Schecter19

Hello All,

Looking for any and all advice to get my car back in order! I've looked through several threads describing similar issues but haven't found anything that has helped my case thus far. To start off my car threw a random misfire about 2 months ago. I didn't think too much of it and cleared the CEL to see if it would come back. Several hundred miles later there was no code, and then one day it was back. The CEL would stay on for about a week, then disappear for a week... sometimes it would be gone a couple days, sometimes a few weeks. It seemed to come and go, and I started to notice that it would pop up when I stayed in idle for an extended period of time, after the car would start to shake. The car shakes at idle occasionally, but drives completely fine once I give it gas and it doesn't seem to have any noticeable impact at speed. I am by no means a mechanic and am trying to digest the info provided in the forums as best as I can, I bought a OBD2 scanner to help with the diagnostics, but am not sure what to look for and notice when a number is out of line. I will list the problem I am having with the car, and what I have done per recommendation to fix the issues. If the weather has any factor on this, I want to include that the car is kept outside in North Carolina weather conditions (almost never snows).

Problems: Car shakes at idle and throws CEL random misfire code. Misfire CEL will appear first in one cylinder then move to random cylinders until all four show a misfire. I have noticed that occasional when I approach a stop-sign soon after starting the car, the revs will drop and the car feels like it is about to stall out but never does. Seems to drive perfectly fine otherwise, and shaking at idle stops if I give it a little gas.

What I've done so far (all within the span of a year):
Took my car in for the routine 60,000 mile maintenance
Took it to the dealership to get a valve adjustment
Dealership suggested changing spark plugs so I did
My usual mechanic suggested coil pack, so I replaced them all
My usual mechanic cleaned fuel injection lines
My usual mechanic ran a compression test and I was told that all cylinders were in reasonable deviation of each other.
I was told to take it back to the dealership, and see if the valve adjustment I had done was still good.
Dealership said of course the valve adjustment was good because they did it, and suggested it was a bent valve because the car shakes at idle
They told me that this was caused because I over-revved the engine or miss-shifted into the wrong gear (I asked if there was any other way this can happen, as I have not miss-shifted it ever).
My mechanic told me to ask if they looked through the plugs with a parascaltic scope to see if the valve was bent and they said they did not.
The dealership recommends me to ship the engine off to get it rebuild (with only 60,000 miles on it) for $2400 and only have suggested that the problem is due to me miss-shifting the car.

At this point, I don't know what to do. I am very hesitant to ship the engine off for a large amount of money when the car seems to drive perfectly fine, only having shaking when idle. The CEL seems to be staying more than it is gone at this point. I uploaded some fuel trim data that I captured using OBD fusion to see if there is any red flags. I would like to note I daily drive this car, and never redline or miss-shift it. The dealership mechanic simply kept telling me that I or the previous owner (owned 30,000 miles prior) must have miss-shifted the car, and wouldn't believe me when I said I truly had not.


^At speed, don't understand why short fuel bank 3 is not moving similar to bank 1?

^At idle, tried to catch it when the car began to shake. This dip seems to be when it is shakes

I have greatly enjoyed having a s2000 these past 5 years, and would love to get it back to perfect working order. Thank you all for any help that you can contribute, I will try my best to digest any advice and put it to good use! I am new to using an OBD2 scanner, however, I have OBD Fusion available to me for any further diagnostic I should take a look into. Thanks, Josh.

RolanTHUNDER

Just a thought, have you checked your IACV?

s2000maniac

Mis fire/Shaking at idle is usually a sign of bad fuel injectors. I know personally 2 s2000’s that had similar issue and new injectors fixed it.

RolanTHUNDER

That's definitely plausible.

Schecter19

I haven't I'll have a look at that and also check out the injectors. I did have the injection lines cleaned, but doing that wouldn't help me if they were bad injectors to begin with. I'll try to clean the IACV this weekend, and I'll see if that does the trick, thanks!

Schecter19

I'll see if I can test the injectors before buying a new set, but luckily it looks like new injectors won't break the bank. I actually probably should've changed those out prior to coil pack! Also my mechanic noted that there was fuel/gunk buildup around the injectors, which is why he offered to clean them in the first place, in hindsight probably should've had them checked to make sure they were all still good. I'll look into that, as well as the IACV, thanks!

RolanTHUNDER

Hopefully new injectors will solve the problem if you find out that your old ones are definitely bad. Might as well just buy a set if you can even before testing the current injectors especially if you don't plan to upgrade your injectors for boost down the line...
Let us know as soon as you fit the new injectors

project2k4

Bro mine started with the same symptoms as you, rough idle & CEL but then it would clear up & drive fine. Replaced all the parts you listed, among a few others, did not do a compression test(as it was done a year prior) or pay to scope out bent valves. I would suggest you take off your Fuel Injectors & have them sent off to be untrasonically cleaned.If you decide to go this route: Injector Repair LLC: Our Injector Service purchase the full cleaning & read out. Email Jim@injectorrepair.com & mention you are having a similar issue to Collin. He's a stand up guy, refunded me the money for those he couldn't fix. I'm 99% sure it's my injectors. When he got them for the first test he said they were horrific & no car should run on these. Luckily with some cleaning & some used OEM injectors(sent out for cleaning before install), we are looking close to solving the problem. If you're interested in my notes of tracking down the culprit of the dreaded P1399 code, below is the link. Let me know of any questions. My car is just sitting there, waiting & hoping.

https://www.s2ki.com/forums/s2000-un...-help-1194476/

Schecter19

I cleaned the IACV, and performed the idle relearn procedure on my car. The code went away, and I drove it long enough to allow the ECU to reset fully. It has been about a week since I cleaned it and the CEL has not officially reappeared. It did appear one time after I started the engine, sitting at idle, it flashed twice then went away. I don't know if that fixed it 100%, but it definitely has a more consistent idle and the rough idle is much less frequent (one time in a week). I'll attach pictures of the IACV before and after in case others have this same issue, I

IACV before

IACV after
definitely would recommend doing.

Schecter19

One more quick thing I would like to add. I am waiting to see if the CEL comes back before ordering the new injectors. However, I was installing some coilovers onto my s2k when I noticed this on my exhaust. Is it at all possible that this is causing the misfire codes, probably a really dumb question, but I had read online that air leaks in exhausts can throw misfire codes and mess with ECU fuel readings. Thought it was worth at least bringing up... Btw I only noticed this because when I started my car the exhaust would rattle, and the left tip had way more give when you push on it than the right one did. I looked over everything while I had the car jacked for my HKS coilovers, and this is what was causing the rattle, does this make sense or am I overthinking this...


Right exhaust, wielding seems sealed (Comptech Sport Exhaust)

Left exhaust, heard rattling, more give when pushed, not sealed...