Late 80's/ Early 90's GM TBI - Thoughts? Known Issues?

Looking at buying a late 80's/ early 90's GM truck with a 5.7 V8 and TBI. Just curious what the thoughts are on reliability of this system, common problems, likeliness to get stranded by 25-year old electronics, etc. Thanks!

I berkeleying love these systems. All but reliable as gravity. Cts sensor and ignition modules are about all that ever really goes wrong. Also the tbi itself will need rebuilt and cleaned at some point. Check for vacuum leaks. Bump the timing a few degrees, clean out the egr system. Enjoy.

Oh, and ditch the factory y pipe and cat. That and the ultimate tbi mods, you'll pick up gas mileage and power. After that the manifolds are the big restrictions.

To repost here the conversation we already had as well as add some things:

Rear end pinion seals have leaked or will leak. Check this as it can wreck rear ends quickly.

The 700R4 can be great or can be disastrous depending on rebuild status and generation

The old school 350 will have a rear main leak

Starters and alternators are available crazy cheap because those ones suck. Expect the typical low priced parts store ones to last about a year. Also changing those starters is annoying because you have to bench press it in place and it can easily fall onto your face if you don't get the funky knurled bolts in just right.

Sliding front calipers need lots of antisieze in your climate

the trucks he's looking to all have 1 piece rear mains.

tbi is about as reliable as one would expect a simple system with a few sensors and 2 injectors can be. i've never actually had a coolant temp sensor fail but i believe the ignition module has failed in my 350 tbi roadmonster.

i've been driving for 17 years and the last 15 i have not been without at least one 88-94 TBI truck. i've had an 88 305 1500, 89 350 1500, 90 350 suburban, 90 305 1500, 90 454 3500, 92 4.3 1500 that got 305 swapped, 94 305 1500, 94 350 suburban, any my current two 92 3500HD 454 and 90 4.3 1500 that is now 454.

TBI is so simple you can pop out a 4.3 and throw in a 305, 350, or 454 just by plugging it in and swapping the chip. the wiring is all the same minus a couple differences here and there like TPS plug on the big block or extending a temp sending unit wire.

i've never had to rebuild a throttle body, i've only ever encountered a couple with injector issues and it was easier to snag a complete unit at the yard. i have a shopping basket full of them now.

These are the simplest, easiest, and cheapest to maintain systems. Not made for big power or high revs, but for "normal" use will not give you any issues.

Are any of these issues (coolant temp sensor and ignition module) "stand you on the road" failures, or are they "can limp to the nearest parts store" sort of thing? Better to keep spares on hand, and swap on the road if needed?

I know all about parts store remans. They're basically good enough to get you home, at which point you either mail order an OEM GM piece or have a good local shop rebuild you one.

The rear end on the truck I'm looking at now is clean, underside is clean (no active leaks, just the usual coating of oily/greasy residue that builds up over time), truck has pretty low miles and appears well taken care of. Rust is minimal, considering age and location.

I had a 1/2 ton GM pickup once that shattered a rear end on me. The truck literally would not even roll. That was not fun.

The 10 bolt and 12 bolt were not GMs finest work, for sure. There are bolt on 9" and Dana solutions if that worries you. Check the seal during routine maintenance. Mine have all failed very slowly.

As far as the rear main seal, I hadn't considered this limited to TBI, but you're right, the TBI changeover happened at the same time as the one piece rear main changeover.

FYI, we're looking at a truck like this:

But without the whitewalls.

This is sort of related to two threads; the "sell my F350 and her Jimmy" thread and my resto of the '68 Chrysler Town and Country, which has turned into a bigger project than I'd planned, and we need something that will work as a family hauler now.

Cts and module are keep spares inthe glovebox failures. Those are the only two that ha ever left me stranded. Cts cause it fouled out the plugs. Module is an instant dead fail in my experience. Probably done right at 200k in high mileage, neglected severely, scrap price beater tbi trucks. Have blown up a couple 700r4 and rear ends.

I loved tbi to the point that I converted the 64 over to it.

