unixpilot

Hey all,

Ok here are the details of the problem or maybe this is normal?

Everything else is in good order (general engine health, boost pattern, etc) but I can't understand why my car is running so rich

'95 base model automatic
Greddy SP CB
Downpipe
High flow Cat
Power pulley
Stock intake & ECU (as far as I can tell, visually checked ECU no aftermarket stickers/ etc.)
gas mileage normal (averaged 21 mpg on a long highway trip doing 75+ most of the way)
had a Pettit tune up less than 10k miles ago.
Last week I pulled the leading & trailing plugs on one rotor and their pretty black.

Get light blue smoke on cold startup until it warms up. Then exhaust is clear. No toxic fumes. Idle is rock solid

I get a huge black puff of smoke during a redline 1-2 shift, I don't usually see anymore black smoke after that.

At idle in neutral, when I gradually bring the throttle to 6500+ rpms there is no black smoke, however if I floor it its clear up till 6000rpm or so and then its black until redline.

No real backfires or flames on deceleration, but often I will get a quick series of 4-5 pops on deceleration.

I know without having a aftermarket ECU to adjust the fuel/ignition maps, and access to a dyno with wideband O2 to see what the real A/F ratio is I'm pretty much helpless.


So my questions are:

1. How many of you puff black smoke? (besides bonghits/etc...)

2. I know running overly rich is a bad thing, but what about in my case? It seems to really only run overly rich during high boost / near redline situations.

3. Is there anyway to determine if my ECU and or maps have been reprogrammed without opening the ECU and looking around? Are there any traps involved with this?

4. Maybe I should get an intake to help lean things out ......urgh......must say no to cheap power...ahh...body strong...mind weak....


Thanks for the help in tracking this down

7-sins

My mods are similar to yours except I have the Power FC. I seem to be running a little rich, or somethings not tuned correctly. I am going to try and get new plugs/wires when I get some cash. That is the best I could tell you, sorry not more in depth.

SAGE

better then running lean is all i got to say mine had the same problem and it was not big deal uses a little more fuel but who cares anyway i just filled up for .87 cents

SAGE

7-sins

Yeah it makes me feel better I wont pop my motor.... but.... there seems to be this high RPM miss, blowing black smoke, and an idle that likes to die.

Foz'sRX-7

Mine runs rich also.....re: weekly carbon buildup on rim of exhaust.

Mechanic not concerned. Have the following mods with stock ECU:
Pettit Cold Air Intake w/K&N Filters, Pettit 3" Downpipe, Apexi Dunk Exhaust, Pettit Power Pulley.

My understanding is that I can't add anymore mods without ECU upgrade. Next project will be: Hi-Flow Cat, Greddy Profec B Boost Controller, ECU Upgrade.

Then, I'll have to upgrade Radiator & Intercooler.

maxpesce

Try a new O2 sensor - as they go bad the CPU thinks the engine is running leaner than it really is and adds fuel to compensate

unixpilot

Ya but I thought the O2 sensor only controls the a/f mixture when your below 3000rpm or something, and not at WOT...

I am running overly rich in WOT near redline conditions

rx7_lover

oh my... my 7 does EXACTLY the same thing.

- running overly rich
- light black smoke at high RPM
- small pops during deceleration
plus
- less vacuum (14~15)

did u check your pulsation damper and injectors? you can smell fuel around black vacuum tank area if they are leaking.
make sure they are not leaking any fuel.

i did go through the whole vacuum lines more than 3 times and found no problem. now ill go check my injector duty since i have PFC installed yesterday. if anything comes up, ill let you know.

unixpilot

Ill check out the pulsation dampner and injectors, thanks... Ya without any diagnostic tools its pretty tough to track this down.

Maybe that's how I can rationalize a PFC purchase....Yeah..."Diagnostic Tool" I mean, come on honey...Sink busted? I need wrenches and pipes right?

Car not running right? I need a PFC, midpipe, SMIC, M2 airbox, etc...