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Old 12-22-2012, 08:14 AM   #1
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Is a little pulse/surge normal?

This is my first manual car, so I'm not sure.

When stopped and I engage the clutch for reverse, and just use the clutch to go without using the gas pedal, I get a little surge and pulsation in the engine.

Sometimes I get it too in first with just the clutch to move the car and not in first.


And sometimes after I drive the car, turn it off, and then on again, the idle has a little surge as well. Usually idle is smooth otherwise.


54k miles, is this normal or does it indicate something needs to be changed?

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Old 12-22-2012, 09:44 AM   #2
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Normal.

On start up, the ECU will occasionally command a little more rpm (like up to 1,000) to ensure a good smooth start. After this initial blip, the RPM's should immediately go to 700-800rpm and be rock solid and smooth. In the summer time, you'll also feel a bit of RPM fluctuation when the air conditioner is on.

It is normal to feel the engine "surge" at very low RPM's and very small throttle openings (forward or reverse does not make any difference). This will definitely happen when letting out the clutch with no additional throttle or when starting out on a hill when the RPM's are low.
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Old 12-22-2012, 09:53 AM   #3
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To clarify - I know on cold startup the rpms are higher and go down.

This is different- let's say I've been driving for an hour, stop and turn off the car for a few minutes. Then I turn it back on, and that's when rpms surge.
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Old 12-22-2012, 10:06 AM   #4
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The ECU is commanding the slight increase in RPM's even at warm engine temps to ensure a smooth start. This **might** be an indication that something is slightly amiss (like low voltage from the battery or several other parameters that the ECU takes into account to determine what RPM to comand through the engine start process. I can look up that list of parameters but I don't recall all of them from memory. My car does the same thing all of the time and to be honest, I just have become used to it.
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Old 12-22-2012, 11:05 AM   #5
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Yup there is a slight pulse/surge. I noticed that even when I cleaned my MAF and throttlebody. Nothing to be alarmed about, but do clean both if you feel an increase in pulsing.
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Old 12-22-2012, 12:53 PM   #6
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Glad it's normal. Not to start something off topic, but I also heard a strange noise.

It happens when going over rough road at slow speeds, sounds like a 2 metal plates clanging against each other.

I've searched, could be a suspension issue? Or is some metallic sound like that normal?
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Old 12-22-2012, 01:06 PM   #7
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If it right behind you almost like under the back of the seat. it the bushing in the trailing arm but I'll be criticized for this Porsche doesn't call it that. Link arm from body just behind seat to lower control arm at first it is just a solid thud later it can gets to be metal sounding. You could also check for something in the transmission guard or a loose shield riveted on the transmission guard.
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Old 12-22-2012, 02:26 PM   #8
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Probably a rusted-out bolt in the catalytic converter shields. Reach underneath and see if either shield has play in it.
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Old 12-22-2012, 02:32 PM   #9
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If it right behind you almost like under the back of the seat. it the bushing in the trailing arm but I'll be criticized for this Porsche doesn't call it that. Link arm from body just behind seat to lower control arm at first it is just a solid thud later it can gets to be metal sounding. You could also check for something in the transmission guard or a loose shield riveted on the transmission guard.
I feel like thats what's wrong with my car... A terrible thud. :/ However; None of the suspension has play in it when I put it up on the lift. That would be pretty unusual and a new one for me if it has no play and still worn out.

Possibly struts?
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Old 12-22-2012, 03:27 PM   #10
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Originally Posted by rondocap View Post
When stopped and I engage the clutch for reverse, and just use the clutch to go without using the gas pedal, I get a little surge and pulsation in the engine.
Sometimes I get it too in first with just the clutch to move the car and not in first.
What you are experiencing is called "bucking". It is fairly normal for any manual transmission vehicle to do this at very low RPM's. I'm not sure what the mechanics of it are, but I can surmise that it is caused by trying to make the engine run at too low of an RPM for the given load, and an oscillation develops between the engine and drive train. You need to have a little bit of throttle open to keep it from doing this. If you experience it again, just push in the clutch quickly to stop it from continuing
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Old 12-22-2012, 04:57 PM   #11
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You guys are great! I'm definitely learning a lot, this being my first manual car.

I pushed down on the car's hood and back, but could not replicate the metal like grind I heard over bumps. Who knows what it is without looking under I guess.
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Old 12-23-2012, 05:10 PM   #12
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Since I've asked a few different questions here, I figure I'd continue:

In the manual it shows the onboard computer that you can activate by a stalk, and tells you mileage remaining, average consumption, etc.

I don't have that stalk. Is there a way I can still access this information? Or is it something that has to come from the factory and there is no way around it?
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Old 12-23-2012, 07:54 PM   #13
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Yes, very common mod, just do some searching.

The lower trailing arm bushing is the source of your rough road issues. You won't be able to feel any play when on the lift because the link will be quite loaded at that point. One of those things you just have to trust is the problem.

I bought rebuilt links from vertex auto and they have worked out fantastic.
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Old 12-23-2012, 08:29 PM   #14
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Thanks, I will make a note of that. It really rarely makes that sound and only on exceptionally rough roads. Should I be OK for now, or is this something that I should replace immediately for safety?
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Old 12-23-2012, 09:36 PM   #15
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Thanks, I will make a note of that. It really rarely makes that sound and only on exceptionally rough roads. Should I be OK for now, or is this something that I should replace immediately for safety?
No hurry. You can do it when you have time or just wait and eventually it will get worse and make that sound all of the time to continually remind you.
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Old 12-24-2012, 07:03 AM   #16
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At 80mph I seem to be getting vibration and a little sideways motion from the steering wheel, do you think that's related to the tires or suspension, or is some of that normal feedback levels for this car?
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Old 12-24-2012, 07:08 AM   #17
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At 80mph I seem to be getting vibration and a little sideways motion from the steering wheel, do you think that's related to the tires or suspension, or is some of that normal feedback levels for this car?
Generally, a vibration at only high speeds is due to either worn tires/ out of balance wheels.

It could also be worn steering linkage, or a wheel bearing. But much less common for that symptom.

EDIT:

Just to clarify. What control arm links are we talking about here?

a.

b.

c.

Last edited by Mrmaddbrad; 12-24-2012 at 07:10 AM.
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Old 12-24-2012, 07:15 AM   #18
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I had a bent right rear wheel that caused my steering wheel to vibrate at around 70mph. My indy found it when he was replacing my rear tires and noticed it during balancing. The indy sent it to a local shop that repairs these things and it was solved.

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