Rough Starting Explorer

KEITH SMITH

MEMBER
FORD EXPLORER

1999 Explorer Sport, 4.0 SOHC V-6 108,000 miles. After sitting overnight or for long periods of time, vehicle runs very rough at start up, high to low idle and occasionally dies. Problem goes away after engine warms up. Shows the code for lean bank 1 and 2. Had it diagnosed at a recommended shop that said it was definitely the MAF. I replaced this and it didn't help at all. THey said they tested the intake manifold gaskets, but I have no proof. I've also replaced fuel filter and plugs. Air filter looks clean. Any help on where to turn next is appreciated.

7 Replies

BRUCE HUNT

MECHANIC
3,754 POSTS

Coming from a Honda forum to assist, try these thoughts. The intake manifold will usually cause the surging of the engine to be a constant thing. But air in the cooling system can cause problems. Also, you must have something like an Idle air control and it could be plugged.

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Thursday, November 23rd, 2006 AT 9:34 PM

AARON

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3 POSTS

I also have the same issue. I have a 02 Explorer Sport Trac. It idles hi to low and dies. But when warmed up runs fine. Called the ford dealer, wanted 100 bux to hook to a computer but told me sounds like a Idler Air Control valve. They wanted 300 bux to fix. Bought the valve at Autozone for 75. But did not fix the problem. I googled the same question, majority of the responses had "coil on the plug bad?" Let me know if you have any luck.

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Wednesday, December 6th, 2006 AT 2:47 AM

CARUNDELL

MECHANIC
602 POSTS

Hey Keith,
Bruce has you pointed in the right direction and its a common ford issue, with the "plastic" intakes. The seals (not gaskets) fail and when cold don't seal, when hot everything expands and it seals. Its not to terrible of a job for the avid DIYer, and you can get the seal kit from ford for cheap money!

Regards,

Chris

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Wednesday, December 6th, 2006 AT 4:50 AM

AARON

MEMBER
3 POSTS

Have also did the fuel filter and new air filter, no dice. Chris so you think the seal kit would fix the issue? Mine starts good RPM's up to about 2k and when sinks back down you'd think the engine is getting strangled with all the spittin and sputtering it goes through! If I don't sit in the truck and hit the gas when it almost dies, it will. This has also happened a few times when its warm then go to the bank drive thru for ex. Its died!

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Wednesday, December 6th, 2006 AT 6:08 AM

CARUNDELL

MECHANIC
602 POSTS

Hey aaron
Please bear in mind that its very hard to diagnose an issue with out being right there in front of the vehicle, but given the history and symptoms of the vehicle I would say yes, the vacuum leaks @ the intake will cause the IAC to act erratically as the PCM is trying to compensate for the additional "air" coming in (simplified) Second, the p0170's codes point me in that direction too as it indicates both banks are lean.

Having said that, there are also issues w/ the MAF causing p0170's codes and even if the MAF specs out ok. Additionally, there are also IAC issues too but they usually pop a code and its pretty obvious.

You need special equip to nail the diagnosis though, be able to graph the O2 on a scanner or labscope and some carb cleaner sprayed on the intake mating surfaces is my favorite quicky test for an intake seal test. Do it when its cold and spray the carb clean and "watch" the O2 go fixed rich and your pretty much done

I would have to recommend taking the vehicle to a trusted shop and get it diagnosed properly.

Anyone else out there got any good quicky tests? Hope this helps!

Regards,

Chris