so i was contracted to build a custom wire harness for 91 civic drag car, (its all obd1, which is why im posting here). the owner had two requests, he wanted the engine to run, and he wanted brake lights, so thats what i did. all non essential wires have been removed, the harness is wired in to a moroso switch panel with start button. for gauges all it has is an autometer tach, oil pressure and temp. the engine fires right up and idles smooth, but as soon as you hit the gas its like somebody kills it the engine keeps spinning but makes less noise and doesnt rev at all, if you play with the pedal it will rev up but always stumbles. its throwing two codes 20 "eld", which makes sense cause its not there anymore and its got a code 15 "ignition output signal" i have tryed 3 different igniters, two different distributors, two different ecus, i have also gone through the harness and checked and rechecked everything, and all is well as far as i can see. im stumped, does anybody or has anybody had this code 15 and how did you fix it?!

thanks

here are some pics of the harness...

 

you sure the tps and map plugs aren't crossed??

 

Please create thread titles that summarize the tech problem or question - edited.

You obviously need to focus on clearing code 15.

Have you done all of the input tests?

 

pretty sure, as the tps sensor plug is no longer long enough to even reach the map sensor.
thanks

apologies, thanks for the edit and the quick reply, i have done all the tests multiple times, everything is normal, i replaced the igniter, the code still persists. there has actually been three different igniters and two different distributors, im at a loss. i know it is probably something simple and stupid, i just cant put my finger on it.

 

Post all of the voltage readings obtained from the tests.

Did you check the Yel/Grn wire for a short to ground?

If all is fine, then swap in a known good ECU.

 

blk/yel to chassis = 12v
wht/blu to chassis = 12v

yel/grn no shorts to ground, continuity from igniter to ecu pins a21 and a22

ill see if i can get my hands on an other ecu and igniter and post the results.

thanks.

 

Also, does the igniter unit output about 10V on the Yel/Grn wire at ECU connector pins A21 and A22? Any damage of the A22/A21 pins seen in the connector or ECU?

 

i got my hands on an other p75 and all is well, no more code 15 and it runs like a champ. thanks for all the help!

 

ok i own the car i got the car back and the wiring was awesome but there is still the same loss of power concern. the p75 is still in the car and it starts up,idles, and revs all the way to limiter perfect when it is not under load. as soon as it is under load it is back to the same stumbling and backfiring concern from where i started. as soon as it dies you hit the switches and it fires right up. there are no codes present besides the eld but it is removed. i tried the old ecu in the car and the code 15 came back so i am not bringing that back into the mess.

-fuel pressure is on the money
-fuel volume should not be a concern cause it has a walbro 255lph
-timing is dead on.
-new gas
-new fuel filter
-plugs and wires are all good
-distributor has been checked and rechecked
-map sensor and all the wiring to it and from it has tested good.

any ideas?

 

im stumped, doesnt make any sense. im thinking the car is cursed! lol

 

Does the ECU match the engine?

Have you checked the ignition timing with a timing gun?

 

-yep timing light was set at 16 and is dead on
-ecus i have tried are a p75, pr4, and a crappy p05


here is what i did last night with no luck;


-triple checked the timing belt and timing marks

-took off valve cover to verify cams were stock ls cams

-tried another ls distributor and it's ecu off a car that runs and drives perfect

-i noticed when not in motion and i was slowly going into throttle the tach would start to jump above 4 grand so i improved the thermostat ground all the way to the battery with 4 gauge wire and the jumpyness went away and is now smooth.

-swept both the tps and map at the correct ecu pins and both are smooth

-load tested every sensor wire, signal and reference (not ground) by unhooking the ecu putting a positive batt voltage to it and on the other end putting it threw a headlight for three seconds to test for good continuity

-compression test yeilded 190 every cylinder

-checked valve lash

-found it runs really good in reverse and when it is not in motion but when you put it in first and start to go forward it falls right on its face like someone is playing a joke on me. after that unhooked vss and tried it again found it did the same thing.


i have never had this much trouble with a car. i am going to do a fuel volume test back to back with my other car that has the same fuel pump tonight. but if i dont find an answer soon i am putting it and everything with it on craigslist.

 

ttt