Failed smog BIG time...need help

[Viggen]

Well, there are two temp sensors on the 3.9. One is for the temp gauge and it is functioning correctly and there is another one that serves as a sending unit for the ecu to either lean or enrich the mixture. There is no black soot and it is leaning out the faster the motor is spinning or its just burning the fuel thats pouring into it. I took it to the shop today to pick the brain of the guy there and the timing is spot on, the throttle response is crisp and perfect, the O2 sensors look new but will be replaced, it has a new IAC valve in the intake, and after all of that, there only two things left. One is that temp sensor and the other are cats and Im really hoping that its not them.

 

[Viggen]

FYI: NTK (division of NGK) makes direct replacement O2 sensors for the truck and they also manufacture the Lucas OE ones. I pulled my O2 sensors today and found one with Lucas stamped on it ABOVE NTK and NTKs part number. There is no reason to but OEM ones since they are just rebrands.

 

[Viggen]

Failed again...on only idle HC section of the test. I have done:
- Oil and filter
- Air filter
- Trans flush and fill (unrelated but it needed it anyway)
- MAF cleaning
- Fuel injector cleaner/ Land Rover "Fuel system conditioner"
- Brand new NTK (what Lucas rebrands as their own) O2 sensors
- New coolant temp sensor (the computer one, not the sending unit for the gauge)
- No vacuum leaks or bad hoses
- New IAC valve (done by PO)
- New distributor installed by Roverland and timing is correct (done by PO a couple months ago)

Still running rich at idle but not at speed. It idles great. Doesnt bog on acceleration and always idles down smoothly. Mileage has increased greatly since the above have been done but not in rich running condition.

Im running out of ideas here. I have only a few avenues to go down now.
(1) One theory, the muffler is installed/ welded in backwards. Yes, some idiot saw the "INLET =>" as a suggestion and welded it in so that it is now the outlet. One theory, baffles are facing the wrong way and causing issues with the sensors since spent gasses arent able to make their way out at idle but are under speed since there is significantly more pressure to force spent gasses out.
(2) Second theory, there is a lot of carbon build up in the combustion chambers leading to a "sticking" valve. The fuel/ air mix enters the chamber and when the piston comes up to burn the mix, it isnt able to as the chamber isnt completely sealed and since that is the case, the unburned fuel is being moved out the exhaust manifold. Ive scheduled for one of those BG cleanings for tomorrow, sort of like a Seafoaming but a little more in depth.
(3) Computer issue. Dont know where to go from there.
(4) Using that rich issue and a match to blow the pig sky high :Wow1: . So, not seriously that since I love the truck but I need it to pass...

Need some serious help here.

 

[R_Lefebvre]

I just don't think it's a misfire or sticking valve issue. I don't think the HC is showing up because you have unburnt mixture going into the exhaust. Here's why:

The Air/Fuel Ratio meter, O2 sensors, and the "dilution" sensor on the test rig do not measure fuel content in the exhaust. They measure O2 content. If you have unburnt mixture due to a misfire, or a stuck exhaust valve, you are pumping raw O2 into the exhaust. This will peg the O2 sensor into the lean zone. Because your ratio is showing rich, you can't be passing unburnt O2. Only unburnt fuel. We also see that in your HC emissions.

Did your dilution change? How long did you drive the truck on the new O2's? It will take a little while for the computer to re-adapt, unless you can force it. This was easy on Fords, disconnect the battery, and step on the brake to drain any capacitance. That kills the memory. Apparently on Rovers it's not that easy.

 

[Viggen]

The valve might not be sealing completely, not allowing the gas to completely burn off and allowing some of it to escape out the exhaust unburned. My dilution numbers are around 14.0, down from when it REALLY failed in both categories. Now, the dilution numbers are lower but Im passing at speed and failing at idle. The O2 sensors have about 50 miles on them now of mixed driving at highway speeds and putting around town.


Any thoughts about the muffler? Would that cause an issue? One hypothesis is that the muffler is acting as a road block and not allowing the spent gasses to exit easily at idle and messing with the sensors. I pass the at speed portion because the revs are high enough to make up for any blocks by pushing past the baffles that might be serving as a hindrance.

The only thing left after that is the ECU but why is it working well at high revs but not at idle?

I dont understand how it can fail now but pass last year with less than 500 miles in between. I just dont get it.

