New guy with a problum

[DaBears1285]

Hi my name is Sean and i recently bought a 99 PG sho, i'v been doing some research and cant seem to find a problum like mine, I drive probably 50 miles a day 50/50 HW/city and i' been getting a whooping 14mpg if im lucky. :cry: Did some test and found the pre cat 02's were both lazy, I swaped them out and found no improvment. When I drive im not laying in the throttle, i cruse at about 70 and keep the secondaries closed most of the time. Any help you guys could give would be great.

Thanx

 

[turbotbirdguy19]

Hi and welcome!first off are you welded?If not do that first!You dont go to U.T.I do you?I know someone who has a green 99 at my school.Anyway,That is crappy gas milege.How do you know that both post O2's are bad?Did you run a scan and check the cross counts on them or was your SES on?Winter gas will have alot to do with it,Mine sucked gas (totaled 99 TR)with the crappy gas we have now.How many miles?100,000 mile tune up IMHO is too long.When I changed my plugs at 60,000 they looked bad.Did you get bosch O2 sensors?Maybe IMRC is stuck upen but I dont think that would make you fuel milege that bad.You could try a fuel injection cleaning (worked great on my car)Also do you have the heat on vent?When its in any other position the ac compressor cycles and that can cause lower mileage(I think)Hope thats some help to ya

 

[SHOMEX]

You may just need a good tune up, a year ago I helped a guy that want to sell his SHO because his car mileage was horrible (like 10 miles per gallon or less). After 8 new spark plugs(motorcraft) and 4 used coils (good ones). His car runned like a champ and he kept his sho. The problem was 4 bad coils and I mean it, where totally dead but no SES light. So getting back to you if your car is not welded do that and at the same time check your coils. That most likely will take care of your low mileage problem.

 

[turbotbirdguy19]

Yeah,I didnt even think about the COP's.You could always do a cyllinder power balance test to see if any are weak since they are not exactly cheap to guess at replacing.

 

[hoboprodigy-]

when you are getting your cams done that would be a fantastic time to change plugs and at least your rear bank of coils. i think most people will put new ones in the back and rotate the ones from the back to the front because they are a helluva lot easier to change.

 

[DaBears1285]

Acualy I do go to U.T.I, i think i sit next to you dude , I already ran through the rall cleaner through it, i know the 02's were bad cause the Ford class scaned it and showed me the pattern, as far as the tune up, i put the car on the 5-gas and it gave me perfect results (H.C-0, CO2-16.86's, low 02 and C0 that were balanced to) I'l try running the HVAC on vent to see if that helps. Finaly im not welded but am saving towerds it, i know it needs to get done.

 

[turbotbirdguy19]

cool,small world!I hope you can figure since gas is so damn expensive.See ya around school bro!