2008 Explorer Sport Trac 4.0 V6 Stalling/rough Idle issue Mystery, Experts help needed please! | Ford Explorer - Ford Ranger Forums - Serious Explorations
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2008 Explorer Sport Trac 4.0 V6 Stalling/rough Idle issue Mystery, Experts help needed please!


New Member
October 21, 2018
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Year, Model & Trim Level
2008 Explorer Sport Trac
Hey guys, so my father in law has been having bad luck recently where his truck is symptomatic of the notorious rough idle/stalling issues. Being that it is such a typical event he took it to an indy shop for diagnosing and fixing.

At the shop they changed the intake manifold with a new one and gaskets because doing a smoke test revealed a crack in the old intake manifold causing a vac leak. After the truck was at the shop several times the issue still has not been resolved. I recently had my first born and have my hands full at the moment but because I do have a mechanical background (although the medical field) he asked if I could take a look at the truck as the shop is saying that they can't do anymore for the vehicle because they believe its an electrical issue that needs to be looked at by an electrician (never heard that one before).

Upon receiving the Sport Trac and letting the vehicle warm up fully these were the following symptoms that I experienced while the car was just parked and left to idle.


- After warming the truck up for about 20-30 minutes the vehicle would randomly stall/rough idle almost like 2-4 cylinders aren't firing and while its stalling there's a distinct vac/air noise coming from the intake manifold area. (take note, the vehicle will stall for several secs/mins then kick up in idle, smooth out and be fine for the following 2-5 mins then repeat)
- While this is happening, with the a/c running, the ac compressor clutch stops engaging and the a/c compressor will no longer engage (I checked the whole a/c system; pressure switch, diode, fuse, relay and everything is in working order including the idle bump supplied to the PCM when the cabin ac button is engaged. I even removed the old freon, placed the system under negative pressure which held and resupplied the system with 0.87kg or 31oz of 134a freon. Pressures on my manifold gauge are within normal limits given the ambiet air temp. Powering the clutch directly to +12v engages the clutch and a/c works as normal but obviously I don't want it to be ran that way)
- While the stalling is occurring there is distinct smoke coming from an area at or near the EGR valve.
- Low and behold no check engine light throughout this process.

Ideally, I'd like to take the whole intake manifold system apart, test each electronic part to see if they're within spec but its just too time consuming considering my newborn situation. I'm just looking for guidance to point my father in law in the right direction to save time and money. I do find it a coincidence that the rough idle/stalling causing the a/c clutch to disengage and find it more interesting that the smoking occurs when this happens only after the vehicle has warmed up.

If anyone has any reference points please let me know. The more the better. I've spent countless hours trying to do research over the net for possible fixes with similar symptoms with no success. I even changed the Crankshaft sensor for ***** and giggles due to its relatively low cost and ease of access. Still with no changes in symptoms.

Thank you for reading and look forward to responses if any.



Active Member
June 14, 2018
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City, State
Cedar City
Year, Model & Trim Level
2009 Adrenalin 4.6
Welcome to the forum.
You have put extensive work into diagnosing your problem but you didn't mention any codes. Have you or anyone else put a code scanner on this truck and if so what were the results?