Rough Idle / Stall / Misfire

[desert_rat]

Hi folks,

I bought an '02 last August, and since I've had it it's run very rough at idle, and you can hear a soft 'poot-poot' sound in the exhaust (although it's random, not rhythmic). It tends to get worse, then get better apparently randomly. I thought it might have been associated with the weather or the level of fuel in the tank, but apparently not. I frequently get the misfire codes (300-4), but nothing else...

Here's what I've already done:

1) Rebuilt the head. some keepers/retainers were cracked, but the valves looked to be in good shape. Replaced all intake valves in any case, since the mechanic doing the job thought there was an outside chance a valve had touched a piston at some point.
2) Replaced coil packs and spark plugs
3) Replaced fuel filter
4) Replaced MAP sensor (the new one with the nifty zip tie holddown)
5) Removed, thoroughly cleaned, and reinstalled the IAC

I have another friend who is a mechanic. He removed the fuel injectors and said they were pulsing normally, although he didn't do a fuel flow test. We've hooked it up to a diagnostic computer with no result. We removed all the sensors we could find, and appropriate codes were thrown.

None of this work has had _any_ effect at all. This is driving me freakin' bananas :) I love my car, but when it's bad it stalls at intersections...

Can anyone advise me on this? Could it be the injectors and, if so, is there a definitive way to test?

Thanks!

Bryan

[trackit]

Of all of the missfires and rough idles I've repaired the culprit has been exhaust valves and damaged retainers. Replace all retainers and keepers as well as exhaust valves. Perform a leakdown test first, this should tell you where you stand.

[joe_s2k]

Back in 2000, I had a similar problem with ECU codes indicating cylinders 1-4 misfiring. After nearly a month of Honda Master Techs, Honda Corp. Master Techs, leakdown test(everything within spec), replacing everything you already stated, it ended up being the fuel injectors after all.

You might want to swap injectors with another S2000 after you do your leakdown test just to be sure. Good luck!

[desert_rat]

Leakdown and compression tests are absolutely rock solid (both before and after head rebuild:) How much am I looking at for new injectors?

B

[WestSideBilly]

I have the same problem although mine doesn't stall (idles down to < 500 RPM and recovers).

My tech is going through a rather time consuming process to verify the injectors are bad.

[WestSideBilly]

Leakdown and compression tests are absolutely rock solid (both before and after head rebuild:) How much am I looking at for new injectors?

B

I was quoted $900 to replace the injectors (which I think is a bit steep). I think the injectors are about $90-100 each and are a fairly simple replacement.

[desert_rat]

OK, so new injectors it is. Has anyone ever heard of an IAC going bad? Also on the lunatic fringe side of life, the possibility that the cam occasionally either shifts into VTEC when it shouldn't, or doesn't shift out. Wouldn't a cam in VTEC on position cause these symptoms?

B

[Goku]

I could be wrong, But I belive the car wont even idle if the vtec cam is engaged. the lobe is to strong. And there is a CEL code for that. So the ecu would know if vtec was engauged.

[joe_s2k]

I have the same problem although mine doesn't stall (idles down to < 500 RPM and recovers).

My tech is going through a rather time consuming process to verify the injectors are bad.

PM Trackit (Curt) with this problem Jeff. This sounds like something he's got the answer too.

[repiv]

Has anyone ever heard of an IAC going bad?

Yes, I've heard of the IAC solenoid going bad. Replacement fixed the odd idling problem.
Can you be sure the valve adjustment is correct and the timing is good when the head was put back together. It sounds like symptoms similar to bad valve adjustment or timing being off a bit.

[desert_rat]

Curt down at Tracktime in Houston did the head, so I assumed it was done right :) I'm going to go for replacing the IAC and then the fuel injectors. If that doesn't do it......

[WestSideBilly]

PM Trackit (Curt) with this problem Jeff. This sounds like something he's got the answer too.

The tech working on my car is quite good and thorough. The problem is that the car doesn't cooperate by misfiring when he's got it. I'm sure it's the same problem you went through back in the day, but I'd like to make sure before I start throwing parts at the car.

