I did a search but did not fine a problem like mine listed. So here goes.

I was doing an open track event yesterday. After about 4 laps I could feel the car losing power. I pulled into the pits and found my NO. 1 plug wire was loose. I have had trouble with this wire in the past. The metal sleeve for some reason causes it to come loose. Well I scraped the sleeve and pushed the plug wire in place. Went back out and all was well. I ran for a while till the oil temp got up to 280* (outside air was 80*). then came in to let it cool down.

Shortly after I started my next run I felt the miss come back. Pulled into the pits and checked all the wires they were all OK. There was a code said engine miss or something like that.

Well took the car home and worked on it today. I pulled all the plugs and check the gap all but one was fine they only have about 2,000 miles on them. It was plug #7. It was wet and smelled of fuel. I switched the plug with another cylinder and put everything back together. I used liberal amounts of Dialectic grease. Upon restart I felt the same miss. I pulled #7 and it was wet again and smelled of fuel. I pulled the plug wire and inserted a screwdriver in the boot. I shorted the shaft against a ground and did get a spark, so it is firring, or at least juice is getting to the plug.

The oil is clear no water that I could see.
One other thing. I did not warm up the car but I went to the back and put my hands up to the exhaust. The left side was blowing hot, the right side seemed cool. But again the engine was cold.

Any suggestions as to what I should look at next?

 

Check compression in #7, it's a KNOWN cylinder to implode. get numbers for 2 or 3 other cylinders to compare it to.

 

I will check the compression tomorrow, but what do you mean by "implode"?

 

Cylinder #7 is a known problem, do a search-it usually destoys itself when pushed hard for extended periods, many people have had #7 issues. Also check valve train, the needle bearings on the rocker arms and valve springs are also a KNOWN weak spot, broken springs and dropped needle bearings. I would geuss you have low compression in #7 so you not igniting the fuel in that cylinder, are you also getting P0307/P0300 errors??

Check this out: http://forums.corvetteforum.com/c5-t...aspirated.html click on the pic and notice the piece missing. Do a search on "Cylinder 7" in c5 tech!!

 

Yes I remember a PO300 but not the PO307 but could have. Makes sense that the compression is low and fuel not igniting. So if I have a broken valve spring wouldn't the valve drop into the cylinder? And in a broken rocker arm the valve won't open so it should have compression. I smell gas on the plug so at least the intake valve is opening. Well one step at a time. I will check the compression. If low I guess the next step it to pull the valve cover, and look around.
Thanks for the information.
Jay B

 

Well I got some preliminary results. I did a compression test(well somewhat). I pulled the #7 plug, hooked up the compression tester and got a reading of 120. I then went to #1 pulled the plug and tested it and got 120 also. I ran out of time so did not squirt oil into into the cylinder to check it.
I am thinking that the results so far indicate that #7 compression is OK and the miss may be caused by something else. I am getting spark. When I put a screw driver into the plug boot I got a spark, about an inch long, but it was thinner than I wold have expected.

Any suggestions?

 

check the #7 injector resistance against others. your injector might be going south

 

Yeah -- swap the #7 coil with another, then run the car long enough to get it to start missing again -- if #7 is now firing and the other cylinder now misses, you'll have an answer. If the miss is still at #7, you'll have ruled out the coil (but obviously, not the wiring to the coil) -- at least a step in the right direction. Worth trying before you put money into parts.

HTH,
Mark

 

I checked #7 injector against #3 and they are the same.

Good suggustion though.

Does anyone know how to check the coil's?

 

If your injector is going south or If injector wire is not Hooked up it will feel like a miss also ,i had this happen to me ,but the Dic showed a code & it went straight to the injector wire ,not saying thats what it is but check your Pcm codes & if u have it back together & your driving it & theres an issue you should get a code ,i know u said u had a missfire code before u put the #1 wire back on ,when u drove the car home did u continue to have any pcm codes ? Check them frequently i would also think that gas being on that plug is telling me u may be in need of a tune,also when u pulled the valve covers did u check the roller rockers out ,I had 5 bent cromemoly pushrods that was making my car tick ,sound horrible check your roller rockers & the needle bearings while your valve covers are off ,Keep us informed with what u are finding out

 

Well u can swap them around ,thats what i would do lol ,I havent had to do that but i would think if u had a bad coil it would tell on itself by swapping them around U may be able to pull your p;ug wire off your coil pack & it should start missing shooting fire ,if so u have a good coil if not you either have a bad plug wire or a bad coil ,keep the motor running while doing this & Keep the lights off so u can see your fire jumping & Listen to your motor

 

Everyone seems to be focusing on the injectors, but in the original post, he mentions that #7 is wet -- seems like the injector is flowing, so unless it's stuck open (and thus flooding #7), I don't see the fuel delivery system at the head of the likely suspects list.

