1991 3SFE failed NOx emmsions

[daveO]

Hello I'm new to this forum,
My '91 camry, auto 2.0 #SFE just failed NOx sniffer by over 500 parts, 1700+ where I think its supposed to be 1200.

Things I checked already:

Spark plugs: new (2 mos) but already whitened=high engine temp

cooling system: just flushed with new thermostat, temp sensor in spec

Intake vacuum at idle: steady at 23 in Hg

IAC: in spec according to chiltons

O2 sensor: in spec accoring to chiltons

MAF: in spec according to chiltons

TPS: out of spec, replacing in 2 days

EGR: new modulator and BMSV check valve, EGR valve in good shape and opperates properly according to chiltons, EGR pipe has no build up and appears to have no leaks. To be noted though vac. reading between EGR valve and modulator at 2500rpm fluctuates between 7-12 in hg rapidly. I assume this is exhaust pulse from EGR pipe and OK.

All vacuums lines appear to be good with no leaks.

Car starts and runs well, doesn't hesitate (good throttle response) and appears to have good power although I have only owned this car for 6 months and don't have a standard to compare the power to. Car averages 23-26 mpg with mixed driving. Never runs hot according to temp gage.

Other than replacing the TPS what should I look at that might be causing the high NOx emissions? Is there a way for me to check the catalytic converter? It was already replaced 4 yrs ago by the previous owner. The car has good flow out the tail pipe without the "Pop or Sputter" it would get if the exhaust was blocked/clogged. Also is there a way to check the fuel pressure regulator?

I also intend to check the ignition timing to see that it is close to 10', not over advanced.

Thanks in advance for any input, sorry for the long post.

[daveO]

Aslo, does anyone know the compression values are supposed to be for the cylenders, psi?

[atobe]

around 130 i think as long as it's all even it's ok... no more than a 10% difference between cyln

[88 LE]

Originally Posted by daveO

Also is there a way to check the fuel pressure regulator?

http://autozone.com/servlet/UiBroker...3d8013f011.jsp

^ Look around in that section.

I also intend to check the ignition timing to see that it is close to 10', not over advanced.

Make sure you short TE1 & E1 together on the diagnostic connector before checking the ignition timing.

Shorting TE1 & E1 places the ECU into diagnostic mode.

Originally Posted by atobe

around 130 i think as long as it's all even it's ok... no more than a 10% difference between cyln

130 psi. is low.

I got between 190 - 200 psi. across all cylinders on my 3S-FE, before I grenaded a piston.

[Kep]

I expect that you have already looked but when I cleaned my EGR valve I found a carbon blockage where it attatched to the throttle body and found heavy buildup in the lower vaccum hose going between the modulator and the egr valve.

Just a thought,
Kep

[daveO]

thanks for the replies.

I have the chiltons manual which I believe autozone based their repair manuals off of. Neither of which outlines how to test the fuel requlator, just how to replace it and test for overall fuel system pressure.
--> like I stated previously, I don't think i have a fuel system issue as the car runs too well and has throttle response. But the plugs are white which could be caused by a lean condition. So I need to rule out the fuel system.

Oddly enough, neither the autozone site or the chiltons manual states what the spec for compression is. I know that the cylenders should all be with in 10% of one another though, but I will check to see if they are close to 190-200 psi based upon your suggestion.

Could a clogged cat cause the white plugs? I would think it would darken them, but I'm not an expert.

Could a cylender mis-fire cause the white plugs? eg ignition firing too early or more then once in an egine rotation.

Thanks for your guys input.
dave

[daveO]

Originally Posted by Kep

I expect that you have already looked but when I cleaned my EGR valve I found a carbon blockage where it attatched to the throttle body and found heavy buildup in the lower vaccum hose going between the modulator and the egr valve.

Just a thought,
Kep

I checked the EGR system, all the ports are clear on the T-body and pull around 10 in hg at 200 rpm. The modulator appears to be working properly acording to chiltons, and the temp vavle in the water neck is new. The only thing in the EGR system that is suspicous is that the vacuum fluctuates bewteen the EGR valve and the modulator at 2000 rpm, bewteen 7-12 in hg. The hose between the EGR and the modulator is in good shape with no leaks and the EGR valve is lean with no build up as well as the pipe from the exhaust to the egr.

[88 LE]

Originally Posted by daveO

Could a cylender mis-fire cause the white plugs? eg ignition firing too early or more then once in an egine rotation.

Well, white plugs = lean. And black = rich or your burning oil.

Plugs should have a brown and white color to them.


As for ignition firing to early, check the ignition timing with a timing light. And if the engine was mis-firing, you'd hear it.

A simple check is to start the engine. Pick a plug wire and unplug it. The engine should start running shitty, if not theres something wrong with that cylinder. Plug the wire back in and repeat the process on the other cylinders.



Are all the plugs white or just certain ones?

[atobe]

i checked spec is suppose to be 180 psi

[daveO]

Sorry for the delay in response, my home computer won't let me get on the forum for whatever reason....

88 LE wrote: Well, white plugs = lean. And black = rich or your burning oil.

Plugs should have a brown and white color to them.


As for ignition firing to early, check the ignition timing with a timing light. And if the engine was mis-firing, you'd hear it.

A simple check is to start the engine. Pick a plug wire and unplug it. The engine should start running shitty, if not theres something wrong with that cylinder. Plug the wire back in and repeat the process on the other cylinders.



Are all the plugs white or just certain ones?

All of the plugs were white, which tells me that there is a problem affecting all cylenders.
I checked the spark timing at idle with the motor hot, 15' where it should be 10', but i don't beleive that is enough to cause the lean/high cylender temp situation.
I replace the TPs and adjusted it (what a nightmare) but now it is running rougher than before when warm. Somehow the TPs managed to migrate on me and I had to readjust it agian, but now my reading are stable.

0 ohms closed, 150-300 ohms at .020", no continuity at .028", 4K ohms at full open, 5K ohms through VC+E2 independent of throttle postion.

I also noticed that the 02 sensor is reading 0.75v when warm which tells me that car might think its running lean, when I pulled a vac line the voltage drops to .012v which tells me the 02 sensor works. What could make the 02 think its running rich? A backed up/clogged exhaust?

also is there any way to test the Vacuum swith on the firewall that controls the fuel pressure regulator? Is there anyway to test the regulators themselves? It looks like there is one on the manifold and one on the fuelrail itself.

I'm beggining to run out of ideas...
thanks for all of your replies, DaveO