Running rich and then Very lean...

[2500avalanche]

My truck has run very normal Wideband (AEM) always worked. Put the truck away for winter. Started it up a few times, and even drove it during the 1 nice day, and ran great. Went out to the garage last week. Literally NOTHING has changed (meaning I didnt mess with a thing, hood still closed!). Went to start it up, and was VERY rich (around 9 on the wideband). Shut truck off, started it, and went extremely lean. Tried it 2 different times, and did the same thing rich , shut off, and then lean. I thought it might be the 02 sensor, replaced it for the wideband, and the same result. Very frustrated as it ran pretty good prior to this... No idiot lights or anything like that. All other items are coming up normal while monitoring.
A few people think it is the chip (TT), but I did nothing to it for it to change this drastically. Not sure what is up.
Any hints? I have videos of this crap....
BTW, truck is a very clean example that is maticulasly taken care of.

 

[gmemony2]

You mentioned the TT chip, so this was my first thought. Did the battery go dead or was it disconnected at all? Those chips lose their tune if they lose power correct?

 

[Slyclone]

Sound like it could be a possibility the coolant temp sensor is going bad.

There are 2, one sends signal to the gauge on the dash the other sends signal to computer. I've battled them before and I am under the understanding that when they go the truck will act funny. Try to source a Delco brand

 

[2500avalanche]

You mentioned the TT chip, so this was my first thought. Did the battery go dead or was it disconnected at all? Those chips lose their tune if they lose power correct?

Battery never went dead. I did disconnect it when this started to think that it needed to re-set. I have the tune saved, so this was the first thing, but thank you for the thought

 

[2500avalanche]

Sound like it could be a possibility the coolant temp sensor is going bad.

There are 2, one sends signal to the gauge on the dash the other sends signal to computer. I've battled them before and I am under the understanding that when they go the truck will act funny. Try to source a Delco brand

I will try these. I did replace the one that sends to the guage last year, but not the other one. I was wondering if my map sensor is bad too? I will try that as I have 2 good ones (3 bar)

 

[Slyclone]

Do you have a scan gauge to verify your numbers? For MAP? Just wondering. I had speculation that mine was also bad so I went ahead and sourced a new one.

Not saying it's bad.

I'm just more leaning towards the temp sensor reading funny.

What type of reading numbers were you seeing. Did truck get up to operating temperature

 

[2500avalanche]

I didnt let it get to warm up temp, but I did previously with no change...
I have an additional coolant sensor. I will try that today.
And then the map too. Fuel pressure is good, it does not change

 

[2500avalanche]

Not the upper temp sensor...

 

[2500avalanche]

not the map

 

[2500avalanche]

I am leaning on it being the chip. SOmething must have occurred... not sure what though

 

[2500avalanche]

So, after talking with some OG's on here, and investigating, I reached out to Eric at TT. He gave me a few great suggestions. I put the TT chip back in it, and I backed the truck out of the garage and it died 2x while sitting at idle for 30 seconds. Frustrated as NOTHING has changed with the truck. I started it for the 3rd time, and put it in drive foot on brake and started to give it gas to see if it would die. And what do you know it didnt die. I pulled into the garage (still in gear), truck and fuel ratio back to normal (around 14). Totally confused, I back out and let it run idle for 20 minutes at the dismay of my wife who asked what I did to make it work. I said "Nothing"
Now, truck is acting normal. The ONLY think I changed in teh process over the last 2 days was a new coolant temper sensor and a new 02 sensor.
The gremilns....