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I have a 1989 chevy s10 that has two problems, when started ...
Sent to Car Experts October 30 11:19 PM

I have a 1989 chevy s10 that has two problems, when started it idels at high idel for about five seconds and then goes to the proper idel this happens every time you start it even when at running temp. The other problem is that after it is warm when you revv the engine it stays at high idel for several seconds after you let off the throtel. I have replaced the following things: IAC,EGR solinoid,temp sensor,oxygen sensor,map sensor,cleaned egr and ports, completly rebult throttle body,tps,and cleaned everything and it still has the same problem. If you could tell me what the problem is if it need a new computer chip (prom)or what, that would be great, thanks

Optional Information: 1989 Chevrolet S 10 4.3 v6

Customer (name blocked for privacy)
Status:  Closed   Value: $10
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November 3 11:31 AM (3 days and 12 hours later)
         
I wanted to let you know that when you rev the throttle and it stays at high idle for several seconds, it does not do it when it is cold


Edited by Customer (name blocked for privacy) on November 6 2005 at 12:15 AM
Customer (name blocked for privacy)
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November 5 11:36 AM (2 days later)
         
Relist: No answer yet.
I am very anxious to find out what you have to say about my problem
Customer (name blocked for privacy)
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November 6 1:14 PM (1 day and 1 hour later)
         
Relist: I still need help.
Customer (name blocked for privacy)
Answer
November 6 1:39 PM (25 minutes and 27 seconds later)
         
ACCEPTEDCheck Mark

S-10 2wd/4wd?Blazer/PU?Is the actual throttle cable returning to it's stop on the throttle cam.You can check this by having a helper snap the throttle pedal and watch the linkage to see if it returns quickly to it's stop or creeps to it.The cable may be gummed up inside or the pedal pivot or return spring on the pedal.If you have addressed the other items,thats all that's left.Unless someone fooled with base idle or timing on the vehicle.What is the TPS voltage at idle position and at WOT?You rebuilt TPS?Not likely.If you replaced it,did you set it properly or just bolt it on?Is the check engine light illuminating and if so what codes were retrieved?So far with the info you have provided the most common cause is a vacuum leak or bad PVC valve which in effect would be considered a vac leak as well.To find vac leaks use a can of carb clean with extension nozzle attached and with engine running spray in small spurts all around the intake and vac hoses while listening for idle fluctuations to occur.You should have an underhood vac system decal to guide you here. The other thing is a faulty Coolant temp sensor that will not always set the MIL on.

For vac leaks refer to this.

Images available only to Customers.

Testing the CTS.

Figure 1

The Engine Coolant Temperature (ECT) sensor, sometimes referred to as the Coolant Temperature Sensor (CTS), is a thermistor (resistor which changes value based on temperature) mounted in the engine coolant stream. Low coolant temperatures produce a high resistance - 100,000 ohms at -40°F (-40°C), while high temperatures cause low resistance - 70 ohms at 266°F (110°C).

Images available only to Customers.
Fig. 1: Coolant temperature sensor and connector


The control module provides a 5 volt reference signal to the sensor through a resistor in the module and measures the voltage. The voltage will be high when the engine is cold and low when the engine is hot. By measuring the voltage, the control module knows the engine coolant temperature. The engine coolant temperature affects most other systems controlled by the module.

TPS

TP sensor is connected to the throttle shaft of the throttle body or carburetor. It is a potentiometer with one end connected to 5 volts from the control module and the other to ground. A third wire is connected to the control module in order to measure voltage from sensor. As the throttle angle is changed (the accelerator is pressed down), the output of the sensor changes.

At a closed throttle the output of the sensor is fairly low (0.5 V). As the throttle opens, the output voltage should rise towards 5 V. By monitoring the sensor output voltage the control module can determine fuel delivery based on throttle angle.


Images available only to Customers.

REMOVAL & INSTALLATION

  1. Disconnect the negative battery cable.

  2. Remove the air cleaner assembly or air duct, if necessary for access.

  3. Disengage the TP sensor electrical wiring connector.

  4. Loosen and remove the sensor attaching screws.

  5. Remove the sensor from the carburetor or throttle body.

To install:

  1. If equipped, position the seal over the throttle shaft.

  2. Make sure the throttle valve is closed, then position the sensor over the shaft.

On most applications, it will be necessary to rotate the sensor counterclockwise to align the bolt holes.

  1. Make sure the retainers are covered with a suitable thread-locking compound (Loctite®262 or equivalent) then install the bolts and tighten to 18 inch lbs. (2 Nm).

Some earlier model vehicles, such as some applications of the 2.8L engine, utilize an adjustable TP sensor. If so equipped, the sensor should be adjusted after the retainers are threaded, but BEFORE they are tightened. Please refer to Fuel System in this repair guide for TP sensor adjustment procedures.

  1. Engage the sensor electrical connector.

  2. If removed, install the air cleaner assembly or duct, as applicable.

  3. Connect the negative terminal.


Battery Low Mode

If the computer module detects a low battery, it will increase injector pulse width to compensate for the low voltage and provide proper fuel delivery. It will also increase idle speed to increase alternator output and, in some cases, ignition dwell time to allow for proper engine operation.



Edited by railman on November 6 2005 at 2:03 PM

"It is much wiser and cost efficient to ask a question than to stumble blindly through your auto repairs".Please Click Accept if my answer was helpful.
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Michael -- Auto Service Technician -- 99% Positive Feedback on 598 Car Accepts
21yrs.Foreign and domestic driveability diagnosis and repair/ ASE Cert./Fuel Injection Specialist.
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November 6 3:23 PM (1 hour and 43 minutes and 44 seconds later)
         
Reply to Michael's Post: I have replaced pvc and temp sensor and tps,forget to mention it, I have checked for vaccum leaks and there are not any. My tps does not have an adjustment that I know of or could find in the manuel. I have replaced throttle cable and checked it the you said to but it still has the same problems. The check engine light does not come on.

Edited by Customer (name blocked for privacy) on November 6 2005 at 3:24 PM
Customer (name blocked for privacy)
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November 6 3:27 PM (4 minutes and 14 seconds later)
         
What is the base idle?



Edited by Customer (name blocked for privacy) on November 6 2005 at 3:29 PM
Customer (name blocked for privacy)
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November 6 4:10 PM (43 minutes and 11 seconds later)
         
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Michael -- Auto Service Technician -- 99% Positive Feedback on 598 Car Accepts
21yrs.Foreign and domestic driveability diagnosis and repair/ ASE Cert./Fuel Injection Specialist.
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November 6 8:43 PM (4 hours and 32 minutes and 36 seconds later)
         
I have not checked the timing yet but I am working on it. i was wondering about the temo sensor, the one I replaced was on the intake manifold on the front of the engine and has a plug on it with two wires coming from it. which one are you talking about
Customer (name blocked for privacy)
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November 6 9:05 PM (22 minutes and 32 seconds later)
         
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