Running Lean Boiling Coolant

[Xero_Tolerance]

I have tried searching through the forums, but this problem seems a bit different than anything I could find.

My engine runs great when I first start it up. It's stoich and engine temp seems normal, after warming up of course. As I continue to drive for... over 15-20 minutes I'd say, the car starts to run very very lean, though the engine temp, according to the gauge, is still normal. I usually start to smell some burning coolant and by the time I stop driving, I can hear air escaping at a pretty high velocity around my radiator cap. Last night after driving home the coolant was boiling from under the cap and coming out. I'm guessing this means a bad cap, but what explains the leanness?

Thanks.

 

[PIMking]

Replace the cap and see what happens.

 

[Xero_Tolerance]

Good plan. I'll do it right after work and post back on results.

 

[Xero_Tolerance]

Replaced the cap and replaced my upper radiator hose to no avail. It seems to delay the car from running lean and the coolant no longer boils out of the cap, but the car still runs really really lean after about 15 minutes of normal driving.

 

[PIMking]

Well I see that you have link and a wally 255. Do you have a AFPR? If so when was the last time you replaced you fuel filter?

 

[lccynmbr13]

I see you used the word stoich... Are you using a wideband or a narrow band air/fuel guage? If it's a narrow band you might as well pretend you don't have a guage and not worry about it. If you have a wideband what is the actual air fuel ratio we're talking about?

 

[Xero_Tolerance]

PIMking - I replaced my fuel filter about 10,000 miles ago. It should still be in good shape, I hope.

Iccynmr13 - It is a narrow band, but has been functioning perfectly well for the last couple years and is only now starting to exhibit this behavior, which is my reason for concern.

 

[PIMking]

PIMking - I replaced my fuel filter about 10,000 miles ago. It should still be in good shape, I hope.

Iccynmr13 - It is a narrow band, but has been functioning perfectly well for the last couple years and is only now starting to exhibit this behavior, which is my reason for concern.

To be quite honest Narrow bands are worthless. Its a pretty light show for the ladies.

You can get an AEM uego wideband sensor and gauge for 200 shipped. that would help out alot.

Whats your fuel pressure at?