My 98 gt seems like its running on 3 cylinders. No codes present, I checked the timing and its good. It had an o2 censor code so I replaced it but no change in his it runs. I'm wondering if a bad head gasket would not throw a code.

 

Thanks

Dp213

how old are the plugs and plug wires? Is there any oil on the plug boots?

No oil on them but not sure how old they are

move the wires around if they'll reach and see if the misfire follows the wire. Some folks have found arcing by water-misting the coil and wires of their idling engine at night. If the easy tests don't find anything, might need a compression/leakdown test or drop the exhaust manis and see if a valve guide has shifted?

Edited August 26, 201411 yr by 1 Lucky Texan

MAF

 

if it idles fine but has on power when you step on the gas

Edited August 26, 201411 yr by lmdew

Is it shaking/ shuddering like its misfiring?

Or not firing on all cylinders.

if you think it's a single dead cylinder, carefully pull the plug wires one-at-a-time. The wire that doesn't kill the motor/makes the least difference in idle = the bad cylinder.

Looks like #1 & #3 aren't firing. I changed the plugs, wires, and distributor. No change.

The cylinders fire 1-2 and 3-4. If both are not firing on the same side, look at the timing belt, has it jumped?

Timing is good. I thought the firing order was 1,3,2,4.

If it has no distrubutor (which it shouldnt) it has coil packs, which are waste spark systems. In a waste spark system the coils will fire in pairs, hence 1-2, 3-4. It gets a little confusing, ignition order (firing) is as you said.

Firing order is 1-3-2-4

Plugs are fired in pairs 1&2, 3&4. The coil fires both plugs at the same time. It's a waste spark system. One plug fires on tdc compression, the other on tdc exhaust stroke.

 

Cylinders 1&3 are the right half of the block so if those are misfiring the problem could be jumped timing.

Have you thrown a vac gauge, or done a compression test yet? 

 

What are you calling a distributor ? 

My bad. Coil pack. Had the blazer on my brain for a second

Doing a compression check after work tomorrow and going to see if I can find a vacuum gauge also

put a dollar bill very close to the exhaust.  if it gets pulled back into the pipe while running you have a bennt valve or hg leak