Ok heres the scoop... i had just gotten my t-78 installed by rx7store and finally took it out one night, and after i got in a traffic jam i noticed it was idleing kind of rough..and if i gave it gas it would really start hesitating..so i parked it for the night and the next day i took it out again to see whats going on and it seemed fine until i got on it just a bit and it missed and backfired very badly and then just died...wont start just cranks over and over..and the PFC, avc-r and turbotimer wont turn on... but all other gauges and lights work ....... i posted this thread a month ago...... https://www.rx7club.com/3rd-generation-specific-1993-2002-16/what-should-vacuum-readings-438794/

update.....so i just got a new engine harness (goes from the ECU through the firewall and into where the injectors are)... and was ready to install it but i noticed that the other engine harness that wraps all the way around the inside of the engine bay and splits up by the relay box next to the hood latch and runs into the side of the fenderwell then into the cabin and has 2 connectors for the ECU...

my question is.....(since I'm thinking that there is no current/ volts getting to the PFC, avc-r and turbotimer)...which harness carries the power to the ECU?


heres the harness i just got...thanks to Joe (Kyro-2)

 

You need the front harness. What you have there is the EM harness.

 

ok thats what i thought......i noticed that the (F) harness..the one that runs around the entire inside of the engine bay has a split right by the relay box (by the hood latch)..and this split runs along the fender and into the side of the fender wall and then into the side of the cabin and has 2 connectors for the ECU.....is it possable that this small wiring that splits from the (F) harness is my problem and not the entire F harness..if so is just that small section available?

 

Before you do anything or do any wire harness swap check all the fuses first...

 

yeah i pretty much checked all the relays and fuses

 

i noticed that where the wires split off of the F harness near the hood latch ...there is a box of somesort where these wires run into ...right in front of the relay box itself......is it possabel to replace the wires there or do i need to replace the entire F harness through out the egine bay?


i'll post a pic of what im talking about so let you guys know..i need all the help i can get


Ryan

 

If you're talking about the wires leading into the relay box, I would pull the relays and test it. The ground terminals of each relay should have continuity to engine ground, and the B+ ones should have 12v when the ignition is on (be careful to not short anything!). Then if you want to be real thorough, check continuity between the last relay contact and the engine harness at the ECU plugs.

Unfortunately buying new harnesses like this kick you right in the wallet and ***** at the same time. Check the parts list diagrams that you can download from www.iluvmyrx7.com.

Dave

 

well i checked the relays in the box next to the latch and all seems fine....now the harness goes around the headlight area and then goes to 4 individual relays all bunched up by the coolant refill cap correct?..where does it go from there i cant seem to follow it....i know it ends up going into the cabin through the side of the fender wall correct?

 

/\..is that correct....anyone..need some help here

 

You need to replace that entire harness. There are no connectors along the wire between pin 1B on the ECU and the EGI relay, except the one at the ECU and the one at the relay. You already tested between these points, and found no continuity. And if one wire is damaged in a harness, chances are that there are more.

 

ok...i was following the harness up to the point by the passanger side ligh..where does it go from there..( i know it ends up going into the cabbin on the passanger side fender)..

 

It runs above the wheelwell liner, underneath the fender.

 

ok so under the cross member in front and under the passanger light fixture

 

anyone happen to have a full engine bay (F) harness then

 

/\

 

well if no one has one for sale,heres a question for all you electrical guys out there...has anyone every replaced a bad wire in the harness with success?

 

To replace one wire, you would pretty much need to remove the entire harness. These cars get very hot, so the wires tend to become brittle and fail prematurely. It's very likely that you'll damage more wires when you remove the harness.


There's a saying: "Do it right or do it twice."


Removing that harness won't be easy. If I were you, Id replace it with a new one. This thread has some photos of the engine wiring harness, in case you haven't seen exactly what you're dealing with yet: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/removing-un-needed-crap-wiring-harness-400525/

Good Luck,
-s-

 

PS, download the electrical manual here:


Factory Service Manuals:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/94-fsms-available-download-449950/

 

yeah i already replaced that harness....I'm talking about the main (F) harness, that wraps around the entire engine bay from the battery and fuse/relay boxes under the front cross member and back up the passanger fender and into the cabin from the passanger side fender.....this is the harness that powers the ecu im pretty sure

 

I talked to a dealer and they said 2K for the harness....can this be right?...they also said its 1K for just the engine harness which i know is wrong

 

Damn, $2000? That's crazy. Did you try calling Malloy Mazda?

You could also try calling around to junkyards. FDs are pretty rare, but they're out there. Try to find one that was wrecked in the rear.

 

yeah i may have found one from silver93..it has 100K on it but if its in good shape it should be ok..i hope

 

Just buy a roll or two of self-fusing silicone tape and retape the areas where oil/heat have toasted the existing vinyl tape.

Dave

 

yeah that and some heat shielding wire lume...if they make it big enough for thr diamter of the harness

 

im getting ready to pull out the total harness....but was wondering how often this has happened to anyone?....has anyone had this happen to them?