I have a 87 s10 pick that won't pass emissions did cap rotor plugs wires and emissions r still to high any suggestions

SOURCE: where are the timing marks for 1991 f250 4x4 7.5 gas engine

your timing marks are on the dampener pully and you need a timing light to perform the timing of the engine and i am not sure if you have a gas or diesle so just let me know and i will let you know if i can help you

SOURCE: wont pass emissions, repaced cap and rotor, full

try getting the carb adjusted first most of the times you can get the h.c under control ? but the high nox could also be a stuck egr valve pull it off and see if its stuck open? get back after you do this if it dosnt fix ya up

SOURCE: 87 chev van 350ci,failed 1 of 4 emissions test(HC

Hydro Carbons are usally from an engine missfire. It may be that it is such a sligh miss that you cannot feel it. What is your timing set at? I would try setting it at 2* advanced and see what that does for you.

SOURCE: misfires #2, replaced plug, wire but still

A vacuum leak,fuel injector,or valve problem will cause a missfire.If the spark plug is black when removed you have too much fuel,if its white[like new] not getting enough fuel, and if it comes out wet with fuel and a darker color thats a valve problem[compression].

Harvey N Tawatao

• 3854 Answers
• Posted on Apr 19, 2010

SOURCE: 1991 chevy s10 4.3 v6 new rotor and cap new spark

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.

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.

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.