: # 2 cylin misfire

03-25-10, 02:37 AM
whats up guys just wondering if a broken intake plenum gasket can cause the # 2 spark plug not to fire.i checked everything fuel pres,injectors,canged coil bank,compression test ,spark plugs i cant figure out why # 2 spark plug wont fire also my o2 sensors are reading very low between 50-60 any insight is appreciated

03-25-10, 09:28 AM
A cracked plenum (the bottom of the rubber bellows area, #2 in the manifold drawing) usually causes O2 sensor codes, not a single miss. Start the engine and remove the beauty cover. Squirt a tad of choke cleaner down under the plenum clamp - any idle speed change is a cracked plenum. Dealer item only, $43. You can do the change with hand tools and an inch/pound torque wrench - all morning. The intake manifold bolts require 89 in/lb of torque - that's not much.

A single miss is one coil in a cassette has gone bad, a tracked spark plug connector boot, a cracked plug insulator, missing plug ground electrode, bad fuel injector, faulty ICM (one in each coil cassette), or PCM ignition or injector trigger signal.

Use the sticky thread at the top of the main Northstar Performance or Seville Forums page titled "How to pull codes" - read the entire post and use the links to decipher any OBD-2 codes found.

03-25-10, 09:44 AM
thanks submariner im going to spray the plenum today asnd see what happens

03-25-10, 12:12 PM
sprayed plenum no change in idle i changed front coil bank about 6 months ago is it possible i got a bad coil bank. it is a delphi

03-25-10, 12:58 PM
Not to likely. Listen to the injectors with a stethoscope or rubber hose and see if no. 2 is not pulsing like the others.

03-25-10, 01:18 PM
all the injectors workin properly listened w/ a stethoscope and ran a test with a tech 3 code reader

03-25-10, 02:41 PM
Fortunately the front coil pack is the easier of the two.......check the plug boots for good contact and "tracking" - hairline black carbon lines either on the inside rubber surface or on the plug insulators.

03-25-10, 03:39 PM
tomorrow i will swap in a new coil pack and see wht happens keeping my fingers crossed and thanks alot for your help

03-25-10, 08:55 PM
Yeah - Sub is on the right track - he brought it up twice, but in case you didn't notice - make sure you inspect or better yet change out the boots also

03-26-10, 09:06 AM
i moved the boots around and it stil comes back to # 2 cylinder i will do a new coil bank this afternoon i will be back with results thanks guys

03-26-10, 01:32 PM
changed the coil pack no change ses still on and miss on #2 cylinder my mechanic think its the intake manifold gaskets or maybe the plenum. i will buy both gaskets tomorrow and give it a try any input is appreciated thanks