Do you not want to simply install an aftermarket ECU in the place of the stock computer? This could require very little wiring work... essentially cutting off the stock ECM's connector, and terminating the wires with the correct connector for your choice of aftermarket ECU.
I think it's possible to install a bigger injector in the stock TBI.
There are many versions of the Iron Duke some putting out 110 HP but IIRC that was a higher compression version. Spending $750 on a new TBI unit that may prove to have a minimal increase in power may end up being a big expense for very little. I have not studied the evolution of these engines very well but in the junk yards you may find later Duke engines with a larger throttle body and a less restrictive intake. These may or may not bolt up (depending on your model year) so some research is required. IMO, that would be the more cost effective solution for a bit more horsepower.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Thanks for the ideas but I'm running the notorious '84. I don't know of many aftermarket ecu or wiring harnesses I can replace the stock with. I've spent over twice that amount $$ for the sniper in trying to diagnose and fix a longtime issue with idling with both my stock TBI and with my Holley 3739 I have on it now. Just thought it may be the time to take another path to resolving an issue that has plagued me for a very long time. I know it's a good engine cause I had the upper half rebuilt 4 years ago. The sniper lets me replace all the old with new. I'm thinking of doing at when I drop the cradle to refresh the engine bay this winter.
Originally posted by snyderman: I don't know of many aftermarket ecu or wiring harnesses I can replace the stock with.
MegaSquirt, Haltech, AEM and that sort of thing come to mind. I'd expect that they would work with the stock HEI distributor, and the stock TBI unit.
The stock Iron Duke is pretty simple to control; I think that pretty much any aftermarket computer would have the required number of inputs/outputs to run a stock Iron Duke.
[This message has been edited by pmbrunelle (edited 09-08-2020).]
If you currently have the factory Distributer with a carburetor (holley 3739) how are you currently handling spark advance? The Factory Dist. is advanced via the ICM with the ECU, an HEI distributer would normally use a vacuum advance (something from a carb'd Duke: 1979-1981.
pmbrunelle- Thx for your help, but your 3 recommendations are all in the same price range (or more) and are not self tuning as the sniper is. I think I'll stick to my plan.
da.slyboy - they are from a 2002 Jetta with 225x45x17's. Direct fit. I think they are Monte Carlo.
fierowannabe - Sorry if I didn't explain things correctly but I'm running a 3739 TBI on a matching Holley intake so there was no distributor to change and I'm still running stock.
RWDPLZ - Yes that's exactly it.
[This message has been edited by snyderman (edited 09-09-2020).]
pmbrunelle- Thx for your help, but your 3 recommendations are all in the same price range (or more) and are not self tuning as the sniper is. I think I'll stick to my plan.
da.slyboy - they are from a 2002 Jetta with 225x45x17's. Direct fit. I think they are Monte Carlo.
fierowannabe - Sorry if I didn't explain things correctly but I'm running a 3739 TBI on a matching Holley intake so there was no distributor to change and I'm still running stock.
RWDPLZ - Yes that's exactly it.
My mistake, i thought you had been running a 2 barrel on the stock duke. It all makes more sense now.
What exactly is the idle problem you are having? Assume you've already changed out the IAC and TPS???? If the problem is caused by something like a vacuum leak, then this won't fix the problem. Also, Self Tuning is not always all its cracked up to be. I think Fierosound first tried a self-tuning setup on his SD4, only to find it didn't work even after hours with their tech support.
The issue that I've had for the last 12 years I've owned it is high, uneven idle, and always running rich. I've changed everything except the wiring. This includes the ecm and prom at least twice. I rebuilt the head, added a new intake and Holley TBI and no change so I know it's not a vacuum leak unless that can come from the bottom of the engine which I have never touched. I even took it to a GM dealer that used to sell Fieros and they also were stumped. I know when to cut my losses so I'm going to take a new direction and will try the Sniper. I'll let you know how I make out. Thanks for all your interest.
My hunch is that you will solve nothing.. sorry to be blunt. Can't you monitor your ALDL and see what is happening? Look at short/long term trim? At least verify leak/no leak? Play with propane and tell us the results? The stock TBI if working correctly would not account for your idle behaviors.
Regarding the self-tuning aspect, I wouldn't get too worked up over that. That's just for fuel trims. "Self-tuning" is marketing wank IMO.
