Greetings: I own a 2003 Ford Explorer Limited V6 4 Flex Fuel with around 142K miles. About 6 months ago, I notice my truck would have a hard start. (Hard as, it wont turn over. All the lights come on, the beeping, rev, rev, but wont catch). Once it does start, it can stall out, or tries to stall out (the stalling out is not consistent). If the weather outside is above 50 degrees, starts up no issues. The lower it gets the more turns it takes to get starter. Once it hits 32 outside, you can try for over 10 minutes. (Car is parked outside in TX). Runs great after it gets over it's issues (normally about a block lengeth). It will rev up on its own once it catches... I dont have a problem for the rest of the day, starting it up. Only basically when the engine is cold, as I would explain it.

Things done in the past 6 months. New Battery, New spark plugs and wires. New Fuel filter, New Fuel pump, Idle air control valve motor, new MAF sensor, and a Fuel/Induction cleaning. I have had it diagnosed twice by two different mechanics, both basically given up on the car (as in they said , It start fine this morning, had to hold the key longer, but it started, 1850 please, have a nice day).

I have paid for 3 different diagnostics. All say there is no vacuum leaks, power to the pump, everything reads fine.. I wanted to install a fuel pump relay, I was told they either work or they don't. Others say they want to change the starter, but can't explain to me why I don't have starter issues any other time. I got the car checked at an autoplace. Results: Good Battery: Voltage- 12.78V, Measured: 765 CCA. Rated: 700 CCA. Temperature: 91 Starter test: Voltage: 10.95 V, Amps: 186.9A, Time: 765mS. Charging system test: No Load: 14.18 V. Loaded: 14.02V No Load: 13.8A Loaded: 39.0A.. Drain test - .14A (My husband did forget to turn off a back fan while doing the test). One mechanic said my starter is dying and should start there.

I have read that My ford is famous for a Fuel Module going bad, but I guess it is not attached to the bumper, but is located behind the passenger side panel. Any suggestions on what it can be, and why? I really don't want to keep sinking money into this, but I need the car until I can get a steady paycheck to get a new one..

I do have a coolant leak somewhere in my system. I have asked different mechanics if this can be an issues. They all said no, its your starter.. Leak is where the upper and lower coolant housing is, and this is also where the temp sensor is located. there is white residue on top of it near where the rubber house attaches. But there is no white residue anywhere else on the engine. I do not see any rips, tears or cracks in the house. So I am not sure if it is just leaking because this part was already fixed once about 2 years ago. Thanks

  • Forgot to add. The mechanics says there are no computer codes except for cruise control. Which I knew stopped working
    – Andrea
    Feb 23, 2017 at 16:37
  • You can edit that into the question by clicking the edit link. Feb 23, 2017 at 16:40
  • Could it be that leaking coolant has damaged the temp sensor and the ECU isn't feeding the engine a proper cold mix?
    – Spivonious
    Feb 23, 2017 at 17:58
  • @Spivonious - The worst that would do is keep the engine in open loop mode, which would mean poor gas mileage, but it wouldn't keep it from running. Remember, the temp sensor is in the coolant ... well, at least one end of it is :o) Feb 23, 2017 at 19:05
  • To OP: So I understand better, you say when it's cold, you turn the key, then starter engages the engine and the engine turns over (cranks over and over), but it doesn't want to start (a "cranks-won't-start" situation)? Or is it actually that the starter won't even make the engine turn over? Feb 23, 2017 at 19:07

5 Answers 5


Got to thinking about this being a cold start only issue. You said above 50F you don't have problems. To an engine, 50F is still COLD. So I was thinking why is this a factor. It got me thinking of what could be different below 50F. Rubber seals shrink when it is cold.

These engines use o-ring style intake gaskets. Over time they lose their elasticity, shrink and don't seal as well. This causes air leaks and super lean fuel condition. Once it heats up, the gaskets can seal as they expand and the problem goes away.

I even found a video of a 1998 Explorer with the 4.0 V6 having the similar issue to what you described. The fix? Intake manifold gaskets.

  • This is a great call and I'm thinking this could be the problem. Feb 23, 2017 at 21:40

Sorry it won't let me leave a comment for some reason, I don't have enough reps.

While starting, it cranks, but just won't start. It's does everything it is supposed to except start, if that makes sense. Then it starts, revs up really high like I stepped on the gas, but I didn't. Then it might stall, or stall after I drive it away, even after it's warmed up.