[ExploreRPG]

My car has started stalling at intersections as well.. Funny thing, I believe it is the gasoline. Many gas stations are starting to mix ethanol (10% or more) in their gas. Be sure to read carefully the gas you put in your car. I noticed a big difference when I put a lower octane (non-ethonal) gas in my s2000.

Here is a few link:

http://www.ec.gc.ca/cleanair-airpur/CAOL/transport/publications/ethgas/ethgas.pdf
http://www.cartalk.com/content/features/alternativefuels/flexfuel.html

I was in the process of spending the $$ to trace down this problem, but I truly believe its cause by ethonal blending..

Tye

[repiv]

My car has started stalling at intersections as well.. Funny thing, I believe it is the gasoline. Many gas stations are starting to mix ethanol (10% or more) in their gas. Be sure to read carefully the gas you put in your car. I noticed a big difference when I put a lower octane (non-ethonal) gas in my s2000.

Here is a link: http://www.ec.gc.ca/cleanair-airpur/CAOL/transport/publications/ethgas/ethgas.pdf

I was in the process of spending the $$ to trace down this problem, but I truly believe its cause by ethonal blending..

Tye

A 10% ethanol content in your gas is not the problem. I typically run this in my car during the winter as it's a natural gas line antifreeze. I occasionally use it in summer when I want to bump up the octane a bit. My car does not suffer from it in any way.
First of all, we must not allow ourselves to get into the "I've the got the exact same thing" syndrome. Falling idle and even stalling at intersections or when we come to a stop is not uncommon with this car (and some other kinds of cars, too), especially when combined with hot weather and air conditioner use. Please tell us ..................... does it drop idle dangerously low at times to the point that the engine and car shakes? Does this happen especially when you approach the intersection and you push the clutch in? Do the following as a "test":
Adjust your driving technique such that when you are approaching a stopping point, downshift as you normally should. Near the stop, be in 2nd gear, NOT coasting. Do NOT push the clutch down till your rpm gets to about 1000 rpm or just BELOW, then push the clutch in and complete the stop. Be careful not to fixate on the tach and run into the car ahead of you. Learn to do this by engine sound and feel so you don't have to stare at the tach. How's the idle doing now? If you've "cured" you situation, then it's normal and I'll explain why when you report back. If it still stalls, then you may actually have a mechanical issue that can be addressed.

[ExploreRPG]

I have a 2000 S2000 and I had already ordered a map sensor, because I was in the process of "tracking" the problem as the original poster. However, my car would stall at intersections very very very badly, regardless of how I drove down shifted, and even coasted in the intersection.

On hot days it is worse, but the car would even stall at 60mph when I held down the clutch and waited for the rpms to drop... down... down.. down.. down.. to zero.. and then off..

Changing the gas to a lower octane has made the entire car perform better. The car even sounded totally different. It began to "roar" again when I hard accellerate. With the ethanol, the engine seemed noticably quieter. Sure, it could be spark plug, sensors and other things.. but this is a cheap fix while I track the problem and I thought it was definately worth mentioning. (and if it never happens again, how is it NOT the solution?)

Since I've changed the gas, it has not stalled 1 time.. (Normally it would stall at least 2 times when ever I drive the car, more on hot days.)

just my two cents.

[repiv]

On hot days it is worse, but the car would even stall at 60mph when I held down the clutch and waited for the rpms to drop... down... down.. down.. down.. to zero.. and then off..

This is not a good thing to do. It only confuses the ECU. It sees that you have road speed from the speed sensor, yet you have low manifold vacuum (no engine breaking when letting off the gas). The ECU can't resolve why you are asking for idle when you are going at speed. This is not a good test.
"Coasting" to a stop is also not a good thing as it is related to my point above. The fact that it may not stall just because you use a lower octane gas may only be an indirect result and not address the real problem. I'm curious why you change to a lower octane gas and not change to the same octane gas but without ethanol. This would be a better test. Ethanol "can" contribute to slightly clogged or erratic injector performance, especially if the injectors are on the edge of acting up anyway. Properly operating injectors should not be affected by a small amount of ETOH.

