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Discussion Starter · #1 ·
Hello all: I've got an '81 280zx turbo (had it since 1998) and has been garaged for most of the time I've owned it, not to mention hardly driven in the last 20 years. But with springtime and mid-life crisis setting in I've had some renewed interest in the car I upgraded the turbocharger to a T3/T4 hybrid a number of years ago after the stock turbo died. I added a home-built intercooler system to it in the hopes of one day tinkering with the boost, but the rest of the engine and fuel delivery/ECU system is 100% stock and I've had little time to tune it (with three young kids and all). The car idles nicely enough but when I try to stomp on it while driving the engine sputters and backfires (sounds like a popping noise) through the intake and loses all power. We're talking about 2000-2500 RPM and the car will not accelerate faster than about 40-45 MPH. I suspect a fuel delivery issue (with the bigger turbo compressor). A fuel pressure test shows 30 lbs @ idle and 37-38 lbs momentarily when accelerator is pushed to the floor. But I don't know if that's enough to keep up with the air movement. Fuel filter and spark plugs are new. Any help with this would be appreciated!!
 

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The fuel pressure sounds OK. But when you start swapping turbos, I'm out. I would suspect electrical.

Has it ever run correctly since the turbo swap?
 

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you also might have an issue with your AFM. did you mess with that at all? do any adjustments or anything? also.... vacuum lines and hoses. are all of these good? if you have any leaks, broken, or missing hoses and lines, your turbo engine is not going to run right.

Bon
 

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Discussion Starter · #4 ·
The fuel pressure sounds OK. But when you start swapping turbos, I'm out. I would suspect electrical.

Has it ever run correctly since the turbo swap?
Yes--when I had everything first put back together the car ran better at high RPMs than it does now. I put about 250 miles on the car before it started running poorly...
 

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Discussion Starter · #5 ·
you also might have an issue with your AFM. did you mess with that at all? do any adjustments or anything? also.... vacuum lines and hoses. are all of these good? if you have any leaks, broken, or missing hoses and lines, your turbo engine is not going to run right.

Bon
I tested the air flow meter and it seemed to be normal, but for good measure i put a spare one I had on the car, which also tested normal. But you might be on to something with the vacuum lines and hoses. I might replace the vacuum lines, but last weekend I tightened all the connections for the intercooler plumbing, which i think may have made a slight difference? As i mentioned in my response to Pilgrim, it did work better when I first had everything back together. It was only after a limited amount of driving that it stopped running smooth after 40-45 mph. Something like a hose might be a culprit, something dumb and simple...
 

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vacuum lines are the bain of the turbo engine. i'm willing to bet you got leaks hiding in there. also, would you be able to revert back to the original factory setup without the intercooler and stuff?

Bon
 

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Discussion Starter · #7 ·
vacuum lines are the bain of the turbo engine. i'm willing to bet you got leaks hiding in there. also, would you be able to revert back to the original factory setup without the intercooler and stuff?

Bon
Good question. Yes, I could go back to the original setup as I saved all of the parts. How much boost do you think is necessary before an intercooler is required? 10 psi or more?
 

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I'm not a technical guru when it comes to turbos, but I would say anything above 10 would probably be better with an intercooler (I call them aftercoolers) but below that stock is not necessary. also realize that your turbo car has the dished pistons and lower compression, so you might be able to get away with it, but I wouldn't go crazy with the boost. I think in your case, you just want to make sure that the engine is running right in its stock state, and then do your upgrades.

Bon
 

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You can pick up a vacuum gauge kit pretty cheap and you can use it to find leaks. If it reads 10 or more psi boost too, that would be great if you don’t have a working vacuum/boost gauge. I did see you mention what boost you are making.

Is the fuel still reasonably fresh?

Possibly the OE injectors are partially clogged and not flowing well enough, but hate to send you down that road if you don’t have to yet.

Another thought is if the stock restrictor pill (I believe it has one) has been removed for the wastegate actuator it could change the amount of boost you are making.

And I don’t have a ton of knowledge, but the stock ECU programming may not match the turbo very well.
 

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Discussion Starter · #10 ·
I am thankful for everyone's comments here. In my research on my issue I had read that sometimes for an '81 280ZX Turbo it helped to unplug the harness from the ECU for a moment, perhaps also cleaning the connectors with electrical contact cleaner and then plugging it all back in again. I tried that last night and the problem was instantly fixed. I am not sure what exactly happened or why it was fixed--did the ECU somehow "reset" itself? If that is true, then the ECU is properly measuring airflow and fuel metering with the new, larger turbo because the car pulls harder than it ever has above 3000 RPM. Now all I need is a proper boost gauge to assess what boost I'm pushing. Anyhow, I couldn' be happier with the result, but there are numerous little projects under the hood awaiting...
 

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Delighted to hear that worked. I wondered about it but didn't suggest it, and I should have.

I learned that one from Zmanofwashingon; he advised me to try it after I had missing and rough running problems for more than a year and was at my wit's end.

