GM's parts site (and everywhere else) seems to list the d1984a as the proper replacement part # for the Formula's ignition control module, although the d1943a is the one listed for all the other '88s with the 2.8L v6. The only difference I can see between the two parts is that the d1984a is more expensive and the d1943a is "w/o HEI". I haven't been able to figure out exactly what that means-- is it a feature of the ICM or a feature of the vehicle's overall ignition system that needs to be compatible? My understanding was that the Formula is just a GT with notchback styling (and less options included by default, but still available).
On a related note, does anybody know what brand parts the Fiero Store's distributor ships with, or have an opinion on it (or other vendors' "complete" distirbutors)? I'm looking at probably needing to replace the pickup coil in addition to the ICM, and might as well get a new cap and rotor while I'm at it, so just buying the whole assembly is looking like an attractive option.
FWIW, I'm getting a code 42, car now won't start, but started the other day (from a jump after stalling out halfway down the block) and drove for ~50 miles throughout the day. Last week I replaced a leaky heater core and flushed the coolant, did spill a little antifreeze by the thermostat housing when filling it back up, but have had the code 42 for longer than that. I tried to check the ignition system with a multimeter per those instructions that are floating around online, I think the ICM is definitely bad but the whole distributor assembly is looking sketchy. The holes for the mount/ground screws, and the connectors between the ICM and pickup coil were corroded as seen here:
And the rest of the pickup coil is not looking so great either (looks like the connector clip is disintegrating too):
Just trying to get this all done correctly in one go so I can get my workhorse back on the road. Obviously money is an issue, but I am willing to spend what it costs to get it done right.
EDIT: and yes, the ICM I removed is made by Standard, not AC Delco, which is why I'm not sure which part # to get to replace it with.
[This message has been edited by echocharliepapa (edited 07-19-2022).]
...the connectors between the ICM and pickup coil were corroded as seen here:
CLICK FOR FULL SIZE
IMO, those corroded terminals alone could be causing all your issues. Clean them up, put some dielectric grease on them, put some fresh thermal compound between the ICM and distributor base, and see what happens.
The surface rust inside the distributor is normal. It's caused by the ozone being produced by the high voltage inside the cap. Your distributor looks pristine compared to how mine looked years ago.
Doesn’t even look like there was ever thermal paste on it. Looks like the magnet is cracked too…..more than likely it wouldn’t idle right. Card one made a new…not rebuilt, distributor that was complete and the magnet portion is improved. I bought one from Rock but now I see they only have rebuilt ones…but they are improved.
So a little more context, I have been having some overheating problems too, both leading up to the heater core replacement and following it. Tons of nasty crap in what I had drained-- and caked on the inside of the overflow bottle-- leads me to believe someone had gunked up the coolant system with stop-leak which caused a blockage in the heater core that allowed pressure to build up and the car to chronically overheat until it sprang a leak. After clearing all that out and putting the new core in, I didn't notice at first that the seal on the radiator petcock was deformed, because I put the stem back in blind reaching under the car after I had flushed the system with water. It didn't feel right by touch, but it was holding fluid without dripping so I stupidly thought it was fine. That caused it to dump most of the brand new coolant I had put in it all over the road once the system was under real pressure and not just being burped in my driveway. I limped the few miles back home a couple hours later, but it got dangerously hot while I was trying to get it to a safe place to park first. The lesson I chose to take from this experience is to check *everything* when working on a particular system and replace anything iffy.
Anyway, I figure all that extra heat (in the middle of a heat wave here, too) finally killed the ICM that had already been acting up intermittently beforehand. There was a *touch* of thermal paste on the underside of the module, but it looks like it was the clear stuff, and it was not spread evenly. This car is a survivor not because it's been well-maintained, but out of sheer stubbornness. I've decided to stop taking it to other people to have work done, unless it's something I don't have the tools or garage capabilities for. It may sound like I'm an idiot who doesn't know what he's doing and is going to ruin this car, and that may be true, but I think at least the fact that I care about it (been in my family since the early 90s) makes me a better person to have working on it than a tech who wants to get it rolling out of their shop so they can move on to another vehicle. I try to pay attention to how it operates after I've done work, I just don't always know what to look for. I am hard on this vehicle, it has been a food delivery workhorse for most of the decade or so I've owned it, but I also try to address issues when they arise if I can.
And the rest of the pickup coil is not looking so great either (looks like the connector clip is disintegrating too):
On mine, that plastic clip was so disintegrated it had broke in half and got lost years earlier. Those two wires were attached to the module just by the little metal tabs! Sort of friction fit. Eventually I started having issues and while attempting to investigate, I realized the two wires were so faded and burned (by the ozone?) that I could no longer even tell them apart. Time for a new pickup coil!
If there are many cracks it will make a difference. A mechanic I used to deliver parts to had a 88 that they could not figure out why it ran so shitty… he replaced so much stuff, entire exhaust, complete tune up, numerous sensors….finally a year later they replaced the whole distributor and it ran like new.. I seen the dist…the magnet had a ton of cracks. I have two spare dist and both of them were cracked.
