Chevy & GMC Vans

I have a 5.7Liter (aka 350 chevy) in my Safari and I'm about ready to shoot it! Why you ask? It has a nasty miss and we (being a couple of mechanics an' me) can't figure out why it misses. I've changed plugs, EGR Valve, the solenoid that controls the vacuum to the EGR, and plug wires and it still stutters, stumbles and even stalls at lights!

It's fine under acceleration but the minute I try and run at a constant throttle setting it starts stumbling and missing, or if I stop at a light and don't put it in neutral it will just keep idling down till it finally stalls!

HELP! I don't know what else to do but turn to you all for advice!

cheers!
Aiyana

Carb or EFI ? What year motor and fi system? have you done a compression check?

Compression is good, the engine has the Throttle Body EFI system...circa 1991 or 92

cheers!
Aiyana

I would look at your idle position sensor. Also look at your Throttle position sensor. You can try and take the idle position sensor out and clean it. I might a TPS sensor here in my spare bits I will look around and see what I can find. Also try swapping the computer for the other one I gave you incase it is a computer issue. I remember my 89 was doing that before I sold it but it had a 4.3l

Good luck
Kevin

I think Kidhauler might be on the right track. The idle air control valves wear out over time. You can try cleaning the pintle on the end of the shaft and the port into which it fits with some carb cleaner. It's highly likely that it's due for a replacment. If so, take it with you to the autoparts store to ensure the replacement has the same diameter pintle on it. GM, in their infinite wisdom used IAC valves with multiple diameters on the TBI injection systems.
If the IAC valve does not completely resolve the issue, the throttle body may be due for a rebuild. Rebuild may sound ominous, but it really is not. It amounts to disassembling the throttle body, cleaning and replacing gaskets. The bottom end of the tbi units carbon up incredibly bad.

We played with it for hours last weekend. Checked the pcv, IAC, TPS,MAF,everything you could think of. The van is running better but still not right. The only thing we can think of is putting a rebuild kit into the TBI. Possibly the fuel pressure regulator baffle and spring might be gooped up and not working right. At speed the engine runs fine but on a idle it will just cut out and die. Also if you turn the steering to wheel lock it will stall when the pump loads up.

Kevinator,
Aiyanna called me & had mentioned that the van had stopped dying under
parasitic drag on idle.According to our measurements the TPS was out of range.
She recalls the van to slightly miss under light throttle.As far as I know the dizzy cap,
rotor,& leads have not been replaced.
James made a reccomendation & I forewarded it to Aiyanna.

Dumb question, but have you checked for a vacum leak? suckin in more air than it should at idle then getin enough gas to not miss but run lean under throttle. I had run into this problem on other cars but not my Stro.

Things that sound dirty but are not.

Oh I missed this all!
When is the next time you are getting greasy together again?

Yes we did check for vacuum leaks but couldn't see any. We did patch 2 lines that looked like potential leaks in the near future.

Never "look" for a vacum leak. Take a can of starting fluid and spary around areas that could have one. I fixed a truck a guy was getin ready to junk because the intake gasket blew at the back of the engine right above ne of the runners. Couldnt see a thing but when I shot some starter fluid over it engine reved up big time. Pulled the intake replaced gaskets ran great. Could be one of these "hidden" leaks giveing you all this trouble, or it could be somethin else altogether. Just a thought, i know how much of a .... pain it can be to find a gremlin.

Kidhauler wrote:Things that sound dirty but are not.

Oh I missed this all!
When is the next time you are getting greasy together again?

oops!
Well As long as Sanja keeps your quote on his sig hah ha.
It is pouring out rain today; are you guys meeting up?