Engine stalls uphill only!

[Alan001]

Thanks for dropping in on this, a bit of a last ditch call for advice and help.

I have a 98 Ford Ranger 4x4 with the 4 liter engine and auto transmission (145,000 kilometers). The engine stalls or hesitates when going up steep (back-country road) hills. The stall is more like a hiccup, lasting a second or less and then recovers. However, on very steep inclines it will repeatedly stall/recover (about 4-6 times) in quick succession until the engine just stops. This only happens on the inclined parts of the rough, bumpy, back-country dirt roads over which I travel most of the time. On paved highways and the grades encountered on highways the engine performs well (or so it appears), even when accelerating up a paved incline at highway speeds (40-80 KPH). But at slower speeds (5-20 KPH) on inclined back-country roads (with the engine under greater load, perhaps) there is a problem and regardless of whether the tank is full, half full or nearly empty. However, the engine only stalls/hesitates when going forward. The CEL flashes on only at the moment of the stall but does not stay on (there are no stored codes). The engine generally works fine in reverse though (perhaps an occasional, very rare stall), backing up any hill no matter how slowly, steeply inclined or bumpy. The fuel tank has been removed, inspected and was found to be very clean, the main fuel filter replaced, all fuel lines inspected, and the pump appears to be working. A mechanic from a garage I use went out with me for a road test with a fuel pressure gauge and the fuel pressure checked out OK for city and highway driving.

I brought the truck with me from Canada to Nicaragua where I now live. Most mechanics in Nicaragua know very little about fuel injected gasoline engines since most vehicles sold in this country are diesel. Unfortunately the garage I have to use is 4 hours away (one way) and usually involves an overnight trip. Equally unfortunately they do not have access to the type of road conditions on which I am having problems and cannot observe or reproduce the problem. So, any thoughts or help with what the problem could be would be greatly appreciated. Many thanks.

Alan Harvey

 

[Alan001]

Just in case anybody comes across the same problem.

The consensus from other forums, plus the local Ford dealer in the hometown of some friends in Canada who rallied to help, was that the problem could be with any or all of the coil pack, high tension wiring harness or the plugs. Turns out it was the plugs. I replaced them and the engine runs fine.

As a side note, it appears the problem was specifically with the 3 plugs on the right side of the engine (left side if you standing in front of the vehicle looking at the engine). The long white ceramic insulator that the cables snap onto all had dozens of small, vertical cracks in the top half. The 3 plugs on the left side of the engine appeared fine. Does anybody know what would cause such cracking/crazing and why it would only happen to the plugs on one side of the engine? (I would post some photos but it isn't obvious how to do that).