7.4 Vortec lower intake coolant leak?

[weaponoffreedom]

Looking for a bit of help.

Been chasing a negative fuel trim issue, sometimes near -18 on both banks.

Fuel pressure is good. 58

FPR is functioning and new

Injector pulse test 60-30psi, all the same, and new style bosch not rochester, I changed them myself.

Lower intake manifold gasket is leaking, at least externally.

No combustion gasses present in coolant

No coolant known in oil



Question is:

If coolant is getting into the intake, can this cause the O2 sensor to read rich and call for -15 % LTFT?

I did notice a leak in the exhaust manifold that was "bubbly"

Any help is appreciated

 

[454cid]

I would guess the injectors flow more than the originals and the PCM is adjusting for it. I'm no authority on fuel injection, though. Several guys here do their own programming and may know better.

 

[Schurkey]

Been chasing a negative fuel trim issue, sometimes near -18 on both banks.

Computer is in lean-command. Reducing the fuel quantity that would normally be injected.

Lower intake manifold gasket is leaking, at least externally.

Leaking WHAT? Coolant?

If coolant is getting into the intake, can this cause the O2 sensor to read rich and call for -15 % LTFT?

Not that I know of. HOW OLD are the O2 sensors?

I did notice a leak in the exhaust manifold that was "bubbly"

"Bubbly" as in coolant boiling off?



You need to fix the intake manifold leak, the exhaust manifold leak, probably replace the O2 sensors, and see what happens.

 

[weaponoffreedom]

@Schurkey

correct, commanding a lean conditon, which means reports are rich

yes leaking coolant

o2 are new 6 months, installed with Banks power pack headers

yes bubbly.


no gas was detected in the coolant, i have ordered the requisite stuff to fix.

Insteresting thing, on my last trip, it was telling me "lean" on bank 2, +12 ltft........misfire trend on 4........now, both banks are rich, no misfire.............got me thinking about distributor wear.

 

[454cid]

@Schurkey

o2 are new 6 months, installed with Banks power pack headers

Are you SURE the exhaust is sealed? If there's a leak, that's a spot for extra O2 to enter the exhaust and mess with the O2 sensor readings.

 

[weaponoffreedom]

Are you SURE the exhaust is sealed? If there's a leak, that's a spot for extra O2 to enter the exhaust and mess with the O2 sensor readings.

100% sure, no. But I know therre is a coolant leak, and on startup I see "bubbles" around the flange on bank 2, and the exhaust has some steam in it. No exhaust gas in coolant. So I am going to repair the leak, and retest. It wouyld have to be done ayway