Truck Not running right.

[fighterofwars]

Okay, I bought a 1987 Chevrolet K20 with a 350 TBI this summer. The truck has 186,000 miles on it with many of the original parts. Well, the guy before me didn't drive it very much in the past 7 years and maybe a few times to the field to work. Well, it sat for awhile before I bought it. It used to run alright with no problems, but he said after it sat for awhile in his shed and he drove it out it took awhile for it to start. And when it did start the engine would speed up and slow down, speed up slow down.

Well, I bought it, put fresh gas in it, changed all the fluids, new thermostat, new air filter and its still doing it 3000 miles later. I thought it was just the old gas but it might have just improved a tab but hardly noticible since I first started driving. Also, if I try and drive it while its still cold the engine sounds like its not running on all cylinders halfway through the pedal, if I go about 3/4 of the way the engine really gets with it for like 2 seconds then starts doing it again. This happens in summer, winter, rain, or shine.

Sometimes it likes to idle really high. Like cruising speed high. I drove the truck 10 miles, shut it off. Went out a couple hours later and let it warm up. Started and ran back inside because it was around 13 degrees. Well I come back out and the truck is running pretty fast. So I get in and goose it a couple times. It stays the same. So I drive it home another 10 miles and it still is idleing way too high. So I shut it off, and start it back up and it idles at the right speed.

I already tried the TB gasket where I sprayed carb cleaner around the base and it didn't change the speed. I might try it again though just to make sure.

Sorry for the long winded post but I tried to give as much info as possible.

[jefferias]

just a couple thoughts...
  fuel filter, dizzy cap/rotor, what do the plugs look like?, plug wires, is it throwing any codes on the dash?

[fighterofwars]

Where would the codes come up at? The only lights on the dash are the check engine light, 4wd light and Parking Brake light. The Check engine light is not on. But comes on when the truck is off but key is on so I know the bulbs not bad.

[4x4Cowgirl]

The same thing happened to my boyfriend when he bought his 350 from this guy. He had the glass fuel filter on backwards to where it wasn't getting hardly any fuel and it caused the same problems you are having. You might check to see if it is on the right way. Just an idea.

[jefferias]

k your good im assuming if the check engine light is off--thats where you pull the codes if its on

[fighterofwars]

Yes, as soon as the truck starts the check engine light goes off.

[Layne]

Have you considered your Idle Air Control Valve?

[Blue 82]

The IAC is most likely the culprit unless you have a major vacuum leak somewhere
should be ACDelco#  217-429   217-437
Your local auto parts store should have one for about $50
It should look something like this

[78 Chevyrado]

Here's the free and easy way to check your computer codes.  I used to do this on my 87 1/2 ton.

http://www.freeautomechanic.com/diagnostictroblecodes5.html

Also, I'm don't remember the procedure, but there it a way to reset the IAC and I  have seen this help some people out.  just something to try before buying a new one.  Maybe somebodys know how to do it.

[1980c10]

you can cross two leads on your computer plug in(in the top corner can't remember what side). it will flash your check engine light 12,12,12,your trouble code(s) three times each and 12,12,12 when it is done and start again. your key must be on without the engine running. or you can use a scanner but isn't reeally needed. then google the codes. hope this helps.

[Captkaos]

top 2 right holes on the ALDL.

[VileZambonie]

If it's idle hunting all the time, cold start, warmed up etc then you most likely have a vacuum leak and yes the base gasket is a common failure

[fighterofwars]

Sorry for the long wait on the reply, I replaced the Fuel Filter, no change, put new cap and rotor on, no change, checked the TBI to Intake gasket and it didnt change when sprayed, we cleaned the Throttle body pretty good. But, I have gotten 3 codes now. One is Spark Timing, and Rich exhaust, and Lean exhaust. We checked the timing with timing light and it is spot on at idle.

Another thing, it seems like it doesn't have much power at crusing speed. For example, I'm driving along and I come to a very little hill, it suddenly feels like I let off the pedal and it shifts down, it does this at every hill and sometimes just driving on level ground it will slow down and down shift. And then sometimes it will slowly accelerate till about 70 all the while the pedal is in the same spot, of course this is just what I can tell, my foot might be moving a little bit and me not noticing it.

[Layne]

Sounds similar to my prob... Did you check your TPS and EGR solenoid? That was 90% of my dilemma

[Lt.Del]

Truck Not running right.

try turning left