TBI idles very poorly
 

Hi,
I have a 1990 Chev Silverado with a 350 TBI engine, 700R4 transmission. The truck runs, but has a very poor idle, it stumbles as is if it wants to die, but it doesn't. If you give it gas it runs fine. I am going to give it a tune up tomorrow, but could there be anything major. The engine is bone stock, but the emissions have been removed, I don't get the S.E.S light and there are no codes. I will change the air filter, fluids, oil filter, spark plugs, wires, cap, rotor. Could the MAP sensor need replacing ?

Start with the basic tune up that you have planned. Make sure you check your base timing and change your 02 sensor as well. Check all vacuum lines as well as the seal between the TBI and intake manifold. You may have a slight vacuum leak.

EGR too?

I had a 95 chec truck with the same set up, i had that problem once, and it was the egr, but my friends truck started doing that about a week ago and just changed his wires, cap and rotor, and plugs and it seemed to clear it all up, but the tune up is definitely a :goodidea: .

And if it starts running like total dog crap, maybe ya did what i did and broke a valve spring, but if it runs fine at higher rpm, then thats definitely not the problem

Well I went through the engine this morning and here's what I got, I definitly need a new air filter, I checked all the plugs and they are in mint shape, except some of them were loose in the holes, so I tightened them up snug. The wires were okay but the boots at the plug were very chewed up, so I gave them some silicon sealant on the tears and put electrical tape over the silicon (just til I go to the city,tomorrow). Also the cap on the distributor is held on with chicken wire. WTF !!!! So I need to get a new cap and I'll get a rotor too. I put a ring of silicon where the TBI meets the collar ofr the air filter housing too.I finished up my tune up, did everything back up, hooked the battery up and started her up and she idles alot lot better, I think it was the chewed up spark plug boots, poor spark at low rpms I guess, that's why it wasn't noticable at high rpms cause there's more spark. I need to weld some leaks in the exhaust too, But I'm happy.

HUH????
 

Mr. Snake brings a whole new meaning to the "band aid fix"......

suprised the motor even ran in the first place......you gotta give him credit for the creative fixes.

That's not creative, been doing it for years. I just need it to last til I'm in the city tomorrow, I'll get the new stuff after work !!! HaHa !!!