Wideband reading rich

[DSM newbie]

Hey everyone,

My Eclipse is running rich after 5-10 mins of driving. Car idles and runs great until it starts running rich. Car starts right up and idles at 14.7 afr, driving around it hovers around 14.2 afr unless I accelerate or decelerate of course. Under boost it drops to 10-11 and on deceleration it shoots up to 19-20 as it should and then levels out at 14.2. After driving the car for 10 mins or so it starts running super rich at 10 afr or lower when not in boost. After I park and let it sit it get a little better at 11.6 but obviously that is not where it needs to be. I would park the car for the day and come back and it would do the same thing, be perfect and then run rich.

Does anyone know what would cause this? And what would be the fix? I ordered a new O2 sensor and MAP sensor. I also already replaced my coolant temp sensor during my rebuild.
Anything would help! Thanks again.

 

[Vegas Smith]

If I were to guess I would say it's an exhaust leak that maybe opens up as the metal heats up introducing extra air to the o2 sensor. When the extra air from the leak tricks the o2 sensor into thinking the car is running lean the ecu will inject more fuel causing the car run rich. Just my guess.

 

[BLACK'98DSM]

Where is your wideband sensor tapped in? I've seen them too close to the exhaust port and when they get too hot they provide false readings.

 

[DSM newbie]

If I were to guess I would say it's an exhaust leak that maybe opens up as the metal heats up introducing extra air to the o2 sensor. When the extra air from the leak tricks the o2 sensor into thinking the car is running lean the ecu will inject more fuel causing the car run rich. Just my guess.

I used the JB weld high heat paste all the way around the manifold cause I believe I have a small leak there even though all the bolts are tight. I will see if that will help.

 

[DSM newbie]

Where is your wideband sensor tapped in? I've seen them too close to the exhaust port and when they get too hot they provide false readings.

It was tapped in half way down the down pipe by the exhaust shop. If that to close do you think?

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[dondmon]

What about a boost leak test?

 

[dustyboner]

I used the JB weld high heat paste all the way around the manifold cause I believe I have a small leak there even though all the bolts are tight. I will see if that will help.

are you using a composite or MLS gasket for the manifold? If you have one of the multi layered steel gaskets, you could try a composite gasket. If that doesn't work, your manifold might need to be resurfaced. Not all shops can resurface something that small so finding one might be a pain.

It was tapped in half way down the down pipe by the exhaust shop. If that to close do you think?

its in a good spot.

 

[DSM newbie]

are you using a composite or MLS gasket for the manifold? If you have one of the multi layered steel gaskets, you could try a composite gasket. If that doesn't work, your manifold might need to be resurfaced. Not all shops can resurface something that small so finding one might be a pain.


its in a good spot.

Ok so I took the manifold off. I am using a composite gasket and not a multilayer one because I heard those have some issues. I also applied some JB Weld extra heat paste to seal the manifold and as of yesterday and today I haven’t had any issues with my afr readings. So as of right now it is fixed but I will be checking on it through the week/weekend. It must have been an exhaust leak right where the manifold meets the head. Thanks for your help guys and I’ll keep you posted!

 

[DSM newbie]

What about a boost leak test?

That was the first thing I did and everything checked out. Thanks for the suggestion!

 

[dondmon]

What about tossing in a new set of spark plugs, driving it around for a little bit then "read them"?