1985 TPI Failed
Thread Starter
5th Gear
Joined: Sep 2017
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1985 TPI Failed
Good day, the 1985 TPI system is a one off item and has issues that other C4's do not have, like a burn off relay and all the electronics that goes with it.
Some issues I have are with the age of the system, that the car has been wrecked, rebuilt, raced, altered and spent 10 years, off and on, in storage.
Today, it will run great for a couple of hours, days, weeks, or (if I'm lucky) months. But randomly it will run like poop or not at all. The money required to repair or replace the EFI system would cost as much as I paid for the car. I love the EFI, when it works. When it doesn't, I ponder carburation. I'd love to keep EFI but it lookl like it would be cheaper to buy a later model C4.
Has anyone found an option (other than FAST, MSD, Holly, etc.) that works and cost less than $1000?
Some issues I have are with the age of the system, that the car has been wrecked, rebuilt, raced, altered and spent 10 years, off and on, in storage.
Today, it will run great for a couple of hours, days, weeks, or (if I'm lucky) months. But randomly it will run like poop or not at all. The money required to repair or replace the EFI system would cost as much as I paid for the car. I love the EFI, when it works. When it doesn't, I ponder carburation. I'd love to keep EFI but it lookl like it would be cheaper to buy a later model C4.
Has anyone found an option (other than FAST, MSD, Holly, etc.) that works and cost less than $1000?
Safety Car
Joined: Nov 2009
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From: Adelaide South Australia
Tech Contributor
Joined: Oct 2008
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From: Custer, WI
Melting Slicks
Joined: Apr 2007
Posts: 2,616
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I feel your pain as I also have an 85. But I cured that with a Holley HP and spent more than 1,000.00. Very happy now! Now I can tune with a laptop and have learning or self tuning along the way. Completely eliminated the MAF , burnoff stuff and have a reliable car. You give up the CEL codes but you don't need that after the conversion anyway. I can self monitor in real time.
Last edited by 856SPEED; Sep 18, 2017 at 02:02 PM.
Oil Producer
Joined: Apr 2014
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I fixed mine and it ran perfectly. If its your burn off, sure thats a pita. but you can just pay the bucks to fix or convert to the later system if you like project work.
as for the "slow computer", it is slow on the datalogging/real time scanning and in fact you cant even datalog it without putting it into field mode wich forces a 1000rpm idle among other things on the system thereby altering what you are logging...you cant ever log it in the same state that has the issue.
The chip in the 85 is awful, upgrade to the last chip released in the very begging of 86 as a "fix" for folks complaining about the 85. It made the car run exactly the same as my 87, but beat the 87 racing because of the higher stall rating on the 85. But its not too slow that the car cannot run! Its the baud rate of transfering scanned data that is slow is my understanding.
Is your sustem that bad that it canmot be returned to factory running specs? They run strong and smooth unless you have deep engine issues!
Auto or 4+3?
as for the "slow computer", it is slow on the datalogging/real time scanning and in fact you cant even datalog it without putting it into field mode wich forces a 1000rpm idle among other things on the system thereby altering what you are logging...you cant ever log it in the same state that has the issue.
The chip in the 85 is awful, upgrade to the last chip released in the very begging of 86 as a "fix" for folks complaining about the 85. It made the car run exactly the same as my 87, but beat the 87 racing because of the higher stall rating on the 85. But its not too slow that the car cannot run! Its the baud rate of transfering scanned data that is slow is my understanding.
Is your sustem that bad that it canmot be returned to factory running specs? They run strong and smooth unless you have deep engine issues!
Auto or 4+3?
Last edited by VikingTrad3r; Sep 18, 2017 at 02:46 PM.
Melting Slicks
Joined: Apr 2007
Posts: 2,616
Likes: 111
I will say, the 870 gets a bad rap with slow baud rates, etc. However, after I brought my car to TPIS to have it tuned, the upgrade to the Holley provided little to no performance gains according to passes at the track. I was surprised on that end. But I changed for the reasons the original poster describes above. Anything that is obsolete or hard to find I try to retrofit with updated parts (if I can) in a professional good workmanship like manner.
The system itself self is a dinosaur, particularly the 85 , a one year only ECM and buroff relays specific to that year.
The system itself self is a dinosaur, particularly the 85 , a one year only ECM and buroff relays specific to that year.
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Thread Starter
5th Gear
Joined: Sep 2017
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TPI Fail
That is one of the oddities with my car. It doesn't throw codes!? Also I can start it and it runs like cr@p, and then I can leave it sit for a half hour and it will run fine. It's so random!
Melting Slicks
Joined: Apr 2007
Posts: 2,616
Likes: 111
Holley makes several standalone ECM's/wiring harnesses/etc. for fuel injection. The system I use is the Holley HP which is VERY versatile with many inputs/outputs for your needs. I completely eliminated the old 870 and have this in its place. It even comes with its own O2 sensor, fuel injector connections, TPS connections, connections to the IAC, etc. If I decide to make any modifications to the motor or other parameters, I just input the data now. If I went FI (forced induction), this could handle that as well. I had mine professionally installed and dyno tuned at the same shop. It also comes with the disc to download the software of course.
