the cars below are first one 91 civic dx second one 89 civic dx

while im driving below half throttle it will do this weird surging much like when you have a air bubble in your coolant system only anywhere in the rpm range i can find very few other instances of this here is one though

https://honda-tech.com/forums/showthread.php?p=855721

it went unanswered

ok heres what ive done to it
it ran just fine through all these mods/fixes
bottom end rebuild 8k ago (new stock internals with king race bearings)
top end rebuild 4k ago d15b7 (port and polish, valves, seats, springs, gides)
cometic HG
AEM cam gear retarded 2 deg
dpfi to mpfi
270 cc injectors
blocked off all coolant based sensors on the intake mani

It ran pretty awesome at this point

then my car got totaled and i swaped all this into another EF
but while i did that i broke the tps off of the throttle body
so i swapped the whole intake mani for a d15b7 one and blocked off all the same stuff
but i kept the obd1 injectors and took out my resistor box i think their 180cc

all this work was done by me
any help at all would be great.

 

Is the car throwing any codes at all?

Is the car tuned? If so on what?

 

it is not tuned its running a 90 civic lx obd0 ecu and its throwing iat and code 19 automatic transmission lockup but its a manual transmission i had no problems before from this

oh ya and i got a weird one code 20 which is some charging system code but with the car on im putting out 14.3v... i heard i need to switch out my fusebox or something i think they might have put that in the 90-91's and maybe not in the 88-89

 

Code 20 is ELD Electronic Load Detector, and yes it would just involve swapping out the fuse box, as the load on the car increases so should the voltage output such as turning the lights on, heater etc.

The lockup code is because the ECU is for an automatic and you have a manual. No big deal though.

If you are using a obd0 sedan lx model ECU that's a DPFI ECU not a MPFI, the EX and Si are the only MPFI SOHC ecu's.

I am not sure how the car ran awesome on a DPFI when your car is MPFI.

 

what he said lol. also without a tune you should be using anything other than stock 240cc injectors. running the larger injectors will cause your car to run rich.

 

ok, please dont post here without doing some reading of my first post, first of all I stated that my car ran fine on that ecu before the swap from one car to another car, so that would be one indication that the ecu is multipoint, second of all this has nothing to do with this problem i am having sure when my car were to run on 1 cyl because im using a dpfi ecu that would be a problem but it would be much different i would be barley able to drive it, when the ecu saw the 02 had low voltage it would cut fuel on that 1 injector running down a lot and the car would most likly stall when it got to Closed loop

Edit: sorry i guess you were right about the lx being dpfi but i bought a whole 4door civic with a mpfi d16a6 and a auto transmission for this swap, and it had lx tags on the back.... i am positive it is mpfi ecu..

 

i was leaning out on the high side with my port and polish and everything else, but now 240cc obd1 injectors are what im running, cruising at 3 grand my fuel trim could still compensate for the 270cc injectors i maintained 02 voltage between .4 - .6 volts

 

I'm just saying I have seen some crazy stuff I'v bought a CRX with p29 pistons running a stock pm6 ECU. I wouldn't put it past someone to run a DPFI ECU because they couldn't afford the ECU for the MPFI etc. Everyone seems to cut corners everywhere.

Have you checked to make sure the TPS is calibrated correctly or if that one might be bad? If the only thing that has changed is you having to swap the motor to a diff car and swapping the intake mani, since the TPS was broken, I would check there first.

And by surging idle do you mean it kinda bucks when in part throttle?

 

yup it bucks, i checked my tps and map with a osiliscope they were both good, i think it might be my injectors cause another kid from the school i go to had the same problem he on a 92-96 civic and he went turbo and changed em out with 550's and it went away he got tuned too

 

its like while your crusing the injectors just completly cut out and depending on where your at in the trottle it could be 0-10 seconds untill they come back on if you find the right spot you can make it buck on and off very fast, but it never does it above half throttle its like theres no problem at all when i go there i cant cruise i just keep going faster and faster

 

I would check the injectors maybe run some cleaner through it, or maybe change out the fuel filter if it hasn't been changed in the new car? Also check to make sure that each fuel injectors is getting the same amount of voltage.

 

changed filter with no change i want to do a injector balance test sometime next week if i dont change the injectors before then

it would be realy cool to figure this out tho and post it that way people dont go through all the tests i have