Ignition blues: quad 4 1993

93 Grand AM SOHC Quad... Driving along and the engine severly stumbled; barely made back to the house (approx 5 miles). Cat was glowing red so I figure it was dumping unburned fuel through it. I replaced the coil housing(AKA what would be the distributer on a regular car)... no workie. I Ohmed the coils and found 1 bad and 1 "ok"... so i replaced them both... non effective. i thought maybe i jumped a tooth on the timing chain (220K so far) but i understand these engines eat valves when that happens and i have 185 to 195 cranking compression. does any one know of any thing else other than the $200 ignition computer? I also tried the water coolant temp sensor...nope. thanks in advance for any all advice.

Will the engine rev up or does it act like can't reach 2-3K. If so then the issue may be the cat itself. If it revs then I would start with the plugs and then the injectors. If the injectors are sticking they can dump raw fuel into the cat. Also if the plugs aren't working efficiently that can happen too. Finally, I thing you would be surprised at the cost of a new ecm for this car. You can try car-part.com for a used one or try advance or autozone for a new one. I got one for an 88 Cimarron for $100, refurbed but it worked great.

Good Luck and welcome to AF!!

It does sound like a catalitic converter issue, pull the exhaust off and see if that helps, try the cheap stuff first! Check for spark, all it takes is 4 plug wires & and an old spark plug or spark tester. Find the problem then use your money to fix, I tried thowing money at one of these cars, it never quits taking it! Your Ignition Control Module can be checked by autozone! But first find out where you have spark & where you don't, post that and we'll help you narrow down your parts.

Could also be a bad Oxygen sensor, did you get a service engine soon light? If you did you can have the computer scanned to help narrow down the search.

I have a 1998 Grand AM quad 4, it started missing bad. I've replaced the plugs and boots. My check engine light is not coming on. A friend of mine said as bad as it's missing I should have some type of reading. My check engine light appears to works because it lights up with the other lights before it starts.
Could my computer be bad? Would a scan pick up the problem even if the ck engine light is not coming on?

Thank you

I have a 1998 Grand AM quad 4, it started missing bad. I've replaced the plugs and boots. My check engine light is not coming on. A friend of mine said as bad as it's missing I should have some type of reading. My check engine light appears to works because it lights up with the other lights before it starts.
Could my computer be bad? Would a scan pick up the problem even if the ck engine light is not coming on?

Thank you

You could stop by an Autozone and have the car scanned for free, it might help you narrow things down a little. If that doesn't help narrow things down id check for spark on all 4 cylinders, 1 missing spark is usually a coil housing, 2 missing is usually a bad coil .... good luck and keep us posted.

Thanks for all the replys...
checked the exhaust: it's not the cat. I also checked fuel pressure... 46 (key on) & 38 running (per spec). A more defined symptom has appeared; it will be running like crap underload (moving uphill) and then all in the sudden it runs great for about 2 seconds and then goes back to trying to die. I tried disconnecting (one at a time) the IAT, Coolant temp, and the MAP. All of them turned on the Check engine light and made the car get WORSE. Again, at idle, it runs good (most of the time) and it revs freely. Under load (slight hill) it falls all over it's self. Thanks for all the advice thus far... if any of you have any better ideas before i buy that damn ignition computer ($$$), please let me know.

You may want to check the injectors. This sounds like they are going bad and are experiencing high impedance and not allowing fuel to go into the engine. Happens with high mileage engines and will exhibit the symptoms you indicate. Worth a try although a little expensive. You could try a u-pull it junk yard and get a set for a few dollars.

I thought I'd post the end result: I decided that it won this round and ws going to take it to the mechanic (it might make a mile or two). When I went to put the dash together (it was apart for main computer access and general wire harness survey), I had a sad time getting the harnesses positioned back where they are supposed to go. But when I started the car... it ran fine. It has been running for a while now... So i likley have a short somewhere and I am living on borrowed time. Thanks.:banghead: