Poor Gas Mileage after Isolator Bolt repair

Hi All,

Back in July I performed the Isolator Bolt repair as a result of the P0171/0174 CEL. Along with this repair I changed the plugs (not wires), PCV, and an EGR hose that was crumbling. I did not change the valve cover but modified the baffle myself. The CEL went away for a week and then came back on with the P0401/0402. I changed the DPFE sensor and all was well after that with the exception of the main topic, Poor Gas Mileage.

With the first CEL the van was getting about 13-14 mpg. After the DPFE sensor we only noticed a slight increase to 15 mpg. Now here's the strange part, before changing the DPFE sensor the family went on a long road trip and we noticed 22 mpg. Ever since its been 15 mpg but we haven't been on a long trip again and my wife mainly drives around town.

If anyone has any ideas, please let me know.

Thanks,
smf

Hi
For what it is worth, 15/22 is pretty standard for my van - '96 with 3.8L. I would think that if your van were running particularly rich, you should trigger a CEL. Where are you running your tire pressure? Ford says 31 for mine, but I usually push that a bit higher.

Good Luck

busboy4,

I usually set my tire pressure to 35psi. Before I had the P0171/0174 CEL the van was getting around 20/22. Also, this van is a '99 3.8L with only 60k miles.

smf

You may want to regap or recheck the plugs to make sure there with in spec.
Also did you put plantium plugs like auto-light or motorcraft.?? Also the wire gap set tool is alot better than a disk type gapper which I must say I used before but had trouble with them so I use the wire type gauge..

garync1,

Yes I did replace the plugs with fine-point platinum Motorcraft plugs (old ones were more blunt) from the dealership (of course I paid too much for them:banghead: ). One thing I didn't do is use a gap tool on them because the tool I had was old and was not thin enough. I did check the gap by using a piece of something??? laying around my shop that measured to the correct thickness with my precision caliper and checked it with the spark plug.

I would hate to have to take these plugs out again as they were quite difficult to get out. Mainly the wires themselves in the back as well as having to take the cowl off again.

Thanks for the reply, keep the suggestions coming please.
smf

when I did my plugs for the back I went under with the van on ramps. Flying blind but was not bad at all. On my 2001 with 95,000 miles, mpg not bad. as for checking tire psi, clean intake filter ,mobil synthetic oil new fuel filter and spark plugs and same old plug wires still ranging 20 city 27 hwy. there have been times
I have had 16mpg city and a 15.9 not sure why maybe my wife had a full crew with her but mpg are within reason I guess. I would hunt around for some minor vacuum leaks or recheck spark gap. I did my tsb update a while back after my fuel mpg droped and CEL came on.Runs like a champ now. knock on wood..

I would be checking the EGR/DPFEgr loop closely.