Exhaust lambda value too high

[GTamas]

Did the smoke leak test today on the intake and exhaust. I have some questions, could you help me guys please?

I noticed two leaks on the intake side: the EGR (strong leak) and on the throttle body side (smaller leak). What's the name of the part on the TB side which leaks on the mating surface plastic to aluminium? Could this couse lean mixture? How should I fix it?
The EGR valve will be replaced.

I also smoked the exhaust from the tailpipes.
Noticed that the condensation holes on both mufflers are leaking a lot of smoke, so I plugged them for the rest of the test. Then I noticed some smoke leaking from somewhere the top of the driver side muffler and from the side of the passenger muffler. The side leak is obvious, but where could it leak from the top of the other muffler?

Do you think this exhaust leak could cause lean reading at the tailpipes?
I'm also wondering if the condensation holes can draw air during operation and cause also a false lean reading at the tailpipe? I'm thinking of plugging them for the next smog test. What do you think?

 

[lwarrior1016]

Plugging the muffler holes for the next test wouldn’t be a bad idea.

The plastic piece on the throttle body that’s leaking is the throttle position sensor. There might be an o-ring on it that you could replace. I think you have to remove the idle air control valve to remove the throttle position sensor, so you’ll need a new gasket for that as well.

 

[TRS666]

Do you think this exhaust leak could cause lean reading at the tailpipes?

The muffler leak absolutely. Not sure of the part at TB but probably throttle position sensor. They usually have a large O-ring sealing against the TB. All leaks together and quite sure you have fixed it.
Lwarrior was faster!

 

[Finn]

Do you still have the air pump? If it is there and the inspector does not know what/how to test with it analyzer can show peculiar values.

With my MOT test earlier this month I was wondering why the inspector was running the engine with 2500...3000 rpm. It was because of the air pump but he knew what to do. Clean emissions on mine.

 

[lwarrior1016]

The air pump is a good point that I hadn’t thought about. That will push fresh air in to the exhaust and absolutely make it read lean in the tail pipe

 

[GTamas]

Yes, I tried the smog test with the air pump disconnected, it improved from 1,65 to 1,1. Still too high as limit is 1,03, but I think with these leaks fixed and AIR disconnected, it might be okay.

Thanks everyone for the tips.

 

[GTamas]

I can't find a seal for a TPS separately. Is there sure one used there, or is it only available together with the sensor itself?

 

[ttocs]

I don't remember a gasket for that sensor myself. If it is leaking it is leaking out of the tb that I thought made the seal there around the tab that rotates to tell the sensor its location. I would take it off and see what it looks like under it.

 

[GTamas]

I don't remember a gasket for that sensor myself. If it is leaking it is leaking out of the tb that I thought made the seal there around the tab that rotates to tell the sensor its location. I would take it off and see what it looks like under it.

Thanks, that's my plan, as soon as the IAC gasket arrives.
I also ordered two new mufflers: AP Challenge, should be close to stock specs as I understood. I'd like to keep sound level and tone close to how it sounds now. I wanted to order the Walker QuietFlow stainless stell mufflers, but the passenger side was everywhere on backorder and I need these fast.

In the meantime I will replace the EGR valve.

 

[ttocs]

I have seen where people find leaks there at the throttle body on the other side, not sure what they did to fix it though

 

[Mustang5L5]

On the fox cars there is an o-ring at the tps sensor. Not sure if that’s the same on the SN95.

For the egr, you need to determine if the leak is at the EGr diaphragm side, or coming up through the egr passages from the heads.

A diaphragm leak indicates the car may not have total egr control. Usually I test these off the car by simply pushing the plunger in and putting your finger over the vac port and letting go of the plunger. If it’s good it should hold. Short of that you can use a handhel vac pump to see if you can move the piston by applying vacuum.

If the diaphragm is good, the seat is likely leaking. I’ve tested a lot of EGRs and they all leak here to a degree. A gross leak would affect air/fuel though. Might be worth pulling the egr off to clean the piston seat sell and ensure you aren’t getting bypass at idle.

I’ve smoke tested NOS here and found them to leak a tiny bit here.

 

[TonyCH]

Do you still have the air pump? If it is there and the inspector does not know what/how to test with it analyzer can show peculiar values.

With my MOT test earlier this month I was wondering why the inspector was running the engine with 2500...3000 rpm. It was because of the air pump but he knew what to do. Clean emissions on mine.

Same thing here. Couple of weeks ago I went to the annual test and the inspector was running the smog test for a long time and complained about excessive O2. I pointed out that the car (1995 GT) has an air pump and he relaxed and passed me right away. Said he didn't remember some American cars had those back in the day.

 

[TonyCH]

They put a sensor into the tailpipe, ca. 40 cm deep. Then measure it at idle and ca. 2500rpm. Without load.

I just checked my inspection results:
CO2: idle 8.90, at 2500rpm (?) 8.50
HC ppm: idle 6, at 2500rpm (?) 6
O2: idle 8,00, at 2500rpm (?) 8.50
Lambda: 1.700

My car starts and runs normally and like I said was passed on smog test after pointing out the air pump.

 

[GTamas]

Do you still have the air pump? If it is there and the inspector does not know what/how to test with it analyzer can show peculiar values.

I just checked my inspection results:
CO2: idle 8.90, at 2500rpm (?) 8.50
HC ppm: idle 6, at 2500rpm (?) 6
O2: idle 8,00, at 2500rpm (?) 8.50
Lambda: 1.700

Thanks for your inputs. I am now sure I failed because of the air pump. Without the air pump I got 1.1 lambda reading, since then I fixed some vacuum leaks and next week will replace the mufflers which also seemed leaking. Then without the air pump I think it should be within limits. But I will also point it out to the inspector.

 

[ttocs]

interesting, let us know how it goes for sure.