this has been an ongoing problem for a while, bothering me enough now to see if I cant figure out why it does this. when i first start my truck, and try to get it out of park and go quickly (within 15-20 secs of starting) its very hesitant. then suddenly kicks in like it just woke up and drives normally, never have issues when driving, starts up normally, fuel pressure was tested after new FP this fall, everything passed from regulated pressure to fp output tested at the fuel filter.

i had a full tune up 25k ago, all ac delco from plugs cap rotor ignition coil, etc. and I just cant figure this out

fuel filter is within a year old, just did an oil change and all fluids were fine and air filter was replaced a week ago

any help is greatly appreciated

thanks in advance

 

Could be a problem when the PCM switches from open to closed loop. On a cold start, (vehicle sets without running for 10+hours) Connect your scanner before you start it. Turn the ignition to RUN, (don't start it) Compare IAT, ECT, and ambient temperature. They should all be within 2 degrees of each other. Post all three temps.


Next, go to a screen that shows loop status, (open/closed). Start it up and immediately start driving. Watch loop status when the engine acts up. See if the engine runs differently the instant it switches to closed loop.

 

i will be able to access my scanner in the next 2 days, it is back at my place. as soon as i get the opportunity I will post results. thank you for the quick reply captain!

 

I also have a thought..clean or swap on a good MAF sensor...just a thought...if a known good one is accessible or you can give cleaning yours (with the proper cleaner) a shot. Although cleaning won't fix a 'defective' MAF..Jerry

 

Did not have time this am to do the loop....iat and ect were both at 59....I'm not sure if my scanner is supposed to get ambient temp or I go by the actual temp outside...its 57 outside according to the trucks thermostat and weather
I did not see a setting for amb temp on the scanner

 

The scan tool will not show ambient temp, one of the local weather apps or a thermometer will be fine. Both sensors at 59 and ambient at 57 is not a problem. Check loop status when you can, and post the results.

 

so i let it sit again for 10+, put it in live data before starting it, could not find anything that says loop status. is there something else its called? i have the innova 3160d, just not sure on live data what it is im looking for

 

Pretty much an entry level scanner, but it does have some nice features. I would think it would show loop status somewhere, but maybe not. It might just show "open" or "closed" on one of the menu or data lines on the screen. I noticed that the refresh rate is 30 seconds, (should be live) which really won't help you much when it comes to pin pointing if the issue is when it switches.

 

When using live data when driving, it was picking up changes in rpms and mph and other stats instantaneously....would this be in o2 sensor part? What exactly are we looking to see what's open TB or an o2 sensor

 

Loop status has to do with how the PCM controls fuel mixture. In open loop the PCM ignores oxygen sensor data, and uses data from other sensors to control fuel mixture. In closed loop, the PCM uses oxygen sensor data to control fuel mixture which is far more accurate.


On each start up, the PCM operates in open loop. Several things must happen before the it switches to closed loop. The colder the engine is, the longer it takes to switch to closed loop. What we're looking for on yours is: Does the problem occur precisely when it switches to closed loop.