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NEED VTEC ADVICE


sandwarrior
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can any one running a 3.2l or 3.5l vtec motor tell me what ECU you are running? My car is running a 3.2l but it wont rev up over 4800 rpms, Im not sure if there is an ecu problem or some thing in my harness. This is a stock ecu and harness that I wired up. I dont have the funds rite now to go out and buy one already done so Im trying to figure it out on my own, thanks for any info/advice you might share with me

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I'm getting a couple trans codes po753, p1753, and p1298 that's a voltage code, I'm trying to figure out if the ECU isn't seeing a gear other than neutral or park does it limit RPMs ? or also becuase there is no VSS signal would that limit the rpms? I've been messing with it but have yet to find the missing link.

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Is this motor and ECM setup new to the car or have you run it for a while? Just wondering if this problem came out of nowhere or if you are starting from stratch and working out some bugs with a motor swap.

 

Some trans codes are normal, but I don't think not having VSS or trans input would affect engine rpm. Mine sets numerous trans codes and runs fine.

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I've been running this setup for a couple years,(runs fine fr normal dunning) thinking it just didn't have the fun factor that my turbo VW had, then spent some time chatting with Neal Rideout and seen how well his runs stock made me dig into it. Are you running a OBD1 or OBD2 ecu?

 

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Mine is OBD2

 

Is yours turbo?

 

If it isn't revving over 4800, I would still check the Vtec solenoid and switch. It is a very common issue that would prevent the motor from revving and making good power up top. That's about when it kicks in and lets the motor scream. Neal actually had his go out earlier this season and that's what the problem was.

 

 

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your input is helping me eliminate possible issues, mine is not turbo'd and OBD2, so that should eliminate the ECU, Ill mess with the VTEC solenoid, Neal was telling me his wouldn't rev over 3500 when his solenoid was bad,mine hits 4800-5000 and acts like its on a chip, my harness is a wet mess so it could be an issue there. some where to dig deeper into. Heading to Dumont next Wednesday so I hope I can figure something out soon,, I love the way it dunes, just lacking on top end. Thanks DuneFreak

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Hmm, it sounds like it's gonna be difficult to figure out, but not impossible.

 

Start simple. Check all of your grounds really good. Then ohm out the VTEC solenoid and switch to make sure they at least test out ok. You can find the resistance spec online. I just googled it when Neal had his issue. 

 

If it's cutting out like a rev limiter it sounds like it may be ignition related...which, in turn, sounds like maybe an input issue like a crank sensor. I don't think the motors are known for those going bad, but it would be worth hooking up a scan took and trying to watch the rpm reading when it cuts out.

 

I'l try to think of anything else it might be. I can't emphasize enough...don't skip the simple stuff. Make sure your plugs and fuel are good. And again...grounds! Make sure all your connections are good.

 

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Neal mentioned the crank sensor as well, but Im not seeing any codes for it,  Ive only been watching the tach not the scan tool while its hitting the limit, that's easy enough to check, I will also OHM out the VTEC solenoid and re check the ECU wiring for it. Just a thought, I noticed that the VTEC solenoid had its own pressure switch and a second switch that appeared to only run the oil pressure on the factory dash , I replaced that one for my oil pressure gauge, could the ECU be looking for both oil pressure inputs? 

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The one oil press switch is for the idiot light only. That much I'm sure. I also know for sure a VTEC problem, (solenoid or press switch) and crank sensor problem will limit you to 3000 rpms (Been there, done that). Having seen your issue, I'm still stumped. I know of no sensor that would do that. Brandon who goes by Kraut n Rice on Glamis dunes is an expert on the Honda motors. He was a tech on them for years and does the computer mods and harnesses. I've called him several times during my build and he has been spot on so far. I have his number if you want it. Your engine should rev out way more than it does.

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thanks Neal, I even bought a different ECU off Ebay, learned how to remove the immobilizer and it does the same thing, I'm stumped as well but not giving up yet, I just don't have the spare funds to buy a ECU and harness rite now, especially with the season winding down.

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I have the 3.2 also and I kinda had this same problem over presidents not sure what it came down other than the motor and connections getting wet, but it wouldn't rev above 2000 had most of the top end apart changed the plugs unplugged every coil every connection to all sensors disconnected the battery for 30min or so and used some dielectric grease put motor and connections back together fired it up and went back to revving at 6800. Car ran great till I blew the clutch slave out.  I need to hook it up to a scanner though still to make sure nothing else is going on. 

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Well sh"t, went thru the ecu wiring again and didnt find any thing I might be missing, ran the engine up to the rpms it starts cutting out and manually engaged the vtec solenoid and heard a change in the engine but no extra rpms, I'm wondering if the valve springs are just shot and floating??? O well a slow and mellow trip is better than no trip at all, see you all next weekend

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Thanks every one, I know ill figure it out, the car still runs pretty good and its a blast to drive. You guys that are running a 3.2 or 3.5 OBD2, do you have any thing plugged in to slot D on the ECU, this is mostly transmission imputs/outputs ? currently I do not have any thing in that port and Im still leaning towards to ECU thinks the car is in neutral or park and limiting RPM's Looking at API"s web site, the picture they show for there  set up is using this port, I have played around with it but no Joy...

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On 3/12/2017 at 6:57 AM, sandwarrior said:

Thanks every one, I know ill figure it out, the car still runs pretty good and its a blast to drive. You guys that are running a 3.2 or 3.5 OBD2, do you have any thing plugged in to slot D on the ECU, this is mostly transmission imputs/outputs ? currently I do not have any thing in that port and Im still leaning towards to ECU thinks the car is in neutral or park and limiting RPM's Looking at API"s web site, the picture they show for there  set up is using this port, I have played around with it but no Joy...

I don't know if this will help but here's a couple pics of my ecu from API IMG_4516.JPGIMG_4517.JPGIMG_4518.JPGcan't remember which wire this is but the one in slot d is spliced into this wire from very right side it's the 3rd on the left in slot c 

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Thanks Hawaiian, those pictures will help allot, I dont have any wires on D but I will now and I have more than 2 on A, I can look up the pin out from those pictures and go from there, thank you for taking the time for me and sharing this. you rock!!!!

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  OK  so the blue wire going into "D10" is the speed sensor, and they tapped into C20 the top dead center sensor that pulses, the VSS looks for a pulse so I added this wire but it didnt seem to change any thing, I need to go out and drive it now and see, hard to tell sitting in the shop.                                           

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DDR Thank you for all of your help, its fixed!!!!!!, after I took it out for the first test run Wednesday evening It ran much better but after one pass my fuel cell cracked, after 2 days of messing with that finally got it sealed only to have my fans start drawing more amps than normal and popping fuses, after the clean up I finally got get out and get some dunning in and it was like a whole new engine, Cody thanks for sharing the pictures of your harness, it was the missing link I needed.

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On 3/14/2017 at 11:29 AM, sandwarrior said:

  OK  so the blue wire going into "D10" is the speed sensor, and they tapped into C20 the top dead center sensor that pulses, the VSS looks for a pulse so I added this wire but it didnt seem to change any thing, I need to go out and drive it now and see, hard to tell sitting in the shop.                                           

Neal, the ECU was looking for a VSS signal, and it was picked up off of the #1 TDC sensor

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