Mechanics

QUAD 4 NOT FIRING 1 & 3

1994 Pontiac Grand Am

My 1994 Pontiac Grand AM 2.3 Quad 4 lost power on me on my way to work and then would not start again. Once I got it back to my house my cousin, who is a mechanic of 15 years, and I tore into it. We checked “almost” everything there is to check and still couldn’t figure this one out. It has 158000 miles on it by the way and we got it to start once we replaced the lazy starter. The problem is when you pull the #1 and #3 plug off of the injectors nothing happens, but the #2 or #4 plug kills the engine. We have good compression, spark on all four plugs, pulled the fuel rail and have good mist on all four injectors, changed the crank sensor, since it broke on us, checked for continuity in the coil housing and swapped out with another “old” one, changed the coils with two different “used” sets and swapped them around all three times, swapped out the computer with another one “from another quad 4 ‘same year, ’” changed the plugs, checked the boots “good condition almost a year old” same problem. The only thing we can think of is the module but that is a $160 guess and we tried another “old” one. There is no CEL on; would a bad module through a code? Is it worth spending the money for a diagnostic $90 + getting it there? We are both stumped. We’ve got spark, gas and air but no fire. What else does #1 and #3 have in common? Please HELP! Thanks.
Avatar
Gm problems2
April 3, 2006.




You have a bad coil pack for those cylinders

Tiny
Losone
Apr 3, 2006.
I have swapped out the coil packs (six of them) and it is always the same cylinders. I am also getting spark on all four plugs.
AD

Tiny
Gm problems2
Apr 3, 2006.
Sounds like you have an injector problem. Check for 12V on each injector gray wire. It comes from the oil pressure sw with key on and oil pressure above 7 lbs.

If you have voltage you will need a noid light to check for a ground pulse from the computer. The computer has two outputs that pulse the injectors. 1-3 and 2-4. You can't check the ground pulse with out a noid light because it will load the computer circuit.

The outputs are on C-10 and C-12 of the computer. I strongly suspect one of the two problems.

Broken 12V connection to 1-3
Bad computer output for 1-3 pulse

It can't be the module because it provides reference to all 4 injectors to the computer (2 wires lo and hi on pins D-8 and D-9)

Let me know

Tiny
Losone
Apr 3, 2006.
We removed the fuel rail and all four injectors were spraying the same. We did find a cross fire in the coil housing between #1 & #3. We replaced the housing with another one " old" but good and still have the same problem.

Tiny
Gm problems2
Apr 3, 2006.
We found that the coil housing was cross firing or fused becaused when we ohmed out the contacts we got a reading between # 1 & #3 on two of the coil housings that we tried. We suspect that the good housing is also cross firing but not bridged yet. We are going to run a test when I get home I ll let you know.

Tiny
Gm problems2
Apr 4, 2006.
Injectors are hard to check without being installed. The noid light is a simple easy check to make. The injectors might be spraying in a static mode but not under pressure. Good luck

Tiny
Losone
Apr 4, 2006.
FIGURED IT OUT! It was the coil housing. Thank god, it only cost $38, and 6 days. I read somewhere that quad 4's were notorious for the ignition housings to burn out. The housing we had ohmed out just fine but it was bad never the less. The thing that made us suspect the housing was that #1 & #3 contact points were just a little off color. They looked a little more yellow, like they were heated up. So we took the plunge and bought the housing and purred like a kitten it did. Thanks for everyone's input, you guys are great.

Tiny
Gm problems2
Apr 4, 2006.

AD