I looked through the pdf instruction manual available online, and there are plenty of settings to be adjusted; settings which do not self-tune.
I'd say that I went through 50 hours of my time and 500 litres of gasoline to get a good tune on my Fiero's programmable computer (MS3) this summer. I did this over approximately three months.
Experience of the tuner and complexity of the car/engine will affect the time needed to get a good tune.
I suspect that you have a good amount of work ahead of you!
[This message has been edited by pmbrunelle (edited 09-11-2020).]
My ALDL is pulling the code 51 which is a bad prom. I changed it out using 2 others so it may have been my ecm so I changed that out too. So even if it was working what code would help me find any leak as I think that's what your suggesting...no?
My ALDL is pulling the code 51 which is a bad prom. I changed it out using 2 others still the same. So thought it may be a bad ecm so I changed that out too. So even if it was working what code would help me find any leak as I think that's what your suggesting...no?
In the past, I borrowed an old code reader that had an ALDL reader plug in.. and discovered that the intake temperature sensor was bad.. who knew. So if possible, read all of the ALDL data to see what it is doing. I believe that someone here on the forum sells an ALDL reader system? But I forget the details. If you can dig out any real clues, then maybe we can point you in the right direction.
I have an 84 with the same high idle issue,...changed the iac, tps, sent the tbi off for check and refresh,....replaced all vacuum lines,...checked with pressurized smoke for leaks,..and am convinced its in the ecm. I've got a Sniper on a 383 that I built 3 years ago, and it's nothing but smooth sailing,...couldnt ask for anything better,....so now considering the Sniper swap for this. Is there any updates on how this went?
I've been running the sniper for a couple of years now and it's the best thing I did. It fixed all of my issues I was having, including high idle, stalling and reliability. I ended having Scott Clark at real tuners do a remote tune and it's never run better. I am not using it to control my timing so I see need the ECM, but it was worth the investment and I recommend it. But that's just me - I prefer new technology to old.
Originally posted by snyderman: Scott Clark at real tuners do a remote tune.
You are a lucky guy! That same Scott Clark promised me a tune for my MS and after I paid him $450 for the tune he never delivered, took the money and ran. Nice car by the way!
You are a lucky guy! That same Scott Clark promised me a tune for my MS and after I paid him $450 for the tune he never delivered, took the money and ran. Nice car by the way!
You got laid on that deal. $450 for a mail order tune is highway robbery
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Holley 3739 is the family name for the Holley 300 series replacement TBI's, like the Fiero's 500-1
I cringe whenever I see pictures of this Holley TBI unit... the reason is, I had one, and completely gave it away. I had a 1984 Fiero 2m4 SE that I bought back in 1997 for $1k... it was really nice. But as a kid, it had to sit in the South Florida sun as I didn't own a house at the time, and the sun basically destroyed the paint and seals. Eventually, I gave the entire car away for a bottle of rum in like 2003 or something. Along with it, I gave away a Holley TBI unit that I'd bought new. It had less than 1,500 miles on it. I thought to myself... "I'm never going to own another 4 cyl Fiero, probably not an early Iron Duke at least..."
Now, my daughter has a 1985 Fiero 2m4 SE in which this would have dropped right in.
I just checked eBay really quick again before posting this. They are so rare now, that I wouldn't even believe they existed unless I had actually had one previously.
P.S. I'm not changing the engine. So don't bother trying to take me in that direction Thx.
So, just wanted to address this... as I'm currently going through an Iron Duke rebuild with my daughter (we actually just finished it last weekend). Is your desire to keep a stock look, or you don't want to go through the hassle of changing out the motor? I ask because if you want to keep a Duke in there, there were several enhancements over the years.
Mid-1985 and up got a roller cam, which is quieter, and typically takes less wear. 1986 I THINK got a new intake and TBI unit. 1987 got an entirely new belt-drive system (serpentine), along with DIS ignition. 1988 got a new balance shaft which improves "smoothness of the engine," along with a different crank, pistons, and rods.
Each year saw a culmination of the previous year's improvements that went from 92bhp as a rackety "Iron Duke" tractor motor in 1984, to a much smoother running 98-100hp "Tech-4" in 1988.
So if you're OK with swapping out Duke motors, there's a lot of improvements you can get. I'm rebuilding my daughter's 1985 motor (which has a roller cam), and there are several improvements we're making, including replacing a LOT of the accessories (see this video here):
... bottom line (what you should take away from the video), every single one of the belt accessories has a more modern replacement that will literally "bolt in place."