Supporting Vendor
Joined: Oct 2004
Posts: 761
Likes: 68
Upgrade
Good day, the 1985 TPI system is a one off item and has issues that other C4's do not have, like a burn off relay and all the electronics that goes with it.
Some issues I have are with the age of the system, that the car has been wrecked, rebuilt, raced, altered and spent 10 years, off and on, in storage.
Today, it will run great for a couple of hours, days, weeks, or (if I'm lucky) months. But randomly it will run like poop or not at all. The money required to repair or replace the EFI system would cost as much as I paid for the car. I love the EFI, when it works. When it doesn't, I ponder carburation. I'd love to keep EFI but it lookl like it would be cheaper to buy a later model C4.
Has anyone found an option (other than FAST, MSD, Holly, etc.) that works and cost less than $1000?
Some issues I have are with the age of the system, that the car has been wrecked, rebuilt, raced, altered and spent 10 years, off and on, in storage.
Today, it will run great for a couple of hours, days, weeks, or (if I'm lucky) months. But randomly it will run like poop or not at all. The money required to repair or replace the EFI system would cost as much as I paid for the car. I love the EFI, when it works. When it doesn't, I ponder carburation. I'd love to keep EFI but it lookl like it would be cheaper to buy a later model C4.
Has anyone found an option (other than FAST, MSD, Holly, etc.) that works and cost less than $1000?
Tech Contributor
Joined: Oct 2008
Posts: 3,729
Likes: 190
From: Custer, WI
Upgrade to later ECM requires Harness Repinning, adding the MAF Burnoff and Power relay circuits to the Harness
Jim's Performance redid my 85 Harness, but I had to provide a new harness, the old harness, and he put it all together. He did it for a good price, but in the end it would have been cheaper to just upgrade to a new EFI system that provides a harness.
Unless you can get your hands on two harnesses really cheap, ECM, different MAF for the 86-89 cars, the burnoff relays, it's cheaper to go to a new EFI system
Jim's Performance redid my 85 Harness, but I had to provide a new harness, the old harness, and he put it all together. He did it for a good price, but in the end it would have been cheaper to just upgrade to a new EFI system that provides a harness.
Unless you can get your hands on two harnesses really cheap, ECM, different MAF for the 86-89 cars, the burnoff relays, it's cheaper to go to a new EFI system
Safety Car
Joined: Aug 2009
Posts: 3,751
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From: Melbourne, Victoria, Australia
Exactly get a 85 shop manual and check the codes, the car will indicate what is out of spec.
My 85 has done 170,000 miles, never a problem with the burn off module. I did buy a spare some years ago for $45 as I saw the prices going up, you can always go to a later ECM means re pinning a few wires and having burn off relays.
Check your codes, it may be a cheap simple fix to get it running right.
Racer
Joined: Jul 2015
Posts: 313
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From: Modesto Ca
You can rent an online copy of the Gm service manual from www.alldata.com .Its $24 a year and you can print pages from it.If you get an error code for a sensor and change the sensor and the code comes back you usually have a connector or wiring problem.Rock Auto and www.diyefi.com sell replacement connector pigtails if you have a worn connector.Most aftermarket efi systems use Gm sensors so usually the install is just running wiring.There are many efi systems on the market.From Megasquirt to full race systems that datalog and have remote control.
Race Director
Joined: Aug 2000
Posts: 11,470
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Exactly get a 85 shop manual and check the codes, the car will indicate what is out of spec.
My 85 has done 170,000 miles, never a problem with the burn off module. I did buy a spare some years ago for $45 as I saw the prices going up, you can always go to a later ECM means re pinning a few wires and having burn off relays.
Check your codes, it may be a cheap simple fix to get it running right.
w/ the above, in fact same here, except, my 85's at 161K w/ zero issues with the burn-off module. I also bought a spare around 15 years ago, and as I recall, paid about the same $45 price. personally, i'd sort through the 85's issues and address them first. the OP never stated that he has a bad burn-off module, only periodic performance issues. i'd start with the basics, fuel system, including TB cleaning, injectors, filter, etc, then plugs, wires, cap and rotor. look at all the vacuum lines - this puppy is 32 years old, and if it's anything like mine, most of the vacuum lines were toast. run the codes, and repair things accordingly. once everything is sorted, you'll find the 85 to be a pretty reliable platform. baby steps!
to the OP: if you don't have a FSM, get one.
Last edited by Joe C; Sep 24, 2017 at 04:35 PM.
Pro
Joined: Apr 2008
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From: Pine Barrens New Jersey
I have no info about this but ran across it while perusing something at some point.
http://www.ebay.com/itm/New-FAST-GM-...1REUFz&vxp=mtr
http://www.ebay.com/itm/New-FAST-GM-...1REUFz&vxp=mtr
Thread Starter
5th Gear
Joined: Sep 2017
Posts: 5
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I have no info about this but ran across it while perusing something at some point.
http://www.ebay.com/itm/New-FAST-GM-...1REUFz&vxp=mtr
http://www.ebay.com/itm/New-FAST-GM-...1REUFz&vxp=mtr