My Truck keeps stalling - PLEASE HELP ME

[harley72]

1988 Chevy K1500 4x4 TBI 350 TBI Jasper rebuilt 38,000 miles, automatic

 

My truck keeps stalling. In the morning when you first start it, it will sit an idle fine but then after about 3-4 minutes it dies. After that it will die about 4 seconds after being started. Once in a while it will start and run fine and I can drive it around but then something happens and it goes right back to stalling again, When you know it's about to stall out, you can give it a little gas and it will continue to run. This morning I took it on a two hour road trip and it didn't stall out at all but now that I am back home it just starts and dies immediately. I can continue to drive the truck as long as I always keep my foot on the gas but intermintantly it will run like nothing is wrong.

 

Here is what I have done to the truck.

 

Replaced Fuel pump & fuel filter

Main fuel relay

replaced IAC

replaced TPS

replaced ignition module

replaced cap, rotor, plugs & wires

sprayed all vacuum lines down to check for leaks

sprayed all around throttle body for leaks

checked on fuel lines for leaks

Checked all fuses and removed unnecessary fuses to see if those components might be causing a short.

unplugged egr and capped line off

verified that both injectors are sryaing a very nice conical pattern.

Took every wire off main wiring harness and cleaned with wire brush and reinstalled

 

THE TRUCK DOES NOT THROW ANY CODES!

 

 

The day this problem started was the same day a mysterious clear oil developed on my garage floor. The oil came from the passenger side of the truck so I figured my AC finally crapped out. Could a faulty AC pump cause this problem even though the AC fuse is out? I took the fuse out and tried the truck but it still did it.

 

So I'm wondering about fuel pressure regulator as well as puck-up module.

 

BUT...... why would the truck run fines sometimes and not others?

 

Any ideas folks?

 

Thanks

 

Harley

[harley72]

The more I read I am really leaning toward the pick-up coil in the distributor. Is there a way to test the pick-up? Also I wondered about the coil itself - is there a way to test this? I heard that spring in the fuel preesure regulator often breaks Can a regulator work once in a while and not others?

[GM-Tech]

The more I read I am really leaning toward the pick-up coil in the distributor.

 

Very good guess. Had lots of problems with those back then. Sometimes they'd crack and other times the magnetic material in them would just degrade to the point that it would no longer trigger the module, particularly at idle rpms.

 

You can test the resistance of the pickup coil (I think it should be 800-1500 ohms) but you can get a good resistance reading and still have a problem with it. All you're checking is the windings, not the magnet. I'd just replace it and clean the terminals on the module, which are usually green and corroded in the older ones.

[harley72]

a couple of guys from work were outside with me looking at the truck and they said they could see the injectors quit spraying right before it died. I would think it would be strange for both injectors to be bad so I wondered if the fuel pressure regulator would cause this??

[GM-Tech]

I wondered if the fuel pressure regulator would cause this??

 

<{POST_SNAPBACK}>

 

 

 

No. The injectors stopped spraying because the ECM is not telling them to inject. This could be due to the pickup coil. If the ECM thinks the engine is not running, as would happen with a pickup coil that is not generating a signal, it will not pulse the injectors.

[harley72]

Ok great info! So the pick-up coil will definately work or not work intermentently as is my problem. So it soumds to me that I need to try this part. So the question is... Do I spend $11 on the pick-up coil or $100 on a new distributor. Is the pick-up coild a tough repair for a guy that has never done it.

[GM-Tech]

It's not a difficult repair. Just pull the distributor, knock out the roll pin that retains the gear, slide the shaft out and replace the pickup coil.

 

Personally, I'd just replace the pickup coil, not the whole distributor. However, make sure you check for any side play in the dist. shaft. If the housing is worn, you'll need a distributor.

[harley72]

Thanks for the help, GM-Tech. I really appreciate your time and the great service that you are offering to all of us. I plan to buy the pick -up this week and will see how it goes.

 

Thank you,

 

Harley

[harley72]

I have a guy telling me that it is possible to change out the pick-up coil without removing the distributor. He said thjat you bump the starter until the rotor housing opening alligns with the pick-up coil. I find this hard to believe since even the manual shows you having to take out the distibutor.

[GM-Tech]

I have a guy telling me that it is possible to change out the pick-up coil without removing the distributor.

 

The shaft has to come out to get the pickup coil off. In order to pull the shaft, the dist. has to be removed. Trust me, there is no other way.

[harley72]

Thank you!!

[harley72]

Last night I came home and went into the garage and started my truck. It idled fine for about 15-20 minutes and then started stalling. It stalled everytime I started it. I unplugged the MAP and plugged the line going into it and when I did that it would no longer stall - It stayed running but ran in a surging kinda way - it would idle way down like it was going to stall but then it would kick in and idle up and then back down. I plugged the MAP back in and then it stalled everytime again. Does this mean anything like a bad MAP? Also, I tried sucking on the line going to the EGR and it didn't really do anything - I even put an allen wrench underneath the EGR and tried to push up on the diaphram but it would only move maybe an 1/8". Should that diaphragm move more then that?

Thanks!

 

Oh, will the pick-up coil work sometimes and not others? I am just so curious as to why the truck runs great once in a while.

[GM-Tech]

Disconnecting the MAP is not a very valid test. Didn't run very good, did it. I would ignore what it's doing when you do that.

 

There are several types of EGR valves... negative backpressure, positive backpressure, etc. They don't all open when you just apply vacuum. It might be the type that requires exhaust backpressure.

 

Yes, the EGR diaphragm should move up more than that, but It's a pretty strong spring and don't know if you can apply enough pressure with an allen wrench. You should be able to get your finger in there. But I don't see what the EGR has to do with this. If it won't open, that won't cause rough running or stalling.

[astrohand]

Disconnecting the MAP is not a very valid test.  Didn't run very good, did it.  I would ignore what it's doing when you do that.

 

There are several types of EGR valves... negative backpressure, positive backpressure, etc.  They don't all open when you just apply vacuum.  It might be the type that requires exhaust backpressure. 

 

Yes, the EGR diaphragm should move up more than that, but It's a pretty strong spring and don't know if you can apply enough pressure with an allen wrench.  You should be able to get your finger in there.  But I don't see what the EGR has to do with this.  If it won't open, that won't cause rough running or stalling.

 

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I too have a 88 pickup, your problem is close to what is going on with mine.

 

Mine runs fine when cold- then- sometimes even when I let off the gas for a few seconds, even at speed, it dies.

 

No codes -

 

This only happens when it has warmed up, I can let it sit an Idle and you can notice the rpm's dropping down - and this will be for a few seconds and then it cuts off and I can smell gas form the TBI.

 

Now I have been able to remove the PVC valve hose and it will Idle back up and does not cutoff....

 

thanks

 

Daniel