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Old 10-14-2009, 03:21 PM   #31
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94 chevy 4x4 truck problem


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Originally Posted by tecate1987 View Post
the truck has the central intake system,

started couple weeks ago, its not used much, just for plowing. I had it running in the summer just to move it etc.
truck is running rich, sputtering when acceleration in neutral, will bearly idle.
smoking with gassy smell. no check engine light ever came on. It will light when first starting the engine, but dont stay on.

plugs are bosch gapped at .045
has new air filter, temp control sensor, and thermostat. wires are only 1 year old,
going to check cap and rotor and timing today.

I did put some gel for batteries on the plug ends so they wont stick, but I cant imagine this would hurt, its mostly on the rubber boot.
Does this have TBI (throttle body injection, looks like a carb) or ported injection? How many miles?

Start with the basics check the cap and rotor for carbon tracking.

Check the PCV and EGR valves. Both are calibrated vacuum leaks and will give a lean misfire.

With the air cleaner installed spray carb cleaner around the intake and vacuum line. If it changes you have a vacuum leak.

If you have a good pair of insulated spark plug wire pliers you can carefully remove one plug wire at a time at the plug and note idle. If it changes, that cylinder is working. Be careful, secondary ignition voltages are high.

High mileage check timing chain. Remove distributor cap and by hand rotate the crankshaft pulley in opposite normal rotation, until the rotor moves. Rotate crank by hand in direction of rotation and note the number of degrees the crank moves until the rotor moves. It should not be more than approx 10.

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Old 10-14-2009, 04:41 PM   #32
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94 chevy 4x4 truck problem


Quote:
Originally Posted by tecate1987 View Post
the truck has the central intake system,

for firing order which is #1 plug on the cylinder fire wall or rad driver side.
#1 would be on the forward most mounted head twards the radiator.

CFI or "Central Fuel Injections" is another term for TBI or "Throttle Body Injection". One and the same. You do not have a mass air meter.

Bosch Platinum are not the best for your model, but they will work. Best to have Delco plugs in there.

If the vehicle sits most of the time, you should be starting it once a week and letting it get up to temp. A vehicle that sits for long periods of time without being driven is not good. The rot seems to set in.

Sounds like you are getting a code 12, which just means you are in diagnostic mode. Best to check that ignition system real good.

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Old 10-14-2009, 05:43 PM   #33
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94 chevy 4x4 truck problem


I did find the numbers for the firing order on the intake. It is also correct firing order.
I took off the dist cap, didnt look real good. corrosion, little ball in the middle was about gone, replaced cap and rotor. Still no better.
It wont even move, it does seem to get worse when it gets warmer.
I sprayed carb cleaner around the vacuum lines the other day, no change in idle. I tried running truck in the dark to see if any sparks in wires or anywhere. Nothing.

Truck does have 186,000 miles on it, ran good all last winter, and few times this summer. Yes, throttle body injection. I will try pulling plugs when running, and
Quote:
Rotate crank by hand in direction of rotation and note the number of degrees the crank moves until the rotor moves. It should not be more than approx 10.
but I wont be able to get to it til friday.
Thanks for all the help so far, very informative.
where is the egr valve on this truck ?
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Old 10-16-2009, 07:36 AM   #34
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94 chevy 4x4 truck problem


Also remove the wires from the distributor cap (one at a time) and check for corrosion.
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Old 10-20-2009, 08:03 PM   #35
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94 chevy 4x4 truck problem


got to work on the truck a little today.

It runs, when I took plug wires off, the right side 6, 4, 2 wires, one at a time it changed engine very little when I disconnected a single wire.
Even put #6 and 4 wires in each others location, really didnt change the idle as much as it should.
The left side, it made the engine either stall or chug really bad like it should.

