idle misfire, scope says its random

[BlazerLT]

Check the wire between the coil and the cap.

The connections might be corroded on the coil.

I know mine was.

[charleseich]

Originally Posted by Max Crax

I have replaced the cap and rotor. Starting is much better. How did you discover the cracked coil?

If fire is good, the engine should not miss. If coil is good, everything else is new AC DELCO, so either the computer is confused or it is a fuel injection issue, right?

I have been trying in vain to have a garage test fuel pressure. I am just going to have to buy my own dadgum gauge and do it myself. If it is fuel - either too much or not properly sprayed, that might result in idle misfire...

I've had the same problem AGAIN after changing the Dist. Cap twice AND the Coil. The local mechanic replaced the Cap AGAIN for free without an explanation. I then talked to the original mechanic, ( who had refered me to the 2nd one ) and he informed me that NAPA told him that the OEM Dist. Caps are VENTED and the aftermarket ones have been being produced UNVENTED and EVERYBODY has been having problems !!! ( See post above about cap moisture. ) The problem has apparently been rectified, at NAPA anyway. Make sure you ask for and use a VENTED one.

[BlazerLT]

have you been replacing the rotor with the cap?

[Max Crax]

Originally Posted by Max Crax

I have replaced the cap and rotor. Starting is much better. How did you discover the cracked coil?

If fire is good, the engine should not miss. If coil is good, everything else is new AC DELCO, so either the computer is confused or it is a fuel injection issue, right?

I have been trying in vain to have a garage test fuel pressure. I am just going to have to buy my own dadgum gauge and do it myself. If it is fuel - either too much or not properly sprayed, that might result in idle misfire...

Final answer on the engine turned out to be Failed Fuel Pressure Regulator putting 62 psi at the injectors flooding the engine. New catalyst(watch out that distributor cap is not injured when replacing it - mine was broken and dealer insists muffler shop broke it) and pressure regulator (injectors were blasted clean by excess fuel) gives much better starting and gas mileage.

Thanks for the help.

[BlazerLT]

Originally Posted by Max Crax

Final answer on the engine turned out to be Failed Fuel Pressure Regulator putting 62 psi at the injectors flooding the engine. New catalyst(watch out that distributor cap is not injured when replacing it - mine was broken and dealer insists muffler shop broke it) and pressure regulator (injectors were blasted clean by excess fuel) gives much better starting and gas mileage.

Thanks for the help.

Change the oil ASAP.

It will be loaded with gas and damaging your bearings.

[Max Crax]

Originally Posted by BlazerLT

Change the oil ASAP.

It will be loaded with gas and damaging your bearings.

Blazer,

I have always used synthetic oil just in case. I recently noticed oil smelling like gas so I changed it and filter before going to have it tested.
Now that it is fixed, the engine is silky smooth. I guess the engine flushed itself out. Hopefully the bearings are ok - I have not heard any ominous knockings.

Do you have any ideas on the ac switching from defrost to dashboard vents? I get cold feet and frosted windshield but hot cabin!

Thanks for the help with the engine. I think I will polish the truck this weekend to celebrate having it run right again!

[BlazerLT]

Originally Posted by Max Crax

Blazer,

I have always used synthetic oil just in case. I recently noticed oil smelling like gas so I changed it and filter before going to have it tested.
Now that it is fixed, the engine is silky smooth. I guess the engine flushed itself out. Hopefully the bearings are ok - I have not heard any ominous knockings.

Do you have any ideas on the ac switching from defrost to dashboard vents? I get cold feet and frosted windshield but hot cabin!

Thanks for the help with the engine. I think I will polish the truck this weekend to celebrate having it run right again!

Yea, the gas in the oil is not good, just make sure you don't use a FRAM oil filter.

As for the vents, you have a vacuum leak.

Check all vacuum hoses in the engine compartment for leaks or cracks or from them not being attached.