IAC Swap
 

My 87 Jimmy Sierra Classic had a full tune up....94K miles with the 350/700r4. its been getting 15.8 to 16.4 mpg with mostly driving in 2WH at 55+ on the country roads, 140 miles daily round trip for work.

I had a case of the wandering idle. Only on a hot restart and never while idling hot or cold.....just the hot restart time. In addition, it had an occasional idle miss, random and only after about 2 to 3 minutes of idling at lights or in traffic. No other issues.

The tune up consisted of plugs, cap, rotor and new coil, coolant sensor, 195 thermostat, new injectors, 14 lb regulator, 1/4" injector spacer and timing set to TDC with the brown wire disconnected.

Full checks for vacuum leaks, including the intake manifold bolt torque, all correct, sound seals and hoses.

Still had the wandering idle, only on hot restart and the occasional idle miss.

I replaced the fuel filter today with an AC Delco. I also replaced the IAC with a standard motor products unit.....

measured it from pintle to mounting surface, 1 1/8" so I did not have to adjust the pintle length. installed it in the tbi with a new gasket.....did not have to do any iac relearn. A very simple 2 minute job with a 1 1/4" wrench.

Fired up and I immediately noticed the idle was lower and steadier than ever before. Took it for several rides today and so far no wandering at hot restart and no occasional miss/stumble waiting at lights.

Probably report back in a few days. if i'm lucky, its done. If not, i'll check the fuel pressure and then move on to those 30 year old ignition components.