ROTORHP

I have been reading threads about this but everyone has more grief than me it seems. My car starts fine and runs rich for a little bit(30 sec to 1 min) but it idles rough only when cold. The guy I bought the car from said he phoned Pettit Racing and they told him it was a blown EGR gasket(so he says). Anyone heard of this? I found a vacuum line that was disconnected and reconnected it. It seemed to help a bit, but did not cure the prob. What else could it be? The other thing is that when the car is warm, sometimes it does not want to idle back down to 750 rpm, it will stay at about 1100 rpm till I lug the clutch at a light then it will go to 750rpm. Any thought would be appreciated.

ROTORHP

doing!

duboisr

Adjust the air screw under the elbo to see if that helps, if not just return it as before. My first guess would be to back it out a little (more air).

ROTORHP

K, I'll give that a shot..... thanks. Is that the most probable cause? Is that for just the high sticky idle or both issues?

spurvo

Idle at 1100 at stop light for a few seconds after moving is normal, I think. ECU has a speed sensor, and can tell if the car is/was moving. It'll keep the rpms up for a few seconds in case you decide to go again to reduce the lurch from low rpm condition. I'm pretty sure it uses the ISC for this, though it might also use the dashpot. For that matter, a slow acting dashpot will hold the idle up. However, you say the idle drops to normal when you "lug the clutch". Does this mean pop it in gear and let the clutch out slightly to drag the motor rpms down through load? I would think that the rpms are therefor ebeing held high by the ECU, most likely through the ISC. The clutch switch and/or the 1st/2nd gear switch are then telling the ECU to lower the rpms when you lug it. Or am I completely full of it?

ROTORHP

I dont' know if you are full of it or not. What you say makes sense but I don't know if it is because of the computer telling it to stay up of if it is mechanical. I'm used to sourcing out carb problems where all the probs are mechanical. You sound like you could be onto something though.... could anything change physically to drop the rpm or would it only be a computer related component causing it? Thanks for any input.

FDjunkie

The deceleration dashpot is designed to slow the rate at which the primary throttle plate closes the last few degrees, but should not result in more than a 1-2 second delay in full closure.

RX7SpiritR

iTrader: (1)

you know what...just a thought but could it be his clutch switch causeing this? If it goes back down when he pushes in the clutch slightly, that's what it sounds like to me, but that's my .02!

Nathan Kwok

I have the problem of the idle not wanting to go down past 1100rpm too. I was told the same thing, the ecu keeps it up there, but sometimes it kind of sticks. If I use the clutch to drag the engine down then then it won't go back up again, so its probably some kind of dashpot sticking. Since it doesn't happen that often its no big deal, but it would be nice if the car had a bit less "character". I do know for a fact that the idle won't go down to 850rpm when you are coasting, this is normal and most cars do the same.

ROTORHP

I don't think it is the clutch switch because it isn't the fact I am touching the pedal but actually mechanically using the clutch to pretend like I am stalling the car. It must be a dashpot prob. Little things like that bug me sometimes. I'd like to fix that. Can a guy free up a dashpot or does a guy replace it? Are they expensive? Spanks for the help guys.

EviLPeNeviL

iTrader: (2)

What does "dashpot"mean?

When you guys talked about the clutch switch problem, I thought I had the same problem a few months back when I had the clutch down and just holding it in first gear, my idle would go up and down and would eventually die.

After replacing my spark plugs and wires I never had that problem again.

-Dan

FDjunkie

Here's an edited engineering description of of a dashpot along with some of my experiences.

DASHPOT - The dashpot is used to produce a damping force, which opposes motion and is linearly proportional to the velocity of the relative motion.

In the case of the FD's throttle dashpot, think of it as a small shock absorber that uses air instead of oil, and operates to slow down the final closing of the throttle plate whenever we lift off the gas pedal.

Some common failures:

(1) Dirt and/or debris that blocks the orifice(s) resulting in too much resistance to closure which can lead to a ‘sticking throttle’ condition; occasionally higher than normal idle speeds, maybe temporarily corrected by blipping throttle, etc.

(2) Ruptured diaphragm leading to no shock action and therefore immediate closure followed usually by a stumbling idle at a low RPM (350-500) for a few moments, and depending on the engine it may recover and idle fine, or it could stall completely.

(3) While its position is adjustable it would almost never require this attention once installed; it usually either works or is failing.

ROTORHP

It seems like mine would be the plugged scenario. Sometimes I can blip the throttle and it will idle correctly, but I usually go to the dragging the clutch method because it works every time.