Question about 1991 Chevrolet S-10

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1991 chevy S 10 EST not working

Hi i have a 1991 S10 with est.i have replaced all distributor parts and computer twice. I have checked the continutiy on all of the computer harness wires.they are all testing good.Yet the timing will not advance.I have no trouble codes and it starts fine.please give me some ideas?

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  • mixerman264 Jan 10, 2009

    i forgot to mention that the engine is a 2.5 liter 4 cylinder...there is no knock sensor.....any other suggestions?

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Check out the Knox sensor & or the Blue wire going to it if it is Grounded , the timing will not Advance, Knox sensor is there to detect knock then it grounds if it catches a Knock to Prevent
Pre Ignition Ping-SPARK KNOCK-

Posted on Jan 09, 2009

  • Ronnie Wilson Jan 11, 2009

    Facing the Engine look to the left of the throttle body theres a Component there with like i think 5 wire plug goin to it , Thats the spark control modual , May be that.

    If you have checked ALL the OBVIOUS like power to coil pack-power to Ign Modual, to me it sounds like A PRIMARY Ignition Problem.

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91 firebird 3.1 v6, if timing is set at 0 degrees instead of 10 degrees btdc would it cause strong exhaust and carbon on plugs


Here is the procedure for setting the timing:
1991-92 Vehicles

See Figure 2
When adjusting the timing, refer to the instructions on the emission control sticker inside the engine compartment. If the instructions on the label disagree with the procedure listed below, follow the instructions on the label.
  1. Locate the timing marks on the crankshaft pulley and the front of the engine.
  2. Clean off the marks and coat them with white paint or chalk, if necessary, so that they may be seen.
  3. Run the engine until it reaches normal operating temperature, then shut off the engine.
  4. With the ignition OFF , connect a tachometer to the distributor, and the pickup lead of an inductive timing light to the No. 1 spark plug wire. Connect the timing light power leads according to the manufacturer's instructions.



WARNING Never pierce a secondary ignition wire in order to connect a timing light. A pierced wire may lead to engine misfiring and driveability problems.

  1. Start the engine. With the engine running at normal operating temperature and all accessories OFF, disconnect the EST bypass connector.

An ECM code will be set when the EST bypass connector is disconnected.
  1. Aim the timing light at the timing mark. The line on the balancer or pulley will line up with the timing mark. If a change in timing is necessary, loosen the hold-down clamp bolt at the base of the distributor. While observing the timing mark, rotate the distributor slightly until the line indicates the correct timing. Use the timing specification on the emission control label in the engine compartment. If this label is missing or damaged, refer to the Tune-Up Specifications chart in this Section.
  2. Tighten the distributor hold-down bolt and recheck the ignition timing to make sure the distributor was not moved when the bolt was tightened.
  3. Turn the engine OFF and remove the timing light and tachometer. Reconnect the number 1 spark plug wire, if disconnected.
  4. Connect the EST bypass connector, then check for and clear the ECM code by disconnecting the negative battery cable for at least 30 seconds.

To prevent ECM damage, the key must be in the OFF position when disconnecting or reconnecting battery cables.

0900c1528008e3bd.jpg

Fig. Fig. 2: EST bypass connector

Feb 01, 2011 | 1991 Pontiac Firebird

1 Answer

What and where is the est circuit connector on a 1989 chevy pick up 2500 5.7liter.


Hello johnballard8: My name is Roger and I will answer your question. I assume you are looking for the est wire in order to set the timing. Look in the area of the distributor. Usually on the left side. Locate a single wire (tan with a black stripe) Should be taped to the engine wire harness. This is the est wire remove the tape and unplug the connector. This will set truck to base timing. After you set timing reconnect the wire. You may need to reset the computer as this operation will set a code in the ecm. Just disconnect the battery for 10 seconds and this will clear the codes. Be sure to disconnect the negative cable so as not to spike the ecm. Should you need further help please just ask. Please rate the answer. Thank You for using Fix Ya. Roger

Dec 18, 2010 | 1995 Chevrolet S-10 CA Edition

1 Answer

Hi .....i recently bought a honda accord 1991 ex r .............it was running fine but all sundden one day its havd problems ........it would start up fine ........and driven for say 20 minutes then it...


