Exhaust Leak cause high fuel trim? (1 Viewer)

[florida95fzj]

Has anyone seen an exhaust leak on these trucks be significant enough so that the O2 sensors tell the ECU it needs +20% long term fuel trim?

I have an exhaust leak that I can hear when inside the vehicle but I don't know if it is really impacting performance. I was half expecting to find the exhaust manifold cracked in half when removing the heat shields. However, I don't see any holes or cracks from the manifold to the muffler. That said, the exterior surface of the parts/pieces look pretty rough.

I've already been through looking for intake leaks (none found) and replaced the vacuum lines, PCV valve, intake manifold gasket, air filter hose, etc... I haven't dived into the fuel system, pressure check, or changed the fuel filter yet.

 

[bigredmachine]

find where the exhaust leak/s are at and if they are before the o2 sensors then it will affect the fuel trim.

 

[White Stripe]

It would have to be a bad exhaust leak. Find the leak and post up a pic. Is your intake hose cracked? Is your brake booster leaking? How many miles are on the fuel injectors? Does the evap system have any leaks after the purge valve?

 

[florida95fzj]

Thank guys. Yeah, I was hoping it must be a very large exhaust leak to cause this and be worth opening up this can of worms. I think I will put a shop vac exhaust on it and walk around with a soapy spray bottle. I have not been able to find it by looking at it or listening. Hopefully it's small and I can leave it alone and find the real problem.

Yeah, the intake hose was very stiff and I replaced it. I replaced the brake booster hose but will need to figure out how to check if the unit itself is leaking.

Injectors may be original - 90K miles, 1995.

The PO replaced the charcoal canister but I think those hoses appear to be original. I need to look into the purge valve you're talking about. I recall seeing what I thought was some kind of check valve but I didn't try to figure out if it was working or not. I honestly forgot I didn't give this area any attention mostly because that canister was recently replaced.