As usual, looking for some suggestions. My 2003 S-Type 4.2 has run perfectly all day, taking 2 short trips (around town 10 miles each at about 30 mph) and 2 longer trips (45 minutes at 60 - 70 mph). Then, leaving work, it was difficult to start - starting and conking out within a few seconds. After 3 tries and reving accecerator, it finally started and stayed running. Pulled into a parking lot and ideled very lumpy, turned off for errand and same starting problem. Once got running was able to get home (approx. 7 miles traveling between 30 - 50 mph) and car ran fairly well again, even driving slowly down driveway for approx 1/2 mile but by time I was stopped in garage and ideling, it was super rough again. No 'Check Engine' light has come on. Just turned 107k miles today. Been running premium fuel. Any ideas on what is going on??

 

Sounds like extra air is getting in, either vac leak or maybe bad MAF? I'd still hook a code reader to it and see if there are any pending codes.

 

thanks for reply 'Michael S'. I will plug the Code Reader as you suggested in the a.m. (i left my comp. at office so have to wait until then). I will update afterwards. Thanks again.

 

Many codes don't flag till the problem occurs on 2 separate drive cycles and in similar conditions. Pending codes may show, though. Be slightly wary of them as they might be ones that will self-clear.

If you can, look at LTFTs (see below) at idle & 2500rpm (in P or N).

 

Thanks to all it was a broken breather hose from the pcv to the intake manifold. I did a temperary patch and it is running great.