honeywheel11

Not sure if anyone will be able to help me, but I have an 03 Silverstone with about 80k on it. Current mods to the car include AEM CAI and Invidia q300 exhaust. Not too long ago, I started noticing what I thought was a valve tap in the engine. It would come and go intermitantly and usually I wouldn't hear it until it got close to mileage/time to change my oil. The past few times I went to get my oil changed I asked the tech to check it. They said that I had my valves adjusted at my 60k tune up, so not to worry, but said that they would keep an eye on it. Everytime I went I asked them to check it. Evertyime I got the car back they told me the car was running fine.

Recently, my car threw a CEL for the secondary O2 sensor. I took it to the dealership and they said I needed to replace the cat and then quoted me a price of $1,400. I decided to take it to the mechanic that did my exhaust and he said he could get me the cat and replace the sensors @ cheaper cost. He does the work, car runs fine, no more check engine light...until two weeks ago.

The check engine light came on and would come and go even though the car ran fine (one day it was on the next it was off kinda thing). I figured it was a faulty sensor. I let this go on for a week and finally checked the code and it said P0420 (Catalyst System Efficiency Below Threshold (Bank 1). Im like "wtf" is this? The cat is brand new. The next morning on the way to the dealership I dont make it a mile before car starts to run really rough and begins to backfire between 1-2500 rpm, and drives rough at low rpm, but once i got over that rpm range the car ran fine. I get it to the dealer and it throws the same P0420 code and now P1399 (Engine Misfire any cylinder pending).

They hold the car for the day and then tell me they cleared out the codes. The CEL comes back on for P0420 code and that basically I have a faulty cat and need to get it replaced. They mention something about the back pressure and my exhaust possibly being the problem - I know very little about cars but I thought that the larger the exhaust the more it reduced back pressure. I call the mechanic who did the the cat install (its under waranty) and he says to bring the car back to him and he will look at it and replace the cat, but that he thought it might be something else. I go to pick up my car and the dealership tells me the car is running fine now with no sputtering/backfiring - I ask them if they are sure it is OK to drive? "Yes," was the reply. I dont make it down the road 1/2 a mile before the thing starts doing it again. Even worse, as I turn around to take it immediately back to the dealership, the car shuts off on me at 55mph.

Now they quoting my all these different prices in the 3-4k range (including sending something to the machine shop because my valve clips are going bad?). None of this makes sense to me and finally they call me and admit that they cant figure out what is wrong with the car and that they will have to rip the engine down further to give a better diagnosis - At this point i dont trust them anymore.

Has anyone run into anything similar? Can anyone recommend a good mechanic in the Howard County/ Baltimore area?

thanks.

Uncoolron

Sorry to hear all issues with your car but all I can say from reading your long story is, stay away from that stealership you are dealing with and your own mechanic sounds kind of shady also.

If you posted for help before all of this happened we could have saved you some money but that is besides the point now. I wish I'm close to you but there a lot of good members in this community that can help you out in your area. For me the best way to figure out what is going on is to thoroughly check all your ignition system.

Good luck.

TrumpetTitan

I had the P0420 code when my S had roughly the same mileage as yours, but I had no other symptoms.

I ended up replacing the stock cat with a Berk high flow cat because the Berk cat actually cost less than an oxygen sensor from Honda. It was an easy job, just liquid wrench and then 5 bolts.

I'd recommend the Berk cat, it'll cost WAY less than what the stealership will quote you on an OEM cat. Can't help with your engine sounds though.

honeywheel11

I actually had the Berk HFC on there for a while, but then I got tired of listening to the gf (at the time) complain about driving in a race car.

LagunaBlu2k

If the sensor is bad replacing the cat isn't going to fix it because you'll be.plugging the same sensor back in. My stock cat are my o2 sensor at around 20k dealership told me it was my problem. Your mechanic sounds shady/lazy. If you pay somebody to do something doesn't matter if it needs to be done or not. It's what you want not what he thinks you should have.

e3opian

e3opian

Did your mechanic replace the cat with an OEM or OEM equivalent? That could be cause for Cat efficiency code... As for the misfire... and now resulting failure -- Has any one checked your ignition coils? They can be problematic as the car ages. I'm just waiting for mine to go. You can swap with someone else pretty easily. Main thing is get the car out of there and get someone that knows the S2000 involved.

Olegator

Where are you (the car) located?

If you are mechanically inclined I suggest taking the car back home and dropping the cat to see if it is, in fact, going bad. (One way to tell is to hit it with the fist and listen for rattling while it is still on the car). If it is bad - replace with BERK high flow unit.

If the cat seems fine, then check the Bank1Sensor1 O2 sensor. That is the only sensor that can cause the car to behave like you said it does.

I have a computer that I can plug in and monitor both sensors' output. By looking at the data I will be able to tell you exactly what's going on.

Easy.

BTW, monitoring O2 sensor output/hitting the cat is the only thing needed to diagnose this.....it's beyond me that mechanics at the dealership can not diagnose this. : /
(I'm ASE Master tech...just to give my words some credibility)

Monch

Oleg- With a majority of mechanics at stealerships today, if the engine doesn't spit out a code that specifically spells out what's wrong and how to fix it, they seem to be lost in the sauce. It's kind of ridiculous. Kind of like, remember when the guys at Advance and Autozone knew a damn thing about cars?

honeywheel11

Thanks everyone. I appreciate all of you taking the time to comment.

Olegator - I am in Columbia. The car is now 20 minutes north.

Update - I had the car towed out of there today to a mechanic that works on hondas and has done work on s2000's (a friend of the family recommended this individual). Hopefully, I found someone reliable to work on the car going forward, but that remains to be determined. As far as the previous posts, I am in agreement with everything that has been said. I had the dealership doing the oil changes and what not, mainly because I work so much that I don't have time to do them myself, well let me rephrase that, I am willing to pay to have them done instead of doing them (lazy). To address some of the questions/comments above:

Before I purchased the Berk HFC, I had the factory cat in there and it started to go bad. The thing was making a loud rattling sound when the car was running as all the particle matter or whatever they call it had deteriorated to the point where I could here it moving around in there. I think the movement of this stuff actually caused the demise of my secondary o2 sensor. Instead of paying 1,400 to replace it, I opted to get the berk hfc as a cheaper alternative. I purchased a new secondary o2 sensor as well. When I had the berk hfc in, everything ran fine (minus the intermittent tap I referred to above). The drone eventually started to get to me and I had the berk replaced with an oem equivalent (which i am now realizing may have been a big mistake after reading some of the other boards on here). I should hear back from the mechanic tomorrow morning. I am wondering if:

The oem equivalent cat that I put on the car is crap and has now clogged or is messing with the back pressure somehow which as a result is causing the sputtering/ backfires. I had also wondered about the Bank1 o2 sensor (olegator) and if it might be bad or because the cat isn't working to spec could hypothetically be reading levels that would affect the air/fuel mixture (maybe running too rich??). The mechanic said he would monitor this to determine if that was the case. I am also wondering now if (based on the post above) if one of my ignition coil packs has gone bad. I will post an update tomorrow.

thanks.