Accidently down shift to 2nd going 110 mph, need advice

[NSX/MR2]

I was going 110mph at a 1/4 mile run when I accidently down shift from 3rd to 2nd instead of 3rd to 4th (it happened for just a millimeter of a second), my rpm needle was bury. Now my exhaust is of sputtering (not smooth), strange noise not sure if it is coming from the engine or the exhaust. The engine kinda shake a bit, but no check light came up. I am very concern. Did this ever happened to anyone? What do you think happened, is my compression messed up, is it the valve, something misfiring (spark plugs)? I need some help gentlemen. Thank you!
De

 

[Jimbo]

Could be a bent valve...could be worse. Obviously you shouldn't run it AT ALL and someone will have to check it out.

-Jim

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1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
http://homepage.mac.com/jimanders/PhotoAlbum1.html

[This message has been edited by Jimbo (edited 15 September 2002).]

 

[smoore]

bent valves is what it sounds like

 

[Runutzzzzz]

Yup it sounds like a bent valve.. eww.. sorry to hear about that...

 

[BadCarma]

as the rev limiter does not work on down shifts you indeed buried the tach.tow dont drive it in.sorry to here it man
let us know the outcome
david

 

[NSX/MR2]

Now to check this, i gotta take off the valve cover right? I wonder if I can do this job myself, or if have someone do it, how much do u think it will run me, $500 buck or more. What do u guys think. The vehicle is running fine, not weaken or anyhting, and the noise subside quite a bit, just the exhaust note is still kinda sputering.

 

[tunapie]

The damage will not go away. Do a leak down check of all cyl. to know for sure the state of your valves. If you keep driving the car you are going to really pay.

 

[NSX/MR2]

You guys are getiing me very concern. the vehicle is running fine, no check engine come up, pulled strong. so whta happen if i still drive the vehicle.

 

[W]

Funny thing is I could have sworn I saw him redlining his car all day long today. Seems to run fine but I would have an expert check it out. De, why don't you give Mark Basch a call to setup an appointment at Area 51?

 

[bayareansx1999]

it could also be a burned valve too. the first thing you should do is a compression check on the engine. i am pretty sure you have either a burned/bent valve. even if the car drives smooth, you should still get it checked out Asap.

 

[nsx2000]

It wouldn't cost you too much money if you do the checking and repair at this point.

It will be more expensive later on when the real problem arise.

Don't drive it anymore. Check it first.

 

[NSX/MR2]

What is Mark Basch's contact numbers. Thanks in advanse for all the help. maybe it is time i get the valve job done, too

 

[Yellow Rose]

The car may be running fine, but could still have some bent valves. Driving to the tech's garage *gently* will not bend the valves any more than they already are.

To confirm this, you need to do a leakdown test. A compression test is not mandatory, but would be good to do, since the tech is already in there. There is no need to remove the valve covers for either of these tests, but the coil pack and spark plug must be removed for the test connection.

This is a routine test that virtually any certified tech should be able to perform. I had the tests done on my NSX at a Honda dealership for less than $200. In fact, with the proper equipment the average weekend mechanic can do the test. There is no need to call Mark Basch just for this simple diagnosiss. But if the tests confirm the bad news, that is a different story.....at a minimum the heads need to come off to replace the valves and perhaps the valve stem guides.

Ahh, the price we pay when playing with HP.

[This message has been edited by AndyVecsey (edited 16 September 2002).]

 

[Jimbo]

Deqle,

First... DON'T RUN THE ENGINE!

It's not going to get better by itself. I'm surprised you kept running the engine and drove it home.

Since you're not exactly sure what's involved in checking this out, I would strongly suggest that you do NOT attempt to check this out yourself.

I also can't stress enough that you don't run the engine. I disagree with Andy here. I can't see any reason to take a chance running the engine. To save a few hundred dollars on a tow bill and risk screwing up a several thousand dollar engine? Why?

You could have bent valve and maybe you can get by with replacing the valve(s) and guides, but if you're driving it around, testing it to see if it's "weak" then you're just taking a chance that a valve could let loose, or hit a piston, or other nasty things that could really be expensive and force you to rebuild the entire engine.

I've seen engines with bent valves have the valve retainers damaged and let loose after the fact. It's not a pretty sight to see what a loose valve can do inside the cylinder.

I doubt it's a burned valve since you said this all started after a missed shift.

And, yes, if the heads need to come off, which I'm 90% sure they will, it obviously makes sense to get a complete valve job, etc.

-Jim

------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
http://homepage.mac.com/jimanders/PhotoAlbum1.html

 

[Larry Bastanza]

I agree with Andy 100%. Do the leakdown. If you start with a compression test and you have low compression in a given cylinder, the leakdown can/will confirm the actual problem. You can listen to hear where the air is leaking: intake, exhaust, or crankcase

Respectively, you will find: bent intake valve, bent exhaust valve, bad ring(s).

Deqle,

This test should take 1-2 hours tops, so I also agree with Andy about the price: $150-$200 tops.

Based on the past experience of many, you should probably have the oil pump gears inspected/replaced, unless your car has the Comptech kit already. Since you buried the tach, these gears really do not like that.

HTH, Good Luck.

