Surging idle on cold start

[Schurkey]

Dont buy the first gen of anything.

My '88 was first-year of the GMT400. Service manual has a copyright date of '86.

The service manual has so many mistakes and bad info that they had to publish a "Service Manual Suppliment" to correct most of them.

 

[K-Man]

Okay, so last night I took air cleaner off and started her up to look at the spray pattern and the throttle body was REALLY LOUD! Sucking sound, mechanical sounds, all from the throttle body, and the surging/miss, that went away after the two minutes. Then it quieted down and ran great. Any ideas??

 

[Schurkey]

the throttle body was REALLY LOUD! Sucking sound,

IAC open farther than normal to accommodate the faster, cold idle?

mechanical sounds,

Injectors clicking?

What is your fuel pressure?

and the surging/miss, that went away after the two minutes. Then it quieted down and ran great.

Engine got warm enough that the computer discontinued the fast idle?

 

[1997]

Okay, so last night I took air cleaner off and started her up to look at the spray pattern and the throttle body was REALLY LOUD! Sucking sound, mechanical sounds, all from the throttle body, and the surging/miss, that went away after the two minutes. Then it quieted down and ran great. Any ideas??

did you just remove the lid or the whole air cleaner?

 

[K-Man]

did you just remove the lid or the whole air cleaner?

The whole air cleaner

 

[K-Man]

IAC open farther than normal to accommodate the faster, cold idle?


Injectors clicking?

What is your fuel pressure?


Engine got warm enough that the computer discontinued the fast idle?

The injectors were clicking and fuel pressure at 13. The motor was hunting and surging and missing during the loud startup.

 

[1997]

your air cleaner doesn't have the flapper schurkey is talking about?
i assume you plugged any vac lines if needed.
Thinger says his 94 doesn't have the flapper, just the tube from the exhaust manifold, my 95 has both.
if it ever stops raining i'll take a pic and test mine.

 

[Schurkey]

A picture would be good. I have trouble imagining that GM would put a heat stove and hose on the air cleaner...and NOT install a flapper.

But unlike the older ones, the GMT400/TBI flappers are not vacuum-operated. They've got a wax lump inside a mechanism, similar to the coolant thermostat. When the wax is cold, the flapper allows hot air into the snorkel. When it gets hot and expands, it shuts off the hot air. In-between, it's regulating the air temp inside the air cleaner.

And the whole thing is hidden, internal to the air cleaner.

 

[Schurkey]

The motor was hunting and surging and missing during the loud startup.

Yep...you need a scan tool.

 

[K-Man]

Yep...you need a scan tool.

Is there a way to use that Tunerpro RT without buying an $80 usb?