here are some pics the soot is mostly around the tailpipe... and that is a brand new bumper installed after I was rear ended, washed 3 times

Edited July 2, 201114 yr by grantf

There's really only a couple of things left, if you're sure that al of your parts are Nissan stock and correct for the year. Are you running the stock ignition system, no dual spark or MSD type? I only ask because the ECU fires the injectors after every third discharge of the coil. That would probably show up as a higher tach reading though,since the tach is on the same circuit. Does your tachometer work correctly?

It's usually a bad idea to replace parts without being sure but for $10 you might be able to at least look at another ECU. This guy is in your neighborhood and has your ECU #, I believe, for $10. He's just cleaning house. Worth a thought - http://forums.hybridz.org/index.php/topic/100893-ecu-blowout-10/page__p__945646__hl__ecus__fromsearch__1#entry945646

I have read of ECUs going bad and running rich, but never for as long as you've been driving.

I don't know enough about the inner workings of the injectors to guess what happens to them when they get really worn. Maybe the flow rate goes up. That's really all there is to the system - ECU opens injectors for a "calculated" amount of time (based on temperatures and other inputs) and fuel flows out of the injector at an assumed rate.

I just thought of one more option and again I don't know what would happen if, but the TPS has three positions, idle, cruise and full enrichment. Maybe your TPS is stuck on full enrichment. The ECU thinks that you have the throttle close to wide open. It could also be stuck on Idle, I suppose, since that is also an enrichment position. Again, probably best to test at the ECU. The pin numbers are in the Fuel section of the FSM, and are the same at the ECU plug. I would do that before anything else, it's easy.

Edited July 2, 201114 yr by Zed Head

Testing the TPS would be a real good idea. Make sure it is working properly. If it was stuck on full or idle enrichment it would cause you to run rich.

The CTS sensor resistance does seem a little high. Replace it. It's cheap. You can get one from a local parts house. 100 ohms out would make a noticeable difference, I don't know if it would be enough, but it might help and it's a common failure. When they start to go bad, resistance gradually goes up on them.

Follow Sarah's suggestion and run the car with the AFM cover off, and finger the wheel around a little to see if richening it up or leaning it out helps. Hook a vacuum gauge up while it's running and see what direction you have to move it in order to get vacuum up to 18 or so.

I've read about plenty ECU's going bad and running lean, I've not read of any going rich. Personally I don't think it would be the ECU but its' possible I suppose.

Also, what condition are the tune up parts? Plugs, wires, cap, rotor ?

new wires, cap and rotor day before this thread was started, new plugs (and I gapped them) same day I posted the photo of them in thread. it's getting late. Also I am pretty sure I have a ZX dizzy (new cap for a 77 280 did not fit, new 79 cap was identicle to my old one.

I have not really played with the TPS yet. Will do some reading on it tonight and look tomorrow morning.

I am trying not to through parts at the problem for two reasons, 1: it is expensive and 2: I am really learning a lot about the efi system and my engine in general tracking this down systematically has lead me to make minor repairs along the way that I normally would not even look at for example the PCV hose I found out yesterday was so loose I could slip it off with my fingers on the crank case end (tightened up now).

Edited July 2, 201114 yr by grantf

Systematic is good, grant. Although Eric is right that the CTS is a pretty cheap item, I suspect there's something else going on besides a failed sensor. I say that because resistors (including thermistors) tend to fail by opening up (infinite resistance), rather than shorting or partially shorting. I suspect there's some issue in your wiring. Either that, or you're not looking at the correct pin when looking for #13.

I'll be very interested to find out what your finger tweaks of the AFM mechanism reveal. It's very quick and easy and will tell us quite a lot.

Ok I am trying not to run in circles, but I think I noticed something strange: It appears that perhaps the connectors for the thermotime switch and the temp sensors have been swapped. I checked for continuity between the connector that is plugged into the cold start valve and the temp sensor and I got continuity on each pin respectfully! I need to look again but this strange. Also I checked the continuity between one pin on the connector that was plugged into the termotime switch and got continuity to pin 13!

Edited July 2, 201114 yr by grantf

Ok I drove around a little and warmed up the car (mostly I needed coffee). guessing that the water temp is around 160, tested resistance and got .26 k .So though this is not accurate as far as temp and it seems a little low this is closer than the .05 ish I was getting before.

Regarding the tps: at idle both contacts are closed I adjusted it to open between center and right contact between 1300 and 1400 rpm, it was staying closed till about 1600. not much of an adjustment at all. one thing is that the left contact always seems to stay closed is this normal? no adjustment seems to effect the right contact. I verified these settings with a meter.

Edited July 2, 201114 yr by grantf

Regarding the AFM: since swapping the sensor conections my vacuum has dropped back to 14 in HG, though I suspect it is due to a vacuum leak somewere. While the engine is idling if I jently move the wheel on the AFM clockwise I get better vacuum, around 16 in Hg the engine idle increases and sounds better . CCW and the engine sputters. I would say CW about 5 to 8 degrees at most before the engine starts to degrade.

Here are some better pictures of my AFM guts. It almost looks like it has been set way on the rich side. Am I wrong?

Edited July 2, 201114 yr by grantf

Ok sorry about so many posts. I revisited the tps and readjusted it. it looks as if the left contact was almost always closed. I noticed this by unplugging it and the engine ran better, also the vacuum jumped back up to about 15 hg. again I played with the AFM wheel and this time only a slight improvement but moving it cw by about 2 deg. (my vacuum climbed to near 16). I believe that my previous AFM test was compensating for the TPS not being set properly.

So I have found two potential culprits, but I don't think I am out of the woods yet. yogurt cup test later today for shure (my girlfriend saved a cup for me).

update:

Edited July 6, 201114 yr by grantf

update:

So far I have rectified the sensor plugs being swapped, I am surprised my car ran at all. Adjusted the TPS, I am sure this contributed to my problem. Replaced the vacuum lines that were in doubt, I still only have between 15 and 16 in HG though it is quite the improvement over what I had before, also tightened down the valve cover bolts, they were really loose and tightened the PCV hose, I could turn it with my fingers before. Adjusted the timing to 10 deg at 800 rpm and tested the vacuum advance it advanced about 5 deg with vacuum applied using a mighty-vac, though "I had to keep pumping it to maintain vacuum, does this mean the dash-pot thingy is leaking? also I noted that after getting the water temp sensor to operate correctly my engine ran rough until it warmed up, this makes some sense though if it is enriching the mixture on an engine that already is running to rich. the ohm reading for the temp sensor makes sense now and seems to coincide with the chart pretty closely. I have been checking it hot (I believe around 180 deg to cold, around 75 deg and it seems about right. another thing I did was back out the idle mixture screw about 8 turns, it was about 6 turns out from bottom and the engine idles really well now. so next my car was on empty so I wrote down my mileage and put 10 gall in. When I am on empty again I will post my results. I am hopeful but a little pessimistic. Also I did do the yogurt cup test, It was inconclusive, I now understand how it can help diagnose a vacuum leak but in my case I could not pinpoint where it could be coming from other than the manifold gasket itself, I understand that this could be an unfortunate reality, but as my car is running good I will put this idea in my brain's closet for now. I have read up on Fastwoman's thread along with Cozeye's problem and mine seems to be coming from the opposite direction, though I now understand why you put the resistor in line from the WTS. I think I need an anti resistor!! anyhow time will tell (or ten gallons).