I have a 1995 C1500 that I bought in 1996. I've put about 215k miles on it myself, total 240k. Very reliable. Worth the $16500 I spent back then. Now it's rusty and ugly, but still every bit as reliable.

I had a '90 Suburban with a 454 TBI. Don't have much new to add, but I can second most of what has already been said, including that I had an alternator failure on it myself. Very basic, pretty dependable, as long as you keep in mind it's not meant for performance.

The wife and I are pretty basic people. If it goes down the road, cruises at 70, doesn't get single-digit fuel economy and doesn't hit us with big repair bills every time we turn around, we're cool. She doesn't even really care about paint too much, says we'll just scratch it up anyway. We live kinda hard.

Nothing much to add, the most expensive single part I've bought so far has been an Alternator (the parts store specials will fail, my next one will be rebuilt at a local shop) And that's been around $100. Parts are cheap, any half-competent mechanic can work on them and they are about as reliable as gravity. Expect mid-teens fuel economy no matter what you do. Put some good rubber and shocks on it, stick a nice head unit in it, recharge the AC (The old compressors work well with 134a) and enjoy the ride.

I swapped a TBI into my old Caprice, and I've found it to be a great system. There are a few things you can do easily to improve performance (Ultimate TBI mods, injector pod spacer, salad bowl, use a 454 throttle body with the bigger butterflies). Even if the CLT fails, you're not stuck, it just won't run very well. Injector driver failure would get you stuck, because the injectors wouldn't be opening.

It's worth checking fuel pressure on these - the factory set them between 9 and 13 psi, and they run quite a lot better if you're towards the high end of that range. Factory fuel pump is only reliably good to maybe 15 psi, though. The only other trouble spot I can think of is that the throttle shaft bushings tend to wear out, especially on manual transmission vehicles. This will result in weird idle issues and a sticky throttle if it gets bad enough. I went through 4-5 junkyard units before I found one that wasn't too worn for me to use.

Otherwise, it's all normal SBC stuff. For a fuel injected engine, it doesn't get much simpler than this. Note that the ECM only samples sensor data every 1.5 seconds or so (changed to every .5s on later models), so any modifications will make the thing run poorly for a few runs through the rpms until it has 'learned' the engine again.

Went to look at another old 'Burb last night. This one was a '91, last of the old body style. It has a few miles on it (175k) but doesn't look abused. The underside was amazingly clean- some surface rust, but way better than most trucks I've looked at, and all the structural points were good. The 350 started right up, no oil smoke, no leaks or odd noises either. Took it for a test drive and the transmission sounded good, shifted through all the gears with a nice feel. Rear end wasn't leaking and felt good- very little play. Steering felt good and tight.

The body and interior are what I'd call "cosmetically challenged" but since we plan on putting it through baby and dog and life in general, that's not a deal breaker. Taking Mrs VCH to go check it out tonight, and if it gets her approval we'll probably drive it home. Gotta admit, I'm kinda looking forward to having a big old 'Burban again.

as long as the wiring harness is in good condition the TBI should be fine. My issue is that my truck's wiring is a hell of a mess so after pricing out a few sensors and connectors, it was cheaper for me to slap a carb on it and enjoy.

I get 10mpg towing and 13 unloaded.

Trooper has a 3.4 V6 with TBI from a 4.3 V6. It's pretty much the perfect system for an old truck. Simple, cheap, easy to fix, and works well.

i got a 90 burb at 239k that my buddy pulled the original engine out of and stuck in a 74 camaro. we put a reman engine/trans in it and my dad put another 161k on it. original rear axle never made a peep, and it was retired at 400,000 by a flood.

just brought home another TBI truck today, so i've currently got 3 454 TBI trucks.

If you saw this here, you know I finally pulled the trigger on a '91 'burban with the GM TBI. After some work, and a tune-up, the truck runs and drives great. There don't seem to be any TBI issues knock on wood but I'm curious about what common mods are out there to make the TBI work better. I'm primarily interested in fuel economy (I know, I know, it's a rolling house!) and reliability. Not afraid to get a little dirty, but don't want to have the truck off-line for a week with a major project- or spend big bucks.

