I get a rattle-shake-knock kind of sound under a few different circumstances. I would appreciate help with this...

1. While letting out the clutch when the engine is not rev'd high enough in both forward and reverse. Most noticeable case. This kind of take-off typically would induce drive train shutter in most vehicles.

2. When the engine is at idle (clutch in or in neutral) and the A/C compressor turns on. Very subtle in this case, doesn't always happen.

3. Sometimes when the engine is turned off. Less subtle then the A/C case.

It sounds like it is coming from the front half of the car. I thought maybe a broken engine mount or some other mount, but I have not been able to check. I could use some pointers on how to do this with a manual transmission. The sound does not occur under fast take-off or hard acceleration and shifting.

I bought this car three weeks ago... it's an MY00 with 25k miles, SB for clutch (new FD and FW re-surface) done in Dec 2003 at 22k miles. I've been lurking around s2ki for about two months now. It's a great resource, much apprecitated. I will be posting other questions soon.

Thanks,

Rob

 

Some more information observed today...


The sound I hear happens in all cases when the engine speed dips down below 1,000 RPM. It looks like down to about 500 when the AC comes on, but then the engine speeds back up. When the speed drops I hear a rattling sound. The sound itself mostly sounds like the engine shaking, this can also be observed in the shift lever. So this drop in speed obviously would also occur when the ignition is switched off. In the case of letting out the clutch to fast with the engine not rev'd high enough the speed also drops down below 1,000 RPM. The idle speed with the engine warmed up is right at 1,000 RPM.

Has anyone observed this? Is it normal for this engine to just shake hard when the RPM drop this low?

 

I get the engine shake too when it drops just below 1000 RPM... but it only happens once in a while.

 

Mine does it too, under 1000 rpms.

Some blame the MAP sensor and take it out and abuse it - kidding - there IS a MAP whack solution, followed by a reset of the ECU.

Works sometimes, doesn't work for mine.

MAP sensors are covered under the extended HondaCare warranty, but good luck getting that request honored.

Hockey

 

This is a typical engine "shake" when it is getting close to the stall point. It simply does not have enough rpm to maintain a healthy idle. The ECU is then fighting with timing, fuel, idle air control and probably bunches of other stuff that doesn't come to mind at the moment. This part is normal.
Now, the question is, "Is it normal for the rpm to go that low?" Yes and no. All 3 of the scenarios you cited is normal. When you take off with such low rpm, the engine is not producing enough torque to motivate the car. You are "lugging" the engine. When the A/C cycles on, it is suddenly adding a parasitic load to the motor and it takes a second for the ECU to compensate for the slight dip in rpm.
When you are operating the A/C for the first time after a period of non-use, it has been reported (witnessed by myself) that as you approach a stop (no throttle application) and then push the clutch in thereby disconnecting the engine from the rest of the drivetrain (and thus no longer have the car's momentum to drive the engine), the combination of the A/C drag and slowing down gives the ECU a momentary brain fart. It cannot compensate fast enough to keep the idle speed up. People (at least in my case) will realize that after a few "episodes" of this low rpm (near death) behavior, the ECU finally does "learn" and the engine will not do this anymore until there is another lengthy period of A/C non-use. This is the part that some folks may consider as abnormal. I don't think it's a big deal and just give the ECU the learning time it needs.

 

Thanks for the feedback, I at least now have some peace of mind. Misery loves company!

[QUOTE]Originally posted by XVIPER

 

[QUOTE]Originally posted by Random1
I find this a somewhat embarrassing sound when turning off the engine. It's kind of analogous to those seventies cars that used to run on like diesels after they were turned off.

 

My car is not "dieseling," I was just trying to convey that the low RPM rattle sound of the engine is embarrassing. I was just sighting an embarrassing example from the past. Sorry if I confused.

My next question, since I plan on auto-xing this car under SCCA rules, would be what are the stock class modifications that I can make to this car? I know I can do roll-bars, shocks and maybe some other minor tweaks. Can I put on a cold air intake in this situation? I saw the thread on the intake manifold gasket, that would be another consideration. I was going to save these questions for the racing forum.

I will try the map wack and ECU reset as soon as I can. I will also take the car out early one morning just before sunrise when the temps are low to see what the behavior is like.

 

No modifications to the intake except for filter. You can do shocks, tires, and front anti-roll bar along with alignment.

No exhaust, header etc.

That will keep you in B-Stock.

BTW I get the shudder all the time, I am still not used to revving it up so much to get the car going.

 

I did a test drive early this morning before the sun came over the mountains (~70F) and found that the symptoms did not occur when turning off the engine or A/C coming on. I could still get it by lugging the engine down to low RPM when letting the clutch out, but that is really a forced condition. I therefore conclude that, at least in this particular case, that the hot Arizona weather is pushing the limits of the envelope for ECU compensation at low RPM.

I'm sure if my conclusion is off base someone will let me know! Please do.

Thanks for the help.