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So I'll start off by saying the truck ran perfectly fine before I broke the '84 NA ECU that was running it, totally my fault. I decided it was a good time to switch to an '88-'89 NA ECU. In a trade it was socketed for Nistune and sent to me. I wired in 6 6.8ohm 10W dropping resistors. Well, I plugged the ECU in and went to fire it up all excited to have my truck running again. It started on the first crank then sputtered and died after 2 seconds. Doing the start-die thing. I can keep it running with my foot on the gas but it's running absolutely pig rich, billowing black smoke and fouling the plugs. Sometimes I'll get lucky and it'll idle at 1-200 RPM if I'm very careful but that's few and far between. I can rev it out but it sounds like a 2-stroke shaking and sputtering. If I induce a massive vacuum leak it'll run at 600 RPM but still billow black smoke. I've probably ruined the oil by now.
I've checked the wiring over and over and over. I've been working on this for 3 or 4 days now.
ECU gives codes 12, 13, 14, 22 - MAF and CHTS are the ones that mean anything. No VSS and the fuel pump isn't wired through the ECU. The common circuit between those two is ECU pin 26 ground so I checked it again and found that the CHTS wiring had a circuit to chassis ground before the ECU, obviously a mistake I had made many many moons ago when building the harness but I thought maybe the old ECU didn't care. I bypassed the harness anyway and ran the MAF and CHTS together straight to ECU pin 26. Didn't change a thing and the codes are still present. At that point I actually took the harness out and went through it, it's fine.
All MAF wiring is correct as is the CHTS wiring. CHTS ohmed perfectly in spec. I checked the diagrams between '84 and '88 to be sure - nothing important is different.
Thinking the wrong EPROM got put in the ECU, I was shipped 2 other ones to try. One didn't work at all (wouldn't read the CAS signal) and the other made it run the same. With the other EPROM that does work the ECU still gives codes 12 and 13.
Tried running with the CHTS unplugged - didn't change a thing.
I tried two different MAFs, one with the adjustable POT and fiddled with it - didn't change a thing.
Tried running with the MAF unplugged - didn't change a. single. thing. You're thinking "well it should have rev limited at 2,200." NOOOPEE, the engine will still rev to the moon with the MAF unplugged!
I've been assured that the ECU "tested fine" before shipping.
I really don't know what else to try other than another ECU. I'll reiterate that it ran fine until the new ECU was put in. Any input is appreciated, I'm running out of borrowed vehicles time! lol! -
Swap ECU. Go for an 87na this time.Cha iro
enjoy building it yourself.
if it fails, fuck it.
at least you gave it a whirl. -
Why '87? I went '88/'89 for the CHTS fail safe and because the NA oxygen sensors are the same incase I wanted to run one. -
Same 02 sensor, same CHTS failsafe, but capable of driving lo Z injectors. I'm not a fan of using hi Z ECU to drive lo Z injectors since they require high current to operate properly. It's an improvement over stock if one should run hi Z injectors with an lo Z ECU.Cha iro
enjoy building it yourself.
if it fails, fuck it.
at least you gave it a whirl. -
So you're saying try a low impedance '87 ECU and keep the dropping resistors I just installed. I've never heard of this problem happening before, its driving me nuts. -
i just socketed a nistune board for RedDemon again due to a wiring issue he had. I plugged it in and realized it works and connects but it runs shit on my car because i have lo z injectors and no resistors for the 88NA board i put the nistune (hi z type ecu). i dont plan on putting resistors because i was just testing the ecu for connection…
but that's not what seems like your problem.
what could be happening in your case is that your injectors are actually hi z, and your previous lo z ECU can run both styles fine without resistors. so now you've probably put resistors across hi z injectors which don't need them.
what year are the INJECTORS from? -
Instead of asking the year, ask him to ohm test them -
you'ze not da boss'a me!G-E;341606 wrote: Instead of asking the year, ask him to ohm test them -
Injectors are from an '84. :/ -
2.9-4.3ohms -
Don't have time because I gotta go help my sister move, but I think I'm going to ohm the dropping resistors. Got a lot of shrink wrap and e tape to get through first but I wonder what the chances of having a bad batch of them are? -
I burned out some resistors when I used a low-imp ecu on the low-imp injectors without removing them… ended up ordering bigger resistors, then found a good deal on large high-imp injectors so that'll solve it anyway -
not likely. also, with sharp voltmeter probs you can poke the heatshrink or wiring without removing all of it.Kingman;341628 wrote: Don't have time because I gotta go help my sister move, but I think I'm going to ohm the dropping resistors. Got a lot of shrink wrap and e tape to get through first but I wonder what the chances of having a bad batch of them are? -
Nistune uses different latency values for lo and hi Z injectors respectively. Technically speaking dropping resistors is a bandaid. Lo impedance injectors need higher current and faster reaction from the ECU for optimal operation.
In electronics it is ideal to use a lo Z source to drive a hi Z load which is why I said a lo Z ECU is perfect for driving a set of hi Z injectors. This makes the 87 ECU the most versatile. It is as strong as the 84-86 and almost as smart as the 88-89 if not just as.Cha iro
enjoy building it yourself.
if it fails, fuck it.
at least you gave it a whirl. -
that's absolutely right. it definitely is the proper way of doing things even if putting resistors. the actual values are different as you said.
haven't people here reported success with just adding resistors and changing ecu's? or was that mostly for people with large injectors? could have sworn people have had success here for daily drivers?
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