I'm not well-versed in how electrons regulate fuel, either, so any mods involving those round copper things that carry electrons or the black boxes that tell them what to do need to be simple enough for a 6th grader in the remedial reading group to understand.

In reply to volvoclearinghouse:

First read this: http://www.hotrod.com/cars/project-vehicles/ccrp-0406-1993-gmc-pickup-project-jake-tech/

Then this; http://www.hotrod.com/cars/featured/ccrp-0407-1993-gmc-350-pickup/

They're old articles but the parts used, or very similar parts, should still be available.

Ultimate tbi mods. Bump initial timing a few degrees. Flip the air cleaner lid.

I've read changing the collector on the Y-pipe to a Flomaster Y250300 helps a bunch, and going to a single 3" exhaust.

The truck had the cat removed when I got it (And it's tagged Historic in MD, so no emissions test) but in the interest of having a non-smelly exhaust and being a family hauler, I'm thinking about putting one back in. There's some better-flowing ones than the stock cat that supposedly won't hurt fuel economy.

Is THIS what the "ultimate tbi mods" refers to?

I'm going a different way. I detest the TBI, partly because I worked for Rochester Delphi when it was being developed. Yes it is pretty reliable. The nozzles (they're NOT injectors) will start leaking, but they are cheap to replace. The valve seals will leak and you'll get a big puff of smoke when you start it. Fix it, live with it, your choice. 700r4 is not happy with all that weight. Be very nice to it. Almost all TBIs have flat tappet cams which comes with its own set of troubles with modern oil.

The TBI flows horribly. Everyone claims 500-600 cfm, but wet flow with nozzles installed is 390 tops. Very well suited to the 180 hp the engine makes, but if you plan on bumping hp more than 10-15, throw it in the trash and put a Qjet on it. If you want to improve your MPG, throw it in the trash and put a Qjet on it. The whole top end; heads, intake, TBI, cam, compression is perfectly suited to the 180hp it makes. Getting over 225hp will require lots of work.

If you want to keep it bone stock, not tow, and never break 13mpg, it will serve you well. It just rubs me the wrong way that such terrible technology is passed off as good stuff just because it sucks equally at everything. It squirts liquid fuel at low pressure, it gets terrible fuel economy, barely squeaked by EPA standards (a Qjet was actually better on all but HC), and doesn't make enough power to get out of its own way. It is a big conglomeration of completely inadequate parts that live perfectly happy lives because it only makes sub-200 hp.

Having said that, it is a reliable setup, but be prepared for 1/2 the power and 2/3 the mpg of something 96-up. If you're going to keep it 100000% stock, then you'll have a reliable, boring, unsatisfying lump.

3" cat an exhaust to start. Dump the A.I.R. pump to help de-clutter the engine bay. An air cleaner lid from a 454 will allow a taller element and you can homebrew a second intake snorkel fairly easy.

For oily bits, a used LT1 cam is the way to go. You'll need to do valve springs too, but its not hard. You can knock out the job in a weekend. A chip will need to be made for it at this point. You should get away with just an increased pressure spring on the TBI's fuel pressure regulator.

TBI is a good, simple system. You can make power, but yes it's a niche market and not the cheapest when compared to a carb. For a quick 20-40 the above should do it on a GRM friendly budget. I did this on my 305 and figure a new total of 195.

The TBI forum on the third gen camaro site is very good. thirdgen.org The 350 is the L05 engine.

No problems with the FI on either of my tbi burbs. One went 302k before I bkew a head gasket and the other went 180k plus before a tree limb totalled it. Like others have said, not super powerful, but reliable as can be. I had the trans rebuild in my 89 at 180k or so then 2k miles later the tree limb fell on it. I bought it back from the insurance and still have it, but have not done the blazer roof mod or anything yet.

http://grassrootsmotorsports.com/forum/off-topic-discussion/damn-ice-tree-limb-smashed-my-suburban/80415/page1/