Why am is my car running rough at idle and sputters at any RPM?15mpgs?

WINDSBRA12

MEMBER
1994 GEO PRIZM
235 MILES

I have a 94 geo prizim with 235k 5 speed manual, im getting 15 mpg hy, the car has a rough idle and sputters at any rpm you hold it at! But if you are acellerating it dose not lack any power and gos fine but I can tell its running Rich. I tryed getting engine codes off of it but, all I got was a continuous. Flash (no codes) I have replaced cap and rotor, sparkplugs, with the right gap, .042, new wires new air filter, fule presher regulator, that was off ebay? All the vacume lines are on. Tge timing is on. I also tested compershion in all cylinders cold all at about 200psi orerating temp 180. I unpuged the o2sensor and drove it to work and it did not run any different and the cheack engine light dident come on?
I need some help this car should atlest get 25 mpg! Any suggestions

4 Replies

KHLOW2008

MECHANIC
41,814 POSTS

If equipped with EGR, check its function. Have the MAF, throttle body anc IAC cleaned and retest.

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Thursday, August 16th, 2012 AT 8:02 AM

WINDSBRA12

MEMBER
3 POSTS

Thank you tons! My map sensor vacume line was on the wrong place! I was looking around trung to find the map sensor, and unpluged the wireing harnes to it and the idle came up and it was tunning better! Then.I remembered whe I replaced the the clutch I was looking for the nipple for the vacume line that came off. Then it clicked ! I took it off where I put it and placed it on the map sensor and pluged the wires back in. Perfect! Im getting 37 mpg now! 75% hyw ! Thanks again you pointed out the problem ! !