Rough Idle at Cold Start

[Spikely15]

Hey all,

I've been putting up with a rough idle and cold start up on my 98 V6 SOHC for a while now, but with the winter temps coming in, she's becoming a lot more difficult to deal with.

I have a check engine light on and its throwing two codes - lean burn on both banks 1 and 2. I've checked for any cracks in the vacuum lines and, from what I can see, it doesn't look like there are any. I haven't replaced the fuel filter yet, but that's on my list for the week. I gave the fuel tank a shot of Seafoam but that didn't seem to change anything. The only bit of insight I've thought to try is to unplug the MAF, which lets her start up much more easily and eliminates the rough idle...but you can definitely smell the exhaust a lot more when that happens. When I unplug the MAF, the check engine light doesn't go away, but that may just need a set amount of time before the computer refreshes the alerts, I'm not sure.

Can anyone direct me towards the next steps to try?

Thanks in advance!

Dustin

 

[swshawaii]

Lean condition procedure
http://www.explorerforum.com/forums/showthread.php?p=2364255

2000StreetRod's Helpful thread list
http://www.explorerforum.com/forums/showthread.php?t=263665

 

[PAExplorerXLT]

It is amazing how people have been reporting virtually identical symptoms for this problem for years( I have a thread a few lines down and what I have replaced so far) and there is still no good answer.

 

[BustedKnuckles24]

Upper and lower intake manifold gaskets. I had the exact same problem, and chased a dirty MAF, looked for, but never found, a cracked or leaking vacuum line, even ran a fuel pressure check. After a really cold morning while camping in the mountains, the engine idled very rough, stalled twice, and the CEL came on with those two codes. Finally decided to replace the upper and lower intake manifold gaskets. The Fel-Pro kit was around $20-25 and a couple of hours with a set of torx sockets on a Saturday morning, and I haven't had a problem since.

 

[lobo411]

I don't have a SOHC but my OHV definitely picked up when I replaced the lower intake manifold gaskets. Also, while the rubber elbow to my PCV valve was intact and I heard no sounds of a vac leak, I did notice a light oily buildup around the PCV valve, the vac line to the brake booster, and the intake manifold near the vac lines. I replaced the elbow and the oily buildup never came back. So it's possible for that rubber elbow to leak due to overstretched/hardened rubber w/o making much noise.

 

[PAExplorerXLT]

Where is this rubber elbow everybody is talking about? From what I gather, it is on the passenger side of the engine but what do you have to remove to actually touch it?

 

[lobo411]

Where is this rubber elbow everybody is talking about? From what I gather, it is on the passenger side of the engine but what do you have to remove to actually touch it?

It's the thing that connects the PCV valve to the manifold vacuum. On the OHV it's just a rubber elbow, but I think on the SOHC it's the rubber elbow that connects the PCV to the vacuum hardline.

 

[Spikely15]

Upper and lower intake manifold gaskets. I had the exact same problem, and chased a dirty MAF, looked for, but never found, a cracked or leaking vacuum line, even ran a fuel pressure check. After a really cold morning while camping in the mountains, the engine idled very rough, stalled twice, and the CEL came on with those two codes. Finally decided to replace the upper and lower intake manifold gaskets. The Fel-Pro kit was around $20-25 and a couple of hours with a set of torx sockets on a Saturday morning, and I haven't had a problem since.

I'll give the tips that SWS linked to a try first, since its just more poking around, but I'm going to guess that its probably the manifold gaskets. She has around 180K miles on her and they've never been replaced, so odds are good (or not so good).

Thanks everybody for the quick replies. Time to dig in!