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Engine shuts off after about ten minutes of driving and will not restart

Tiny
KAM
  • MEMBER
  • CHEVROLET TRUCK
My 1989 truck 4x4 truck with 180,000 miles, TBI 350 will start good cold and run for about 10 minutes until hot then idles up and produces slight black smoke and then shuts off and will not start back up. I've rebuilt the throttle body and installed a completely new distributor.
Any help?
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Sunday, July 22nd, 2007 AT 8:53 PM

10 Replies

Tiny
KAM
  • MEMBER
  • 6 POSTS
Fuel pressure is running 11 psi. Started up and ran for about 15 minutes until hot. Then shut down again. Fuel pressure never changed. Checked spark after shutting off and had spark at number 1 cylinder.
Seems the fuel is flooding the engine out. A lot of fuel is spraying in when I try to recrank after shutting off. Also just before it shuts off, it seems to idle up slightly and then bogs down and smokes out of exhaust like it's running rich.
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Saturday, July 28th, 2007 AT 12:59 PM
Tiny
KAM
  • MEMBER
  • 6 POSTS
History on this old truck. A lot of the sensors have been disconnected since I've owned the truck. O2 sensor is not connected nor any smog stuff. Also I only use this 4x4 truck for hunting and it sits for a while sometimes. I had to replace the battery two times before any of this happened. New batteries were dead and not rechargeable.

Today I pulled all of the plugs just to do a compression check. The plugs were covered in carbon very badly. Cleaned them, re gaped them and put back in. Ran engine again and it's not dying now, but idling up higher than normal. Fuel psi is still 11 psi. Seems to try and stall sometimes, but catches up and idles up and continues to run now. Still not driving it on road. Worried about shutting off still.
The vacuum hose to the diaphragm type EGR valve has been disconnected for a while too. It would rough idle when idling slow. Disconnecting the vacuum hose to it solved the problem about 1 year ago.
I know, I've got a mess.
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Saturday, July 28th, 2007 AT 8:44 PM
Tiny
KIN CHAN
  • MEMBER
  • 453 POSTS
O2 sensor start taking over fuel control once the ECM see the engine temperature is warmed up. EGR system lean out and cool off engine combustion temperature.
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Sunday, July 29th, 2007 AT 4:25 AM
Tiny
KAM
  • MEMBER
  • 6 POSTS
I've owned the truck for about 10 years and the O2 sensor is in place, but not connected. Never has been since I owned the truck. It's run fine for the last 10 years until lately after I let it sit up for a while.
He EGR valve on the valve cover is operating properly. The EGR diaphragm on the manifold is not functioning properly. If the vacuum line to this device is hooked up, the truck tries to run very rough idle when moving slowly.
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Sunday, July 29th, 2007 AT 11:27 AM
Tiny
KAM
  • MEMBER
  • 6 POSTS
I replaced the EGR valve along with the EGR sensor. Truck is still starting up and running now and not shutting off, but it still idles high. Start up cold and it idles high as normal until warm and then idles down to normal. Then if I put it in gear or drive it, it starts to rough idle and then idles up high like the throttle is trying to stick. Throttle is not sticking though. Remember I'm trying to make an 1989 engine with 180,000 miles on it run better for now. I'm planning on changing the engine when I can afford it, but feel this problem is not due to the worn out engine. Unfortunately since someone before me has unhooked numerous devices the OBD tool doesn't work or tell me anything. Makes it tough to troubleshoot.
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Sunday, July 29th, 2007 AT 5:24 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Try doing a compression/cylinder balance test and vacuum check. Could be a vacuum leak when the engine is warm-up and showing up.

https://www.2carpros.com/articles/how-to-test-engine-compression
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
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Sunday, July 29th, 2007 AT 6:22 PM
Tiny
GTX440SIX
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Check the MAP Sensor vacuum at the rear of the throttle body, if no vacuum remove the throttle body and clean the restricted port.
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Friday, August 10th, 2007 AT 5:41 PM
Tiny
KAM
  • MEMBER
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Thanks for all of the suggestions. I just rebuilt the throttle body and the ports are all clear.
The truck starts and runs now, but still has a high idle once it's warm and driven. I'm looking into testing the IAC, (Idle air control). Maybe this is my problem. It idles high when first started and then idles down to normal after a few minutes. The start driving and it idles back up high and stays there.
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Sunday, August 12th, 2007 AT 1:09 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
It very well could be the IAC. Here is a guide on how to service them. You could also have a vacuum leak so we will need to check that as well.

https://www.2carpros.com/articles/idle-air-control-valve-service

https://www.2carpros.com/articles/engine-idles-too-high

Run through these guides and let us know what you find. Thanks
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Tuesday, March 24th, 2020 AT 2:34 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,205 POSTS
Hi,

I agree with KaseKenny1 regarding the idle issue. An idle air control can cause issues. However, I noted that you indicated black smoke from the exhaust before it would stall and the condition of the spark plugs.

Black smoke is usually a good indicator that there is a rich fuel mixture. Take a look through this link:

https://www.2carpros.com/articles/engine-black-smoke

Okay, if I am correct and it is a fuel mixture issue (based on fuel pressure there is no change) I have a strong feeling it is related to the engine coolant temperature sensor. There are two on this vehicle. One is for the gauge (see pic 1) and one is for the computer (see pic 2). Now as the engine warms up, the computer uses information from the sensor to determine what the air / fuel mixture should be. If it thinks it's cold, the mixture is made richer. As it warms up, it leans the system. If this sensor is sending the wrong signal, the computer may be making the mixture richer than it should be causing the car to basically flood or run poorly. Additionally, the black smoke will indicate the engine is running rich.

Take a look through this link:

https://www.2carpros.com/articles/symptoms-of-a-bad-coolant-temperature-sensor

Here is the trouble. The computer doesn't know the temp so it doesn't realize a reading could be wrong. So, there could be no code related to the issue. However, it is a good idea to check for diagnostic trouble codes. Here is a link that explains how. You don't need a scanner. All that's needed is a short jumper wire or even a paper clip.

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

Now, if there are no codes related to this sensor, the next thing is to check the actual sensor. If you look at pic 3, it shows what the resistance should be based on temperature. You will need a multi-meter to do this.

Based on what I have already read, you seem like you are very knowledgeable. However, I am going to add a few links you may or may not need to help with testing. The first link is related to a volt or multi meter. The second deals with testing wiring.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-to-check-wiring

If you find the sensor is bad or is not accurate, here is a link that shows in general how one is replaced:

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Here are the directions specific to your vehicle for replacement. Take a look at the last sentence in the heading portion.

_______________________________________

1989 Chevy Truck K 1500 Truck 4WD V8-350 5.7L
Coolant Temperature Sensor (CTS)
Vehicle Powertrain Management Sensors and Switches - Powertrain Management Sensors and Switches - Computers and Control Systems Coolant Temperature Sensor/Switch (For Computer) Service and Repair Procedures Coolant Temperature Sensor (CTS)
COOLANT TEMPERATURE SENSOR (CTS)
The coolant sensor must be handled carefully. If sensor is damaged, fuel injection operation will be affected.

1. Disconnect battery ground cable.
2. Drain coolant from radiator so level is below sensor.
3. Disconnect coolant sensor electrical connector.
4. Carefully back out coolant sensor and remove.
5. Reverse procedure to install.

_________________________________________

Let me know if this helps or if you have other questions.

Take care,
Joe

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Tuesday, March 24th, 2020 AT 8:44 PM

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