I recently had some major work performed on my 2001 Ford Ranger 3.0L V6 automatic due to a radiator fluid leak behind the timing chain cover. I took my truck to a local engine repair shop. Because of the difficulty in replacing the timing cover seal, the shop recommended removing the engine and basic perform a complete reseal of the the whole engine. I decided to go with their recommendation.

While the engine was being worked on, the shop replaced the EGR valve gasket, thermostat and gasket gasket, water pump and gasket, accessory belt tensioner assembly, drive belt, plenum gasket, exhaust pipe gasket, oil pan gasket, front cover crank seal, refrigerant, ATF, engine oil, coolant.

When I picked up my truck, I noticed that it had a rough idle on startup. I took it back to the shop and they recommended replacing the spark plugs and wires so I went ahead and had them do that as well. Even after new spark plugs and wires it still idles rough on startup.

I've researched the internet where other ford ranger owners have reported a similar issue. Replies that I have read suggest looking at the air filter, MAF sensor, IAC valve, coil, spark plugs and wires, fuel injectors, etc...

I've cleaned the MAF sensor with MAF sensor cleaner, cleaned the IAC valve, checking the coil with a multimeter, checked that the spark plugs and wires are connected in the correct sequence, put fuel injector cleaner in the gas tank. However I still have a rough idle on start up. If I let the engine idle for several minutes before putting the truck in gear, it finally settles down and runs fairly smoothly although it still feels like there might be a misfire. If I put it in gear without letting it warm up, it will run rough and I will get a P301 code (misfire on cylinder 1). Occasionally I'll smell gas from the engine compartment. I replaced the fuel filter recently since it was due for replacement but that hasn't helped either.

I'm hoping that someone might have some suggestions as to what might be causing the problem? I don't want to take the truck back to the engine shop because I think they just want to replace parts rather than trying to diagnose the problem. Thank you for your help.

 

Been chasing this myself. I need to check the fuel dampener to make sure its not leaking fuel into the vacuum line. I have checked everything else you've mentioned.

 

Could be the sock at the bottom of fuel pump plugged up, or non return valve in fuel pump housing.......check your fuel pressure... i have stumble at cold starts for about 8 seconds, and sometimes get code PO 303 i know there is no fuel pressure in the rail when its sits for a few hours, it drains back into gas tank overnight.... got new fuel pump on its way...

 

FYI about 2 weeks ago i replaced a few crumbly vacuum lines and it didnt fix it. Decided to pop the vacuum line off the fuel dampener and check n see if it has fuel in it (shouldnt) and it was bone dry. Putting it back on it was hard to push on but kinda "popped" into its old groove. Thought hmm that was weird. I sprayed this joint in the past with carb cleaner while it was running and it had no effect. SO i backed it off 1/4" and started the truck. Hey! no more weird idle stumble! Drove it down the road and felt like it ran smoother and had a bit more oomph. Every start since then its been perfect.

1 of 2 things happening is had such a slight vacuum leak on that tiny hose that the short time the carb cleaner was present it didnt noticeably help. OR that tiny hard plastic fuel line was pushed flat against the nipple of the dampener and plugged it so the dampener wasnt doing its job.

SO try it its a 10 sec "fix" to test out is just slightly back that vacuum line off a hair.

 

I did the 10 sec fix about three weeks ago when i was trying to figure it out.. i still had the problem, i have the new pump just waiting to install soon..

 

The vacuum line doesn't help the fuel dampener to work, you could totally disconnect the vacuum line and block it off and the dampener would continue to function normally.
The vacuum line is simply a safety feature so if the dampener would ever rupture, fuel would not spray all over the engine bay, it would get sucked into the upper intake manifold.
The truck would run like crap, but there would not be an engine fire.

What the dampener does is cancel out the waves of oscillation of the injectors opening and closing hundreds of times a second at speed when going down the road.
With out it, the fast action of the injectors opening and closing would affect the fuel delivery to the engine in an uncontrolled way causing poor running and bad fuel economy.

 

11/03/2018 Update: I finally bit the bullet and took my truck to a local shop to see if they can figure out what the problem is. It turned out to be a bad coil pack. Thank you to everyone who provided suggestions.

 

weird just on cold startup? usually coils go wonky once they get hot.

 

It could be a cold or hot start up. Anytime I started the engine I would get a rough idle for the first 1-2 minutes then it would smooth out.

 

Sure seems like a grounding issue for the coil ..

 

Thank you for your response! I ended up taking it to an auto repair shop. They replaced the coil pack and that solved the problem.