These cars had two very common problems. #1 The pgmfi (main) relay has solder joints that go bad, I would repair or replace this first as they are not very expensive. It is likely your problem, if not, it will be one day so do it for maintenance if nothing else. # 2 is distributors. There are several components inside the distributor that can go bad, the easiest and cheapest solution in the long run is to just replace the whole thing with a new one (not rebuilt). Most aftermarket parts stores sell these fairly reasonably now.

Replace the relay. If that does not help, do the distributor. The ignition switches had problems as well, but they usually prevents starting...be ready for that one day as well.

Dec 16, 2010 | 1991 Honda Accord

1 Answer

Cant find the wire to unplug and dissable est on 1991 s-10 to set timing


I believe it should be a 4 wire plug. There should be 4 wires coming out of the distributor with a plug. I know some GMs had a single green wire with a plug also.

Jun 14, 2010 | Cars & Trucks

1 Answer

Crossed up plug wires on 1991 chevy s10 2.8 need diagram


For the 1991 Chevrolet S10 or T10 Pickup 2.8L V6:

Firing Order:
1-2-3-4-5-6

Cylinders:
.......(back)........
|..5..|........|..6..|
|..3..|........|..4..|
|..1..|........|..2..|
.......(front)

Distributor:
....(back)
....3...4.(+)-screw
2...........5
(+)1...6
....(front)

Let me know if this helped, or if you have additional information or questions. Feel Free to contact me at FixYa.com!


Apr 22, 2010 | 1991 Chevrolet S-10

1 Answer

1991 chevy s10 4.3 v6 new rotor and cap new spark plugs and wires and still not running smooth skipping andy suggestions


Check your knock sensor, and timing.

The distributor is controlled by the computer and springs, I can't recall but I don't remember seeing springs in there. Regardless, check anyways to see if there is any binding to your counter weights in the distributor.

Start with finding out why your check engine light is coming on, this way there is no expensive guessing work. Here is a link for you to retrieve the DTC codes and post me back. Be glad to help you get your S-10 running 100% again soon. eek.gif

http://www.troublecodes.net/GM/
Recheck your timing and you'd notice more difference if you increased your static timing advance from the stock setting of 10 Deg BTDC to 15 deg BTDC or so. Be sure when you adjust timing to disable the ESC circuit according to the manual. Otherwise the timing will be off scale and you won't even be able to see where it is with a timing lite.

The connector you're looking for is located in the passenger footwell, sometimes covered by the carpet/floor mat. It is a black connector, that has a tan/black wire in each side. Disconnect this wire and you will be able to see the base timing.

The ECM will control the timing with that wire connected. When it is disconnected the timing advance is controled strictly by the ICM (Ignition Control Module) located on the base of the dizzy.

How to set:
The vehicle emission control information label, which is found underhood, will often contain specifications or procedures for checking and adjusting timing that have been updated during production.

Set the parking brake and block the drive wheels, then warm the engine to normal operating temperature. Shut the engine OFF and connect the a timing light to the No. 1 spark plug (right front 2.8L engine, left front 4.3L engine or front plug on in-line engines):

If using a non-inductive type, connect an adapter between the No. 1 spark plug and the spark plug wire; DO NOT puncture the spark plug wire, for this will allow a voltage arc.

If using an inductive type, clamp it around the No. 1 spark plug wire.
If using a magnetic type, place the probe in the connector located near the damper pulley; this type must be used with special electronic timing equipment. Do not under any circumstances pierce the insulation of a spark plug wire in order to connect the timing light.

Clean off the timing marks, then label the pulley or damper notch and the timing scale with white chalk or paint for better visibility. If the timing notch on the damper or pulley is not visible from the top, the crankshaft should be bumped around using the starter or turned using a wrench on the front pulley bolt, in order to bring the mark to an accessible position.