At least on the late r 280ZX Turbos, there's nothing to lose by disconnecting all cables to the ECU, letting it sit for 15+ minutes, then re-connecting it. It's the computer version of a "hard reset."
 

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Discussion Starter · #12 ·
Delighted to hear that worked. I wondered about it but didn't suggest it, and I should have.

I learned that one from Zmanofwashingon; he advised me to try it after I had missing and rough running problems for more than a year and was at my wit's end.

At least on the late r 280ZX Turbos, there's nothing to lose by disconnecting all cables to the ECU, letting it sit for 15+ minutes, then re-connecting it. It's the computer version of a "hard reset."
The thing is, I would never have figured that trick out if it weren't for websites like this one!
 

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I am thankful for everyone's comments here. In my research on my issue I had read that sometimes for an '81 280ZX Turbo it helped to unplug the harness from the ECU for a moment, perhaps also cleaning the connectors with electrical contact cleaner and then plugging it all back in again. I tried that last night and the problem was instantly fixed. I am not sure what exactly happened or why it was fixed--did the ECU somehow "reset" itself? If that is true, then the ECU is properly measuring airflow and fuel metering with the new, larger turbo because the car pulls harder than it ever has above 3000 RPM. Now all I need is a proper boost gauge to assess what boost I'm pushing. Anyhow, I couldn' be happier with the result, but there are numerous little projects under the hood awaiting...
No, your ECU didn't reset itself - you fixed the problem when you cleaned the electrical connections to the ECU.

Even though the L28ET ECU is a little "smarter" than the N/A versions (L28E), it still has absolutely NO learning capability or the ability to alter it's own tables. Every time you turn the ignition switch ON the ECU thinks it's waking up for the first time. There is nothing to "reset" because nothing in the ROM changes.

The stock turbo wastegate was set at about 1/2 Bar (~7 pounds) and your replacement probably the same. The stock L28ET manifold has a pressure relief valve that opens at 9-10 pounds of boost pressure to prevent over-boost if the wastegate fails. You won't make more boost than that with the pressure relief valve still installed and working. I doubt your new turbo will be much outside the specs of the stock turbo at the stock pressures. You can't tune that ECU, so as soon as you need to re-tune you'll need a different engine management system and you'll need to modify your intake before you need to intercool.

Drive it, and have fun!
 

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I thought about mentioning it in my post earlier but Jim Wolf Technology can reprogram the ECUs I believe.


And this


Sent from my iPhone using Tapatalk
 

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Discussion Starter · #15 ·
No, your ECU didn't reset itself - you fixed the problem when you cleaned the electrical connections to the ECU.

Even though the L28ET ECU is a little "smarter" than the N/A versions (L28E), it still has absolutely NO learning capability or the ability to alter it's own tables. Every time you turn the ignition switch ON the ECU thinks it's waking up for the first time. There is nothing to "reset" because nothing in the ROM changes.

The stock turbo wastegate was set at about 1/2 Bar (~7 pounds) and your replacement probably the same. The stock L28ET manifold has a pressure relief valve that opens at 9-10 pounds of boost pressure to prevent over-boost if the wastegate fails. You won't make more boost than that with the pressure relief valve still installed and working. I doubt your new turbo will be much outside the specs of the stock turbo at the stock pressures. You can't tune that ECU, so as soon as you need to re-tune you'll need a different engine management system and you'll need to modify your intake before you need to intercool.

Drive it, and have fun!
Thanks for your comments! I failed to mention in my earlier post that I never actually cleaned the electrical contacts on the ECU or the harness connectors; I simply unplugged them and then plugged them back in, and as far as I could tell there was no corrosion or anything on the pins/sockets. So if the ECU does not reset itself as you suggest (and I have no reason to doubt that), some electrical connection must have been reestablished somehow...
 

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We have conflicting reports. Zmanofwashington does believe the 280ZX ECU resets when disconnected for 15+ minutes; Cgsheen does not.

In my 1983 280ZX, the ECU was disconnected and swapped with another ECU about 4 years ago. When I was installing the replacement ECU, I used DeOxit on the pin sockets to promote good contact.

Fast forward to four years later; for a year, I had been fighting problems with sputtering, missing and refusal to rev above 4000 RPM. When I completely disconnected the ECU for 30 minutes and re-connected it, the problems were gone; the car ran smoothly throughout the entire RPM range.

Could the action of disconnecting and reconnecting the pins have cleaned the contacts and solved the problem? Certainly possible, but considering that I had gone through the same process and treated the pins with DeOxit four years earlier, and I live in a low humidity climate which isn't prone to create oxidation on contacts, I have my doubts about oxidation bring the problem.

If oxidation was the problem, then disconnecting and reconnecting each plug on the ECU quickly a couple of times should solve the problem. If not, then disconnecting the ECU for a longer period and re-connecting it would be worth a try.

Perhaps we can agree that if it works, the owner wins.
 
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