Get parts from Real Stores w/ a Warranty you don't have to ship defect parts etc. AZ and others can order Online to get whatever discounts and free shipping then return cores and other returns to local store. AZ and some others track warranty by phone no and go to any store not just same store you got a part at. (Unlike Pepboys before they close stores to only service cars.)
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Get a new AC Delco magnet pole from RockAuto. At the same time but a new ICM D1943A, plus distributor cap,rotor and pick up coil. See how the car runs. Get all AC Delco parts. You can clean the 6 pole terminals with sandpaper. As a perfectionist, I would buy new spark plugs and good set of wires for extra durability and reliability.
Get a new AC Delco magnet pole from RockAuto. At the same time but a new ICM D1943A, plus distributor cap,rotor and pick up coil. See how the car runs. Get all AC Delco parts. You can clean the 6 pole terminals with sandpaper. As a perfectionist, I would buy new spark plugs and good set of wires for extra durability and reliability.
All these parts you can get at RockAuto.
Hope this helps.
What do you mean by magnet pole? I am not seeing anything by that name on RockAuto. The closest I can think is what's listed as the "distributor shaft": https://www.rockauto.com/en...60&jsn=2460&jsn=2460
What do you mean by magnet pole? I am not seeing anything by that name on RockAuto. The closest I can think is what's listed as the "distributor shaft": https://www.rockauto.com/en...60&jsn=2460&jsn=2460
I went out and checked the magnet, it is not cracked that was just some rusty crud and shadows on the photo I took before. So in that case, I probably shouldn't need a new magnet pole/shaft, yeah? I am thinking I am probably going to need to replace the pickup coil still though, it looks pretty corroded all the way around. I'll try to clean things up with an old toothbrush and some compressed air first and see how we're looking then, because I'd definitely rather not remove the whole distributor assembly from the car if at all possible.
First, I appreciate all y'all's input. After consideration of everything you guys said and taking a closer look at the condition of what I currently have in the car, I ordered a new ICM (D1943A), pickup coil, cap, rotor, and spark plugs and wires for good measure. Ordered from RockAuto because they had AC Delco parts in stock for everything but the wireset and their prices are far better than what I can get for mostly aftermarket options at local brick-and-mortar shops. Should be arriving in a couple more days, I'll update the thread with results when I get the new parts in the car. Considered just doing a drop-in replacement but I'd rather keep the OEM style distributor for now, although I may order one of those Cardone units later to keep in the garage as a backup.
Back to the ORIGINAL question of this post. Bumping this because I have an AC Delco D1984A ready to install on my '88 GT. I too see that there are 2 different options listed for the Fiero in the AC Delco brand and bought the more expensive one just because it was not that much more. Anyway, is there a known difference other than cost to the compatibility or durability? Thanks!
Back to the ORIGINAL question of this post. Bumping this because I have an AC Delco D1984A ready to install on my '88 GT. I too see that there are 2 different options listed for the Fiero in the AC Delco brand and bought the more expensive one just because it was not that much more. Anyway, is there a known difference other than cost to the compatibility or durability? Thanks!
I'll be the other side of the coin in your experiment..... I just installed a D1943A in my 88GT.
So far, so good! Car runs great. I have no idea what the difference between the two modules might be.
Late bump, but I thought I should follow up with what happened. Parts arrived from RockAuto, took the distributor out to replace the pickup coil and found the shaft did not want to come out of the rest of it (may have seized up from corrosion or I may have bent it trying to tap out the retaining pin). Decided to just order one of the complete Cardone distributors. RockAuto site was bugging and wouldn't process the order or bring me to a confirmation page, just kept returning the browser to the (full) shopping cart. Originally may have had an issue with the billing address for the card, but cleared that up with the bank and it still wouldn't go through. So I ordered the parts from Summit instead, where actually the total was cheaper and shipping was faster. Not half an hour later I get a confirmation email from RockAuto. Go to the site to cancel the order and the part is already "processing" for shipment, can't stop it (even though it doesn't ship for another day).
A few days later, the Summit shipment arrives, I swap out the distributor and it starts right up, running okay. Need to get a flex-head ratchet to tighten the bottom bolt all the way, but it's in and running. Learned my lesson on why RockAuto is so cheap, I know some of you warned me but I guess I had to find out for myself. Customer service is practically non-existent, consists solely of an automated system on the site where you select your issue from drop down menus and none of the options pertain to my problem (the order was processed even though the site did what it said would happen if it was NOT processed, which was return me to the shopping cart page). No customer service address to email, no representatives to talk to on the phone. Too fed up with the experience to bother with a return, so I guess I've got a backup distributor assembly in the garage in case I need it later.
Now I just need to fine-tune the timing, replace the plugs and wires, figure out what's going on with the transmission (started being loud out of gear and the clutch pedal needs to be floored instead of finding the sweet spot like I had to before), and probably half a dozen other things before I can justify moving on to cosmetic fixes.
That is the downside to using Rockauto. ZERO customer service. Typically I'll use RA to obtain a part number, then i'll search the part through any other online service and local chain.
