1990 2.5 NO spark in plug #3 and #4

Everything was fine except some really bad MPG. One morning it just started refusing to drive right. It was starting but dying when it was put in gear, and stalled at stops.
Have replaced MAP, spark plugs , spark plug wires. IAT, checked injector, oil change, fluid and filter change in tranny, PVC(?) valve. . Checked for spark and there is NO spark in #3 and #4 plugs. If I put B 12 in gas it goes better.
Was getting codes for 33 which is MAP after installing new MAP. MAP is brand new. all lines to MAP are fine.
why are spark plugs 3 and 4 not getting spark?
Now we are not getting any code other then 12 keeps repeating itself.
Can this be an ignition fuse and if so where is it located at?
I forgot to mention it is back firing like crazy and it is getting worse,. I just tried to go to corner store, it made the trip and refused to go more then 5 ft on the way back finally had top push it. on teh few times it actauly stays started it dies when i put it in gear. Timing?

Barb

Welcome Aboard!

There is an IGN fuse but failure of that will cause no spark to any cylinder. It's odd that cylinders 3 and 4 are "dead" since the ignition coil pairings are for cylinders 1/4 and 2/3. Because of this, if cylinders 1 and 2 are indeed firing the plugs, both ignition coils are operating.

Make sure a proper tester is used, since this wasted spark system can exhibit some strange behavior with faulty secondary parts like wires and plugs.

I would verify that the secondary wires are intact (approximately 1,000 ohms/foot ) and that the plugs are properly gapped and not fuel or oil soaked. Since each coil fires both sets of plug simultaneously, there must be some continuity.

Brand new no gap hi capacity spark plugs and wires

I forgot to mention it is back firing like crazy and it is getting worse,. I just tried to go to corner store, it made the trip and refused to go more then 5 ft on the way back finally had top push it. on teh few times it actauly stays started it dies when i put it in gear. Timing?

Barb
add on

Welcome Aboard!

There is an IGN fuse but failure of that will cause no spark to any cylinder. It's odd that cylinders 3 and 4 are "dead" since the ignition coil pairings are for cylinders 1/4 and 2/3. Because of this, if cylinders 1 and 2 are indeed firing the plugs, both ignition coils are operating.




Plug wires routed wrong? I once bought a very sick Olds convertible the previous owner said it needed a valve job or something. When I put wires and plugs in it, it ran worse.

Realized someone had wired it SB Chevy firing order instead of Olds. Switched everything around and it ran like a dream, nothing wrong with it.

Wouldn't think you'd get four wires mixed up, but stranger things have happened. Perhaps there is one dead coil and the wires are going to the wrong cyls...?

What a mess...it would run about as bad as stated...

PS, it's throwing codes for MAP because of the intake backfire, most likely (sudden positive pressure in the intake out of range)...I really wonder if you have some wires mixed up...

Plug wires routed wrong? I once bought a very sick Olds convertible the previous owner said it needed a valve job or something. When I put wires and plugs in it, it ran worse.

Realized someone had wired it SB Chevy firing order instead of Olds. Switched everything around and it ran like a dream, nothing wrong with it.

Wouldn't think you'd get four wires mixed up, but stranger things have happened. Perhaps there is one dead coil and the wires are going to the wrong cyls...?

What a mess...it would run about as bad as stated...

PS, it's throwing codes for MAP because of the intake backfire, most likely (sudden positive pressure in the intake out of range)...I really wonder if you have some wires mixed up...

Let me throw this at you and see what you think. Haynes chapt 1 says spark plug firing order is 13 42 for 4 cylinder cars. Chapter 5 says firing order is 14 23. if your right that would make sense. Will try it and see what happens

You made three mistakes. First, you took the job. Second, you came light. A four man crew for me? F**king insulting. But the worst mistake you made...

...empty gun rack.


love your signature.. LOL

Barb

UseDaGreyMatter,

Is the plug wires correct from what the book says?

UseDaGreyMatter,

Is the plug wires correct from what the book says?
Which chapter 1 or 5?

OK would the plug wires being messed up explain why when it has B 12 in it and will run we cant get it past 55 unless we are on a downhill slope and then it will start backfiring?