97 Tahoe has a miss

[61_FL_Apache]

Hello all,

I have had this issue for several months now. About 6 months ago my cap and rotor was in such bad shape, the truck died on my way to work. So I replaced both and all was good. About 2 months later it started missing just like it did before it died. I looked the cap and rotor and they didnt look that bad. I cleaned all the contacts and it ran great again for a week or so and the miss returned. I had a lifetime warranty on the parts so I got another set. All was great again for about 2 months and 2k miles then the miss came back again to where we are today. Here is a current pic of the 2nd set before I cleaned them again. If you look in the cap you can see some dust around the perimeter of it. The rotor has a spot on the corner of the electrode. I have since cleaned all the contacts on the cap and rotor.

So what is causing this to happen? I have 255k miles on the truck.





Thanks for your input.
Steve

[Kudzupatch]

Cheap made aftermarket parts. They cause so many problems and people assume because they are new, they good. I hold out of Delco parts most time or higher end aftermarket brands.

[Palf70Step]

I was thinking moisture as I read you thread, the humidity in our home areas can cause issues. My thought was the cap wasn't sealing very well, but as I look at it closer I tend to think like above, that may be just bad parts.

[speedygonzales]

Let me give you my experience with these caps and rotors.

I had gotten tired of the original plastic POS distributor. If for no other problem then the dreaded cap screw holes that crack. So I bought a nice Summit aluminum unit and it worked well for several years. Keep in mind I live in the second worst area for humidity. The first being southern gulf states.

Humidity never EVER played a roll in these POS caps. I had gotten to the point where my caps were destroyed in 300 miles. I took a trip to Jersey which for me is 6 hours and 300 miles. I had to put a new cap on and take one with me to change out on the way back. And I did once.

A couple years ago I finally had enough of the problem and I removed the distributor and found the 2 vent holes were completely closed from flaky aluminum corrosion. I did not like that the vent holes in the aluminum distributor were right angle so I drilled straight down to clear them and open a good hole in both of them.

Now my caps last 10's of thousands of miles. So no, humidity did not play a role.

Now let me tell you about the caps and what happens. Once when I had a bad miss show up, I bought 2 new caps and one of them was a Delco cap. Both new caps had a miss right out of the box. Look at the photo below. I drew an arrow to the area that is a problem for ALL manufacturers. I know this area is a problem continually because if you search the internet for 5.7 Vortec miss-fires, you will come across dozens of people that have cylinder 3 miss-fire.

Although I don't have a x-ray of the area in the arrow, my guess is that when they lay the conductor in the mold, either they lay it too close to the center contact. Or the injection process pushes the conductor too close to the center.

Incidentally these people (on the internet) have stated during the bad miss-fire event, if they pulled the cylinder 3 plug wire off the plug, The miss-fire changed dramatically. The area shown in the arrow is the number 3 contact.

There is a TSB on the original distributors to punch out the screen in the vents. So that backs up what I experienced with caps going bad quickly from lack of venting.

Oh and one last thing. When I had the vent problem, my contacts where 100x's worse than those in your photo. The white corrosion was a couple mm thick.

If you want a cap that lasts way WAY longer than the usual aluminum contact caps (like in your photo) get the ones with brass contacts. Like the MSD 8017 available everywhere including O'Reilly's. There are a couple other mftr's of brass caps too.

[61_FL_Apache]

Thanks Speedy for the input..

I was looking at an alum dist from Rock Auto made by UNITED MOTOR PRODUCTS. I currently have a rotor from them and it has brass contacts. The issue did improve, but its not gone.

Hopefully by the end of the year, I will replace the distributor.

[speedygonzales]

What problem do you think the distributor is going to fix that your new cap and rotor didn't?

There are 3 problems associated with the distributor that I highly doubt a new one will fix. The most prominent one is the pickup inside which can be replaced without buying the whole distributor. But if that were your problem, you'd get a code for it. So unless you're not telling us something, I doubt any of that is your problem.

If your still having this issue after more than 3 months and a new cap and rotor, I suggest you go back to basics and start with a proper compression check and possibly a leak down test. Notice "proper" is bold. There is a reason.

I currently have a mis fire of sorts (you can feel it) but it never sets a "300" code. It will very occasionally set a rich bank code. But I have replaced the injectors a few times and I'm not doing it again. The engine is coming out and a 383 with a RamJet will go back in. I been waiting to do it and now it's over due.

Good luck to you.

[61_FL_Apache]

A follow up on this topic. A couple of weeks ago, I swapped out the cap and rotor with a set that has all brass contact points.

Issue has been resolved.

Thanks for the advise as always!

[61_FL_Apache]

well............

That was short lived.

[Redneck Rydes]

Somewhere on here somebody had the same problem,and they went with a MSD red cap with brass terminals,I have the same problem with my 1994,I am going to get one whenever I can get to my truck

[Just call me Sean]

Maybe your coil is weak.

[61_FL_Apache]

Originally Posted by Just call me Sean

Maybe your coil is weak.

That is a thought. I did replace it maybe 5 years ago or so. But it seems that every time I swap the cap and rotor its perfect for a month or more then it starts to go down hill. This time is better than previous and I think that is due to both having brass contacts.

[61_FL_Apache]

This should now be solved when I was able to clear the P1345 code. The distributor was not in the proper position and caused a really long spark from rotor to cap. Once I got that fixed, it should also keep the caps from going to crap in a hurry.

Time will tell.