E16s running lean

slazzy2k · Jun 18th, 2005, 04:11 AM

87 Sentra, E16s, California emissions

Been having a fair bit of trouble with my sentra lately. I discovered that the air/fuel ratio solenoid had no continuity and I destroyed it getting it out of the carb, so I swapped it with one I stole out of an '85 at the local pick 'n pull. Then I thought the o2 sensor was bad, so I found a boneyard replacement for that, too.

Here's my problem: Backprobing the o2 sensor gives me ridiculous readings of somewhere between 0.03-0.09V all of the time. (Both sensors did this). If I force the choke closed the richen things up, the sensor comes alive and starts outputting 0.55-0.65V which seems right. So according to what I can find, this means that my mixture is completely out of whack, and has been for quite some time. (I've noticed in the form of horrible mileage, usually around 24mpg or less highway)

Here's what I've done so far to try and figure out what's causing this:

- Tore the EGR valve off, cleaned it out, tested it for vacuum. Passed.
- Tested the EGR control solenoid. Passed.
- Adjusted the throttle switch to spec.
- Tested the Vacuum Sensor. Passed.
- Checked out the mixture heater and relay. Passed.
- Checked out the air injection system, everything is fine.
- Replaced the fuel filter, air filter, plugs, pcv valve
- Numerous other small things

What's wrong here? There's that screw that's sealed up in the back of the carb, but that's just for the idle mixture and the o2 sensor reads far too lean at any rpm. Tomorrow I will be tediously removing every single vacuum line and inspecting/replacing them as I am convinced that this is a vacuum problem. Any insights? I've been working on this thing for a good 3 days now and it's getting a little tiresome.

Oh, also I think I read somewhere on here that the EGR valve should open up if you rev it up to around 3k or so, I've tried that and the EGR doesn't seem to move, so I haven't ruled that out yet either.

mille-16i · Jun 18th, 2005, 06:18 AM

the easiest way to check for a vac leak is to use either starter fluid (will ignite if you are not carfull) or carb clean and first spray it down the carb to see how the engine responds to it then shield the venturies and sray it on the lines if the engines responds then you know where the bad line/s are and you can continue to pin point where it is. Good luck. Also a O2 sensor will go read rich lean cause what a car dose it go from rich to lean to average out at 14.7 to 1

slazzy2k · Jun 18th, 2005, 08:31 PM

I found today that at both the air temp sensor and the coolant temp sensor, I am only getting about 2.5V from the ECU. Does this mean my computer is bad? Manual says it should be 5V in both cases.

slazzy2k · Jun 19th, 2005, 03:22 PM

In the event that I try and swap the ecu, are different years compatible? There are only a couple of Sentras at the boneyard that might qualify, one is an 85 and has a manual transmission (mine's an AT). I don't think I can find an 87 donor car, and if I could it would probably be fuel injected, making it useless to me. Please help!!

velardejose · Jun 19th, 2005, 09:53 PM

87 us version e16 sentra
I have one...
It had an e-assisted (e-impaired) carb, and was impossible to get decent idle and mileage, besides it had lots and lots of vacuum lines...
Since I switched to a mechanical carb it idles like a clock and got more mileage, had to replace the optical dist too