I have a 90 GMC truck with 350 TBI and just had some general questions about it. I don't know anything about TBI, all of my experience is with the TPI in my GTA. I need to tune the truck up and want to service/clean the TBI unit while I'm at it. I read all the articles I could find and it looks like the main thing to service the TBI, like the TPI, is to clean the passages and throttle bores. I was just wondering if there were any other things I should do while it's apart. Bear in mind I have absolutely no interest in anything performance related, this is a 170k mile truck that runs great and I just want to pull some maintenance and increase gas mileage if at all possible. It seems to return to idle slowly, which I suspect is dirty IAC passages or a IAC that's in need of replacing. My questions are:

1. Can I get gaskets for the TBI at Autozone or Pep Boys?
2. Anything else I should watch out for of be aware of when disassembling the TBI unit to clean it? I don't want any surprises - or any little parts falling into the manifold!!
3. Can the injectors can be serviced by Cruzin Performance like the TPI injectors? If so I want to do this too.
4. Is the IAC the same for TBI and TPI? I replaced the IAC in my GTA before dissassembling it, and if they're the same I would put the new IAC in the truck while it's apart.

Thanks in advance for any help, and please forgive my non-thirdgen post!

Shawn

 

The tb assembly is very simple and no you won't drop anything down the intake unless you get careless. As fare as dissassembly goes it's strait forewared and simple. You'll want to be carefull not to overtighten any of the torx screws exspecially the three that hold the injector pod to the base. PepBoyz and Auto Zone both should carry a gasket kit for the tb. Just jump in and you'll see there ain't nothin to it.

Steve

 

1. Yep, you can get gasket kits at any either of those stores. There is one trick though, they are called TBI tune-up kits instead of TBI gasket kit (should be made by GP-Sorensen).
2. Nothing will really fall in the manifold as long as you know what you are doing.
3. Although I have never done it, I am almost positive you can get TBI injectors cleaned, flow-matched, etc. just like TPI injectors.
4. I am not sure but I wouldn't think you could swap those to IAC valves but I am not absolutely sure.

 

If you take off the unit to clean it (which is the best way) use a tooth brush to clean out the tiny passages in the bottom of it. Remove the TPS sensor though because it can become damaged with harsh cleaners. Make sure that after you clean the IAC you put a dab of clean oil on it so that it does not lock up or become to stiff. The oil will help the srping work right.

 

Turbo City cleanes and flow matches TBI injectors as does Jet Performance also.