ok i have a 93 B13 SER i been having this problem for a while I cleaned the MAF Sensor Checked the O2 Sensor look perrty clean almost new,Also changed the plugs has ngk iridium and fresh plug wires.Also cleaned the Throttle body it had a lot of grime around the edges.And for mods just headers and 2.5 exhuast and CAI. Car runs strong has a Jdm motor with about 90K+ It does back fire under heavy acceleration also notice smell of unburned gas My current MPG is about 20-23 and thats with alot of highway driving not sure *** it is hope you guys can help out

iridium spark plugs are usless whitout an high voltage coil
...chek spark plug cables resistance, verify if some contact have rust and the TPS voltage must be round 500 mV... for me between 480 - 500 mV its fine

iridium spark plugs are usless whitout an high voltage coil
...chek spark plug cables resistance, verify if some contact have rust and the TPS voltage must be round 500 mV... for me between 480 - 500 mV its fine

how would i check the TPS Voltage Newbie here

how would i check the TPS Voltage Newbie here

The easiest way is with Nissan Data Scan. To do this, you need the software (Google it) and the cable to connect your laptop to your ECU through the diagnostic port under the fuse box.

The old school way is to connect a volt meter to the proper wires at the TPS. There is probably a procedure somewhere on the Forum you could find by searching, or it would be in the Factory Service Manual.

The most common issue causing poor fuel economy is a bad O2 sensor. You say that it "looks" new, but that doesn't mean that it is working properly. There are tests that can be done to check functioning of the O2 sensor. Again, you can look for these on the Forum or in the FSM.

PM me if you can't find the info you need and I will try to help out.

Bill

sorry whit a multi tester first chek the resistance on spark plug cables whit the omega sign and if some cable show 0 that means its cuted
...next un the thortle position sensor and also the multi tester but this time on V (voltage) you will see te conector and 3 cables exit from theres, whit this one conected (dont unplug it) put 2 thin wires from behind side by side the cables who exit form it until you tuch the metalic conector inside it ...chek the tester and it must say 480mV - 500mV IF its more than 500mV (0.5V) that means the intectors stay open longer and U have to much gas to burn
I hope this can help U

The easiest way is with Nissan Data Scan. To do this, you need the software (Google it) and the cable to connect your laptop to your ECU through the diagnostic port under the fuse box.

The old school way is to connect a volt meter to the proper wires at the TPS. There is probably a procedure somewhere on the Forum you could find by searching, or it would be in the Factory Service Manual.

The most common issue causing poor fuel economy is a bad O2 sensor. You say that it "looks" new, but that doesn't mean that it is working properly. There are tests that can be done to check functioning of the O2 sensor. Again, you can look for these on the Forum or in the FSM.

PM me if you can't find the info you need and I will try to help out.

Bill

I don't think its the O2 sensor i had another one and gave me the same problem ...i tried looking for it on the forum but no luck how could i test an o2sensor and im going to try checking the TPS as soon as i buy a volt meter... oh and if there is a problem with the TPS how would i fix it

You can test your O2 sensor by putting your ECU in Self-Diagnostic Mode 2. Basically, you will be setting your ECU to send signals to you through the Check Engine Light in your dash. It's been a while since I've done this, and I can't remember the details so I looked it up in the FSM. But I'm having trouble getting clear on what the FSM is saying. Here is my best guess -- no guarantees it will work.

- Warm your car up.
- Turn ignition switch to "On" - the car is not running at this point - just turn the key to "On."
- On the "front" of your ECU - the side farthest from where the harness hooks up, there is a screw that you have to turn with a small screw driver. To get to it, you need to unbolt the ECU from the floor and rotate it to get to that side of the box. Turn the screw fully clockwise and hold it there for at least 2 seconds. Then turn it back fully counterclockwise.
- Start the engine.

At this point, the CEL should be showing you the signal from the O2 sensor. You may want to run the engine at 2000 RPM for a couple minutes to make sure that everything is warmed up. Then hold the engine speed at 2000 RPM, and the light should go on and off indicating that the mixture is swinging from rich to lean (light on means lean). If it goes on and off more than five times every 10 seconds, then your O2 sensor is good. If not, you have an issue.

When you turn the ignition off, the ECU will go back to normal mode.

If anyone has corrections to this pricedure - please jump in.

Bill

You can test your O2 sensor by putting your ECU in Self-Diagnostic Mode 2. Basically, you will be setting your ECU to send signals to you through the Check Engine Light in your dash. It's been a while since I've done this, and I can't remember the details so I looked it up in the FSM. But I'm having trouble getting clear on what the FSM is saying. Here is my best guess -- no guarantees it will work.

- Warm your car up.
- Turn ignition switch to "On" - the car is not running at this point - just turn the key to "On."
- On the "front" of your ECU - the side farthest from where the harness hooks up, there is a screw that you have to turn with a small screw driver. To get to it, you need to unbolt the ECU from the floor and rotate it to get to that side of the box. Turn the screw fully clockwise and hold it there for at least 2 seconds. Then turn it back fully counterclockwise.
- Start the engine.

At this point, the CEL should be showing you the signal from the O2 sensor. You may want to run the engine at 2000 RPM for a couple minutes to make sure that everything is warmed up. Then hold the engine speed at 2000 RPM, and the light should go on and off indicating that the mixture is swinging from rich to lean (light on means lean). If it goes on and off more than five times every 10 seconds, then your O2 sensor is good. If not, you have an issue.

When you turn the ignition off, the ECU will go back to normal mode.

If anyone has corrections to this pricedure - please jump in.

Bill


Im going to give this a try after i check my TPS sensor today

Im going to give this a try after i check my TPS sensor today

Good luck - it really does work, even though it sounds kind of sketchy.

Ok it seems my tps sensor was off I left it at 485_490 my MPG got a little better and here are my results on thanks giving day I filed up my gas tank at a local chevron and put little over 10 gal and my tank was kind of empty drove it to my brothsrs house 180 mi round trip all Hwy doing about 80_85mph the whole and 115mph a couple of times my nephew could nt help him self :D but just real quick we didnt wanna get pulled over and now it has 245 mi on it these were half hwy and city there s a little bit of gas left over maybe enough for 25mi hwy how does it sound is this as good as it gets maybe il change o2 ssensor after a few checks ill post my final mpg tommorrow tel l me what u guys think

ok my final MPG was 259.4 that was on an empty tank reserve light turned on so i guess i avg about 25mpg is this as good as it get or have you guys gotten better

26mpg for going 80-85 mph highway sounds about right. If it has a header make sure the O2 sensor is grounded.

26mpg for going 80-85 mph highway sounds about right. If it has a header make sure the O2 sensor is grounded.

Really I have headers but I don't think its grounded how can I tel l