 

[R_Lefebvre]

Yeah, it is confusing. We're flying blind here because you can't tell us what's going on in the ECU at all. It could still be your MAF. I don't generally believe in cleaning them. Not that there's anything wrong, but that it doesn't really help. I guess some have done it successfully, but for how long?

No, I don't think it would be a back pressure issue. If anything, increased back pressure should hold the charge in the cylinder more at idle.

Is there any chance your HC problem is actually burning oil?

What's the full readout this time?

 

[Viggen]

Yeah, it is confusing. We're flying blind here because you can't tell us what's going on in the ECU at all. It could still be your MAF. I don't generally believe in cleaning them. Not that there's anything wrong, but that it doesn't really help. I guess some have done it successfully, but for how long?

No, I don't think it would be a back pressure issue. If anything, increased back pressure should hold the charge in the cylinder more at idle.

Is there any chance your HC problem is actually burning oil?

What's the full readout this time?

Yeah, there are no codes on the display but from what Ive been told, the ECU is laughingly simple and doesnt throw a check engine light or anything like that. Only thing that I know about the ECU is that fuel and spark get there at the right time to make it idle smoothly and start up everytime.

Well, I cleaned the MAF out and along with the plugs and oil, the mpg picked up and the HC's dropped down. About the oil, heres my question: why is it higher at idle and lower at high revs with no smoke at either? I would think that if it were an oil issue, which I doubt, wouldnt there be more oil being burned at higher revs as the crankcase will be building more pressure and thus venting/ forcing more oil around?

I will get the readout out of the truck after the rain has stopped. Its in the center console right now but I can tell you that I passed at the 2500 rpm range with slightly higher HC and lower dilution numbers and failed at the idle test with higher HC and lower dilution numbers.

How does one check for a leaking injector? Maybe an injector is seeping? Also, there is still "Land Rover Fuel System Conditioner" in the system. Will that skew the results at all? Its weird that the results were worse with new O2 sensors.

 

[Viggen]

Okay:
Numbers with everything but new O2 sensors and temp sensor:
Idle- Failed
HC ppm: 289 out of 125
CO%: 1.00 out of 1.00
RPM: 694
Dilution: 14.0
2500 RPM- Pass
HC ppm: 84 out 125
CO%: 0.91 out of 1.00
RPM: 2384
Dilution: 14.2

Numbers with everything including O2 sensors and "Fuel System Conditioner," except temp sensor:
Idle- Failed
HC ppm: 354 out of 125
CO%: 0.92 out 1.00
RPM: 684
Dilution: 13.9
2500 RPM- Pass
HC ppm: 100 out of 125
CO%: 0.92 out of 1.00
RPM: 2442
Dilution: 14.1

So, I did WORSE with new O2 sensors. Weird. I even checked voltage at the harness plug and it was the required 5 volts. I have the new coolant switch in it but havent had a new check yet. Carbon clean out tomorrow with hopefully the muffler being turned to flow the correct way.

 

[sven]

If you really want to test for a sticking valve, do a compression test. If you find a really low cylinder then do a leakdown test on that one to find out where the compression is being lost. Usually a sticking exhaust valve will cause a very noticeable misfire while in 4th gear on the highway, its very obvious.

 

[David Harris]

Okay:
Numbers with everything but new O2 sensors and temp sensor:
Idle- Failed
HC ppm: 289 out of 125
CO%: 1.00 out of 1.00
RPM: 694
Dilution: 14.0
2500 RPM- Pass
HC ppm: 84 out 125
CO%: 0.91 out of 1.00
RPM: 2384
Dilution: 14.2

Numbers with everything including O2 sensors and "Fuel System Conditioner," except temp sensor:
Idle- Failed
HC ppm: 354 out of 125
CO%: 0.92 out 1.00
RPM: 684
Dilution: 13.9
2500 RPM- Pass
HC ppm: 100 out of 125
CO%: 0.92 out of 1.00
RPM: 2442
Dilution: 14.1

So, I did WORSE with new O2 sensors. Weird. I even checked voltage at the harness plug and it was the required 5 volts. I have the new coolant switch in it but havent had a new check yet. Carbon clean out tomorrow with hopefully the muffler being turned to flow the correct way.

If it's been running rich for a long time and those are the original cats, then that's a definite possibility, as painful as that sounds. They are needed more at idle than any other time.