i have a 1987 iroc z motor in my truck (whoever installed it was a moron.) and it idles between 900-1300 and sometimes will miss at idle, and by sometimes i mean like 4 or 5 times at a light, i am getting a check engine light but to read this i need the 3rd,8th and 10th vin digits can anyone help?

 

3rd digit = 1
4th digit = F
8th digit = F for 305; 8 for 350
10th digit = H (for 1987)

 

Check for vacuum leaks; focus on the hoses in the back, and the plenum-runner-base gaskets. This is one of the most common causes for a slightly high and a rough idle, so I usually check this first.

A vac. leak (or even a failing fuel pump)L can also fool your ECM into setting a lean code or even a MAF code, so start at the bottom before you think about replacing that expensive MAF sensor.