More RPM issues and Stalling

[77mercury77]

A while back I posted a thread about a rare event that only happens within 5-10 of cold start. The event occurs randomly; sometimes twice a week and sometimes once in several months. I thought i had corrected the issue but it has now reoccured two days in a row and worse than before. A bit frustrating as things had been good for several months. Im about done with this and I need some help and opinions.

2010 ESV 105K miles

Within about 5 min of a cold start the engine surges and drops in RPM. This can be subtle or so bad it stalls the engine. I see no issue with electrical delivery during this time. The most recent events the truck has a weak/hard restart after stalling; normal start up is typically strong. Truck drives fine after the event for the rest of the day including restarting after sitting for 9 hours at work. No lights, no codes, several mechanics could not find the issue as it would not reoccur for them. I do not see any weather related connections; hot, cold, dry, raining, etc.

Things I have done recently that are related:
-new alt and newer battery
-checked visible grounds and cleaned off/dressed battery terminal
-new tps
-cleaned maf and TB
-new air filter, changed oil&filter
-checked and monitored fuel pressure KOEO and idle
-ran several tanks of fuel cleaner
-cleaned out and replaced fuel evap system
-plugs/wires are not old
-prob more stuff that i cant think of right now

I was able to capture the event this AM that stalled the engine. Attached are a few outputs and i have more data. Any help is appriciated.

 

[Geotrash]

A while back I posted a thread about a rare event that only happens within 5-10 of cold start. The event occurs randomly; sometimes twice a week and sometimes once in several months. I thought i had corrected the issue but it has now reoccured two days in a row and worse than before. A bit frustrating as things had been good for several months. Im about done with this and I need some help and opinions.

Within about 5 min of a cold start the engine surges and drops in RPM. This can be subtle or so bad it stalls the engine. I see no issue with electrical delivery during this time. The most recent events the truck has a weak/hard restart after stalling; normal start up is typically strong. Truck drives fine after the event for the rest of the day including restarting after sitting for 9 hours at work. No lights, no codes, several mechanics could not find the issue as it would not reoccur for them. I do not see any weather related connections; hot, cold, dry, raining, etc.

Things I have done recently that are related:
-new alt and newer battery
-checked visible grounds and cleaned off/dressed battery terminal
-new tps
-cleaned maf and TB
-new air filter, changed oil&filter
-checked and monitored fuel pressure KOEO and idle
-ran several tanks of fuel cleaner
-cleaned out and replaced fuel evap system
-plugs/wires are not old
-prob more stuff that i cant think of right now

I was able to capture the event this AM that stalled the engine. Attached are a few outputs and i have more data. Any help is appriciated.

Please refresh our memory: Year, model and mileage? Might be best to set this up in your signature at some point.

In the throttle and pedal graph, I see 2 manifold throttle position spikes immediately preceding the stalling event that isn't matched by the absolute throttle position. I wonder if the throttle body is closing momentarily, uncommanded and causing the stall.

I hate to throw the parts cannon at it but if I had to guess it would be the throttle body. Dorman makes a fine replacement that corrects some of the original design flaws. I've been running one in my '07 for 40K now with no problems.

 

[77mercury77]

Please refresh our memory: Year, model and mileage? Might be best to set this up in your signature at some point.

In the throttle and pedal graph, I see 2 manifold throttle position spikes immediately preceding the stalling event that isn't matched by the absolute throttle position. I wonder if the throttle body is closing momentarily, uncommanded and causing the stall.

I hate to throw the parts cannon at it but if I had to guess it would be the throttle body. Dorman makes a fine replacement that corrects some of the original design flaws. I've been running one in my '07 for 40K now with no problems.

I noticed that too and didnt know enough if TB command was from ECU or faulty.

2010 ESV 105K miles (i should have added)

also superimposed scaled RPM onto TB position for comparison. I just dont know if the TB is commanded to move as a way to regain control or if it is the fault causing the stall.

 

[77mercury77]

Shortly after writing this i suspected that the evap purge valve was stuck open or at fault. I replaced it and had no issues for a month. After another issue I deceided to put in a new OEM throttle body and did both pairs of 02 sensors.

The truck was good for about another month or two but in the last two weeks i had three or four occurances which is much higher than normal. I have noticed some patterns to the RPM drop and surge:

- only occurs during warm up usually about 5-10 min into diriving

-The event is a bit violent and lasts for about 5 cycles of drop and surge. It can be enough to stall out the engine but no affect to electronics

- Usually occurs during coasting, coming off light throttle to coast or steady light throttle.

Two examples were taking a left hand turn from stop, i accelerated at a moderate pace and then lifted off the throttle becuase traffic in front of me was slowing down.

Also has occured during coasting before applying the brakes for a red light or upcoming turn.

Has also occured at light throttle, steady driving at speed but doing slightly down hill at approx 40 mph.


Going crazy on this one as i am concerned that it would not be safe but its also so infrequent that i cannot get a mechanic to replicate it.