Model vehicles equipped with EST, the electronic spark timing must be disabled or bypassed to prevent the control module from advancing timing while you are attempting to set it. This would obviously lead to an incorrect base timing setting.

There are 2 possible methods of disabling the EST system, depending on the type of engine:

On 2.5L engines, ground the "A" and "B" terminals on the ALDL connector under the dash before adjusting the timing.

On all other engines using the EST distributor, disengage the timing connector wire. On a few of the earlier model vehicles, the 4-terminal EST connector must be disengaged from the distributor, but most later model vehicles are equipped with a single wire timing bypass connector.

On these later model vehicles the bypass wire is usually a tan wire with a black stripe. This wire usually breaks out of the wiring harness conduit adjacent to the distributor, but on some vehicles it may break out of a taped section just below the heater case in the passenger compartment.

Start the engine, then check and adjust the idle speed, as necessary. The idle speed must be properly set to prevent any centrifugal advance of timing in the distributor.

Aim the timing light at the timing marks. Be careful not to touch the fan, which may appear to be standing still. Keep your clothes and hair along with the timing light's wires clear of the fan, belts and pulleys. If the pulley or damper notch isn't aligned with the proper timing mark, the timing will have to be adjusted.

TDC or Top Dead Center corresponds to 0° mark on the scale. Either B, BTDC, or Before Top Dead Center, may be shown as BEFORE on the scale, while A, ATDC or After Top Dead Center, may be shown as AFTER.

Loosen the distributor base clamp locknut. You can buy special wrenches which make this task a lot easier on certain models. Turn the distributor slowly to adjust the timing, holding it by the body and not the cap. Turn the distributor in the direction of rotor rotation to ******, and against the direction to advance.

Once the timing is properly set, hold the distributor to keep it from the turning and tighten the locknut. Check the timing again after finishing with the nut in case the distributor moved as you tightened it.
If applicable, remove the plug and connect the distributor vacuum hose.
Shut off the engine and reconnect the EST wire (if equipped), then disconnect the timing light and tachometer. biggrin.gif

Also you may want to inspect the EGR to see if it's stuck, which may be causing our issue when the engine is under load.

Apr 19, 2010 | 1992 Chevrolet S-10

1 Answer

Need firing order diagram for 91 s10 blazer


991 Chevy S10 firing order
The firing order for a Chevy s10 depends on which engine you have.
1.9L engine the firing order is: 1-3-4-2 . Distributor rotates counterclockwise.
2.0L engine the firing order is: 1-3-4-2 . Distributor rotates clockwise.
2.5L engine the firing order is: 1-3-4-2 . Distributor rotates clockwise.
2.8L engine the firing order is: 1-2-3-4-5-6 . Distributor rotates clockwise.
4.3L engine the firing order is: 1-6-5-4-3-2 . Distributor rotates clockwise.

Jan 09, 2010 | 1991 Chevrolet S-10

1 Answer

Chevy s10 4 wheel drive will not engage


There is a vaccuum operated switch located on the transfer case that sends vaccum to the accuator that pulls a cable that locks the front end in. Check for vac coming in and out of this switch if no vac out replace it. This switch is a very common problem. You can find them at most parts stores in the help section #49315. please rate.

Dec 08, 2008 | 1991 Chevrolet S-10

1 Answer

Ignition Timing


How to check and adjust the timing
Disconnect the tan/black wire EST (electronic spark timing) by-pass connector located near the heater housing in the engine compartment on the S/T series, or near the distributor on all other V-6 models. Do not disconnect the four- (4) wire connector at distributor. Connect the timing light to the No. 1 spark plug wire. Check timing and adjust to "0" degrees BTDC. With the engine off, reconnect the EST by-pass connector and clear the ECM trouble codes by disconnecting the battery.

Aug 19, 2008 | 1991 Chevrolet Corvette

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