Engine 'shudders' when shutting car off...

[Dizings2k]

Is that normal?

When I turn the key off its almost as if the engine shudders. It shakes the whole car when shutting off.

Anything to worry about?

TIA!
-Dustin

[repiv]

As with your other question, having the car in a good state of tune and maintenance is important. You may have the beginnings of "run on". This is a close relative to "dieseling", pinging and pre-ignition. You're getting an explosion (power stroke) after the ignition is turned off.
Some cars do exhibit a studder when shutting down but on the most part, they should just turn off without any drama. Perhaps you should look into a valve adjustment at that mileage if all other items are in good order. Bad gas, plugs, filter can contribute to this and other symptoms.
Checked your PCV valve lately?

[Dizings2k]

Thanks Xviper.

Sounds like I have some checking/testing to do.

I am taking the car to my buddies personal garage with a lift to give the car a complete going over. I will let you know the results of further testing.

I should have mentioned...

The dealer delivered the car (2 hours away) drove it the whole way on 87, and filled me up with MORE 87! How nice!

The idiot at the dealer filled the car up with 87 in front of me (I didnt notice until it was too late).. so I assume the car had been run on 87 the entire time at the dealer.

I apologize, I should have mentioned this.

This could be the issue with my other problem as well.

I will check everything over and run 2 tanks of 93 through it and report back. FWIW I did add octane booster to this tank of gas.

Thanks again.

[repiv]

The car will run on 87 but it won't run well. The knock sensor will trigger a signal and the ECU will pull timing to compensate. Pulling timing may not be enough to eliminate pre-ignition. This can also contribute to the other problem you posted about.
Adding octane boost would certainly help the situation but even a whole bottle of octane boost may not get you close to the 91 the engine needs.
Run the old gas out and continue to monitor and keep in mind the stuff I've already mentioned.

[thqs2k]

xviper,

i has the same problem too. how do u valve adjustment . r u need to take to the shop for
that?

[repiv]

xviper,

i has the same problem too. how do u valve adjustment . r u need to take to the shop for
that?

You must realize that a valve adjustment is only one of many things I suggested to consider. Without knowing the full details or having first hand involvement with the car, it is impossible to say which suggestion will work. Nobody can even say for sure that you have the same problem and if it is a similar problem, nobody can say if the parameters that have led to your problem are the same. Too often, on these internet forums, when someone posts up a problem, it's almost like a virus that spreads. Suddenly, others have the same problem, when very likely, they do not. The history behind your car may be quite different from the other person's. Dustin's problem may be resolved by flushing the bad gas that was put in previously. I don't think it would be wise to fixate on a valve adjustment at this time. There are far easier and cheaper things to do before targeting the valves.

A valve adjustment is something that can be done by the owner if the owner has the knowledge and the tools to do it. Without both, the job can go very, very wrong and you can do far more harm to the engine than what you are trying to resolve. If you have to ask how to do it, I would suggest you take it to a shop that has S2000 experience doing these types of things.

[Dmucci]

this may be off point, but I have heard a number of reasons NOT to do a valve adjustment... Is it really that difficult to do correctly (by a shop or dealer) it is hard to understand how an adjustment even if not needed would be potentially harmful, (ex to your wallet) if they are adjusted correctly. just a little confused, my 02 has 42,000 and seems a little noisy, so I had thought a valve adjustment might be a good idea - make sure they are right on, not so sure after reading some of the posts lately.

[repiv]

this may be off point, but I have heard a number of reasons NOT to do a valve adjustment... Is it really that difficult to do correctly (by a shop or dealer) it is hard to understand how an adjustment even if not needed would be potentially harmful, (ex to your wallet) if they are adjusted correctly. just a little confused, my 02 has 42,000 and seems a little noisy, so I had thought a valve adjustment might be a good idea - make sure they are right on, not so sure after reading some of the posts lately.

Honda indicates that a valve adjustment on the S2000 is only done "as required". The vast majority of these cars have gone their whole lives without touching the valves. It should always be confirmed that they are either too wide or too tight before going into an adjustment. Too much gap can be determined by a mechanic's stethoscope and too tight can be determined by both the stethoscope and a leakdown test. This is one of the best examples of "If it ain't broke, don't fix it". So many times, have we seen a valve adjustment go bad. If this were not the case, we wouldn't be hearing the following:
"Had a noise. Did a valve adjustment. Seemed to fix the problem for a few weeks (or months). Now the noise is back." It's painfully obvious in these cases, that the valve adjustment was not needed in the first place or that they were done badly. Such things do not "go off" so quickly. A valve adjustment should last as long as the time the car has already existed and then some.
So many things on this engine can make a noise. Anything from the valves to the timing chain tensioner, to the serpentine belt tensioner to the oil pump to the fuel injectors. And they can all sound similar. Until you can determine what it really is ...................................... :crazy:
Why do a valve adjustment if it's some other component making the sound?
Back in the day when people used to do valve adjustments at home on motorcycles, they did it enough they got good at it. These days, very few cars have adjustable valve lash anymore and those that do, keep their adjustment for a very long time. Home mechanics and even professional mechanics don't do them often enough to get really good at it. It's not a tough job, but it has to be done right. It has to be done with the enginge at the right temp. The crank must be rotated in the proper direction. Some mechanics forget that the S2000 engine spins backwards from most other engines. Spinning it backwards when doing the valves will result in erroneous settings.

[Dmucci]

Repiv - Thank you, very good information...I am not sure there is any issue with the amount of noise - it is not significant - I just remember back in the day (80's-90's with 60'-70's vintage cars)when racing 6-10 weekends a year with full time race techs, valve adjustments were done often as a consistent part of maintaining race engines at peak output - what could be bad about that, but clearly I am mixing apples and oranges - thanks for the education that you consistently provide on all topics, you are always helpful and reasonable

[Dizings2k]

Just like my response to my other thread, this problem seems to be smoothing out with less and less 87 in my tank...

I will report back once I have ran a good bit of 94 through her.

[repiv]

Just like my response to my other thread, this problem seems to be smoothing out with less and less 87 in my tank...

I will report back once I have ran a good bit of 94 through her.

Great! This is probably a much better "test" that things are getting better than the "stab" test. Also, a steady good pull to redline is a good test for gas quality. Bad gas will not feel as strong and can produce high rpm misses that won't throw a CEL. This can mimic a bad MAP sensor signal.

[Dizings2k]

Following up with this:

I changed spark plugs, air filter, and have run numerous tanks of BP 93 through her. The old plugs were NGK platinums but looked terrible. The electrode was almost gone and the whole plug was layered in carbon.

She now shuts down perfectly. No shaking or shuddering!

Thanks again!