The car even sounded totally different. It began to "roar" again when I hard accellerate. With the ethanol, the engine seemed noticably quieter. Sure, it could be spark plug, sensors and other things.. but this is a cheap fix while I track the problem and I thought it was definately worth mentioning. (and if it never happens again, how is it NOT the solution?)
You can't always judge engine performance by how it sounds. The "roar" you hear may simply be the ECU backing off timing due to the lower octane. That what it does with low octane. Noise can sometimes make you "feel" the car is performing better (note how a cat back exhaust or CAI makes some owners "feel"). It's NOT a solution because it doesn't really "fix" anything. You may simply be bypassing another issue by making the engine function in a way that is less than optimal in another way. However, if you are happy with it, that's all that counts.

[desmo4]

Coasting is also not recommended in the manuals as it can damage the LSD.

Jonathan

[sebringsilvers2]

Just throwing in a question here. I am working on an 00 with 95k miles on it and it is basically throwing p0304 and a p1399 in the temp dtcs. Eventually the other 3 cylinders will follow with their corresponding misfires. Has anyone seen the timing chains stretching with the older models getting past 100k miles more frequently? We all know that the 100k miles haven't been easy on the engine. I will be back in town tomorrow night and will continue looking into this car, but this is one of the things I have been leaning towards. The only thing I have actually found with the HDS while at idle and no loads is that the spark advance is very retarded. 5 degrees when it should be around 13 degrees or a little higher. Just trying to get a head start on this and see if anyone has ever experienced a timing chain problem.

Kevin

[repiv]

Just throwing in a question here. I am working on an 00 with 95k miles on it and it is basically throwing p0304 and a p1399 in the temp dtcs. Eventually the other 3 cylinders will follow with their corresponding misfires. Has anyone seen the timing chains stretching with the older models getting past 100k miles more frequently? We all know that the 100k miles haven't been easy on the engine. I will be back in town tomorrow night and will continue looking into this car, but this is one of the things I have been leaning towards. The only thing I have actually found with the HDS while at idle and no loads is that the spark advance is very retarded. 5 degrees when it should be around 13 degrees or a little higher. Just trying to get a head start on this and see if anyone has ever experienced a timing chain problem.

Kevin

Misfires like this can be extremely troublesome to resolve and can be attributed to so many different things. I would suggest you first randomly rotate all the coil packs around and check all sparkplugs for condition and proper gap. Try some heavy duty injector cleaner and check the air filter. Put in a known good MAP sensor. Also, a car with 100K miles on it most likely has a pretty dirty fuel sock. Have the fuel pressure checked. The car could also be in dire need of a valve adjustment and could also have a few cracked or sunken valve spring retainers by now. Lastly, if all else fails, consider the ECU itself to be bad.
Timing chains don't tend to be an issue on this car. However, the timin chain tensioner is a fairly well reported issue. If bad, it will tick like a playing card in a kid's bike spokes.

[repiv]

Coasting is also not recommended in the manuals as it can damage the LSD.

Jonathan

Another good reason to not coast. Although coasting can be useful in diagnosing certain types of car ailments, this is not one of them. Coasting, if done as a habit, is generally seen in beginners and those who aren't familiar with driving stick (the proper way) or understand how a modern day manual car functions.
On a side note, for those who have driven a late model N. American automatic car, you will notice that if you are driving at speed and you put it into neutral and take you foot off the gas, the idle will hang way up high and fluctuate like crazy. Now, this is not a direct correlation with what's begin discussed here, but the computer algorithms are not dissimilar. The same ECU confusing brain fart happens, only the results manifest themselves differently. Modern day cars are complex enough that it is very easy to produce a brain aneurysm in these things.

[SheDrivesIt]

Coasting is also not recommended in the manuals as it can damage the LSD.

Jonathan
Now that's something that I was not aware of. Guess I should read the manual again. Can someone explain the mechanics of how the LSD might be damaged by excessive coasting?

