Runs like crap backfires and jumps around.

[Dangerranger390]

well my girl is gettin sick whenever i start her up she starts fine. then then rpms come down after the initial rev and flucuate from 600 rpm to about 900 rpm. now if i put my foot on the gas bringing the rpms up to about 1200 it will stay steady. if i dont warm it all the way up to normal running temp before i start driving it will backfire badly in first and second gear as well as all gears if I make it past third gear and has hardly no power to get up a hill or drive through the neighborhood. even after it warmed up it backfired. im not sure whats going on, was wondering if anyone else has had this problem before. I did replace the map sensor but not the vacuum line itself. I'm thinking it has something to do with f/a ratio but I'm not completely sure that's what it seems like though.

 

[RonD]

The fuel injected engines use an IAC(idle air control) valve to set idle speed, this is basically a controlled vacuum leak.
It is a cylinder located on the upper intake, inside is a valve that lets in air to control idle speed, these valves get dirty and sticky so idle won't work right.
They can be cleaned.

If would run a can of Seafoam through the fuel system once a year, that can help keep injector working as they get older.

The TFI(spark) systems can be troublesome, read here about how they work and possible fixes if yours has an issue.
http://www.therangerstation.com/tech_library/TFI_Diagnostic.html

 

[adsm08]

Back fires are caused by running pig rich or bad timing. Id check timing and tune it up first.

Postin' from teh Galaxy