Another $0.02 deposited

 

You can take an ohm meter to the primary and secondary windings, but I suspect it would be faster to just unbolt #7 and trade it for #5, and see if the miss moves.

 

A leaky injector could cause it. Put a fuel pressure guage on it, fire it up and let it run for a few seconds. Shut it off and see if the pressure bleeds off quickly (it shouldn't), If you have a mechanics stehescope, listen to #7 and see if you can hear anything after the car is off.

 

Mystery solved now what?


Nothing I did gave me the answer so I pulled the valve cover. There was no push rod connected to #7 intake rocker arm. It is gone!!
The hole in the head that the rod should have come out of instead of being "O" in the hole was shaped more like an "8". Looks like the rod has been off center and rubbing for a while. I have not done anything more.

I was going to pull the rocker arm but the nut is an 8mm and I only have 1/4" drive sockets for something that small. Kind of hard to get much mussel on it. I have to look around for an adapter to 3/8 drive which I have somewhere.

But I don't know what the "innards" of the LS look like. Could I fish the broken rod out? and install a new one? But then again where is the top piece of the rod. It was not in the rocker arm galley.

So what is the proper way to fix this?

 

Pull the intake and the valley cover, you need to see inside and possibly replace that lifter too. Pulling the intake is easy, many articles on this, the hardest part is disconnecting the fuel line.

I seem to recall saying you'll probably need to pull the valve cover to examine the rockers and springs early on here.

Intersting you were getting good compression #'s without the intake opening and how was fuel getting in to foul the plug?

I'll bet the rocker it toast too, that's why it "wallowed" out the hole for the push rod.

 

Ok, I went back to work. A neighbor came over with an adapter 3/8 to 1/4 inch and I pulled the rocker. We put a magnet in the hole and out came the broken piece about 2 3/4 inches to 3 inches long. Then back in and the rest came out.

So I am thinking. Could I just replace the pushrod at this point. The rocker arm seems fine. No slack in the bearings and no unusual wear marks where the rod makes contact with it.

 

The pushrod came out for a reason, you need to find out why, next time could be VERY BAD.

 

called a local Corvette guru, I was hoping he had a LS push rod he took off an engine he was modifying. He did not so I am going to the Cheby dealer. He suggested I do a leak down test to see if there is a bent valve. He also said he would check the valve spring pressure because (he said) with 88K miles the springs probably got soft and should be replaced.
So after the holidays I am going to take the car to him to do the leak down test. But since I am going to make the trip to the dealer to purchase 1 push rod, maybe I should check all of them for straightness.
I did many searches on this forum looking for information on valve lash, tdc, etc. from what I read it seems all I have to do when I replace the push rods it to re-attach the rocker arm and torque the nut to 22ftlb's. and will not have to position the pistons in any special place. Am I correct on that assumption?

bTW Dougbfresh yes you were right on in your first reply!! Thanks.

 

I have gotten an education trying to fix this problem. I am going to do all of the work myself.
I am pulling the intake manifold (I bought a fuel line puller tool) and take a look into the into the cam galley, to check the lifters.

Then I am going to remove the rocker arms and check the push rods for straightness. Then with the rockers off I will do a leak down test. I know I can buy the tester kit for $70, but I am hoping to be able to rent one.
There has been a lot of info on this form about doing a leak down test but one thing I have never seen, is how long to you keep the pressure on before you record the results for that cylinder?

Now to the replacement valves. I have a stock cam but 88K miles on the engine (00FRC). So my valve springs may be a bit weak. I don't think I need expensive two piece springs. I have seen a few references on this forum to ZO6 Yellow springs, and was thinking of installing a set, the price is certainly right. Are they a direct replacement? will I have to shim the bottom of the spring to achieve a certain valve height?

Thanks for all the great information!!

PS. After I wrote the above I was surfing around the forum and found a catalog that showed a picture of a bare LS block. Thought the shot was from the side not from above it looks like the heads will cover the access to the lifters. So if I am correct that means I will not be able to check the lifters let alone replace a damaged one. Am I correct in this assumption.