Missing really bad!


Active Member
May 25, 2001
Went to the track today and the car ran perfect. Stopped by a friends house when I got back and talked for about 30 minutes. When I left there it started missing really bad. Feels like it's only running on about 4 cylinders. At idle my vacumn gauge is jumping all over the place. I was just driving normal when it started this. Can't find a vacumn leak. What else would cause this??? Thanks, R.B.
What sort of problems would cause the vacumn gauge to jump all over the place? Would bent push rods cause this?
Not sure on the vacuum guage but when it felt like my car was running on 4 cylinders, it was. Ignition modual went out.
What sort of problems would cause the vacumn gauge to jump all over the place? Would bent push rods cause this?

if you have bent pushrods you would have way more proplems than a missfire. the vacuum guage jumping is just cuz the miss you should check the basics like the plugs and wires and take it from there
well i take it back bent pushrods could cause a miss if there not seating right and ur letting gas back into your intake yeah its possible but you said you just came back from the track its not likely unless you jumped some teeth on the timing but again not likely it would run way worse then that
Worst case scenerio, a Vac guage jumping aroung could be a valve :eek: . If it feels like 2 cylinders are down you could have a bad coil. Remember Wastespark uses 1 coil to control 2 cylinders.
Replaced coil pack/ignition module, plugs, and 02 sensor with no results! Thinking bent push rods! Anybody else???
Not the left bank !!! Get to the other side later. Also it's not showing the cross counts moving on the scan master for the 02's.
If it was just a miss and the valvetrain was okay, then the vacuum gauge would not jump severly. One thing that could cause the gauge to jump would be an intake valve that is not seating and everytime that cylinder comes to TDC it blows the compression into the intake. I would perform a cylinder leak test on each cylinder and see if there is a leak on all cylinders, and if there is, you can listen to where you hear the air escapes. This is a very easy way to determine a valve leaking and which valve.
definetly a cylinder leak down test but what were you doing to make you think that it could be bent pushrods you leaving out some part of the story:eek:
I had over revved it once a while back and bent a couple of push rods. Didn't do that this time though. When I swapped out the coil pack and module the other day, it was with one that I had laying around. Now I realize that this one could have been bad! Checked the towers on the coil a few minutes ago and they read 11.0, 11.2, and 11.2. On my T-Type they read 13.5, 13.2, and 13.4 and it runs great. Haven't had a chance to swap these yet to see if it helps. I know they say they should read between 11 and 13. Don't know if 11 is better than 13 or if 13 is better than 11. Also, if this cures the problem when I swap them, how do I know if it's the coil pack or the ignition module? Confused, R.B.
I usually change both, the ignition module and coilpack as a pair when I do them, or you could just try them one at a time if you have spares.
"I" would swap 'em one at a time.... then you will have your answer as to which one it is/was... if the T-Type runs good, use it as the test mule...... and 13 is better than 11, fwiw... :wink:
OK, here's what I've done with no results! Swapped coil pack/module with known good one, swapped ecm with known good one, new plugs and wires, new 02 sensor. Car is idleing like it has a big cam, really rough. Vaccumn gauge is bouncing between 10psi and 0psi, like a clock, tick toc tic toc. If I slowly raise the idle the vacumn gauge speeds up the ticking. At 3400 rpm it's rock steady! When I gun it from 3400 rpm it sounds really smooth with no missing. Confused! Need help! Thanks, R.B. BTW, I haven't taken off the other valve cover to check it yet.
If the car was running "OK", as you stated, then when you started it again, it started missing... I'd be looking at a valve to guide problem. No reason for a p. rod to "mysteriously bend", unless the valve hit a piston, or the guide grabbed the stem.
Could have been that while you were visiting, the heat soak in the engine, allowed the guide to stem clearance to go away...
Time to pull the heads, go thru them, check the springs, etc.