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High NO levels for smog-FAILING

The sensor has HI and REF marked on the outlets. There are two connection points on the exhaust, the one closest to the intake and egr valve will be REF and the one further away will be HI. REF is the one that gets a drop in pressure as the egr valve opens to intake vacuum. HI means high pressure or the one exposed to exhaust back pressure all the time. The DPFE measures the difference between the two to determine how much egr valve is open. Inside the tubing is a washer with a small hole in it, that restriction between the two pressure read points is what creates the difference in pressure.
 
damn, i dont know if im getting more troubles... i had 4 codes prior to the dpfe installment. P01131, P01151, P0401, and P0171. now i know what they are, but what im confused about is that after changing out the sensor, P0171 isnt showing anymore, but the other three still are, i said, wat the heck, why not try and get it smog anyway? so i reset the code and drove around trying to complete 6 of 8 cycles, thing is, only 3 want to complete, the other 3 dont want to! wtf, i know how to complete the OBDII cycle monitors... i just want to know what other things it can be to cause high NOX lvls? clogged egr pipe too? what else if any?
 
The 1131 and 1151 mean you are lean, maybe vacuum leak. The 401 may mean EGR passages clogged, I hear that's common on sixes. Sensor change out will not touch the first 2 at all, that's not what's making them. You either have old wore out O2 sensors or airleak of some sort. Running lean won't cause the EGR codes, but won't help either, can make NOx go up a bit.
 
amc49 said:
The 1131 and 1151 mean you are lean, maybe vacuum leak. The 401 may mean EGR passages clogged, I hear that's common on sixes. Sensor change out will not touch the first 2 at all, that's not what's making them. You either have old wore out O2 sensors or airleak of some sort. Running lean won't cause the EGR codes, but won't help either, can make NOx go up a bit.
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i've changed my o2 sensors twice now, its not that. i have a hole somewhere... well okay. later today im going to go back and get another smog test, just to see the numbers, if anything changed. and if not, then ill definently check if i have a leak somewhere, and even check for clogged egr passage way. for this leak, what hoses should i be looking at? the egr lines? or just EVERYTHING in general?

edit::
wow, i just got back from smog on the car.. and the results are the same. failing for NO(PPM) over 25mph only... RAWR!!
 
From my earlier post:

"They usually plug right behind the throttle body. Remove the throttle body and clean the passages."

This would be passages in the intake manifold, and in particular where the passages change angle and narrow down so it is easier to clog. Pull off the throttle body and its gasket and the plugged passages (or not) will be evident.
 
the cat has been hot for each test, and i replaced the egr, pcv, and dpfe. but now i will clean out the TB... any tricks i need to know? i noticed that there are a lot of springs around there, not to mention the Throttle cable... anything i need to know before i totally mess something up? are there anytricks on taking this thing out without damaging anything?
 
i failed a emissions test today and got the same result - NOx levels high (5 times the limit!)

So I guess I should start on the EGR.

Is there a way of testing the EGR without any tools?
 
i pulled the tube off of the EGR valve and there was suction.

I also sucked on the valve itself and it made the car almost stall.

So i assume the EGR valve is just fine. So now I don't even know where to look
 
Big Jim said:
...Other things that can lead to high NOX include a very (and I mean very) lean mixture, over advanced ignition timing, or anything that will cause hotter than normal combustion. NOX is formed by combustion being so hot that normally inert Nitrogen is scorched.
Click to expand...
This got me thinking. If you are using higher than 87 octane gasoline, try using 87 octane and see if it will help. You might get some engine pinging but at least your NOX levels will be lower and it might be what helps you pass emissions.
 
1131 & 1151

1131 & 1151

amc49 said:
The 1131 and 1151 mean you are lean, maybe vacuum leak.
Click to expand...
The codes 1131, 1132, 1137, 1138, 1150, 1151 & 1152 all have similar causes / fixes as code 1130. 1131 & 1151 both indicate lean conditions. There are many different causes. The following list pinpoints different areas to check. They are electrical, fuel system, Induction, EGR and base engine. This will give you all the areas to look at. Some are very easy to inspect while other a bit more difficult. If you can print the list, then use it to do your checks. I believe some of the things you have checked / changed have no bearing on your troubles. If you have already completed some of the items check it off the list. Tracking down problems like you are having is easier if you are systematic. The trouble shooting guide below is what a Ford garage would do. I would suggest you try the same format. It will help eliminate what is and is not relevant. Dan

Diagnostic Trouble Code Description Possible Causes
P1130 - Lack of HO2S-11 Switch, Fuel Trim at Limit The HEGO Sensor is monitored for switching. The code will set when the HO2S fails to switch due to circuit or fuel at or exceeding a calibrated limit.
Electrical:
· Short to VPWR or VREF in harness or HO2S
· HO2S circuit shorted to Ground
· Water in harness connector
· Open circuit
· Corrosion or poor mating terminals and wiring
· Damaged HO2S
· Damaged PCM (other DTCs should be present)
Fuel System:
· Excessive fuel pressure (stuck fuel pressure regulator, restricted fuel return lines, etc.)
· Leaking/contaminated fuel injectors or fuel pressure regulator
· Low fuel pressure or running out of fuel (fuel pump concern, fuel supply line restrictions, low fuel level, etc.)
· Vapor recovery system (stuck VMV, etc.)
Induction System:
· MAF contamination
· Air leaks between MAF and throttle plate
· PCV system / Other vacuum leaks
· Improperly seated engine oil dipstick
EGR System:
· Leaking gasket
· Stuck EGR valve / Leaking diaphragm or EVR
Base Engine:
· Oil overfill
· Incorrect cylinder compression
· Exhaust leaks before or near the HO2S
· Secondary air stuck on

HEATED OXYGEN SENSOR (HO2S) MONITOR - HO2S LACK OF SWITCHING
Diagnostic Trouble Code Description Possible Causes
P1131 - Lack of HO2S-11 Switch, Indicates Lean When an HO2S sensor indicates lean at the end of a test, the system is trying to correct for an over-lean condition. The code is set when the fuel control system no longer detects switching for a calibrated amount of time. See Possible Causes for DTC P1130

P1132 - Lack of HO2S-11 Switch, Indicates Rich When an HO2S sensor indicates rich at the end of a test, the system is trying to correct for an over-rich condition. The code is set when the fuel control system no longer detects switching for a calibrated amount of time. See Possible Causes for DTC P1130

P1137 - Lack of HO2S-12 Switch, Sensor Indicates Lean The downstream HO2S sensors are forced rich and lean and monitored by the PCM. The code is set if the PCM does not detect the output of the HO2S in a calibrated amount of time. · Pinched, shorted or corroded wiring and pins
· Crossed sensor wires
· Exhaust leaks
· Contaminated or damaged sensor

P1138 - Lack of HO2S-12 Switch, Sensor Indicates Rich Same as DTC P1137, but indicating rich. See Possible Causes for DTC P1137

P1150 - Lack of HO2S-21 Switch, Fuel Trim at Limit Same as DTC P1130, but opposite bank. See Possible Causes for DTC P1130

P1151 - Lack of HO2S-21 Switch, Indicates Lean Same as DTC P1131, but opposite bank. See Possible Causes for DTC P1130

P1152 - Lack of HO2S-21 Switch, Indicates Rich Same as DTC P1132, but opposite bank. See Possible Causes for DTC P1130
 
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