push down the clutch and try to engage the power smoothly.

The problem goes away once I get going and then I don't get it again .. until the next day on the way home. It doesn't happen every day.

I thought perhaps the clutch was just getting hot and sticky. Is that maybe what is up with yours?

I'd be interested to know of anyone else's experiences and thoughts. I hope my clutch it not about to shit itself.

 

This has happened with many of the modern cars I've owned - Vettes, Viper, Civics - only in manual transmission cars. I think it happens when you are trying to drive very slowly, at or below the cars normal idle speed. The computer has a hard time trying to maintain its idle AND allowing you to drive with such a low engine speed. So, it has a bit of a brain fart and you get this "bucking" which is the computer's way of saying, "must idle @ correct speed, oops, must let driver do what he wants, oops, must idle correctly, oops, must listen to driver............" This whole time, of course, it's trying to compensate for load (vacuum) or no load. I've found that if I have to drive this slowly in, say, bumper to bumper traffic, I usually push the clutch before the rpm gets close to idle and coast with the car's remaining inertia. Automatics can maintain idle even when road speeds would normally take the engine speed below idle.

 

Xviper I think I saw your contributions in the other bucking threads. Do you know if there was any real conclusion on the fix. In both cases where it happens with me it is under acceleration not idle and one case is when the car is cold only having run for a few minutes, the second is after a half hour of freeway at ~60-70mph then a very brief queue for the toll.

Unfortunately I read so many topics on this board that they all start to swim together. I remember that there was one problem where you removed something and gave it a "thump" (a scientific term somewhere between a "bash" and a "solid hit") but last night in my searches I couldn't find anything along that line.

 

I think that referred to the guy in the auto Volvo in front of you who insists on crawling up in the traffic at 5Kph. These guys should get lessons from taxi drivers. There is only full throttle or full brake, nothing in between.

Seriously though, the 'percussion therapy' you refer to is the MAP sensor. Just remove the two screws, and rap it on the side of the intake lightly. Nt sure why this works, but hey, who am I to argue.

 

Sorry, it wasn't me (but you never know with Alzheimers & all . ). I think this is the only "bucking" thread I've responded to. I don't believe that your situation is the same sort of "bucking" that these fellows are talking about. The cold condition you speak of may be hitting the rev limiter @ 6K rpm when the temp is not up to 3 bars. The other you describe is probably as AusS2000's reply. Search for "MAP sensor".

 

The cold occurance is definitely not the rev limiter as I am just pulling away in traffic and always short shift I those circumstances.

Thanks, I will look again under the MAP sensor.

 

Hi Col

I've had several instances where I've been sure it's my foot moving on the throttle (positive feedback causing oscillation), triggered initially by lazy driving or a small bump. I did once have the thing buck on me in city traffic when I was fairly sure my foot wasn't moving, but it hasn't happened since. The throttle's extremely sensitive, so maybe that's all it is? I guess if it's only started to do it recently then something must have changed.

 

My car has 4000km on it and the first time it happened i was coming back from a friends place along Windsor road and the traffic was crawling along, and it started to buck violently, put clutch in and accelerated alittle, that sorted it out, has happened twice since then in crawling traffic...

 

I've had this problem ever since I bought the car and I've observed the following:

1. It only happens at low speeds.
2. It generally happens soon after I have let the clutch out in 1st gear and begin to step on the accelerator. It sometimes happens if I step on the accelerator quickly or slowly while rolling slowly in first with the clutch out.
3. Going really slowly uphill (like in a car park), it happens quite often.
4. Changing into 2nd gear sometimes rectifies it but often you are going so slow that 2nd gear isn't really a viable option.
5. It happens intermittently.
6. There have been threads on this going back to H-A.net days.

I generally have to put the clutch back in and shift to neutral and then back to first to get it to stop or if I am going 3km/h up a car park ramp, I'll live with it.

Rapping the side of a piece of electronic equipment seems counter-intuitive, so I don't think I'll go down that path.