91chevz71

So my engine loves the open loop idle, with command AFR at 14.7, VE around 45 in the idle areas. Experimenting, I switched back to closed loop idle and the O2 will pull fuel until BLM is 100 and INT is 115. When in Open loop, the idle is 95% smooth and doesn't miss hardly. When in closed, it misses and feels like plug wires are disconnected.
Sync PW with open loop is 1.3, with closed it's around 1.1. This makes sense with the computer pulling fuel.
Is my cam the culprit in closed loop idle?
350HO cam-
212/222 dur @ .050, .435 .460 lift
112.5 centerline

THanks
Mike

91chevz71

I only bring this up because I've read threads where guys have bigger cams than this and closed loop works great for them.

RBob

iTrader: (1)

You can decrease the AFR at idle by changing the O2 switch points ('O2 - Idle O2 Window Terms'). That may help out. Raising the idle speed can also help as it lessens the affects of the cam.

Changing the idle SA will also make a difference. May need to go higher or lower on the SA, try 2 - 4 degree change in each direction.

RBob.

RednGold86Z

iTrader: (1)

My friend couldn't get his 350HO (vortec heads) to idle well in closed loop either. Checked things out, and he had a super hot header pipe (or two). Kept burning the plug wire too. Even with a good wire, good plug, good compression (i think), good gaskets, good plugs, darn near anything - still had the same hot cylinders. Tried messing around with the TB position (was a big block TBI on a performer vortec or something like that), but to no avail.

I moved to china, and he sold the car..... Probably something like collapsed lifters or something easy and stupid.

Boring story, with no real point I guess. Hope you can solve it...

91chevz71

I'll keep hacking away...thanks for the advice, guys

Sean82vet

I had the same problem this weekend.
My car has a cam with a 110 lca.

You are going to love this one, - I was adjusting my ve until I had almost no fuel in those areas, but my blm was still bottoming out at 108. When I shut down the car the fan was on and the temperature was 210d

Then I remembered an old post when grumpy said that everything lies - o2 sensor, blm, all of it.

I then decided to go back to my stock ve table and ADD 10% in those areas that were supposedly rich. I smoothed out the surrounding ve cells and low and behold my blm magically returned to 125 in those cells and my engine temp never got above 185d

Even though the engine thought it was rich it was really running lean and the engine temp was the proof

91chevz71

AHA!!!!
I am going to try what you did right now.

Thanks-
Mike

91chevz71

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