'88 305 Trouble Idling On Startup

[Triplel40]

My 88's been acting up every once in a while at startup. It fires up and either dies or barely runs and kinda surges. At first it was only happening every once in a while, but now its getting more and more frequent. While its having trouble running, if you hold the throttle wide open, it continues surging and slowly revs up for a while then it smooths out and runs fine after that. Seems to happen mostly after it has been sitting for an hour or so. If you fire it up right after its been running, it doesn't do it, and if its been sitting over night, it doesn't do it either.

I recorded a video of it as best as I could today, but it wasn't acting up as badly as it usually does. Its here http://youtu.be/5mNb6tB-WCE
--Cell phone video, sorry for sound quality

I'm stumped, anybody have any ideas? Experienced this before?

 

[SCOTTYINWV]

Possibly a sticking IAC? Unhook it and see how it idles. Might need a good cleaning.

 

[Triplel40]

Good chance, don't know why I didn't think about that. Its never been cleaned that I know of, and has 308K miles on it, so it could probably stand a cleaning.

 

[SCOTTYINWV]

It took me a minute before I thought of it when mine failed, cleaned it and it still wouldn't run. Replaced for $40 from Napa. lol don't feel bad, little things usually slip my mind. A good time to pull out PCV and lines and clean them also. See how it runs with it unplugged.

 

[Triplel40]

Sorry for the lack of updates, we just moved and don't have internet at the new house yet...anyway I unplugged the IAC and it started running a little better, but then it started having trouble with acceleration too, so I tore into the throttle body and thoroughly cleaned everything, including the IAC. So far its been running great, but I'll have to see how it does over the next few days. TB was filthy, so it definitely needed cleaned. Got my fingers crossed! Hopefully that's all that was wrong.
Also, I just remembered I have a good IAC on a parts TB in the garage, so I will swap them out if it starts acting up again.

 

[94Sierra4x4]

Sorry for the lack of updates, we just moved and don't have internet at the new house yet...anyway I unplugged the IAC and it started running a little better, but then it started having trouble with acceleration too, so I tore into the throttle body and thoroughly cleaned everything, including the IAC. So far its been running great, but I'll have to see how it does over the next few days. TB was filthy, so it definitely needed cleaned. Got my fingers crossed! Hopefully that's all that was wrong.
Also, I just remembered I have a good IAC on a parts TB in the garage, so I will swap them out if it starts acting up again.

May as well clean the spare TB in your own time so you don't need any unnessecary downtime! Good time to swap out injector filters, do the ultimate TBI mods, and so forth. If your into that kinda thing.

 

[Triplel40]

The spare TB has a bad housing, so is just for parts, so I'm not gonna worry too much about it. Anyways, I didn't get.IAC swapped because I ran out of time before I had to haul a trailer this morning, so I figured i'd just go ahead and drive it. On my way home, it finally got bad enough that it threw on the check engine light, with a #22 TPS voltage low code. So I took the TPS off of the extra TB and threw it on and it runs right! My only problem now is that since I swapped the TPS, the light came back on with #22 again, and #24 vehicle speed sensor signal constant (no pulsing) during engine deceleration, and #44 lean exhaust...
The extra TB (and TPS) is from an '89 350, so are the 350 and 305 TPS not interchangeable maybe?

 

[94Sierra4x4]

The spare TB has a bad housing, so is just for parts, so I'm not gonna worry too much about it. Anyways, I didn't get.IAC swapped because I ran out of time before I had to haul a trailer this morning, so I figured i'd just go ahead and drive it. On my way home, it finally got bad enough that it threw on the check engine light, with a #22 TPS voltage low code. So I took the TPS off of the extra TB and threw it on and it runs right! My only problem now is that since I swapped the TPS, the light came back on with #22 again, and #24 vehicle speed sensor signal constant (no pulsing) during engine deceleration, and #44 lean exhaust...
The extra TB (and TPS) is from an '89 350, so are the 350 and 305 TPS not interchangeable maybe?

They are interchangeable, just checked rockauto.com for part numbers, 305 and 350 tbi use the same tps

 

[Triplel40]

They are interchangeable, just checked rockauto.com for part numbers, 305 and 350 tbi use the same tps

Thanks! I ended up swapping the IAC over along with the TPS. Now Ihave no codes coming up, and it seems to have a little bit better power. I have to haul animals tomorrow so ill see if I can get it to act up, and post an update afterwards

 

[Triplel40]

--Update-- Ran it all last week hauling animals and never gave me any problems. Threw a 44 lean code under heavy throttle for a second last night, but that is probably unrelated. Looks like the TPS and IAC solved my problems. Thanks guys!