VH45DE mega underpowered

[simey_binker]

Hello all,

I've had a VH45DE swap in my 240z for several years now (mated to a Z32 manual transmission), and it currently has maaaaybe 40 hp. can barely get to highway speeds. It has low torque through the whole RPM range. Seems to be fine to get up to higher RPM - just takes forever to get there.

I've done a TCS, EGR, various emissions delete. everything else critical for engine operation (including idle control) should still be hooked up. I've removed and inspected all vac hoses around the intake. my MAF is currently open - no filter - not sure if not having an airbox/filter doesn't give the sliiiight amount of negative pressure the fuel damper requires? I seem to remember this engine putting down more power years back though with the same set up. I've removed the timing chain cover to check to see if the guides had grenaded and skipped a tooth - they seem fine.

My next step is to go over the fuel system; check pressure, swap filter etc. My concern is that some wire has pulled or broke and the ECU is putting me into some artificial limp mode by pulling timing on spark. Is there a way of diagnosing this easier than going through every single wire? It's been a bit, but I seem to remember a piggyback system that you guys were singing the praises of - would it show if one of my sensors was disconnected?

thanks,
Sim

[Yellow4g63]

wire in a consult port and buy the nissan data scan software and consult cable. You can check the codes on the ecu and see what the sensors are doing.

[gsracer]

I'd venture to bet your knock sensors are toast.

[simey_binker]

Hello all,

I've gotten busy with other stuff, but am revisiting this underpowered VH45DE issue. I've recently checked the oil pressure because someone else said that could be suspect - oil pressure is fine.

One of my O2 sensors has dodgy wiring, and someone else said to resolve that first. so I'm going to give that a shot today.

I don't have the original diagnostic wiring hooked up - but I may try and re-wire it for this purpose.

are the knock sensors prone to toasting? is this the failure which is exhibited if they go?

[simey_binker]

Hello all, I'm back,

I swapped the knock sensors with my spare VH45DE engine (which was working fine when pulled), and yes, the knock sensors on the one in my Datsun were cracked and pretty toast. The new knock sensors have not fixed the lack of power problem though. I may buy new knock sensors and harness soon.

if an O2 sensor is disconnected, does the ECU go into a creep mode? That's my next swap; but I think I have to pull the engine to get at them.

wire in a consult port and buy the nissan data scan software and consult cable. You can check the codes on the ecu and see what the sensors are doing.

I'm familiar with the NisTune board, cable and software - but this seems like something else. I see a lot of posts from the past about it, but I can't seem to find a vendor.

[SwervingVH]

Throw that OEM crap away and wire in a proper standalone, beit Speeduino or Haltech2500.
Whatever is appropirate for your financial and electrical background.
Stay away from Holley trash and all their associated brands.

When you get a real ECU and get it wired up, I'll get your tuning sorted out.

The problem is you are dealing with corodded and frayed waire thats 30 years old on clapped out dirty malfunctioning injectors with grandmas coils.

The time has come and went for all those parts.

You have a badass swap in a hotrod. Treat the engine accordingly, or strap on a carb with some crank trigger timing wasted spark getup.

Never not got one running right, Ill stay posted in this subforum

[elwesso]

I always liked the stock ECU to at least get things started. If there's a significant electrical fault (which I imagine there would be), if you pull the ECU codes using the screw on the front of the ECU that will tell you if anything is significantly off. If you have a bad CAS or MAF, that will limit RPMs to ~2000 or 3000 depending on what failed.

I think you're on the right track with checking fuel pressure as well, a bad fuel pump will have the car idle good but have no power at higher load.

How does it idle? If it idles buttery smooth then that's a good indication its something else, but if it idles terrible then you're off looking into injectors etc.