Sprayed carb cleaner around vacuum lines, no change in idle.
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Old 10-22-2009, 11:00 AM   #36
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94 chevy 4x4 truck problem


I'd do a compression test next. Not familar with the exhaust system, but does your truck have one convertor and one muffler or do you have one for each bank?
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Old 10-22-2009, 02:06 PM   #37
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94 chevy 4x4 truck problem


it has single exhaust, single muffler and convertor.
all comes from engine thru Y pipe.
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Old 11-01-2009, 12:33 PM   #38
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94 chevy 4x4 truck problem


I did a compression test, all cylinders were approx 150-153.
cyl number 2 was 146.

got a different coil to try, hopefully today.
any other ideas ?

coil didnt make any difference

Last edited by tecate1987; 11-03-2009 at 02:45 PM. Reason: ad statement
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Old 11-03-2009, 02:44 PM   #39
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94 chevy 4x4 truck problem


here is some pics of the engine.
I have read some other site and all keeps pointing to gas lines under the plenum, does this type of injection system have this and to I have to take the whole intake off or just the throttle body ?
Attached Thumbnails
94 chevy 4x4 truck problem-mvc-001s.jpg   94 chevy 4x4 truck problem-mvc-002s.jpg   94 chevy 4x4 truck problem-mvc-003s.jpg  
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Old 11-03-2009, 03:02 PM   #40
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94 chevy 4x4 truck problem


Here's what you should do....[one step at a time]
1... turn the key on with engine off. Look at fuel injectors .....they should not be dripping with fuel....if they are, then no amount of cleaning will fix it....replace it...

2...You got throttle body injection system, the fuel pressure regulator diaphragm are known to leak and dumped fuel badly.

3.... remove oxygen sensor(s) from your exhaust pipe. Start engine, observed your engine running condition, if it smooth out, then your cat converter is clogged!


FYI... I know I'm newbie here, I'm ASE certified Technician, Senior Ford Master Tech and GM Tech....no bull manure about it...
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Old 11-04-2009, 07:34 PM   #41
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94 chevy 4x4 truck problem


I checked the injectors, there is no leaking or drips from them.
Does this have the spider injection system in it ?
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Old 11-04-2009, 08:15 PM   #42
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94 chevy 4x4 truck problem


Quote:
Originally Posted by tecate1987 View Post
I checked the injectors, there is no leaking or drips from them.
Does this have the spider injection system in it ?

Did you make sure the key is on fully?

No you do not have spider injector system......

do you have fuel pressure guage?
If not, rent one or buy one.
If you don't know how to use it then get mechanic friend to show you, it must be handle with care otherwise you got fire hazards.

Hook up fuel pressure guage and observe fuel pressure with key on, engine not running.
Fuel pressure system should hold pressure, if not then you got rupture fuel pressure regulator.

One more thing.....you asked me about spider injector system......you shouldn't be asking me that question if you did actually look at fuel injectors.
You have 2 fuel injectors, see if you can use MS paint shop and circle the injectors and then post it back here....I want to make sure you know where to look for.
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Old 11-05-2009, 10:03 AM   #43
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94 chevy 4x4 truck problem


In the second photo, are the injector wires insulation nicked?
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Old 11-05-2009, 02:10 PM   #44
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94 chevy 4x4 truck problem


Quote:
One more thing.....you asked me about spider injector system......you shouldn't be asking me that question if you did actually look at fuel injectors.
You have 2 fuel injectors, see if you can use MS paint shop and circle the injectors and then post it back here....I want to make sure you know where to look for
I did look at the injectors, but everything I found online about the 4.3 says spider injection unit, so I didnt know if I had the injectors, that went into a spider unit below the throttle body. I knew it didnt have the normal plenum style.
Anyways, thanks for the info. I will check fuel pressure.
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Old 11-15-2009, 10:40 AM   #45
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94 chevy 4x4 truck problem


truck still not running, wont hold idle, barely runs.
still running very rich, passinger side dont appear to be firing.
new 02 sensor, cat removed.
checking pressure today.

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