Air fuel, O2 readings off, causing weird acceleration

**footballplaya3k** · 02-27-2012

For the first couple minutes of running it will accelerate nice and smooth. After the first couple minutes, it will accelerate with a very slight hesitation every second or so. My AFR doesn't seem too bad, stays around 14.6 to 15. I think the problem is visible in the O2 readings though. It will stay around 800-900ish then drop to under 100 for a fraction of a second, when I presume the hesitation is occurring. Also idle will jump in neutral if the car is warm. No codes.

Thought it was the O2 sensor but replaced that to no avail. Ideas?

Thanks

**Bio248** · 02-28-2012

the o2 sensor is supposed to have pretty big cyclic swings like that.

**BillBoost37** · 02-28-2012

Have you considered that your knock sensors aren't active until 160F? You may have knock a misfire etc etc.

**footballplaya3k** · 02-28-2012

Bio, good because its a new O2 sensor so I'm glad that's not the issue.

Bill, I don't go over 2500 RPM's until I'm over 160*. Aeroforce says no misfires or KR at any point. The issue always occurs when the car is warm (over 160*).

**footballplaya3k** · 02-28-2012

Other things I can think of, when car is warm and in neutral and the idle is surging, Lift's are pegged at 16.4. I would think this is a vacation leak but wouldn't it surge when its cold too, not just when its warm?

**footballplaya3k** · 02-28-2012

Nothing?

**Bio248** · 02-28-2012

+16.4 LTFT is a vacuum leak. find it.

**footballplaya3k** · 02-29-2012

Originally Posted by Bio248

+16.4 LTFT is a vacuum leak. find it.

Believe me I have. When I reset the fuel trims (unplug battery for about an hour) it won't settle in at 16.4 for at least a few minutes. Would that still be a vacation leak?

**Swiggles** · 02-29-2012

yes that with your other symptoms points to a vac leak

**Bio248** · 03-01-2012

a slower leak is still a leak.

**SlowNA06** · 03-01-2012

I wish I had a vacation leak.

**footballplaya3k** · 03-01-2012

Well I've sprayed TB cleaner around the base of the IC and SC, all the vacation lines on the SC, and the TB joints. What am I missing?

**SlowNA06** · 03-01-2012

You still have your MAF screen installed, right?

**matt5112** · 03-01-2012

egr tube?

If you have an intercooler, are you still running garleaks?

O2 sensors oscillate because they're only accurate at finding lambda of one, thus they have to go above and below to attempt to stay close to the centre.

**footballplaya3k** · 03-01-2012

Originally Posted by SlowNA06

You still have your MAF screen installed, right?

Yes sir.

**footballplaya3k** · 03-01-2012

Originally Posted by matt5112

egr tube?

If you have an intercooler, are you still running garleaks?

O2 sensors oscillate because they're only accurate at finding lambda of one, thus they have to go above and below to attempt to stay close to the centre.

Haven't checked the EGR, will do.

No more Garlocs, right stuff RTV now. I couldn't believe how horrible the Garlocs were when I took them off. Oil everywhere.

My wondering about the O2 osculation was, could it be osculating enough to cause an RPM surge or slight hesitation when accelerating.

**matt5112** · 03-01-2012

Slower is a sign of a weak O2.

What are you using to capture these figures?

**footballplaya3k** · 03-01-2012

What do you mean by slower?

Going off of my Aeroforce.

**footballplaya3k** · 03-02-2012

On the way to work today I had p1133 pop up. Looks like bad O2 but I just replaced. I cleared the code and drove for about 20 more minutes and it didn't come back. I recall having this happen on my previous O2 that I thought was bad but turned out not to be. Ideas?