TBI help needed

[Burbdood 74]

88 Suburban, 350 TBI. For the last couple of weeks, the truck has developed a high...low...high...low surge when you first start it. Once it warms up, it's fine except for the fact that the idle is a little too high, (just by guess-timation about 150rpm's too high). But if you just tap the gas, the idle comes right down to normal and stays there until you touch the gas again. It's almost as if the throttle linkage is sticking. Annoying, but liveable for now.

Anywhoo, last night as we were coming home from dinner, my SES light came on and it's throwing a code 44, O2 lean condition. I'm certain I don't have any vacuum leaks because I checked all of my hoses this summer and replaced about 95% of them and I have a new gasket under the throttle body. What is going on and what is causing it to lean out? Could my throttle shaft be worn out causing it to stick and also create a vacuum leak?

 

[scrappy88]

Throttle shaft being badly worn can cause the butterflies in the throttle body to wedge against the bores which will cause this. Is your throttle stiff? I'd check it by wiggling the shaft by hand and seeing if it binds at all when closed.

Also check and clean the IAC valve on the TBI. It could also be an EGR Valve/solenoid issue. Check your spray pattern on the injectors too.

Mine did the same thing for years and I've replaced so much on it that I don't remember exactly what fixed it. It was probably a combination of things. It runs perfect now though.

 

[Burbdood 74]

Throttle shaft being badly worn can cause the butterflies in the throttle body to wedge against the bores which will cause this. Is your throttle stiff? I'd check it by wiggling the shaft by hand and seeing if it binds at all when closed.

Also check and clean the IAC valve on the TBI. It could also be an EGR Valve/solenoid issue. Check your spray pattern on the injectors too.

Mine did the same thing for years and I've replaced so much on it that I don't remember exactly what fixed it. It was probably a combination of things. It runs perfect now though.

The throttle isn't stiff at all and it doesn't feel like it's binding through the pedal but I'll check the shaft to see if it moves at all. The IAC is only 2 years old and the EGR and the EGR solenoid were replaced last year at the same time with AC Delco replacements. I'll check the spray pattern of the injectors. I wish I had a damn pressure guage or knew someone with one, that would make it so much easier.

 

[Burbdood 74]

Ok, I just went out and started the beast and I checked the fuel spray pattern. The drivers side injector is giving a nice cone shaped spray pattern at idle while the passenger side isn't. It looks like the fuel is just squirting out and dripping off the back of the injector throat. Rev it up and there's a nice pattern though.

So, it looks as if I'm going to be replacing my fuel pump next weekend or am I jumping the gun?

 

[Jessie James]

I am not 100% sure about this, but as I understand it the second injector only sprays at higher RPM or under more load (full throttle).

Have you checked the error codes? Directions are in the buyers guide sticky.

It sounds like your dripping injector may be worn out. My second one does not drip...

Replacing them is pretty easy, and they are only about $35 each. Buy two, pop off the harness plugs, get a torx screwdriver, unscrew the 8 screws holding the injector cap on, pry it off, using two screwdrivers (one for a pivot point) pop the injectors up by sticking the second screwdriver under the little lip at the center of the top.

Pay special attention to the TWO o-rings (top and bottom) and ONE metal o-ring (top) under the main o-ring as you slide it out.

Scrape the old gasket off, including the little one at the back where the fuel line comes in, vacuum out the bores of any crap that fell in (or cover the bores with a rag or something first!) pop in the new injectors paying SPECIAL attention to the o-rings (small at bottom, two large at top, metal one under the rubber one) and then put the new gasket in, and slowly screw everything back down firm and tight.

You can also replace the fuel pressure regulator while you have the cap off (it's in the back reservoir of the cap). Follow the directions and take it apart slowly - there is a spring in there which will pop out. Clean it, get the new bits, and put it back together slowly and carefully.

 

[Burbdood 74]

J.J., I checked the codes last night with the paperclip and it's a code 44, O2 Lean condition. I thought that the injectors sprayed left...right...left...right and so on and so on.

I was thinking about it just a few minutes ago but the SES light came on while it was warming up and went away as I was driving home and never came on again.

 

[4xcrazy]

both injectors spray the same amount, not sure about the side to side thing. and $35 for injectors??? must be rebuilt units i am guessing, personally i wouldn't go that route, but that's just me.

I bought mine at Napa, cause the ones at Autozone looked like complete junk.

Paid alittle over $100 for them at Napa, but hane not given me any problems at all. ALSO when you reinstall the injectors, there's a little roll pin on one side, the injector goes in one way only, be awar of this when/if you replace them.

 

[Jessie James]

Mine were $35 new, at AutoZone. They have been working fine so ... YMMV. And they have the pin so you have to put them in properly.

Anyway, that's the extent of what I know so ... I am sure someone else will step in and help!

 

[scrappy88]

You could also just have them cleaned. I just had my injectors cleaned by Witchhunter performance. Cheaper than new injectors but you'll have to remove them from the truck and it'll be a little over a week before you get them back.

The spray pattern on mine is nice and smooth from both injectors at idle.