I'm looking for some advice with regards to purchasing an 80s model Chev
short box pick up or full size Jimmy. My question is whether or not I
should buy an 87 - 91 model with early fuel injection or not worry and save
some money and get a slightly older one with a carb.? I want this thing for
mainly offroad use. What do you guys think?
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!
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 on it from factory and it
performs well at high alt but GM never shipped one and there are
extremely expensive to by in aftermarket today.
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.
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!
"Shades" <shades_1970(at)netins(dot)net> wrote in message
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
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.
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.
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.
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.
I was doing some digging today and found a reference to a bad coil...Arching
and causing a weak enough spark to run rich and fast. Kind of along the
lines of the module idea, but would be constant.
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