2007 Explorer warm start up and stall issue

A warm startup on my 2007 Explorer causes an RPM spike and subsequent stall (half of the time) on the way back down. I've tried a fuel additive, Ford ran codes with no problems...an suggestions?

Your 2007 Explorer probably has a electronically controlled throttle plate (rather than a cable-driven throttle and IAC servo). This may depend on engine, does your Explorer have the V8 or V6? If electronic throttle, I'd suggest you check the back side of the throttle plate and throttle body for a build up of carbon/sludge that may be snuffing out the engine as the plate closes. If cable-driven, then the Idle Air Control (IAC) servo may be at fault.

If you happen to have access to a scan tool that can monitor common sensor data real-time, I'd suggest you monitor the Intake Air Temperature (IAT) sensor data and Engine Coolant Temperature (ECT) sensor data and make sure they seem reasonable. If you have an aftermarket "performance" air filter, there's a chance your Mass Air Flow (MAF) sensor is contaminated. Often they can be cleaned with CRC MAFS Cleaner that is available at most auto parts stores.

-Rod

Rod....thanks for the reply! It's a V6 and I have to admit, I'm a bit of an amateur so I'm beaking down your suggestions bit by bit as we speak but I'm curious, would this problem bypass the code scan? Also, sometimes when i engage into drive after there's been the rpm spike and the motor hasn't stalled, there's a slight delay and then clunks hard into gear. Is that a separate issue or related possibly? Thanks again...I really appreciate it. Marc

Diagnostic codes will only be set if the Powertrain Control Module (PCM) detects a problem. If it believes the data from the sensors it will adapt accordingly and often will not set a diagnostic code. That's where a scan tool comes in handy to monitor the sensor values while driving to see if what they are telling the PCM make sense. Sometimes sensors will go to one rail or another, and that most likely WILL trigger a diagnostic code. Other times a sensor may just be a bit slow to respond, which won't always trigger a code, and yet other times the sensor values may just be skewed due to dirty sensor elements, etc., and again these won't always raise a flag. I've experienced a dirty MAF sensor that caused a significant drop in fuel economy, but my car ran perfectly fine otherwise and there were no diagnostic codes. This was a couple of weeks after I cleaned and re-oiled the performance air filter. The MAF sensor elements got coated in oil (I apparently over-oiled the filter) and skewed the response of the MAF. I used electrical parts cleaner (MAF sensor cleaner was not commercially available at the time), a careful hand, and cotton tipped swabs to clean the MAF and my fuel economy came right back. Now days I just use the spray and don't risk damage from swabs.

As for the harsh engagement of the transmission, I suspect that's unrelated. The 5-speed automatic transmissions in these are pretty well known for valve body and shift solenoid issues that can cause harsh gear engagement, often starting with harsh reverse engagement. It's not horribly bad to replace the valve body, but you'd want to make sure you have a means of refilling the transmission fluid before tackling the job yourself.

While I prefer to do all my own work, I recently let my favorite local transmission shop change the valve body in my Aviator since I suspected there was more to mine than just a valve body, and I use the truck for towing my family and camper around. The estimate for the valve body replacement was $470, but they also had to drill and re-sleeve a couple of worn bores (also common) for a total of $750, including the new valve body. The transmission shop was actually surprised mine needed the bores re-sleeved with only 80k miles, they said they usually don't see that unless there are more than 100k on the transmission. I've only put the last 6k or so miles on this one so I don't know what kind of life it had before me.

-Rod

Thanks Rod...going back to your first post, would the build up of carbon/sludge on the throttle plate/body more align with the RPM spike, the stall, or both? I'm going to start there and see what happens. Additionally, I don't have a scan tool but I will check with a Ford Dealer here to see if they wouldn't mind hooking up a real time monitor so when the Explorer does it's thing, I can get them codes as they haven't been able to even engage the car in this behavior.

The air filter seems to be of the napa sort and slightly in need of a change, so no harm no foul in changing that out either at this point. If I can squeeze it in between football, I may dive into the MAF sensor.

Much appreciate the expertise...cheers bro.

The carbon on the throttle plate could contribute to both the spike as well as the stall, but the spike could be normal as well. How high do the rpms jump up at warm start?

If you can talk your dealer in to hooking up their scan tool and letting you datastream until the issue happens for even $100, I'd be amazed. Quite honestly, you could probably buy a scan tool that would allow you to monitor several sensors for less than the dealer is likely to charge you. And if you have an Android smart phone, a $20 bluetooth OBD-II adapter and free Torque Lite application would allow you to see what you probably need to see.

-Rod

Did you ever find the cause of your problems? My wife's 2007 explorer is doing the exact same thing. Sometimes it acts like it's going to stall at startup. Had the dealer clean the throttle body. Also whenever she stops quickly, or even when she first starts up, there's a delay when she accelerates and then it clunks into gear.