lobing Idle

I'm new to this board but have gotten alot of useful information
from here, I have a 1993 Chevy Silverado,5.7 4x4 extended cab.
has 100,000 miles on it and still looks new, MarkIII conversion.

I been having a strange idle problem, the idle lopes up and down
at times than some times runs fine, but I noticed when i shift out of
park to drive it surges high during the shift and than jerks the shit
out of me because the idle is to high when it shifts in to gear, now
my tranny is slipping because of this. Anybody have any Ideals?

Things I changed.

1 Oxygen Sensor
2 TPS
3. Map Sensor
4. Spark Plug Wires
5. IAC
6. Plugs
7. Coolant temp sensor
8.Cap and Rotor
9. Electronic Spark Control Module ( on Dist)
10. Ignition Coil
11. EGR Selenoid Valve
12. TBI Gasket
14. Intake Manifold Gaskets ( did have a coolant leak)
15. all vacumm hoses
16. Fuel filter ( 1 year ago)9,000 miles

Things I haven't changed

1. Fuel Pump (plan to do this soon)


I also have check the timing (OK).
This problem seems to be worst the colder it is outside, did noticed
the air filter preheat valve is not closing even during cold start ups, its
constantly getting cold air.

Does it still do the same thing when you let it warm up? at least till it idles down?

...and than jerks the shit out of me because the idle is to high when it shifts in to gear...

Does that mean you need a new seat now too? :biggrin:

Any check engine light?

Does that mean you need a new seat now too? :biggrin:

Any check engine light?


No engine light at all, and seems to be better the warmer it is out side :banghead:

my 454 ss does the exact same thing when its cold outside and its not warm and i put it in gear(i think it sounds pretty sweet cause it lopes lol)
i just let it warm up (at least till it idles down) and it returns to normal.

...did noticed the air filter preheat valve is not closing even during cold start ups, its constantly getting cold air.

I didn't see this the first time I read your post. That could be the problem. Fix that and I bet the problem will go away.

I didn't see this the first time I read your post. That could be the problem. Fix that and I bet the problem will go away.



Well I fixed that door but still doing the same thing, but its not as bad so I can live with it now, but still having that real hard(fast idle) shift out of park, any Ideals,,,,,,,, does anybody thing that maybe my torque converter is bad?, what is the purpose of the Torque Converter anyway? what does it do? :banghead:

Big Chevy Man Frank

Picture two fans facing each other and placed very close. One is turned on, the other not turned on. The air currents from the driven fan will cause the non driven fan blades to turn, although at a slower rate. Improvements can be made to the process by placing them both in a "volute" with ribs that direct the flow of air, or in the case of your torque converter, hydraulic fluid. Adding blades to the fan, and having the right pitch also aids in the transfer of motion from one fan to the other.

i have a 93 k1500 5.7L HD 5-speed.
The truck drives fine when steady cruising but when you let off the accelerator to coast before you stop, the engine will jerk the crap out of you. therefore i have to hold the clutch in until i have come to a complete stop. there is no service engine light on . but i checked it anyway and a code 43 shows. anyone know why the truck gallop when you let of the gas

I´m defenitly not a mechanic (nor an english teacher...)
But if the problem gets worse the colder the engine is...
Sounds like a chokeproblem to me?