fuel inj. vs. carb.

With my experience with both, I would have to recommend the Carb years. Allot less expensive to upgrade and modify.

The major benefit to the TBI is that it works at extreme angles and there are is no bowls for gas to slosh around in, but all the components that could go wrong that TBI needs to function could get expensive to fix...if the problem could even be tracked down!

I mostly agree with this except TBI will give much better cold weather performance and starting and better performance if you operate at a variety of altitudes too.

Very true, but only IF, everything is working right...if its not, then it will be blown away by the carb every time.

I'm going to side with TBI.

It's SO simple of a system, and very reliable. There's 3 whole sensors (MAP, CTS, TPS) that can go wrong. Two injectors. The fuel pump (which a carb of course has - but a less reliable one). Wiring & ECM.

Unless you plan to drive under water and let the cab fill up (what fun!) I say go TBI! 1/4 million on mine, and I'm pretty sure all I've ever replaced was the pump, and the TPS (about 15 years ago).

If you maintain it all, it's pretty solid.

I agree. 260,000 miles on a 350 TBI with no problems in Michigan.

OK John and Stephen, if its as simple and easy as you say, do what no one else has been able to do and pinpoint the problem with my '87 TBI 350 or at least give me an educated guess on where to look..

Cold start, fires and dies 6 or so times unless the throttle pedal is pushed slightly. When started cold, it idles about 700RPM, idles smooth, no spitting, sputtering, hesitating, when warm it idles from 1200-1400 in park and about 850 in drive. 19 or so inches of vacuum at idle, 10-15inches going down the road depending on conditions, new cap, rotor, wires, and plugs(all high quality replacement parts). Base gasket is good. Did a spray test for leaks with none found. Slightest blue smoke on start-up.

Bad EGR valve and control replaced, TPS replaced, FPR replaced, injectors replaced, IAC valve replaced, MAP sensor replaced, vacuum lines replaced, oxygen sensor replaced, CTS replaced(and plug(it looked iffy)).

After starting, IAC pintle retracts to full open. If I let the corner of a rag drop into the air passage leading to the pintle, the idle drops to 750 or so and is as smooth as ever but after removing the rag corner, the idle goes right back to the 12-1400 range, still with smooth idle.

Oh yea, no codes either!

Going to try a different computer as soon as I get to a Friends that has a spare at his shop.

Help me out here guys, please!

Don't wanna hijack this guys thread, but...

If you've removed the IAC, and it only goes up to 12-1400... you've got some serious clogging issues. With the valve out... uh... I'm not sure exactly how high it should rev (red line?!) but it should sure be higher than that!!!!

Pull the throttle body assy off. Split the upper and lower part (you're going to want to pick up a service/gasket kit first!) and look for carbon/goo clogged ports. Pull off the TPS, and FPR, and soak the whole thing in carb dunk. Blow out the passages... bla bla... think of it as a carb at that point.

TBI is very easy to keep working correctly. I have one that is now 17 years old (bought it new) with 175K and it has been VERY reliable. Few carbs can adapt properly to thinner air without rejetting them while TBI can do so well because I have had mine more than once from 10 ft MSL to

14,110 ft (pikes peak) with a glitch or hiccup. I do have a 79 J20 that has a expensive altitude compensated carb > Very true, but only IF, everything is working right...if its not, then it

The IAC valve wasn't removed while running. I never claimed it was. I said after starting, the pintle pulls back till it is completely open. The port that the pintle blocks can be seen from the top with the air filter off which is where I we blocking it with the rag corner.

Remove the TBI Unit. Remove all the electrical parts. Disassemble the unit. Have it cleaned just as if it were a carburator about to be rebuit. Once cleaned, check the throttle shaft out. Make sure all the passenges are clean & clear.

Most decent autoparts stores sell a GM TBI rebuild kit. Just like a Carb after miles and time the things need cleaned, inspected, and resealed. Charles

Do you know for a fact that all EGR passageways are clean & clear? Intake manifold can contain a lot of carbon buildup.

Yes they are clear.

Could be a timing issue or ignition module possibly.

On the small distributors(non-HEI) I don't think they have modules. If it does, I will swap it out. One thing though, I have never heard of a module going bad...they have always been black or white...working or not...right?

I've heard of them getting flaky with age, but couldn't confirm it.

I was told of one that would stop working when the vehicle got too hot and spontaneously die while driving down the road. After a cool-off period it'd run again--for a while.

This could've been caused by a lack of the grease that's supposed to go under the module in the distributor, although I think if that were the case the problem would've always been there.

Not sure if this applies in your case, but worth a look.

~jp

I had to borrow my brother in law's truck one day & this is exactly what happened to me. It would go a few miles, stumble, then quit. Let cool down & it would start & run a few more miles & quit again. Checked the old module at the auto store to find it was ok but quite corroded so I replaced it. Problem gone. This told me that ignition modules could certainly be intermittent & cause no code to set.

OK, but I don't have the problem intermittently...it is all the time and very consistent.

Thanks for all the input. I didn't want to start an arguement. I appreciate reading all the input as I might run into these problems when I find a decent truck.

I'm looking on autotrader.com but I need some zip codes for the Southern States where I might find a rust free unit. Living in Ontario, we have to deal with too much salt on the roads so all our vehicles are rust buckets.

Blair

Try here: