: engines misses after teardown

09-21-07, 08:41 AM
ok, R&R my northstar so i reinstalled every connector under the hood. now when i power brake, my engine stumbles and pops and i cannot even turn over the tires. it pulls strong once i get past 2k rpm but it does not idle right. it has a random miss or stumble. i checked every hose, vacuum line, plug wire. I know i timed the cams right so i don't think its mechanical. could it be the intake manifold gasket? no codes. it does crank a little long when its hot. fuel pressure? FPR line is dry, no gas. any ideas?

09-21-07, 10:19 AM
Someone a while ago had an intake cam one tooth off and it ran poorly at low speed.

Did you use a new intake gasket? Even though they are reusable they get hard with age.

It could be a vacuum leak. Try spraying starting spray around the intake. (or carb cleaner) to check for leaks.

09-21-07, 11:14 AM
Are the plug wires OEM or new? Sounds a lot like my problem right after the fuel rail recall was done (old wires moved around). I'm betting a new set of A/C Delco wires will solve your problem.

09-21-07, 02:09 PM
What year?

09-21-07, 10:53 PM
96 STS. 109k miles. i did the headgasket job. the wires are delco, 2 yrs old. i am going to try new plugs tomorrow. i can't even chirp the tires. thats sad. my buddy has a 94 sts with 190k miles and a worse HG than mine and he can lay rubber for 50 ft.

09-22-07, 11:51 PM
if you pull off a valve cover, both cam timing marks should be lined up if you turn over the motor. if you keep turning over the motor, both the L and R cams will eventually line up. i should be able to figure out if 1 sprocket is off fairly easily. they are both timed to be at 12o'clock to the deck surface so they should never loose that relationship. it should be fairly easy to check that they do line up. now, comparing them to the crank timing mark is another story. that means taking off the timing cover.

09-25-07, 10:15 PM
i checked the compression on all cyls. all the same, about 155-160psi. of course that does not mean the timing is right. i put in new plugs and rechecked my plug wires and took it for a drive and it seems better. the miss seems gone. i wound it up to 5k and did some power braking and no more miss/pop. maybe it was ignition related. could have been a crossed plug wire?

09-25-07, 10:18 PM
could have been a crossed plug wire?
Possible. You wouldn't be the first.