Odd jerking at low speeds

A little more info would be a big help... what you describe can be quite 'normal' in stick shift cars where the engine rpm is lugged down too low...

-- Jim Warman snipped-for-privacy@telusplanet.net

It's called "lugging the engine"...................Don't do it again...............

Bill S.

Brian Ober wrote:

Since I got my Prelude, torqueless wonder that it is, I've learned to keep the RPM above ~1500 if I need any sort of acceleration or am going uphill and above 1000 for just putzing around or in traffic in order to keep the engine from lugging or straining too hard. On a couple occasions I have been in too high a gear for the situation, seeing as how fast things can change on the road, or downshifted from overdrive but shoulda went to 2nd or 3rd... Point being, I've lugged it a few times and it jerks a bit. I was wondering why cars do that. I've never driven a manual transmission V8 but I'd imagine it's much harder to lug something with torque. I just couldn't figure out in my head why the car lurches forward but tehn acceleration stops and it will repeat a couple times before smoothing out if you don't downshift. Anyone know why that is?

Cory

Doh! Its a 2001 GT auto trans. I have had the car for a few months now and this is the first and only time this has happened since then.

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When my auto tranny GT is cold, it will run a little "rough" for the first

10 minutes or so with very light throttle, and will tend to "jerk" slightly. Like if I hold it in 1st or 2nd gear (around 1200 rpm or so), just barely pressing the throttle with very little load on the engine, I get a little "jerking" effect... but if I then step into the pedal a bit, it runs fine. When the car is warm this does not happen. I will note that several other newer cars I have driven, including a Chevy and Honda, have acted the exact same way when cold. They will jerk slightly when cold with very little load on them. I would tend to consider this normal. Perhaps they are adjusted to run a bit lean in this condition (cold and hardly any load) causing a tiny bit of surging.

Side note: the reason I experience this is because I always "warm-up" my engine in this manner - I start it up, then almost immediately start driving, but run in 1st or 2nd gear at between 1200 - 1500 rpm for maybe 5 minutes with just a light load on the engine until I see the temperature gauge just start to move (stay on the side streets). This is a much better warming technique than starting a cold car and letting it sit and idle for 5 or 10 minutes like I see a lot of people do. While it may or may not make a huge difference in the long run, I am a firm believer in getting the engine up to or at least near operating temperature before putting a heavy load on it (like having to accelerate hard from zero to 70 entering a freeway, etc). I've seen some guys start a cold engine on a 20 degree day, and then go tearing off at full throttle... not sure how bad this is for the engine, but it can't be good. Oil is still thick, internal clearances are not correct, etc.

I had a similar problem with my '67 Galaxie with a 289 and FMX jerking when cold at lower RPM. I had to adjust my choke properly for the changing season. Perhaps your mixture is obscenely lean for a cold engine due to pollution controls. I doubt there is any way you cna adjust the 'choke' on a modern fuel injected car unless you ahve one of those fancy injection conversion kits that lets you control everything.

I do about the same thing. I keep the initial rpm's below 2K. Be aware that when the water-temp gauge tells you it's in normal temp range, that does not mean the engine (read oil) is at operating temps. It takes longer for the oil to warm up.

Doing this (and 3K oil changes, dino) has helped me keep my 5.0 in good shape. it uses no more oil than it originally did and runs like a new one. It is now at 93K miles which I consider just broken in for this engine. If only everything around it stayed as good. Remove NO-SPAM from email address when replying