View Full Version : HELP! I can't get my car to run right. Running Rich black smoke!

10-01-2008, 07:03 PM
Ok, I have a bit of a problem.

First the car:

97 240sx with an S14 SR20DET blacktop VTC.
New spark plugs
255lph Walbro Fuel Pump
Full 3" exhaust.
Auto to 5spd Swap.


The car (http://zilvia.net/f/#) at idle belches black smoke. It smells of fuel and most definitely is because of the black smoke. I'm new to the Nissan scene, but I've been modifying rotaries for over 10 years. The car idles at 800rpm with about 10-11 in/hg vacuum. The car will rev past 2500 rpm while at a stop. While driving the car, it will rev freely but feels weak, due to the continued rich state. The engine only boosts about 5-6 psi while floored. I do not have a boost controller and I am only running the wastegate off of the intercooler piping.

If I unplug the MAF, the car revs up for a few seconds then sputters out and dies. The MAF voltages check out. The o2 voltages check out. The igniter chip voltages check out. All of the coil packs have the correct voltage as well. I also check continuity throughout all of the systems.

Next I performed a vacuum/boost leak check. I found a leak at the turbo inlet elbow, fixed it, and it did not solve the problem. I used a homemade pressure testing kit, as can be found on this forum and used a Ford (http://zilvia.net/f/#) dealership smoke kit, which pressurizes the system with smoke to find vacuum leaks.

All of the electrical connections are done properly with Ford/aero grade electrical connectors, no cheap butt connectors. Everything is shrink wrapped and neat. The MAF and o2 both have the correct shielded wire.

Replaced my Coolant Temp Sensor - no change.
Reset my timing mechanically to 15 bdtc.

There are no other vacuum leaks, the MAF checks out, the Ignitor checks out, o2 checks out, and the coil packs out. Injectors 11.4 ohms. Did the coil pack pull plug test, no change. Cleaned the IACV.

Checked my IACV and cleaned it. Upon inspection I noticed that the IACV was extremely dirty. I cleaned it out and checked the plunger. The plunger and spring were fine and the cleaning did me some good. No change.

I pulled my plugs as well to check the gap. The gap was fine but they were pitch black. I decided to put the "old" plugs back in, the ones that my engine (http://zilvia.net/f/#) came with, and it ran a little smoother.

When checking the ECU I get a 55 - no malfunction.

Checked TPS - good
PCV - Good
No catch can - factory set up.

Driving Impression:

The car drives smooth under boost. On deceleration the car's vacuum is at 20-22 in/hg vacuum and it decelerates smoothly without any hesitation or bucking.

However, under vacuum the car will buck, hesitate, and run pig rich. The idle is still at 11-12 in/hg vacuum. It runs extremely rich at idle still.

Another thing I noticed:

The car likes to really hunt for idle until the car is warmed up. It will kind of bounce around a bit between 1500-2500 rpm. When the car reaches operating temperature the idle falls to 800rpm and I get the 10 in/hg of vacuum. When the fans come on the idle smooths out a bit. When the fans turn off the idle will surge a bit and slowly bounce back and forth between 800-1000 rpm.

I also replaced the injector o-rings and insulators with no change...

Anyone have any other ideas.. I'm running out of ideas.