how about checking out the engine modulator also, i just bought a 1992 chevy cavalier from a private owner for only 300.00 took it too my mechanic shop and he put it on i think the diagnostic machine and found out it was the modulator, he went and got a used  one for 75.00 only charged me 55.00 for labor and 45.00 towing and antifreze and misc shop parts all for only everything was only 257.57 total and now i got an excellent running car for only 500.00 with 152,000 miles on it a 2.2 4 cylinder, tires great, body in excellent shape no rust, 2 door only but i recommend any one to jr'S AUTO REPAIR OUT BY  JOHN DEERE AND THE PIT STOP BAR RIGHT BEHIND THEM NUMBER IS 563-556-2093,THANK YOU AND GOOD LUCK!!!