LarryB

 

[DanO]

Sorry to hear about your engine

Like Andy says, you probably need a leakdown test to determine the damage. One thing you can do yourself right now is check your spark plugs, they should tell you if you have big problems. Look here for a DIY spark plug write up: www.danoland.com/nsxgarage/spark_plugs/spark_plug.htm

I would NOT start up the engine until it has been serviced. It may be running ok right now but you could be doing $serious$ damage to your lower block if there is excess carbon buildup and/or improper combustion causing cylinder wash.

Replacing valves is not really a DIY project unless you are a DIY masochist. Most likely the engine need to be dropped (it’s not necessary but it makes life easier in the long run), the head(s) need to come off and taken to an engine shop to replace the offending valves.

Good luck and keep us informed,

DanO

 

[nsxtasy]

Originally posted by Deqle:
What is Mark Basch's contact numbers.

You'll find all the information about making an appointment at the San Diego location on the Dali website here.

BTW, depending on how much damage you did, you're about to find out why your action is often called the "money shift".

 

[MvM]

If you've done 110mph in 2nd you must have down 10800 rpm for a (very) short while. That is, of course, if I've down my calculations right.

 

[NSX/MR2]

So this happen to everyone who missed shift, just a fration of a sec and all this damage, everyone. Dang

 

[Poloman]

Call Larry Garcia right now!
http://www.nsxprime.com/FAQ/Reference/dealers_and_service/nsx_modified.htm

Ask him what he thinks.

I trust that dude with anything, except women.

GOOD LUCK!!

 

[Jimbo]

I believe Mark Basch has "offices" right in San Diego!

You can't get ANY better than that.

(Unless you lived in Phoenix, I suppose)

Ooops. Just noticed this was mentioned before. A call to Jane Basch @ 602-244-8010 is probably all that's needed to confirm Mark's schedule in San Diego.

-Jim

------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
http://homepage.mac.com/jimanders/PhotoAlbum1.html

[This message has been edited by Jimbo (edited 16 September 2002).]

[This message has been edited by Jimbo (edited 16 September 2002).]

 

[sjs]

As everyone said, valves are bent. Bank on it. No harm doing the tests, except the extra couple hundred. If that's important, I'd do a quick compression check first. If one or more are low then pull the appropriate valve cover and make sure that something else in the valvetrain didn't fail like a spring or rocker. (unlikely) The leak down is nice and definitive, but given what you did it will only confirm what the compression test already suggests. BTW, you can't do a proper leak down without getting the engine up to operating temperature. Of course, you’re looking for big problems rather than small losses, so you could do it cold.

As for why it seemed to get better, especially after running it hard again, that's to be expected. The valve stems are very delicate (and therefore light and can be reved to 8k), so as they slam closed while running they tend to straighten back out considerably. But they will never be back to normal, and are at greater risk of breaking which trashes the pistons, head and cylinder.

Sorry to say this, but be prepared for a hefty repair bill even if it nailed only a few valves with no damage to pistons or guides it will likely run over $2k in parts, gaskets and labor. As for the “valve job”, you don’t want them touching the valve seats with anything more than lapping compound unless they really need it. The NSX seats are considered non-replaceable so once they’ve beet cut down into the head beyond specs, you toss the head. No doubt there are shops who would gladly install generic seats as is often done on many cars, but then you risks increase significantly.

 

[NSX/MR2]

It seem to me I got lucky. Brought it to a certify mechanic, can't wait too long. He pulled out all six spark plugs, test fire all six cylinders, test the coil over system on top of the spark plugs. Here is the result, all six is firing in their range, the coil system work fine, and they replaced all six spark plugs, then to clean out the inside of carbon dioxide and wath's not, they gave my baby some medication. He said that the engine is fine (steady rpm and sound), took it on a couple of run himself, but he doesn't understand why the exhaust is sort of sputtering, he said that something is probably loose inside, gotta open and check it out tommorow. Now with this test confirm that all six baby are running, am I good or do I need to do anything else.

 

[Jimbo]

Deqle,

I hate to be a killjoy, but it doesn't sound like the certified mechanic did what was supposed to be done. It also sounds like you kind of ignored the advice we offered.

If he doesn't understand why it was sputtering then he's no mechanic. Of course, I assume you told him that you down shifted into 2nd, right?

You've got bent valves my friend and every time you run the engine you risk trashing it. Did he do the leak down test? And why would you drive it and let him take it on a couple of runs?

You need to yank the heads (at the very least) and fix the problem.

-Jim

------------------
1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
http://homepage.mac.com/jimanders/PhotoAlbum1.html

[This message has been edited by Jimbo (edited 17 September 2002).]

 

[W]

De,

sounds like you still have to get the leak down test done.

For those reading this thread, here is a little bit of background information as I understand it (De please correct me if I make an error). The 3rd to 2nd mis-shift happened Saturday night. On Sunday a few of the SD NSXer's went for cruise. De ran his car HARD for over 200 miles in the desert heat. Halfway through the drive, we pulled over to inspect the engine and there was this intermittent noise on the right side of the engine and a sort of sputtering noise coming from the exhaust. One of the other drivers is a mechanic who owns his own shop. He said that the intermittent noise was probably from the air conditioning unit since the climate control on De's car won't turn off (not a new problem). The source of the sputtering is still unknown but it is barely noticeable and I think it was already doing it before we drove on Sunday.