DOHCZCEF9

O.K. I've tried this a thousand times and everyone or atleast ALOt of people know of the problem but no one knows the solution. I have a 91' Civic HB Dx model. It waas converted from DPFI to MPFI BUT not by me. I've done DFPI to MPFI swaps before and never had a problem but I didn't wire my car it was done like 6 years ago. I even checked the TPS wires to make sure the switched them cause DX's read backwards. I had this problem back when I had my ZC and still have it now with my B16. Here's the problem AT only 4,500 RPM or below and only at 30% or less throttle per my AFC my car mis-fires. IF at or below 4,500 RPM if I'm giving it more then 30 % throttle the car does NOT mis fire and I'm thinking I"m loosing spark since when it does it real bad I can smell raw fuel and I changed my plugs and they smelled like fuel.

Now here's the wierd part. If I keep it at 30% or less throttle and ride the mis-fire all the way to 4,500 RPM exactly at 4,500 RPM boom the car runs fine almost like I'm flicking a switch. The car will go from mis firing like crap so pulling like crazy. Why is this doing this. I've tried replacing the TPS didn't fix it, I've tried checking the wiring from DPFI to MPFI and All checks o.k. unless I'm missing something. Also once I stop at idle I can see and feel the misfires at idle but after idling for about 5 seconds it smothes out. WTF ? I'm out of ideas and need some help. I'm running a FUL MSD ignition... External coil , MSD wires, and a MSD SCi-PLUS ignition box. I've tried swaping dizzy's but the dizzy I tried was used but it still didn't fix it. Why am I loosing spark and why does it only do it at 1/4 or less throttle and why does it all of a sudden fix it self ruight at 4,500 RPM ? Thanks to anyone who can help.

HMT-Admin

Shot in the dark, I've seen some werid *** ----.. Try a spare map sensor..

DOHCZCEF9

Well I'm running at teggy MAP sensor cause my DX one was running alittle rich but I'll grab the DX one again a try it. ALSO the wierd thing was when I had my ZC I went threw literally like 8 Dizzys. Someone said it was cause I had my timing tooo advance and thats what was tearing up the dizzys. Well When I put my B16 in I set my timing light to 17 Advance TDC which I hear most people set their B16's at 16 Degrees Advance TDC so that wouldn't make sense unless I do have it too advance is 17 too advance. My MSD box has ignition retard controls but I don;t have them hooked up.

HMT-Admin

Has MSD been installed on all your setups?

DOHCZCEF9

NO when I had my ZC I was running stock ZC ignition. No MSD i was running stock 7mm wires on my ZC and had this problem with my ZC. So after I blew my ZC up after turboing it. I decided I'd go all out and get a full MSD system with my B16 since I'm ready to turbo my B16 but I can't till I fix this problem. Yesterday I tried swaping ignitors , coils ( I have extra MSD parts cause I work at a performance shop ) , New wires , new plugs. and after all that it still has the same problem so if it is the dizzy it has to be something internally. But if my Dizzy is bad why does the car run fine all of a sudden at 4,500 RPM. ABAZ is there something in the DPFI to MPFI conversion that they might have messed up wiring issue wise that could be causing my problems. like the TDC Cyl. position wires. I checked and all are going two the right pins. the two bue wire with yellow and green tracers are going to C 1 and C 2 and the orange and white are in C3 and C4 which is what the honda pins outs say to go for a PR3 ECU unless they're a break in the harness but I'm not throwing any codes. I really appreciate your input atleast your trying all other attempts on other forums no one replied. Thanks

nyc86zc

I am just shooting in the dark and things you probably already checked a million times. Narrow it down one thing at a time:
Check continuity from one end of the harness to the other.
Check each wire to make sure it is matched up correctly from the engine side to the ecu side.
Have some triple check the wiring. Don't tell them anything about what is going on just let them look at it all. Try another harness.
Did you try another known "good" ecu?
I had a similar problem, the cause was bad/incorrect heat range on the spark plugs.
Sorry man. That's all I got. I just feel bad because you have helped many...

SpeedyJAY

What computer are you using for your ZC?

You said you didnt do the install, and I was getting at, that sometimes some Auto ECU's just dont jive well with non auto situations, and make the engine run like Pooh.

Check What computer you have....I can get back to you with the ECU types, Im at work now and cant go look them up

DOHCZCEF9

O.K. I never said the reason was cause of the conversion. All I said was that on other site people say they have heard of this problem and the only solution is it has to do with the conversion but I'm not accepting that because if the only difference between a Si and Dx is the wiring and your wiring the Dx to be a Si whats the difference as long as you have the right pins in the right spot and all the voltage is right it should be the same. Here's what i think may be wrong and tell me what you think.

The problem only occurs at 1/4 throttle or less. Over 1/4 throttle the car runs fine but I can't be driving my car at 50% and try to cruise. ALSO when I'm at idle my AFC is reading anywhere from 0 to .7% throttle at idle. And at WOT the AFC says only 92 % when at WOT it should be 100% and stay at 0 % at idle not moving up and down. I think they ma be a problem in the wiring harness for the TPS. I know it's not the TPS cause I've tried 4 different TPS and all read the same. I"m going to check my TPS wires tomorrow and also the DX TPS reads backwards so maybe the shop fucked with that in the harness or there's a bad connection somewhere. Cause at 1/4 throttle the voltage reading jumps real bad like it'll go from 10% to 20 % back to 15% crazy. I may just run the wires straight from the TPS to the ECU if I have too. I tried my friends B16 ECU back first when the problem came back and nothing changed. I'm running a PR3 ECU now on my B16. Also ABAZ I tried using a difference MAP sensor and still have the same problem. I'll post tomorrow and let you know what I find, Thanks guys

DOHCZCEF9

Also I swaped out the ignitor , another MSD coil , wires and plugs so I'm not sure but I don't know if I'm loosing sprak cause if I am then it's something internally in the dizzy. Shadow recommeded changing my fuel pump maybe it's getting ready to take a crap. I just wanted to let you know what I have changed I had these parts in my tool box and I know they worked fine on the car I got them off of,

B16MIKE

Ground the ---- out of your car.the old grounding cables maybe not be effectivly grounding. i replaced all my ground wires to the motor,battery,ect..and had no more problems.i burned up 2 dizzys in my b16 w/pr3 ecu. at high revs the motor would vibrate and shake loose the wire connections. just my experince with that set up.