Hoping to get an opinion or two on a minor issue.

Backstory: 1992 RHD JDM FD R1

Mods: Intake & Exhaust

I picked up this car in November, she has a blown coolant seal so after about 1 hour of driving/idling she'll purge all her coolant out the overflow container (this is not a huge concern at the moment as I'm having RPM build me a new motor over the winter).

I don't drive the car, she's stored (but I visit on weekends to tinker with the interior that I'm replacing).

However, I did take the car out briefly to get an emissions test (for ***** and giggles, to see if she'd pass because if she does I don't need an emissions test for 2 years and I can get my plates now)

She did FANTASTIC on the at speed test (as far as I'm concerned):

HC (Max allowed): 283
HC (Actual): 132

Co% (Max Allowed): 2.24
Co% (Actual): 0.03

However I failed the curb idle portion of the test:

HC (Max allowed): 300
HC (Actual): 565

Co% (Max Allowed): 1.50
Co% (Actual): 1.63

As far as I was concerned, I thought that was pretty close for the curb idle. I do however, have a very slight misfire at idle, I occasionally get a bit of a "popping" exhaust note and my idle will fluxuate a little... maybe jump or dip a few rpm every 10 seconds or so.

I'd like to pass my emmissions test on my current (blown) motor if possible so that I don't have to worry about tuning my new setup once it's in to pass the test, get my plates, and so I can drive my car to get my swap instead of towing it.

I've ordered a new set of plugs, I plan on changing them as soon as I can. I have no info on how long the current plugs are in the car. I'm betting they're old and very fouled. I'm sure a new set will help get my HC at idle down.

My question: Is there much else that would lead to an occasional misfire at idle?

Any pointers or suggestions would be great!

-Geoff

 

you say you have intake and exhaust. What exactly is your exhaust system? What cat do you have?

 

I'm assuming it's the stock cat, the cat back is 5Zigen. I'm in the dark about most of what has (or hasn't) been done to this car as I imported it from Japan, I have no history on the vehicle.

I have been under the car and the cat looks very stock. (and to point out the obvious, because the car is JDM, I don't have the pre-cat at all).

-Geoff

 

http://www.nichols.nu/tip517.htm

The CO reading tells you about the fuel mixture. For the most part, HC and CO are unrelated, unless the mixture on a cylinder is lean enough to cause a misfire. Lean conditions result from vacuum leaks at hard/cracked/broken hoses, leaking gaskets and boots around MAF/MAS sensors, and partially clogged fuel injectors. Old vacuum and emissions hoses undoubtedly need replacing just due to age on many cars, so getting all new ones and installing them in one session is not a bad way to go.

A poor oxygen sensor might cause a lean condition severe enough to create a misfire, but an engine with reasonable ignition will easily fire with that slightly lean mixture.

 

Thanks for the input.

EVERYTHING under the hood is getting replaced before the summer. I'm just hoping with a new set of plugs it might be enough to squeeze past the emissions regulations before the swap happens.

If not, it's not a terrible loss, it just means I'll have to get the new engine tuned to pass emissions first, the power later.

-Geoff

 

Is the air pump installed and working? I would assume it is since the car passed one of the tests. Spark plugs seem like a good idea, and it's probably a smart move to change the spark plug wires while you're in there. I try to replace spark plugs (and wires) one at a time rather than removing all at once, because the lengths are close enough that it's easy to mix them up.

 

Air pump is installed and working.

Plugs will get changed as soon as they arrived, I ordered a set off of ebay, I'll see if I can find some wires locally.

-Geoff