Engine stumble on acceleration - Diesel Forum

CoralDoc · 10-22-2008, 06:45 AM

Good Morning,

I checked with search, but did not find a thread on this issue.

My wife's truck, a 2004, has developed a stumble/miss when accelerating at highway speeds. This was first noticed when towing a trailer, but it is also present unloaded. Upon moderate acceleration (throttle depressed about half way) the truck will buck slightly and the engine will stumble about every second or so until I either add more throttle or back off slightly. Upon heavier throttle, the engine pulls strongly, but it emits dark smoke. The truck drives well otherwise and there is no check engine light.

There's about 57k miles on it right now, and I've performed most of the routine maintenance myself. Fuel filters are replace every 15k miles, and a recent drain of the HFCM had only a small amount of sediment in it. I cleaned the EGR valve about 5k miles ago as preventative maintenance, before I noticed the problem.

I've had the oil analyzed at Blackstone Labs and wear looks good, but the truck has had an on-again, off-again problem with fuel dilution, ranging from under 1% to 4% over the life of the truck. It was suggested that the short commute that my wife has to work could be the reason for that, since the truck does not get warmed up well each day. When I check the oil after highway runs, fuel dilution is normal (0.5-1.0%). Still, I wonder if a leaky injector could result in both issues - the stumble and fuel dilution. I had the truck in to Ford regarding the fuel dilution, but they reported that there were no issues with the injectors at that time (about 20k miles ago).

Any thoughts before I take it in to the dealer? Many thanks.

Maxfli · 10-22-2008, 09:10 AM

I just got off the phone with a friend of mine about this issue. He said is turned out to be a crank sensor. Hope this helps.

CoralDoc · 10-23-2008, 06:43 AM

Thanks Maxfli. Any other thoughts on this issue?

Engine1 · 10-23-2008, 08:48 AM

I had the exact same symptoms and I had the check engine light randomly come on. The error codes according to my dealer indicated EGR valve needed to be replaced. They replaced the valve yet the truck upon test driving still doing the same thing, I got lucky and had a mechanic who had this happen with a different type of engine. It turned out when they checked the fuel pump pressure only 40 psi ( engine needs 60 ) the low pressure not enough to trip the check engine light or cause error code because the pump would eventually build up pressure. The initial cause bad fuel, this truck came from island most likely saw home heating oil. So change out fuel pump, change all fuel filters and the EGR valve.

CoralDoc · 03-08-2009, 01:59 PM

I finally took the truck into the dealer a couple weeks ago and wanted to report that they replaced the EGR valve with an updated part. That seems to have solved the problem. I towed a 4k lb trailer for about 100 miles and did not have the symptoms. I'll double check with a heavier load in a few weeks.

hooknline · 03-08-2009, 02:39 PM

my truck did the same thing pulling a 10k boat down to the keys. It was indeed the egr valve.

Engine1 · 03-09-2009, 09:21 PM

Even though they replaced EGR valve make sure they check the fuel pressure, as I had the same symptoms when they test drove the truck under heavy load it still did it. Not only had the EGR valve gone but the fuel pump was not providing the required presure and needed to be replaced. Problem solved not had any problems since. They told me the pump was not supplying enough fuel for the engine, causing it to hiccup, belech black smoke, with a loss of top end power and speed.

CoralDoc · 03-25-2009, 08:04 AM

The truck still works fine, even on a 900 mile haul up to Georgia and back.

Now I'll out of warrantee, so keep your fingers crossed for me.