[sebringsilvers2]

Did a valve adjustment, rotated coils, changed plugs, timing chain tensioner is not really noisy, had a ecu laying around so i swapped that, no change. I have a few map sensors which i forgot to swap out. I will swap one out just since i haven't tried it. So what is with the retainers cracking? Is that a pretty common fault? I have had a few injector problems on some i have worked on but that was for one cylinder throwing a misfire and not all of them. Unless that single misfire is bad enough at times to make the crank sensor think it is coming from another cylinder. But i will definitly not rule out low fuel pressure or dirty injectors. I am just leaning towards a more mechanical engine problem.

[repiv]

Now that's something that I was not aware of. Guess I should read the manual again. Can someone explain the mechanics of how the LSD might be damaged by excessive coasting?

I think Desmo was referring to "manual" transmissions rather than the owner's "manual". I'll let him elaborate.

[repiv]

Did a valve adjustment, rotated coils, changed plugs, timing chain tensioner is not really noisy, had a ecu laying around so i swapped that, no change. I have a few map sensors which i forgot to swap out. I will swap one out just since i haven't tried it. So what is with the retainers cracking? Is that a pretty common fault? I have had a few injector problems on some i have worked on but that was for one cylinder throwing a misfire and not all of them. Unless that single misfire is bad enough at times to make the crank sensor think it is coming from another cylinder. But i will definitly not rule out low fuel pressure or dirty injectors. I am just leaning towards a more mechanical engine problem.

If you've rotated coil packs and have done the plugs and the misfire stayed in the same cylinder, then I think it's related to injector or valve train for that cylinder.
Yes, cracked or sunken retainers have become an alarming issue that has come to light only in the past year or so. These are the result of mis-shifts to a lower gear that may or may not have achieved an over-rev. Even the abnormally rapid acceleration of the valve train due to an inadvertent mis-shift can do damage to the retainers. Only upon very close inspection and knowing what to look for, can you rule out damaged retainers as a cause for an engine issue. Such retainers can cause scoring in the cam lobe and also make a proper valve adjustment nearly impossible.

[sebringsilvers2]

Thanks for the info repiv! I will see what I find out and will let you know, especially if it is a retainer issue. I don't remember having a issue or that I noticed anything out the ordinary while I was adjusting the valves. None the less I will let you know what I find out.

Thanks again,

Kevin

[hayabusa1285]

Thanks for the info repiv! I will see what I find out and will let you know, especially if it is a retainer issue. I don't remember having a issue or that I noticed anything out the ordinary while I was adjusting the valves. None the less I will let you know what I find out.

Thanks again,

Kevin

HA! this was my car... it ended up being a bad injector, go figure. anyways i can happliy say the ca has been running good only problem i have seen from it since it was fixed was the battery went bad but that was over 3 years old so i guess it was time

[bimdub]

wanna see how bad a damaged retainer can trash your engine?

well from what I have learned I lost a retainer, valve locks, valve guide, valve stem, rocker shaft, rocker arm, and then the camshaft in my latest fiasco, the car ran actually well, the idle was lees than glass smooth but the car seemed to run decent enough, albeit with a certain amount of valve train noise.

had it not been for the noise I may have never even known this was going on until.....BOOM!

the noise was actually very subtle, like a singer sewing machine in the next room, mostly occurring at 2K rpms or so.....and not load dependent....best heard with the top down. this link carries the photos of the "damage" after only 20 miles of driving with this noise. imagine what it looked like after another 20 miles to the dealer? I can tell you for certain that it sounded much worse by then.....much worse.....more like a dozen singer sewing machines in the same room! the biggest surprise was the complete lack of any warning....not even a single trouble code, let alone CEL? and this was probably just miles from complete and permanent mechanical failure by the time I got it into the shop!

http://forums.s2kca.com/showthread.php?t=24423&page=2

[repiv]

As for how to check for sunken valve spring retainers, Billman sent me this pic years ago and asked me to post it for him. I just found it again and here it is:

http://inlinethumb58.webshots.com/30713/2883497150025981935S600x600Q85.jpg (http://good-times.webshots.com/photo/2883497150025981935mFZXVy)

The one on the right is sunken.