The fuel mix is rich, because I can smell my exhaust after I start it, then get my kids to go in the car. Yes, the fuel pressure has been checked which lead to the new fuel pump. Had another shop do another diagnostic on it (because the other shop that installed the fuel pump, in their words, made a simple human error of forgetting to re-attach the fuel line back on, leading to a gallon of gas being spilled out as I pumped it at the gas station).

Compression test, yes. I had a full non-electric diagnosis done, even by a double team for new eyes. It is like the video but only revs once and it's good. It doesn't keep going up and down, either it revs or stalls. But once it starts no issues. So I can start it, turn it right off or it stalls. Turn it right back on it starts right up. So if it was a gasket issue wouldn't it still have a hard start if you turned it right off again?

It's almost like it lacks pressure and once it gets it, it's good, and it takes a while for the pressure to lessen. Thanks everyone. This might be important too or just the function of the truck. The check charging system light stays on the whole time when trying to start it.

  • Are you the original poster? If so, please log in using the same account and you'll be able to edit the question or comment on it - you can always comment on your own posts.
    – Nick C
    Feb 24, 2017 at 11:32
  • @NickC - The problem is, the original account is unregistered. This account is, though. To OP: Ask to merge the accounts through the control panel. I can add this to the original post, but since this account is registered, I'd suggest you have the original one merged into this one. Feb 24, 2017 at 13:19

Did they check the car for logged errors? Is this summary correct? : you can rev up once it starts and there are no errors in the computer but when cold idling the engine may stall. Then I would suggest checking the sensor values from the car's computer. Of course you or your mechanic needs to know what are 'normal' values.

Some values to check are fuel pressure, fuel trims, MAP sensor, MAF sensor, throttle position, ECT and IAT sensors. Perhaps PCV valve... If possible you should record data stream and it would ease reviewing it. There are many cheap live data recorders. I bet if your mechanic is a good one he would have such device also, it may even be available for borrowing from your mechanic. After all they cost $50 or less.

Here is some good reading material: http://www.autotap.com/techlibrary/solving_intermittent_stalling_problems.asp

Here is exactly same problem reported (unfortunately without a solution but responses may help you diagnose the problem): https://www.reddit.com/r/MechanicAdvice/comments/2mdlph/2003_ford_explorer_40_flex_engine_cold_start/


engine oil like gum, ? bad engine earth strap breaking down under pressure, add a black jump lead bat minus to engine for a try, hot water sensors, you should have 2 - one for the ecu and one for the temp guage, blue one brown one on the thermastat housing or about, swop the wires and try it. (running rich)

crank it a bit as it should have started and check fuel pressure at the schroder valve with a cloth and a match stick, squirt ??

last resort dribble a (little half egg cup) fuel into into the engine inlet manifold with the air filter hose removed. if it sparks up it fuel supply. goodluck.

  • just a note check your disributor cap had a car with a little crack did not seat right, from hot it would suck in cold air and condensate overnight.
    – user26112
    Feb 24, 2017 at 18:12

Sounds like a dirty engine -- carbonized fuel injectors, intake valve stems, stuck piston rings, etc. Use Marvel Mystery Oil in the fuel tank & crankcase for at least 1,000 miles and you will see an improvement.

  • 1
    No offence but do you work for additive industry? Because every time I see a reply from you, it tells 'dirty engine, use additives' :) Feb 24, 2017 at 10:23
  • No offense taken. I do not work for any additive company. I make these posts because, in my 35 yrs. of fixing cars, so many problems are caused by a dirty engine and can easily be resolved by additives. Why spend all that time logging data on a diagnostic screen? Why does a $7 suggestion earn me a negative vote? What are your credentials to be judging me? I thought this was an open forum? Or, is your intention to silence honest people like me?
    – Carguy
    Feb 27, 2017 at 16:05
  • Because if you don't know the reason and you try random solutions you can make the problem worse. I will give you an example. Last year my car was running rough and I connected to the computer and it told me one of the ignition coils was not working and also told which one was broken. I changed the coil and it solved the problem. If I put some additives and drove around hoping that it will cure the problem blindly, problem could have caused damage to my catalysator (due to unburned fuel reaching it). Maybe additives can be cheap, but that is not a reason to use them if they won't help. Mar 4, 2017 at 21:55

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