Stumbling on Cold Starts

[thehata1]

Originally Posted by rennat_2006

P0135 is a 02 heater circuit, could be heater element in the sensor or a ground issue. I cant remember what years silverados and other fullsize trucks/suvs it was but they had a common problem with a bad ground causing that code. The 02 sensor body grounded through the exhaust pipe itself, quick test was to command the heater on with a tech2 and if it didnt work take a piece of wire strip an inch or so bare and wrap it around the sensor body then put the other end on a good clean ground and try it again.

Engine doesnt run off of the o2 sensors until it hits a set temperature, cold starts are all off of the "base" tune aka open loop.

Easy check for intake gaskets leaking is grab a can of carb clean, brake clean, etc and spray down both sides of the intake where it meets the cylinder head BEFORE you start it the first time for a cold start. Spray it down real good then run around and fire it up real quick, if it idles higher than normal that confirms it. You can also smell the brake clean/carb clean in the exhaust if you put enough down.

That’s good, easy test. I’ll try that before I replace the sensors. I’ve already ordered the sensors. So, I’ll replace those regardless. Thanks.

[Wgesnerjr]

I understand the ECU doesn't adjust Air Fuel Ratio until warm. However, in my case, the O2s DID have some kind of affect on start up. I think it's has to do with After Start Enrichment ASE, (thanks Br3w City) which is what old school guys would call a choke.

From the limited info I found, ASE is a table that is used to get the engine started and up to temp then the ECU would take over Air Fuel Ratio. Again, not much info out there. So I think ASE uses the heater in the O2 to heat up the sensor so the ECU can run the ASE table. My stumble was only for first 45 to 90 seconds or so. But the O2 heater did not work on my sensor and caused a rich mixture on that side of the engine. Here is the test I used for the heater check.

https://www.motor.com/magazine-summa...cuit-failures/

Also, in my case the sensor that caused my stumble was a Denso sensor installed during engine swap. But I think the exhaust shop I used may have welded the O2 bungs in with the sensor in place, there by damaging the heater part. I replaced with ACDelco and immediately cleared up problem.

[thehata1]

Originally Posted by Wgesnerjr

I understand the ECU doesn't adjust Air Fuel Ratio until warm. However, in my case, the O2s DID have some kind of affect on start up. I think it's has to do with After Start Enrichment ASE, (thanks Br3w City) which is what old school guys would call a choke.

From the limited info I found, ASE is a table that is used to get the engine started and up to temp then the ECU would take over Air Fuel Ratio. Again, not much info out there. So I think ASE uses the heater in the O2 to heat up the sensor so the ECU can run the ASE table. My stumble was only for first 45 to 90 seconds or so. But the O2 heater did not work on my sensor and caused a rich mixture on that side of the engine. Here is the test I used for the heater check.

https://www.motor.com/magazine-summa...cuit-failures/

Also, in my case the sensor that caused my stumble was a Denso sensor installed during engine swap. But I think the exhaust shop I used may have welded the O2 bungs in with the sensor in place, there by damaging the heater part. I replaced with ACDelco and immediately cleared up problem.

I replaced the O2 sensors and will follow-up after a couple weeks. Thanks.