Really rough idle after more than 10 hours of sitting, lasts only a few minutes. Ideas?

I have a 2001 Ford Escape XLT V6 4X4. About 3 months ago I started to experience rough idle in the morning. It went a away for a month or so, but it is back now. I noticed that it occurs primarily after the vehicle has sat for long periods of time. More than 10 hours, give or take, and it happens, less than 10 and it generally doesn’t. When the issue does occur it sometimes almost stalls. I can tell the computer attempts to make up for it usually. The check engine light came on originally but hasn’t since, a mechanic could not pull any code and could not reproduce. The issue disappears within 3 to 5 minutes usually after everything seems to warm up. I’m had regular maintenance and I am an 75k. I’ve even tried using gas additives and tried a high grade of gasoline to no avail. Any one have any ideas? Thanks in advance!

The next time its been sitting long enough turn the key to the run position without cranking it (just the where the dash lights come on). Wait a couple of seconds & go back to off…back to run…back off - about 7-8 times. (If you listen you should hear a little hum each time which is the fuel pump energizing). Then crank it over. If that gets it to start smoothly then you’d probably have to replace the fuel pump to fix it. The pump has a check valve in it to keep the fuel lines from emptying out when the car sits. If yours is leaking then the rough running would be from inadequate fuel until the lines get filled back up again.

If that doesn’t help at all the next thing I’d do is check the coolant temperature sensor.

I was thining along the same lines as Cigroller, but I was thinking you had a leaking fuel injector causing a rich condition/then lean as the fuel rail fills up. Next time the car is chugging run to the back of it and take a look at the exsaust, is it black??

Like gsragtop, I am leaning toward the likelihood of a leaking fuel injector. If that turns out the be the cause of the problem, at least it won’t be expensive to replace.

I’m thinking that after sitting for 10hrs any fuel that leaked in from a leaky injector will be pretty much gone via evaporation & leaking down into the crank case. Or if its only over-fueling the cylinder when running this would be much more likely to show up after the car warms up when the mixture is supposed to lean out rather than when its first started & it is supposed to have a richer mixture.

I had the same problem in a 1990 Ford Aerostar and it turned out to be a cracked cylinder head that allowed coolant to seep into the cylinder. Fortunately, my situation was covered by the warranty. I hope that isn’t your problem, but it is a possibility.

My vote is with cigroller about the loss of residual fuel pressure. Normally this is due to a leaking fuel pump check valve but I’m reasonably sure the '01 Escape uses a fuel sensor external to the pump and which serves the same purpose. There may or may not be a code associated with a fuel pressure sensor fault.

I appreciate all the feedback. Tomorrow, I will start with the suggestion that cigroller made about moving into the on position without starting car several times and see if this helps. I will post an update here. The back flow valve seems very plausible from what the symptoms are. I just checked the coolant level and it’s actually at the exact same level where I filled it to about 4 months ago when warm. I had to replace the overflow tank because the sensor died and I was tired of seeing the constant red light on the dash after 9 months. Dealership wanted over $350 to replace it. I bought an new OEM tank for just over $45 with shipping and installed it in under 10 minutes. Anyone know how hard the fuel pump is to replace in an Escape? It appaers there’s an access panel to it under the back seat and only about 4 bolts/screws holding it in and electrical lines. Although maybe this is just the tank gauge. I heard years ago that to get to the pump required removing the gas tank on most vehicles.

Update. I did what cigroller suggested. Not conclusive. The vehicle started roughly, but stabalized within 30 seconds and had no issues afterwords. This is a bit different in that normally it takes a few seconds or up to a minute ot two before the issue occurs and it takes a few minutes for it to disappear. I think I’ll try turning the key a few extra times tomorrow and see if it helps more

I vote change fuel pump and filter.

If the ‘key-on, key-off, key-on’ solution doesn’t clear things up like it seemed to just now, it could also be a problem I just fixed on my 2000 Ford Explorer with the 4.0L SOHC V6. The intake manifold seals get hard and start to leak. Heat from the engine helps expand the seals and eliminate the leak after a couple of minutes. My truck started doing just this, but was so mild, it didn’t set a trouble code for a year. It finally set the code, but I checked for leaks and couldn’t find one, and just reset the light. It stayed off for 6 months until it got cold again. After doing the vacuum line checks again, and still finding no leak, I finally broke down, purchased the gaskets, a Fel-Pro set at Autozone, $14.99 for the upper plenum and lower unit. Took me a couple of hours, but fixed it right, and starts up fine, with no morning rough running.

“I just checked the coolant level and it’s actually at the exact same level where I filled it to about 4 months ago when warm”.

This is good news. It rules out my cracked cylinder head diagnosis as well as a bad head gasket.

ITGuy, I just got my car back today from the mechanics. I had to have the manifold gaskets replaced for the same issues you are having. He did a smoke test on it and he said that the smoke was just pouring out of them.

He informed me that as it gets colder, the space between the gaskets gets larger, causing more problems than if it were warm out.

Hope this helps you!

Well the issue subsided dramatically since I last posted. I even bought an OBD tester with logging but couldn’t see anyting odd. I finally caught about 10 seconds of the issue finally a couple days back. When it does happen both the short term and long term fuel banks on both sides go negative (inferring a rich condition) at the same time. Also at issue time, all oxygen sensors show a mild lean condition at the same time. Other than the engine RPMs looking odd on the metrics, everything else around the issue time look normal. I’ve decided I’m going to pull the battery lead this morning to reset the PCM. It’s almost as if the PCM sometimes doesn’t realize what it’s doing during warm up.

Could the water temperature sensor be somewhat how cold the engine is? A reported water temperature way below freezing would tell the fuel to go full rich.

Oops, I edited the comment above and left it messed up. Should say “exaggerating how cold”

This actually started to occur before the temperature hit freezing about 4 months ago. The vehicle is also parked in a garage most of the time and rarely reports less than 38 when I go to start. The temperature looks like it’s be reported accurately on the monitoring. It climbs steadily after starting. This is really a frustrating issue because from a monitoring perspective everything looks good. I’m leaning toward the spark plugs at this point, as I’m at 75k and 11 years on them. I’m thinking if they are a bit fouled that when things are cold they may not work as well. I can see on monitoring, and usually notice, as soon as the PCM detects rough idle it kicks the throttle up to try and compensate.

You should still check the actual coolant temp sensor. Using the dash gauge “guess” all is well is not a good strategy. This is also not at all complicated. With a multimeter - or even better a scantool - and a set of resistance specs this can be done in the space of about 15 minutes.

I’d also love to put a fuel pressure gauge on it and find out how it behaves if you always get the fuel pressure pumped up to specs before cranking it. This is also easy.

Replacing spark plugs is never a bad idea.