Another thing you can also consider doing is replacing all of the pulleys with a 6-groove serpentine pulley, and you can literally have a serpentine belt system, using the alternator as the "tensioner" as you would similar to with a V-belt.
All of that said, my personal opinion, you could swap out the ECM with a new MicroSquirt system and eliminate a lot of the inherent drivability issues ... or so I've heard. I'll be doing this with my daughter on her car this summer.
EDIT: re-reading the thread, I understand all of what you want to accomplish. I agree somewhat with PMBrunell, though I'd recommend a MicroSquirt, specifically, this kit: https://www.diyautotune.com...foot-wiring-harness/
... I really like this kit, and I've purchased one myself. I got a lot of **** for recommending the FAST EZ-EFI 2.0 (which I intend to use for my V6), but I think you'll really like the MicroSquirt. It's exceptionally well laid out, well documented (literally... the back has the entire pinout), and lots of support. I get a lot of flack for this, but the factory ECMs are old. They were fantastic for the time, but they are slow (300 baud) and don't adapt well (or quickly) to changing environment. Hunting idle, 2000-rpm cold idle, etc... all these things could be fixed / eliminated with a newer ECM that makes a better (quicker response) to sensor changes. Of course, it's important to remember that most problems you have before an ECM change, will likely exist after an ECM change. Regardless, I think you'd see improvement by going with a modern ECM.
Note: swapping out the TBI unit won't fix your problem, it'll probably introduce more issues. BUT honestly, your Holley TBI unit is a definite improvement over the factory one, so I think that new TBI unit you posted is probably not worth it. But... all of these things will work better with a good ECM that can take advantage of it.
EDIT #2: (sorry) ... another thing I wanted to mention is, one of the really nice things about the Fiero, and when it was designed / made... is that the gauge cluster is totally independent of the engine management system. Like, there's almost nothing in the gauge cluster that makes use of the ECM. There's the shift light of course, but other than that, the gauges all get their readings directly from the sensors on the engine (some sensors are dedicated specifically to the gauges). So... point being, swapping out the ECM, while not "easy," does not require a complete rewiring of everything... just the wires that the ECM directly uses.
[This message has been edited by 82-T/A [At Work] (edited 04-24-2024).]
P.S. I'm not changing the engine. So don't bother trying to take me in that direction Thx.
I did briefly consider it actually but decided to try my 88s old ecu in my 84 (no it's not a real 88 ecu sadly its a crappy 84 ecu i had to repair with a iron and a whole tray of replacement transitors) I do know what might be causing your ecu code 51 though. clean everything with contact cleaner and verify the ecu board is grounded to case and the case is grounded to the chassis and so on and so forth. can't lose much but time
anywho honestly the sniper setup if your just fed up with the stock wiring would be a fresh start and hopefully a new lease on the fieros life
Originally posted by 82-T/A [At Work]: So, just wanted to address this... as I'm currently going through an Iron Duke rebuild with my daughter (we actually just finished it last weekend). Is your desire to keep a stock look, or you don't want to go through the hassle of changing out the motor? I ask because if you want to keep a Duke in there, there were several enhancements over the years.
Mid-1985 and up got a roller cam, which is quieter, and typically takes less wear. 1986 I THINK got a new intake and TBI unit. 1987 got an entirely new belt-drive system (serpentine), along with DIS ignition. 1988 got a new balance shaft which improves "smoothness of the engine," along with a different crank, pistons, and rods.
Each year saw a culmination of the previous year's improvements that went from 92bhp as a rackety "Iron Duke" tractor motor in 1984, to a much smoother running 98-100hp "Tech-4" in 1988.
So if you're OK with swapping out Duke motors, there's a lot of improvements you can get. I'm rebuilding my daughter's 1985 motor (which has a roller cam), and there are several improvements we're making, including replacing a LOT of the accessories (see this video here):
... bottom line (what you should take away from the video), every single one of the belt accessories has a more modern replacement that will literally "bolt in place."
Another thing you can also consider doing is replacing all of the pulleys with a 6-groove serpentine pulley, and you can literally have a serpentine belt system, using the alternator as the "tensioner" as you would similar to with a V-belt.
