High speed miss

[Don W.]

You can peruse my other posts, suffice to say truck had a miss at idle and wouldn't pass the smog idle test.

Anyway, installed (not all at the same time ) new: EGR, o2, rebuilt (calibrated & matched) inj's, ported TB (my old one had obvious shaft play), rebuilt dist. (had the truck on a scope to find this), new NAPA cap & rotor, wires are 15 month old Taylors. Miss is still there. Installed new NGK iridium plugs today (gap .025), miss is almost gone. Truck starts like it never started before. Very quick. Will retest smog asap.

OK fine, now it misses at full throttle.

What's left?

Wires? Maybe but I thought Taylor's were better than that.
Rebuilt dist bad? I hope not, how do I prove it if it is.
Coil? Stock on there now but I have the MSD Blaster replacement but I don't think that's it because I changed it thinking the MSD might be the prob, no change.
NAPA cap & rotor? I can put back my old (over a year) MSD and see.

I do know timing is just a tad fast, 1 or 2 degrees base, but should that cause a miss?

This is nuts...

Will post a DM from tonights racing later.

Comments? TIA

 

[SY2455]

Re: High speed miss

How old is your dist cap and rotor? The reason I ask is this. When I installed my MSD6A with the MSD coil and plug wires it burn holes in the dist cap and worn down the pointer on the rotor in a 1 month time frame causing a miss at higher rpm. All I did was remove the MSD coil and used the stock coil with the MSD6A and plug wires and all is well. Have the same cap and rotor now for 2 years.

 

[dhorsman2000]

Re: High speed miss

On my stock ignition set up my coil was causing a miss at full throttle, you have a different set up, but if you have a different coil it only takes a few minutes to change it out and see......just a thought.

 

[Don W.]

Re: High speed miss

Dist is recently installed rebuilt. Cap and rotor are brand new NAPA. What I'm gonna do tomorrow is reinstall my old MSD cap and rotor then test. Then I'll reinstall my MSD coil and test. All to see if I can narrow this down.

 

[dgoodhue]

Re: High speed miss

Check the 2 wire pink & white harness that goes from the coil to the distributor.

 

[Don W.]

Re: High speed miss

Check the 2 wire pink & white harness that goes from the coil to the distributor.

Can do, thanks

 

[gjp]

Re: High speed miss

Check the 2 wire pink & white harness that goes from the coil to the distributor.

Don, once I did that my miss stopped. But I only drove the truck a few times afyer and my miss was random. That wire is around 40$ and the dealers carried it.

 

[Turbo6]

Re: High speed miss

How much boost are you running? I remember mine running the best with a .020 gap or so at 25-26 psi. Dont be afraid to gap those plugs on down....you may be suprised what it can do.

 

[Jimmy]

Re: High speed miss

How much boost are you running? I remember mine running the best with a .020 gap or so at 25-26 psi. Dont be afraid to gap those plugs on down....you may be suprised what it can do.

+1 it may be blowing out the spark.

 

[Don W.]

Re: High speed miss

Well so-far I've reset the timing. (I was had been a bit advanced. Truck seems to like 1or2 retard.) And I put the MSD coil back on. Miss seems to be gone. Right now I'm looking into the MAP sensor. Some numbers don't seem right to me. Also ran a DM this morning and boost is solid at 20 with the chip set for 14. Scary. I've not seen this before so haven't fooled with the WG in ages. I have another MAP sensor so think I'll just do a swap and see if there's any difference.