forgive me for posting this b4 looking up the code, but as some know, the last 2 weeks i've been fighting a driveability issue on my DD '84 Fiero and have been bicycling wherever i need to go. well, i spent the weekend watching tmy folks' dogs so they could go to St. Louis, and doing drywall finish work on their basement. i just got back home now, and went to pull the Fiero into the driveway, as i was going to clay bar it today as it seems like a decent day to do so here (cool & cloudy). well i go to fire it up on the street, it starts just like normal, only thing is it wont rev past about 1500 RPM...so i sit there, ease into the throttle, it's stumbling and all that fun crap, but finally revs to about 4k (where i usually shift it) comes back down and will hesitate upon free rev again. check engine light is on so i pull the code, it's poppin code 42. i will look that up momentarily. it's turning into a headache and to be quite honest, i was VERY happy with it when i parked it again after swapping the coil out one weekend, then the ICM late last week, re-timinh it, it seemed to perform better and my slight miss that was occasionaly there (would come and go) was totally gone. i have the base timing set at 12* adv. seems to like it, i'm wondering if i could go more...

any ideas anyone? i plugged everything back in, there wasn't anything i missed. i triple checked that...

i'll post what code 42 is here: Electronic Spark Timing
The ECM will set code 42 under the following conditions:

The ignition module will ground terminal B4 (EST) on the ECM when the system is (supposed to be) running on the ignition module. If this does not happen (ECM is seeing a voltage on terminal B4), the ECM will set code 42.
When the RPM for Electronic Spark Timing is reached (400 RPM) a by-pass voltage will be applied to the ignition module, and the ignition module should no longer ground EST. If it still does, the ECM will set code 42.

There are several reasons any of these conditions can occur. The most obvious is a faulty ignition module. Check all wires coming from the ignition module. Also check your sparkplug wires. Because a high voltage is applied to the sparkplug wires, there could be electro-magnetic interference. Replace sparkplug wires or try rerouting them
taken directly from the main page.


the only thing i can think of is i had a slight problem with the 2 black wires coming off the ICM that go to the coil., i didnt realize that plug came apart @ the coil so i cut the wires (they had already been cut once and weather proof connectors put on them.) when i went to put them back together i pulled one wire out of the terminal @ the plug by accident...could i have wired them up backwards and still have it run? or is there a chance my ICM is bad already?

[This message has been edited by greasemonke50613 (edited 08-10-2009).]

Oh great, the code 42 from heck and beyond.

I've dealt with this code before. In the most simple terms, it is a grounding issue in the ignition system. Pull the ICM and have it tested at least 3 times. Look for corroded ignition connections. The ICM mounting plate on distributor must be clean, use heat sink grease, the ICM grounds through the mounting screws, those must be clean and secure. Double check your negative (-) grounds, you know battery to block, block to deck lid hinge mount, battery to frame (battery tray). Make sure that the distributor makes good contact with the block too. Make sure that you are using the correct spark plugs, they are gapped properly, dielectric grease on the plug boots all around. If you have older wires, you may need to replace them, any high voltage leaking will interfere and cause problems. If you can get it to run, with a glove, spray a very fine mist of water at your distributor, if you get a light show, that's an indication of voltage leaking. Even if you don't get a light show, try to route plug wires, keep them away from the ICM area.

That's about all I can offer besides moral support, each code 42 seems to have it's own little nuances.

I'm sure others will chime in here for you.

I'd like to try to help, but the earliest service manual I have is for the '86, and what it shows is that there should be two pink wires, and two white wires going from the ICM to the coil (no black wires). Hopefully the '86 is similar to the 84, so I'd follow both of your black wires back to see if you can verify a different color other than black, then post what you find. Regardless, it looks as if it would cause a problem if you mixed up some of those four wires.

i can tell that this one's gunna be a doozy...i just got back from a drive with it. it ran like a top, no hesitation or anything. period. no CE light, nothing. SOAB.

You should do the preventative stuff that Jetman posted, and trace back the coil wires. Unfortunately intermittent faults are very difficult to troubleshoot until they set up as hard failures. I'd look for obvious stuff now while you can control the circumstances rather than wait until it happens again at night on a deserted back road far from home.

well...it's raining like mad right now, like usual later in the day lately. i'll pull the car in the garage within the next couple days and take a closer look at the wiring and all that to make sure i get it right.

i'll def be at it in the morning tomorrow, bloozberry @ least this is something that intrests me instead of annoys me like those damn headlights lol.

Still haven't figured those headlights out yet hunh? In my neck of the woods they call electrical stuff "FM".... stands for Friggin' Magic... or something close to that anyways, if you know what I mean. Too bad you're not closer, I'd zip over and give you a hand.

blooz, you have PM. i had another idea on those lights. i'm sure i'm crazy again about it, but their pissing me off...