[txbkr]

So, when I punch it on 2nd, as the RPMs are climbing fast, as it passes 4000, it starts to break up. It feels like it is missing a spark. When it happens, the tach needle bounces erratically. What's stranger than this is the fact that it did not do it when it was cold. As the car got to 180, I punched it 3 times up to 6000 and nothing, pulled like a freight train. I shifted into 3rd and took it to 5500 with no issues. Also, it does not happen if I rev it slow to 5-6k or part throttle.

I changed MSD boxes. It has a new distributor and spark plugs. It's a new long block professionally assembled. The rest of the parts came from the old engine which did not have this issue.The tune good. Any ideas?

Please help. It cost me a good chunk of money and time to build this engine and I want to see it run hard like it should....thanks, Pete.

[93hatch]

mine did that when i had a cracked plug

edit:didnt see you already replaced them, either way i think its spark related

[txbkr]

At first I thought I had reached the rev limiter. But the second time it happened at 4000.

Tomorrow I will have the spark plug gap closed up a bit. I doubt it but it could be that at those high RPMs the fuel and gases are preventing the plug from arcing. It sounds far fetched but at this point I'll test anything because the next step is what, buy a new coil?...distributor cap?...

Thanks for the idea.

[JBIGBOOTSY]

If the tach needle jumps around its prolly the ignition module.

[kilby91]

I used to have a very similar problem and it ended up being a faulty tach... It would rev to around 5,000rpm on the factory tach and would start to miss like a rev limiter.. Ended up it was the rev-limiter, i got a good tach in the car and realized my factory tach was way off in the upper rpm range.. Just a suggestion but get an accurate tach..

Link to my thread when i had my problem....
Need smart people to help figure out my problem!!




Richard..

[grnstang]

sounds like MSD

[vfast]

what is fuel pressure?

[2002BLGT]

need to first verify the actual RPM with an accurate tach , next thing I would do is make sure its holding fuel pressure when it begins to miss .......what are the plugs gapped at ? and whats the entire setup and what plugs are you running ?

[nolife]

I'm sure there are a 100 different things to check but I had something similar and it was the routing of my plug wires. I moved them around and the problem went away. Maybe it was not specificaly the routing or the fact they were crossing over each other a few times but maybe one was bad and moving it was a temp fix. either way, it is one more thing to add to your list of things it could be.

[flyin ryan]

My vote goes to the MSD (my suddenly die)

If you installed your msd box with the harnesses that allow it to be a plug n play ordeal then you should be able to unplug it and run off your stock ignition.. that will tell you if the msd box is fubar'd.. other then that I would pull the plugs and check for any fine cracks and ohm out the plug wires

[JBIGBOOTSY]

If it was a plug problem, the tach would not jump around.

[txbkr]

I just closed the plugs a bit more. They are at 38/1000 and the problem still persists but not as bad...fuel press is fine. No starvation. I dbl checked and I am running the correct plugs. So I think it's that the coil is not keeping up with the load at the indicated RPM. The tach is running well. It jumps from the erratic behavior of the motor. I've ordered a new coil. It should solve it. If not, it's time to crack open the wallet wider....oh well. Parts will break, just got to replace them w/better ones that make you go faster........

BTW, Thanks for the ideas....p.