Suddenly, truck won't idle & heavy fuel smell | Ford Explorer Forums - Serious Explorations

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Suddenly, truck won't idle & heavy fuel smell


New Member
March 17, 2007
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City, State
Year, Model & Trim Level
'99 EB 4.0 SOHC
Hi all,

I've done some searching on this but I think my problem is more than a "rough idle" problem. Wife called me as I got to work today and said truck won't stay running unless she stands on the gas pedal and it revs up ('99 Explorer, 4.0 SOHC, 80k miles). When she lets off, it dies. She also said there is a heavy smell of fuel. She tried again 15 mintues later and this time she said it popped before dying (I assume this was a backfire). This is just after truck ran great on a 700 mile round trip last weekend. No hint of a problem.

I've read about cleaning/checking the IAC valve, but wanted to know if there's anything else someone could think of that would cause this sudden problem. I will be working on it tonight and wanted to get a jump on possible troublshooting.


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IAC Valve. common symptoms your describing

dmac, Thanks for your response. I hope it is as simple as that. Does anyone think it's a complete failure of the valve (since it happened suddenly), or a cleaning might be all that's needed?


Hi All,

I'm new to the forum. I've read through some posts, this is a pretty interesting site. You guys are quite helpful.

I'm having the same issue, mentioned above, with my 2000 XLT (4.0). My problem is only when the engine is cold. It runs like a champ when she's all warmed up. It's almost like the computer isn't "choking" the fuel system until the temp comes up.

I had the check engine light on, but I cleaned the Mass Airflow Sensor and the light went off. Do you think the plugs might be fouled from my running it like that for a couple of weeks?

Also, could someone shed a little light on what the IAC valve is, and where is it located? It almost seems like cleaning that will solve my problem, but I'm not exactly sure.

Thanks for the help!


Check your air intake duct from the air cleaner. Especially if you or someone else has been under the hood prior to the problem. If it's not seated correctly, you can suck air in which bypasses the MAF. Without the MAF involved the computer doesn't mix the gas correctly. Depending on how bad the leak is, it could cause it to run rough, or not run at all.

Thanks eveyone who replied. I should have posted the fix sooner. It was the IAC valve. Completely frozen shut. I fixed it temporarily by cleaning it with carb cleaner, but was leary of it happening again in an inconvienient place so just purchased a new one.