1997 with issues

[PorknBeans]

P0100 = Mass Air Flow sensor > located on the right side of the throttle body > measures intake air via a “hot wire”. The ECU sends a voltage to this wire to heat it up and in rush air flow cools the hot wire and the change in voltage needed to keep the hot wire hot tells the ECU how much air is being taken in.

P0180 = Fuel Tank Temperature sensor > located inside of the fuel tank

P0500 = Vehicle Speed Sensor > located on the transmission

P0505 = Idle Air Control Valve(IAC)- Auxiliary Air Control Valve > located on the left side of the throttle body and needs a cleaning of the carbon build up so that the plunger can slide back and forth upon the ECU commands. Idle increases about 50 rpm when the A/C is turned on as not to stall the engine with the extra load placed upon it.

[jp2code]

Of those codes P&B defined, the MAF and IAC codes would cause engine issues. P0100 will make it run bad around 2200 to 2500 RPM, but I'd suspect P0505 is your idle problem.

[Chainsaw]

Thanks guys.

Since my moving the harness around yesterday, this truck is almost undrivable. It missed more than it ever has on the way to work this morning. Guess I know what I'm doing this weekend... I'll toss a new fuel filter on too.

[jp2code]

If wiggling the harness caused it to drive differently, I would suspect wires that are frayed inside, grounds that are not tightly bolted down, or corrosion on the connections. Wiggle that harness again to see if it goes away. This time, pay attention to what section you are wiggling and see if any connections look suspicious.

Georgia isn't exactly a "hot state", so I wouldn't think the fuel tank temperature (P0180) would be an issue. But, on P0180 OBD-II Trouble Code, I read this: "The engine may misfire, hesitate, and stall if the fuel temperature exceeds normal operating temperatures"

Have you put any fuel additives in the tank? Or, do you park over really hot pavement?

[Chainsaw]

Originally Posted by jp2code

If wiggling the harness caused it to drive differently, I would suspect wires that are frayed inside, grounds that are not tightly bolted down, or corrosion on the connections. Wiggle that harness again to see if it goes away. This time, pay attention to what section you are wiggling and see if any connections look suspicious.

Georgia isn't exactly a "hot state", so I wouldn't think the fuel tank temperature (P0180) would be an issue. But, on P0180 OBD-II Trouble Code, I read this: "The engine may misfire, hesitate, and stall if the fuel temperature exceeds normal operating temperatures"

Have you put any fuel additives in the tank? Or, do you park over really hot pavement?

Not just wiggling, I moved the harness from where it was tucked between engine lift loop and valve cover. I'm sure I'll have to solder that crimp connection mentioned in the TSB.

I do park on asphalt at home and work, But the truck doesn't act up as soon as I start driving, usually takes it a few miles, if it even does it at all. After moving that harness, and having the trouble I had this morning, that has got to be the cause. Truck runs great otherwise. I did add a can of seafoam to the tank when I first started driving it. That was probably 3-4 tanks ago.

[jp2code]

You may have some water in the tank. I'm not sure how to check that, but I think they sell stuff at auto parts stores that you can add to the gas tank that absorbs the moisture.

The harness TSB was put out around 1994, so Nissan vehicles should have all been fixed before your 1997 came around. But, it never hurts to look into the connections! But before you rip the shielding all off, be sure to pay close attention to all of the other connections first.

[street_rulerr]

Originally Posted by jp2code

You may have some water in the tank. I'm not sure how to check that, but I think they sell stuff at auto parts stores that you can add to the gas tank that absorbs the moisture.

.

its called "HEET" and comes in a yellow bottle and a red bottle. its isopropyl alcohol if i recall...it just reduces the stumble till you can get more "gas" on the gas tank. I dont know the difference between the red and yellow bottle though. I DO KNOW that if you run your gas tank down to like nothing, then put in about 6 bottles you can pass emissions testing with that

[Chainsaw]

Plot thickens... maybe.

On page EC-305 in WSM, I did the injector test. Battery V is 12.25 at terminals. Front 2 injectors are 11.68V with injector resistance at 8ohm. Spec is battery voltage and 10-14ohm. I didn't test other 2 as it is a bit damp in Georgia at the moment.

[jp2code]

I suspect only 8 ohms means those injectors are sending too much fuel. That could account for your high idle.

[Chainsaw]

Found a loose ground wire, from fender to block. No change.

Tested the TPS from WSM EC-122 and EC-123. I have power and ground to the plug, but no continuity on the TPS itself.

Voltage at all 4 injector plugs is closer to battery V since tightening the ground. Injectors are at 9ohms now.

Also while driving home, at about 1/4 throttle and 2500 rpm is where my problem is. Can hold foot steady, pop in N and engine will hunt from 2200ish to almost 3000 for as long as I hold my foot. Can return to idle, and repeat consistently.