Hard Start in 96 454. Please Help, this is a doozy

[SAATR]

No easy way to test the IAC, as it is a stepper motor and you would need some kind of function generator to accurately reproduce the signal it uses.

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[98_k1500]

Replace with a known good one? (buddies truck or something)

 

[SAATR]

Easiest test in my experience is to replace it with a known good unit and clean the passage, then drive it. I was wrong about needing a scanner. If you drive it about 35mph it will automatically find its 0 point and self adjust from there. I had forgotten about that :-/.

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[brycebba]

I can see if I can locate one. And check it out. Hopefully I can give some feedback soon. Btw, I pulled a plug after driving about 35 miles on the 350 fpr and the plugs are tanning up!

- Bryce -

 

[brycebba]

Sweet, looks like my Wife's Yukon uses the same one even though it's a 350 so I will swap with hers and see if it fixes me

- Bryce -

 

[SAATR]

Drive it ABOVE 35mph. That's what my post should read. Just take it for a drive with some cruising at speed and see what happens.

 

[brycebba]

I tried that and no luck. Truck is running rough again and sputtering or something again. Took a read on my scanner and saw that bank 1 sensor 2 is at a really low voltage but is steady. Could I have a bad cat? I am going to swap the back sensors and see if I get the same reading from Bank 1 but I will have to wait till it cools off. No bad smells or anything but it is losing power and do shifting where it didn't used to to keep speed

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- Bryce -

 

[brycebba]

And I posted in your other thread, but I'll repost here. Your S1 O2s are fine voltage wise, they jump around when in an open loop. The B2S2 seemed high and may be bad, but that won't affect fuel trim. What it COULD be telling you is that you have a clogged cat, which WILL affect driveability. Your timing looks fine, but IAT seems pretty high. Our MAFs don't have a big response to temps, because (unlike LS1s) we have separate IATs that do it for them.

This is what I am seeing but I guess I didn't process what you were getting at. How can I tell if my cat is bad. Should I just swap sensors like I said and see if I get the same reading from the same banks?

I forgot to add that I wanted to get better tuning and also rule out the pcm being a problem I am going to order a black bear performance tune as soon as they get back to me. Hopefully I hear back soon so I can get one in before a trip next week... If my truck still runs

- Bryce -

 

[SAATR]

B1S2 is either faulty or you have a wiring issue. Minimum voltage you should see from an 02 sensor is 0.1V. Bank 2 is rather rich, as max 02 voltage is around 0.9V, with stoich occurring in the neighborhood of 0.45V. They make exhaust backpressure guages that you can use to test for a plugged cat. The way our trucks' exhaust is built, it's not really feasible to drop the cats and run the engine as you would be running straight out of the manifolds, which will cause running issues too.

 

[brycebba]

Some people say those back sensors don't do anything but tell you whether the cats are there or not but I can't imagine that's true. How significant of a role play or what are those back sensors for

- Bryce -