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Hestation at 1/4 throttle HELP

Discussion in 'HYBRID -> ED-EF / DA' started by bottlefedb16ef9, May 31, 2004.

  1. bottlefedb16ef9

    bottlefedb16ef9 Junior Member

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    O.K. I have and own two 91' Civic HB's both have motor swaps and both I do all my own work. I work at a performance shop so mechanics and swap are nothing new to me but I'm fresh out of ideas and can't seem to figure this problem out. Only my one HB does this and it's my main car that I drive and race. Alot of people have given me BS anwser that it has to do cwith the DPFI to MPFI conversion... thjis excuse is total crap and I don't believe this because I have done many DPFI to MPFI conversions and both my HB's I own started out Dx models. Hel my other was a autmatic DX and now I put int a 5 spd conversion and ZC motor and it runs fine. Here's my problem I will follow with everything I have replaced or checked on the motor to help you guys out. the car is my daily driver/ racer it's a 91' Civic HB wioth a JDM< B16 in it right now. This car has seen many motors from boost I use to have a turbo ZC in it and now I had a turbo B16 in it but I got tired of the turbo thing and now it's on the bottle ( nitrous ) my porblem began when it was turbo. The car would misfire/hesistates ONLY at 1/4 throttle either 0-25% any more throttle it's fine when my AFC 's reading anywhere from 5%-25% and it only mis-fire from 3,500 to exactly 4,100 RPMS. if I'm at 25% or more throttlebelow that RPM range the car runs fine so it's only at that RPM range at that throttle range. everyone understand so far ?

    Wierd thing is if I ride the misfires out keeping it at 1/4 THROTTLE as soon as I hit 4,100 RPM it's like flicking the switch the car pulls and runs fine. First I thought I was detonating so I took and turbo off and it still does it. I know the motor is fine and not messed up /I've since performed a leak test and the car runs fine just feels like it's running alittle lean and it misfriees in that certain range I have yet to spray the motor cause I want to make sure the motors running eright nefore I do. Sometimes when driving and it does it I smell that funny smell like it's running lean. What could the problem be ? Any ideas or has anyone heard of this problem. Here's the list of things I've replaced to let you guys k now what I have done :

    -Thought my fuel pump was bad so I have taken out t6he stock pump and I have a Walbro 255lb pump in there now. I'm still running STOCK honda injectors.
    -Changed plugs, wires, I have a FULL MSD ignition... SCi-PLUS ignition box MSD coil etc.
    - I spent $300 on a BRAND NEW OBD O B16 distrib utwer from a compnay in Cananda that makes OBDO B16 dizzy brand new not re-man.'d problem still there
    -Bought a Second OBD O PR3 B16 ECU cause some people said my ECU could be bad. Now the old ECU was bad but the porblme is still there U fix it some what but the c ar stills misfires buty just not s bad but as soon as I hit 4,100/4,200 RPM the car pulls and runs fine.
    -I Took out my whole Engine wiring harness/ Fixed any connections that looked bad or coroded. still didn't fix it.
    -I ohm'd m,y injectors all are at 2.5 Ohms which honda says if they're from 1.5-2.5 ohms technicly the injector is good IU'm trying to find time this week to just swap out injectors.
    -Also I thought maybe my Cat. was clogged since I had one cat. go bad on me already so now I'm running NO cat. just a resinator and 5 zigen muffler system

    O.k. thats about it any sensors etc I have already replaced... coolant temp , oil , VTec , TPS sensor , etc. I have a hyper ground system so ALL my grounds are fine. Here't the thing that wierd if I unplug the TPS sensor the car runs fine. Of course this put the CEL on and the car is in fail safe mode but it runs fine. For some reason at idle the idle drops real low and I'm reading a TPS signal At idle any where from .1%-.5% which should not be I checked my throttle cable it's fine not too tight and I've tried switching TPS sensors. Also at idle MY fuel pressure gauge fluxuates at idle about 5 PSI it just kind of bounces around but not that big you have to really look at it. MY buddy at honda says that misfire will read on a fuel pressure gaguge and make it fluxuate.

    Also like I said it feels and when I pulled the plugs and its like it's running lean but I have a 255lb fuel pump so it should be getting plenty of fuel. The only things I can think of it that either i have a short in my TPS harness after the fire wall since I pulled the whole engine harness out. OR mybe my fuel filter is clogged I could SWEAR I replaced it no to long ago but I could be wrong but I'm going to replace it tomorrow anyway. I just need some extra ideas or if anyone has seen this problme and know what the solution is. Everyone I've talked to has either said they've heard of the problem but don't know how-to fix it or once I tell them all the stuff I've replaced they basicly say I"m SOL and they have no idea. Can anyone help me. Thanks
     
  2. brian11to1

    brian11to1 Senior Member

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    air delivery? fuel lines, filters?
     
  3. Citizen_Insane

    Citizen_Insane Senior Member

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    Are you sure your TPS wiring isn't backwards?
     
  4. bottlefedb16ef9

    bottlefedb16ef9 Junior Member

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    Yea the wirings right cause I know the DX TPS's read backwards and when doing the conversion you have to swap the two out side wires to read right. I'm getting .5 volts at idle and 5.0Volts at WOT throttle so voltage is fine but the perecnt readings is readin .1-.5% like the gas is pushed in but it's not and Iv know the throttle isn't stuck or anything but it's wired that it ony does it at that throttle range and then at 4,100/4,200 RPMS bam it runs fine. Also if I disconnect the TPS the car runs fine but the cars not as quick cause the TPS is unpluged and it's in fail safe mode. The only thing I'm thinking is either the fuel; filters clogged or maybe there's a break or a wire in the TPS harness is grounding out but it's inside the cabim or after the engine harness cause I pulled the engine harness and it's fine so IU'm just stumped.
     
  5. D See 2

    D See 2 Senior Member

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    sounds like an ignition timing/firing issue.
     
  6. breed

    breed Senior Member

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    I have the same exact problem with my ls/vtec turbo. I'm triin to figure this problem out my self.
     
  7. word

    word Senior Member

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  8. shadowracer95

    shadowracer95 Member

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    You talked about your ignition system and how its all upgraded. No where on there did you mention that you have changed your spark plugs. Maybe time? Also what kinda spark plugs are you using? I just picked up a 2001 GSR and the thing would fall on its face at 1/4 throttle and was very hard to start. I pulled the plugs and low and behold the previous owner had installed BOSCH Platinum +4. IMO the worst plugs ever made. I installed OEM spark plugs one step colder and gap to about .035 and the thing starts like it should and runs like a bat outta hell. Growin' up my auto shop teacher always told me KISS Keep It Simple Stupid. Looks like it paid off again for me. LEt us know how your situation turns out. I'd suggest some NGK coppers either 1-2 steps colder depending on your nitrous setup.
     
  9. 4drcivicb18a

    4drcivicb18a Member

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    i have the same problem but at between 1,000 and 3,000 rpm's i have a 91 b18a1 in a 91 civic 4 door if i hold the throttle anywhere between that is putters or hesatates please anyone knows how to fix this let me know thanks :worthy:
     
  10. erebunicrx

    erebunicrx my name is Dale

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    my ls swap does the same thing but throws a code for the 02 censor. so im with him on this
     
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