S13 Emissions: Failed Idle, Passed Driving

[NateDogg]

HI,

I have been working on my '91 S13 for about a month trying to get it to pass smog test here. The readings were about 260ppm HC (max 108) and 1.15% CO (max .82). The driving test passed fine with same numbers as last year's pass.

The vaccuum gauge reads 20in/hg at idle.

The car drives fine with good power. However, there was a stumble while shifting into 2nd gear at low rpm.

I just finished cleaning the IACV/AAC valves by taking off the intake manifold and sprayed a good bit of Carb cleaner into the EGR. The car idles very nice now but the O2 sensor still reads rich (.75V) and there is moisture coming out the exhaust even at operating temperature.

I have checked every sensor for FSM compliance and there are no ECU codes. The ignition system is fine (lots of spark) and I have just cleaned the K&N cone filter.

I have also added a ground spliced into the stock MAF ground wire to a cleaned part of the body. No change.

I don't know where to go from here. Please show me the light.

UPDATE: So it turns out my cams were *cough* about 30 degrees cockeyed each *cough* OOPS!! I just got it passed emissions today free and clear. Smells like a rose!
Modified by NateDogg at 5:19 PM 10/30/2004

[benemorius]

Try checking the ground and operation of your tps.

[s13sr20chris]

well there are a few ways to go here. disclaimer: we dont have emissions testing here so i dont have experience with it.1)fix the rich condition2)new cat3)band aid

1)you have checked everything and added a maf ground? thats good. if o2 is reading rich and you still run rich then o2 is not the problem. it pretty much comes down to maf, ect, and some mech pieces like inj. or fpr. you could try checking your maf signal voltage. cleaned and grounded it may still be too high.

2)bad cars can pass with new cat so i hear.

3)i hear that a gallon of denatured alcohol in the tank will help you clean up. maybe a small controlled vac leak after maf would help.

[navysnail]

a new cat can help, also make sure the coolant temp sensor is in spec both hot and cold, those can be real trouble when they go bad and for a $25 dollar part its not that bad to replace.

clean the MAF with brake cleaner, be careful not to spray the hotwire directly, it is fragile

a controled vac. leak could help, but if it runs ok, then it could create a lean condition and that is about the worst you can do for the longevity of an engine (it would also put the NOx emmisions off the wall.)

[NateDogg]

Thanks for trying to help guys, I appreciate it. I notice that when the car first starts up, the O2 reading is .3V then as the car is running it gets increasingly more rich. The O2 reads .75V at operating temp. I think that is something to do with the fuel injectors. I had this same problem a couple years ago and it was so bad the car would overheat from one cylinder being too rich and the O2 backing everything off. I will put in new O-rings and see if that helps. Any tips for installing/removing injectors from the fuel rail?

The MAF reads 1.15-1.2V at idle.

BTW the coolant temp sensor reads fine. I will also check the grounds and ECU connection (had a wire come out of the harness).

Also, I can get a video of this thing running if that would help.
Modified by NateDogg at 4:20 PM 9/22/2004

[s13sr20chris]

so your o2 does not cycle back and forth?

[NateDogg]

No, not at idle. The readings I have stated are for only idle. At 1200rpm+, it fluctuates properly.

[navysnail]

that may cause it, but i dont think it would be ok when warming up then bad running, to make sure: the cts does read around .33 kilo ohms (is that the value, its 33 somthing) when warm

[NateDogg]

240kid, yes the coolant temp sensor reads .33k ohms when warm. I was talking about the values from the O2 sensor.

I pulled off the fuel rail and all the injectors are fine, no leaks and they shoot a decent mist.

Back to the drawing board...

edit v=ohms

[180fan]

when was the last time you got a tune up?

with the engine running, the engine temp sensor should read 1.0v - 5.0v.

try the basic tune up first ie new plugs 02 sensor with a check on your timing.

[NateDogg]

Well, I'm starting to think it's the Walbro 190lph fuel pump putting too much base pressure. I will check the pressure tomorrow and report back.

180fan, the car is always tuned up. New or checked everything basically.

[NateDogg]

Well, good news and bad news.

Good news: I found out the problem. Walbro 190 killed my fpr. For two years it ran fine and passed emissions but now the base pressure is up to 40psi with vacuum connected and 50psi without. So that is about 6-7 psi too high. I would assume the 255lph pumps do more damage.

Bad news: I gotta pull out the Walbro and put in a stock one. I can't afford the Nismo regulator, yet. EDIT: I'm having second thoughts that a busted fpr might not even work with a stock pump..I will know tomorrow I guess. Anyone have any experience about this?

Thanks for the help, everyone, especially s13sr20chris. I am so glad I can finally FIX the problem. After going through my entire engine, I now know I won't have to look at that mess again.

This problem should make people aware that any aftermarket pump may cause a poor idle, power loss, increased emissions and higher fuel consumption.

Hope somebody else can learn from my stupidity.
Modified by NateDogg at 10:29 PM 9/23/2004

[s13sr20chris]

my 255 does all of those!

[NateDogg]

You'd think by fixing the fuel pressure, the car would be fine. Well, it's not. Still rich at idle about 13:1 afr. I need it 14-14.7 to pass emissions here.

DAMN!!

[/vent]