High hydrocarbons and misfiring

[Vodkaboy]

well, today was the first day i have been able to drive my Z, and it was runing a bit rough. Anyway, when it is cold it misfires quite a bit, but after it warms up, it misfires less it seems. I also took it into DEQ and it failed hydrocarbons by a factor of 3X (OUCH!). this is not a cali Z, and never was equiped with a cat (nor will it ever be equiped with one if i have any say in it). Anyway, i began to figure that it might just be running rediculusly rich after the DEQ results, also causing it not not/misfire when its cold (and as it heats up it gets enough heat to ignite the rich mixture and is happy).

Would an overly rich mixture cause these problems? how can i adjust the mixture, and when do i know i am at an optimal mixture? note: this is a '77 280Z, so no O2 sensors like in the ZXs.

i have also been thinking about running some ATF with the gasoline to clear out any carbon deposits. Would carbon deposits be a cause for any of these problems, or am i right in assuming im just running FREAKING rich.

the feeling of the misfires is kinda a sudden lurch in the car, and a pop sound.

also, it only does it below 2200 or so RPMs, especially while under load (accelerating, going up hills, etc)... it absolutely never does it at higher RPMs (except for a single pop once at WOT at around 2900)

[Hallaian42]

Man, I have the same exact problem and i still havnt traced the problem directly. Here's what you can do though. Check the spark plugs. If they are all black and smell like gas then you have a rich condition problem. Next thing i would recommend is get a manual and check all sensors. There are numourous causes for this problem. Your coolant sensor might not be working right, the thermo-switch might be causeing your cold start injector to stay open giving you 7 injectors instead of 6. The list goes on and on. For me, i have 72, with the 77 setup so smog is not a problem. I removed the cold start, air regulator, and thermo switch and im still getting rich condition. The best thing you can do is use that service manual, it saves you headaches. Let me know what you find.

--Steve

[sjcurtis]

I also run a fuel injected Z.

I would start by confirming fuel pressure is in range, make sure the fuel filter and lines are clear. check the fuel pressure regulator is operating correctly.

next

check airflow meter flap for smooth operation

next

check full throttle switch in the throttle sensor is not stuck closed. (this will supply full rich by itself)

next

set the igmnition up from base line check plugs, lead, distributor cap internal and external check rotor button and then re tune the ignition.

next

check all connectors around the engine are not loose or damaged.

This is what I call step 1

You should find one or more problems by this point, also your problem rich mixture and poor running should start to improve.

let me knoe how this goes and I will try to steer you through to a fix.

Point of interest

My latest smog test figures are:

CO 2.11 %

HC 270 ppm

6/73 with 100368 miles

Cheers

Steve :classic: