Exhaust lambda value too high

[GTamas]

I've been to an official inspection today and to my surprise they measured too high lambda values during the smog test: 1,7. At the same time CO and HC values are said to be okay, but they did not show me those values unfortunately.
Two months ago at an unofficial inspection it was 1,02 so it was okay. In the meantime I only did these works:
- cleaned engine bay by hand with wet towels. During this I dismounted the airfilter housing and the air hose. Put everything (hopefully) back as it was.
- Replaced one of the spark wires due to slightly burnt outer insulation

I don't hear or feel that a cylinder would be misfiring or something. Sounds normal to me, but during easy, slow start from idle, it feels maybe a bit sluggish.

What should I check? Can you give me any tips?

 

[GTamas]

The lambda values were measured at the tail pipe with gas sensors. Not from any diagnistics port.

 

[GTamas]

High lambda, or lean exhaust gas can happen also due to a leak in the exhaust system, right? I think I noticed now a slight ticking noise. I have to investigate that, too.

 

[Mustang5L5]

Exhaust leak would be a cause. A Lambda of 1.7 means your running lean, assuming the exhaust isn't leaking. 1.7 is pretty darn high though, any chance that was 1.07? If not, it;s gotta be an exhaust leak because you'd have other signs of a lean running engine.

Do you have any EEC-IV engine codes stored? Either engine off, and engine running?

 

[GTamas]

Do you have any EEC-IV engine codes stored?

How can I check this?

 

[GTamas]

1.7 is pretty darn high though, any chance that was 1.07?

Yes, after reading through the net, I began to suspect it is 1,07. Unfortunately I haven't got the values in written. I plan to go to a paid smog test to check the exact values.

 

[GTamas]

How can I check this?

Does this apply to 94 cars, too?

https://www.motortrend.com/how-to/1510-how-to-manually-test-eec-iv-obd1-trouble-codes-on-a-fox-body-mustang-for-free/

 

[Mustang5L5]

Yes, after reading through the net, I began to suspect it is 1,07. Unfortunately I haven't got the values in written. I plan to go to a paid smog test to check the exact values.

Can you get an Innova 3145 code reader in Europe?

https://www.amazon.com/INNOVA-3145-Ford-Digital-Reader/dp/B000EW0KHW/ref=asc_df_B000EW0KHW?tag=bingshoppinga-20&linkCode=df0&hvadid=80195681205772&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4583795269552441&psc=1

If not, there is a way to pull the codes using a paperclip. You jump two pins and count the blinks of the check engine light. There are likely youtube videos that will explain it better than I can type it out.

One thing to point out. Unlike OBD2 there are two (technically 3) different sets of codes. 2 sets are read with the engine off, and then 1 set is with the engine running.

 

[Mustang5L5]

Does this apply to 94 cars, too?

https://www.motortrend.com/how-to/1510-how-to-manually-test-eec-iv-obd1-trouble-codes-on-a-fox-body-mustang-for-free/

Yes, only difference is 94-95 cars (V8 only, the V6 cars were OBD2) use 3-digit codes, so you need to read a different set of codes than the fox cars

OBD-I Diagnostic Trouble Code - Ford 3-Digit Codes - The Ranger Station

Differences in test mode noted as: (O) = Key On Engine Off test (R) = Key On Engine Running test (M) = Memory code Code Definitions 111 System checks OK 112 (O,M) Intake Air Temperature (IAT) sensor is/was low … Continued

www.therangerstation.com

 

[GTamas]

I did a smoke leak test and think it is leaking at the EGR valve. Could an untight EGR valve cause the lean smog sniff test?
Noob question, but it looks to you too that the EGR is leaking?

By the way I did the test with my trusty corncob pipe and connected to that port

 

[Mustang5L5]

It depends where the leak is on the egr.

Is it the vac line that moves the diaphragm? If so, that’s a vac leak and should be fixed.

Is the smoke coming from the egr gas path and just getting past the pintle? If so this is NOT a vac leak that affects how the engine runs. That EGR pathway is under positive pressure when engine is running. Usually the leak is around the conical seat and plunger shaft.

You can pull the vac line off the egr and test like that with it capped. To test the egr diagram you can remove it (should try cleaning the valve seat anyway) and just push the plunger and put your finger over the port. Should hold position until you release your finger over the port.

 

[GTamas]

It depends where the leak is on the egr.

Is it the vac line that moves the diaphragm? If so, that’s a vac leak and should be fixed.

Is the smoke coming from the egr gas path and just getting past the pintle? If so this is NOT a vac leak that affects how the engine runs. That EGR pathway is under positive pressure when engine is running. Usually the leak is around the conical seat and plunger shaft.

You can pull the vac line off the egr and test like that with it capped. To test the egr diagram you can remove it (should try cleaning the valve seat anyway) and just push the plunger and put your finger over the port. Should hold position until you release your finger over the port.

Thanks. I have to dig into it because I never dealt with an EGR before.
If the smoke is getting past the pintle and coming out as seen on the video, that means that also exhaust gas is leaking there, right? So the EGR needs replacing, right?
I have to do the test again, with the EGR-vac line capped, to see as you suggested.

 

[Mustang5L5]

Not necessarily. I have 3-4 plus a NOS unit and they all leak around the pintle. I just let it go

 

[GTamas]

Not necessarily. I have 3-4 plus a NOS unit and they all leak around the pintle. I just let it go

I re-checked with the vac line capped. It looks like it blows by the pintle.
I also tried checking the diaphragm. I don't have a vac pump, so I put a hose on the port and sucked on it until the diaphragm moved, then quickly blocked the hose end with my finger and looked if the diaphragm keeps its position. It didn't move for a couple of minutes.

 

[Mustang5L5]

Sounds like it’s just a small pintle leak. I’d keep it in back your mind and keep troubleshooting

 

[GTamas]

So, if not vacuum leak, then what remains:
- exhaust leak
- not enough fuel (filter, injectors, pump)
- bad o2 sensor
- pcm

Anything else?

 

[Mustang5L5]

I’d dump codes and see if anything stored there. May give guidance as to what to look at first.

 

[GTamas]

I’d dump codes and see if anything stored there. May give guidance as to what to look at first.

Will do the flash counting method. Just curious, will codes get stored even if Check Engine light never lit during driving?

 

[Mustang5L5]

Yes. It’s not like OBD2 where any code sets the light off. There’s only a small portion of codes which display the light and many that will not.

 

[GTamas]

Yes. It’s not like OBD2 where any code sets the light off. There’s only a small portion of codes which display the light and many that will not.

Did the flashing. It seems to me the results are:
KOEO: 564 (Fan control failure A/C and Fan)
Mem: 111 System pass
KOER: 111 System pass
Cylinder balance: 90 all cylinders pass

I find it a bit weird because I did not notice a problem with my fan. Both normal and high speed turn on when needed and I have no overheating issues in slow traffic.
Did I interpret something wrong?
I would be thankful if someone could have a look at the codes: