91 burb going dead after i crank it

[bigblock79]

i got a 91 burb. when i bought it it was ideling a little fast. i idle it down and now when i crank it it goes dead some time. it bugs me that i have to crank it 3 to 4 times and then it runs good they say its got a 90 chevy police car motor in it. plz help me

[willett]

sounds like a carburated engine to me.

does your choke work?

[bigblock79]

nope a tb

[leegrady]

There is no idle adjustment on a tbi fuel system. The idle is controlled by the idle speed control solenoid. It's located on the top left rear side of the tbi housing. It is screwed into the housing with an electrical connector to it.

Is the "check engine", or "service engine soon light on"? If it is access trouble code(s) first. Also, check for vacuum leaks. That might be why it was idling fast.

The idle control solenoid is controlled by the computer, and will try to keep the engine idle speed, and quality consistent depending on loads on the engine. Like if the a/c is on, high beams, or turning the steering wheel puts a load on the engine slowing the idle down, but the computer bumps the idle up with the idle solenoid.

I would clean the cone shaped "plunger" on the idle control solenoid by unscrewing it from the tbi housing. Some times they build up with carbon and don't seat well allowing air to pass by causing higher engine rpm's.

Then set what you adjusted back to the way it was, and check timing following manufacture spec' on that procedure.

[bigblock79]

here is what i have the little hole is where i control the idle

[leegrady]

The computer controls the idle using a small stepping motor that controls the idle air. What you will need to do is run the stepping motor to one end of its travel and then manually set the warm engine idle as a starting point to give the stepping motor enough range to control in all conditions.

This procedure must be followed exactly.

1. Warm up the engine.

2. Turn off the key and stop the engine.

3. Place a jumper between the A and B connections on the diagnostic connector. (ALDL)

4. Turn on the key but do not start the engine. (The stepping motor will now go all the way to one end of its travel and you will be able to hear it clicking when it has reached the end.)

5. Remove the connector cable from the idle air control motor. (the stepping motor is now positioned and removing power will let it stay there during adjustment.)

6. Start the engine.

7. Adjust the idle speed screw to set the low idle speed. Everything off on the truck. Just the engine running, but no lights or nothing. Should be about 650rpm. Not more than 750.

8. Turn off the key and stop the engine.

9. Replace the idle air control motor connector and remove the jumper from the diagnostic connector.


Give this a try. Let me know how it works out for you. Feel free to ask any more questions. I hope I am of some help.

[tmackg]

The TBI motors were notorious for the throttle body base gaskets failing and sucking air causing a high idle. I would check it and the timing.

[leegrady]

Always good to check the tbi to intake gasket, as with any tbi or carbureted engine. Such a vacuum leak will defiantly cause a high idle. This, however, does not explain a possible reason why the truck stalls..."sometimes."

Now that the idle screw has been disturbed, my above mentioned procedure should be done.

Great forum! It has been well documented, what common sense will tell you, and what has been scientifically proven that problem solving is resolved more effectively, expediently, and with superior quality (repair) when people work together.

_______________________

81 GMC K2500 350/sm465/dana 60/corp 14
95 T-Bird Lx 4.6l w/pi heads
replica 65 Daytona Coupe: Fordracing stroked 351w ~385ci. Offy intake, eight single Holley toilet bowls using a modified EEC-4/tremec tko 5sp/ 9" three link detroit locker 355raito 0-60 3.4 / 1/4 11.0 / top speed 180 This car xlo8's harder at 130 than my T-Bird does in first gear.
71 Nova x2 project

Always roll the pedal.

[69BBsuburban]

Try replacing the PCV valve, yeah I know, sounds to easy right??? But, if it's bad, the engine will have a vacuum "leak", and the ecm tries to compensate and idle will be erratic. Even to the point of killing the engine....
I've seen the problem a few times on trucks/suburbans with the TBI engines....

[leegrady]

So I take it you're saying the pcv is stuck open?

68 Charger 440 an't nothin' nice. (smile when you say that)

[69BBsuburban]

Originally Posted by leegrady

So I take it you're saying the pcv is stuck open?

Not completely...just partially...
PCV's tend to get clogged up with engine "deposits" and don't seal....

[leegrady]

Originally Posted by 69BBsuburban

Not completely...just partially...
PCV's tend to get clogged up with engine "deposits" and don't seal....

Okay, simple enough. Check for vacuum leaks, the pcv, remove and clean or renew.

If it's been awhile I'd go ahead and throw a tune on it too. At least I'd check the plugs. A weak coil can also cause the symptom described.

Set idle, to manufacture spec' (takes about ten minutes), and then set timing following manufacture spec'. using a real timing light with advance gauge, and retarding dial.

Man I love workin' on motors!

[bigblock79]

ok im lost on the fix sorry im use to a carb u will need to tell me a dummy book form

[leegrady]

Lets go back to the front.

The truck was idling too fast so you set it lower via the idle adjustment screw you've photographed.

Now the idle is lower, but it stalls sometimes.

Is this correct? Is there any other problems related to idle quality?

[leegrady]

If this your truck's problem then I strongly recommend:

Originally Posted by leegrady

The computer controls the idle using a small stepping motor that controls the idle air. What you will need to do is run the stepping motor to one end of its travel and then manually set the warm engine idle as a starting point to give the stepping motor enough range to control in all conditions.

This procedure must be followed exactly.

1. Warm up the engine.

2. Turn off the key and stop the engine.

3. Place a jumper between the A and B connections on the diagnostic connector. (ALDL)

4. Turn on the key but do not start the engine. (The stepping motor will now go all the way to one end of its travel and you will be able to hear it clicking when it has reached the end.)

5. Remove the connector cable from the idle air control motor. (the stepping motor is now positioned and removing power will let it stay there during adjustment.)

6. Start the engine.

7. Adjust the idle speed screw to set the low idle speed. Everything off on the truck. Just the engine running, but no lights or nothing. Should be about 650rpm. Not more than 750.

8. Turn off the key and stop the engine.

9. Replace the idle air control motor connector and remove the jumper from the diagnostic connector.


Give this a try. Let me know how it works out for you. Feel free to ask any more questions. I hope I am of some help.

[69BBsuburban]

Originally Posted by bigblock79

ok im lost on the fix sorry im use to a carb u will need to tell me a dummy book form

You do know what a PCV is......right?
Change it...it's like $4.00....it's recommmended to change them on a regular basis anyway.

[bigblock79]

i know what a pvc is im know 86 down 350s good i just dont know how to work on the comper junk

[leegrady]

You can always simply plug the pcv line going into the intake temporarily to make sure it is not at fault.

Is there someone you know in your area that knows computer controlled vehicles that might be able to help you jump the ALDL connector, and set the idle to factory spec.?