Continuous TBI problems

[Darth Plasma]

I’m sure you guys are sick of reading these, but my 350 TBI is just getting worse. Now within the past few days it stopped wanting to idle. I did absolutely nothing to it except try to fix the stiff throttle cable, just replaced the TPS today and still did nothing. Truck still stalls coming to stops and it will not idle when it’s on an incline bit if I keep my foot on it there’s absolutely no issue. I took a closer look at it today and there’s a loud sucking sound when it first fires but it goes away in a second, and something in the throttle body is making a loud ticking sound. Do injectors make a ticking sound when they go bad? I think the passanger’s side injector is going bad bc I don’t see as much spray as the other one. The ticking is coming from the injectors because when I touch them they vibrate my hands from the ticking. I checked the timing again, it looks a couple degrees advanced but it’s really hard to tell, and the computer just sets it back anyways. The biggest issue is the stalling and surging/sputtering at idle. I put a brand new fuel pump on it in January. Never had an issue until a couple months ago. What’s going on? It’s just getting worse and worse everyday. Runs like a champ on the road and even highway speeds. Absolutely nothing wrong with it but it just won’t idle/or idle right on a lucky day. And I still have the issue where the service engine soon light comes on after going up hills and the truck instantly bogs down and runs like ****

 

[gmbellew]

intake manifold gasket leak? i had similar symptoms and that fixed it. or some other vacuum leak?

 

[RoryH19]

Have you tried a noid light to test the injectors?
Also when you try to adjust timing have you disconnected the advance wire? It's usually under the brake booster or close to there.

 

[4WDKC]

get a video or picture of the injector spray pattern.
They do make noise.
getting access to live data is essential otherwise you are just throwing parts at it.

 

[1987 GMC Jimmy]

You can perform the aforementioned mood light test to confirm signal receipt. You can also do a low range impedance test; they should be 2.2-2.4 ohms or very close to that (according to my own readings). You can do a cycle test with a small nine volt battery and see if the click is audibly weak. That’s TBI injector 101. If it passes all these tests, and they’re not dirty, which you can send them to WitchHunter to be cleaned, they should be fine. I’d get a fuel pressure reading, as well. You can tee into the fuel filter area, and there are two connectors, one near the front right when the lines turn up and then where it screws into the TBI unit. You’d have to put a Schrader adapter in to utilize these two areas, though. What’s the mileage? An easy ignition verification would be to see that the cap and rotor don’t have carbon tracking and/or oxidation and the distributor isn’t rusted on the inside. You could take it a step further and test the pickup coil and ignition coil.

 

[Sam71395]

could the Idle air control valve be bad?

 

[Rusty Nail]

Dude. Start at the check engine light. What codes are stored?

 

[Hunter79764]

I'm a big fan of Sea Foam if you think you might have injector issues. Clean them up and see if that fixes anything before you pull too much hair out.

 

[BurbanPena]

with the key off instal a jumper wire to port A and B on diagnostic connector turn the key on but don’t start check engine light will flash the idle air control valve on the passenger side of the TB should be vibrating wait 30seconds unplug the connector on the idle air control valve turn the key off remove jumper start the truck if truck will not start you will need to turn up the idle screw if you haven’t all ready you will need to drill out the plug that is covering it.turn up the throttle until it sounds good or use a rpm gauge i believe idle is around 900rpm turn truck off reinstall connector to valve.. disconnect the timing advance connector set timing to 0 reconnect and test truck