All of that said, my personal opinion, you could swap out the ECM with a new MicroSquirt system and eliminate a lot of the inherent drivability issues ... or so I've heard. I'll be doing this with my daughter on her car this summer.
EDIT: re-reading the thread, I understand all of what you want to accomplish. I agree somewhat with PMBrunell, though I'd recommend a MicroSquirt, specifically, this kit: https://www.diyautotune.com...foot-wiring-harness/
... I really like this kit, and I've purchased one myself. I got a lot of **** for recommending the FAST EZ-EFI 2.0 (which I intend to use for my V6), but I think you'll really like the MicroSquirt. It's exceptionally well laid out, well documented (literally... the back has the entire pinout), and lots of support. I get a lot of flack for this, but the factory ECMs are old. They were fantastic for the time, but they are slow (300 baud) and don't adapt well (or quickly) to changing environment. Hunting idle, 2000-rpm cold idle, etc... all these things could be fixed / eliminated with a newer ECM that makes a better (quicker response) to sensor changes. Of course, it's important to remember that most problems you have before an ECM change, will likely exist after an ECM change. Regardless, I think you'd see improvement by going with a modern ECM.
Note: swapping out the TBI unit won't fix your problem, it'll probably introduce more issues. BUT honestly, your Holley TBI unit is a definite improvement over the factory one, so I think that new TBI unit you posted is probably not worth it. But... all of these things will work better with a good ECM that can take advantage of it.
EDIT #2: (sorry) ... another thing I wanted to mention is, one of the really nice things about the Fiero, and when it was designed / made... is that the gauge cluster is totally independent of the engine management system. Like, there's almost nothing in the gauge cluster that makes use of the ECM. There's the shift light of course, but other than that, the gauges all get their readings directly from the sensors on the engine (some sensors are dedicated specifically to the gauges). So... point being, swapping out the ECM, while not "easy," does not require a complete rewiring of everything... just the wires that the ECM directly uses.
Thank you, but I'm not interested in swapping out my iron duke. Everything is running great. Good luck with your project however.
I did briefly consider it actually but decided to try my 88s old ecu in my 84 (no it's not a real 88 ecu sadly its a crappy 84 ecu i had to repair with a iron and a whole tray of replacement transitors) I do know what might be causing your ecu code 51 though. clean everything with contact cleaner and verify the ecu board is grounded to case and the case is grounded to the chassis and so on and so forth. can't lose much but time
anywho honestly the sniper setup if your just fed up with the stock wiring would be a fresh start and hopefully a new lease on the fieros life
Thanks for your support. Indeed it was worth the time money and effort and made my Fiero reliable. No longer worry about hard starting, stalling and high revs.
Originally posted by 82-T/A [At Work]: I cringe whenever I see pictures of this Holley TBI unit... the reason is, I had one, and completely gave it away. I had a 1984 Fiero 2m4 SE that I bought back in 1997 for $1k... it was really nice. But as a kid, it had to sit in the South Florida sun as I didn't own a house at the time, and the sun basically destroyed the paint and seals. Eventually, I gave the entire car away for a bottle of rum in like 2003 or something. Along with it, I gave away a Holley TBI unit that I'd bought new. It had less than 1,500 miles on it. I thought to myself... "I'm never going to own another 4 cyl Fiero, probably not an early Iron Duke at least..."
Now, my daughter has a 1985 Fiero 2m4 SE in which this would have dropped right in.
I just checked eBay really quick again before posting this. They are so rare now, that I wouldn't even believe they existed unless I had actually had one previously.
Well today is your luck day. You reminded me I have a 3739 that was on my Duke before I went to the sniper. As I mentioned previously, it was not as much that I didn't like the performance or the stock or holley TBI that made me move to the sniper, but the old technology for '84 that the sniper replaced. It is so easy to monitor engine performance that it's no longer a guessing game to why the duke wasn't running right.
In any case, if you interested in buying my 3739, please send me a PM with an offer.
Well today is your luck day. You reminded me I have a 3739 that was on my Duke before I went to the sniper. As I mentioned previously, it was not as much that I didn't like the performance or the stock or holley TBI that made me move to the sniper, but the old technology for '84 that the sniper replaced. It is so easy to monitor engine performance that it's no longer a guessing game to why the duke wasn't running right.
In any case, if you interested in buying my 3739, please send me a PM with an offer.
Thx.
