Car jerks during acceleration

[evil_twin]

This one has stumped me guys. It started yesterday on my way home from work. It almost feels like an inexperienced stick shift driver is learning how to drive.

The car idles at 600-700rpms. From a stop, accelerating in 1st gear around 1500rpms the car will start jerking and won't stop until you put in the clutch. I don't hear any clutch chatter. I tried to keep accelerating to see if it would go away, and it jerked all the way up to 4000rpms. It will only go away if you put in the clutch and drop it to 2nd.

On my way to work today, it happened twice in 2nd gear. Both times I hit a bump and it seemed like it through off balance and started doing the same thing.

The tires will squeak and the car will bounce all over the place as if an inexperienced manual driver let the clutch out too early, but it happens even when I slip the clutch and let it out very late.

One of the guys at work thinks it's a clutch starting to go... What do you guys think?

[2.5-12]

if it was affected by a bump, I would be tempted to say (depending on your year) its your in-tank transfer pump.

[jlevie]

That sounds more like a fuel delivery issue or an electrical problem. A flaky relay, flaky fusible link, loose ground, corroded C191 (on a 9/87 or M20), or even a failing DME are all possibiltities.

[evil_twin]

if it was affected by a bump, I would be tempted to say (depending on your year) its your in-tank transfer pump.

It was affected by a bump only today. Yesterday it was fine until acceleration in 1st gear.

That sounds more like a fuel delivery issue or an electrical problem. A flaky relay, flaky fusible link, loose ground, corroded C191 (on a 9/87 or M20), or even a failing DME are all possibiltities.

I was thinking it could possibly be a DME problem, I'll try to switch it out when I get home. Corroded C191?

You think that even if it was an electrical problem that it would stop when I push the clutch in?

[sohc12vm20]

Check fuel pump, or check the fuel pump rely! I had an e30 that did that and it was the fuel pump rely!

[jeffw]

sounds like the fuel is getting there in spurts. what year is it? I had a similar problem in an early model and changed the inline pump and it fixed it

[2.5-12]

this screams fuel to me, a bad o2 will feel really lean some times but a fuel pump going out/or has gone out (depending on your cars year) feels like fuel loss,

I'd check the pumps first (With the FP relay, just jump it with some wire and go for a quick drive) middle of the 3, jump closest and left, looking at it from the drivers side of the car.

[evil_twin]

I'll jump the relays tonight and see if that is the problem. But if it was fuel... wouldn't it happen in every gear, not just 1st and a couple times in 2nd?

[2.5-12]

I'll jump the relays tonight and see if that is the problem. But if it was fuel... wouldn't it happen in every gear, not just 1st and a couple times in 2nd?

with these problems, its almost impossible to guess, something that seems completely unrelated can be the cause of something else, its just something thats free and pretty easy to check :) if that fails to work, I'd check the AFM and 02 sensor next if you don't know the last time the 02 was changed, change it anyway. the AFM, if your car runs fine most of the time I really dont suspect but it could be an intermittent fault inside the box.

[evil_twin]

Yah I THINK the AFM is good because the car runs perfect. I was thinking the o2 sensor could be faulty, and I think it's about time to change it anyways.

But I'll definitely check the fuel pump and fuel pump relay.

[evil_twin]

Dang-it. I'm just retarded. So the problem was unmetered air... it was unmetered between the throttle body boot and the AFM, but only on the bottom side of it was off. So my car would drive fine until the engine torqued up and since I have my AFM bolted down, when the engine moved, the AFM didn't causing a gap and unmetered air to get in through the gap. But... all in all, I'm happy that it happened or else I wouldn't have seen that my front right caliper was seized up and the brake pads were worn out. Thanks for the help everyone!