VG30E Missing/Running Very Rich, Sensor Problem? ECM Problem?

[robertjame]

Ok so I guess I should begin at the beginning,

 

6 months ago my 1994 Pathfinder SE-V6 4x4 AUTO Vg30E was put down to remove the heads to drill out broken exhaust studs and for replacement of the lifters and cams (lack of top end oil and increasing clicking of lifters). The heads were repaired, all new gasket kit installed and she ran like new.

 

4 Months ago I installed a throttle body spacer and an intake manifold spacer/thermal block and E3 spark plugs. Great increase in performance with no failures.

 

3 months ago I installed a Street Fire MSD Ignition System with a new cap and rotor. Amazing low end power gain.

 

So the next step was to replace the coil, wires and injectors. Heres where I lost control of the situation, I installed a highly modified fule rail from a 93 300zx witch on idle ran a little rich but ran very well at any point on the open throttle. I installed an MSD HVC 45000V street Coil with MSD wires. Now the wires I ordered didn't fit, so while I waited for some extra parts to correct this problem I left 3 of my old Bosh wires on cylinders 2, 4, and 6. I knew the coil would burn them out very shortly but I did it anyway.

 

Now this set up worked very well for about a week, but the engine went down as I was trying to wire in a 4000cfm dual electric fan. Now that I've done extensive research I know how stupid what I did was but its to late now. I wired the relays in with the ECM's temp sensor. BURN!! dumb I know. Immediately there were problems, I reversed what I had done, looked into how its really suposed to be done, ordered the after market temp sender that mounts in the radiator and wired it up.

 

Still no change in engine performance. It was missing like crazy, running so rich theres a black spot in my driveway. So I continued to back track. I tested to continuity of the sensor, then the line, then the line and the sensor and nothings wrong. so I checked the plugs, 2, 4, and 6 were fouled black. So I checked there wires, dead all three (the bosh wires). So I replaced them with the MSD wires and cleaned the plugs and test fired them, all were good. I reinstalled and no change. I checked the cap and rotor, good signal all the way through.

 

I un-hooked the MSD box and coil, re-hooked my old coil and no change. So I tore it all down and switched to my old fule rail with no MSD box or coil, no change. So I checked compression on all 6 cylinders and were solid. So I checked for vacum leaks and there are none. No rotten rubber, no broken seals. Its slowly gotten worse so now it wont even stay running with out help from the throttle. The timing is dead on 15. Im at a loss, I think it might be ECM but now Im broke and have a very expensive POS in my driveway.

 

The comp is throwing code 13 temp sender may be open/grounded/or fault, but the temp sensor has been replaced since all this happend and the line isn't broken or grounded. Fault in the ECU itself? What about the oxygen sensor? Unhooking g the MAF just kills it. Then if you restart the engine with it unplugged is acts the same with out allowing hi rev. Maybe the Throttle Position Sensor? Or the Cam Shaft Position Sensor in the bottom of the Distributor?

 

Thoughts?? Pictures will be up by the weekend.

Edited November 3, 2011 by robertjame

[sewebster]

Thoughts: make sure you are messing with the right temp sensor, not the one for the dashboard gauge. If the ECU throws the code then either there is a problem with the sensor, with the wiring or the ECU. You can test the sensor and the wiring... if those check out then you have to try a known good ecu unfortunately...

 

[robertjame]

Yes it is the one for the ECU not the dash, It is throwing code 13 and I know the sensor is good. I have two, one new, one old both measure the same amount of resistance. Now there is a small amount of resistance added to the circuit at the ECU witch is expected due to the added resistance of the wire. What I dont know is how much. Is it to much causing the ECU to read the engine as very cold? Causing it to go in to a "cold start" mode where it dumps gas? Dose anyone have the resistance specs for temp sensor+the wire at the ECU block? Ill take some pictures of my reading and let me know if it seems wrong.

Edited November 3, 2011 by robertjame

[sewebster]

The voltage at pin 18 of the ECM should be between 1 and 3 volts with the engine running (depends on temp). Page EF&EC-129 of the 94 FSM.

 

This is with it connected and a small probe wire carefully inserted.

Edited November 3, 2011 by sewebster

[robertjame]

So I messed with the car some today and heres what I got.

 

First I couldn't get the car to start and stay running without a little help from the throttle.

 

So I checked the cap and rotor, wires and plugs, the voltage to the coil was around 10v +\-

 

The coil fired through every wire to every plug, removed from the head with a good visual spark.

 

So I checked the fuel pressur by squeezing the inline, it was firm and fule was flowing.

 

So I checked to see if all the injectors were firing by touching each one with a flat balde screw driver to feel if it was clicking.

 

All were very obviously opening and closing, so I unplugged them one by one to check there harness voltage, all came up in the market of 14+ volts.

 

So my ignition system from start to finish seems to work fine.

 

All my injectors are getting the correct voltage and seem to be operating fine.

 

So by mistake I found out if you unplug the fule pump relay the engine seemed to run better.

 

Still missing and stumbling though, I could slowly rev it up to around 3000rpm, it would go higher but wasn't happy and I wasn't pushing it.

 

So I checked the voltage of the temp sensor and it was high, to me to high, 5+ volts.

 

So theres something not right there, the + and - lines come from the ECM, no other bodys manage the sensors voltage. So that points to an ECM problem.

 

I purchased another ECM on Ebay yesterday so Ill have that soon, will see if that dose it.

 

Thoughts??

 

 

 

 

 

Edited November 6, 2011 by robertjame

[sewebster]

The engine runs better with the fuel pump unplugged? Presumably until it runs out of gas... maybe your fuel pressure regulator is broken... could try checking the fuel pressure with a gauge.

[robertjame]

Yes presumable till it runs out of gas, I think it runs better when the fule pump is unhooked because the injectors are being told to run to rich.

 

No fule pump with open injectors (pulsing excessively) works better then way to much fuel... Im guessing.

 

So what im wondering is whats causing the rich condition?

 

The computer is putting out almost twice the voltage as spec to the temperature sensor.

 

First off i dont know if thats right or what could cause it.

 

Is the same voltage problem recurrent in other parts of the system?

 

I have a new ECM on the way but will plugging it in risk burning it up too?

Edited November 7, 2011 by robertjame

[JamesRich]

Both wires from the coolant temp switch go straight back to the ECU. I think you fried something in the ECU when you tapped into the wiring for your fan. As long as your coolant switch wiring is back to the way it's supposed to be you should be fine plugging a good ECU in. Did you open your ECU to see if you let the smoke out?

James

[robertjame]

Ok so today my new ECM came in, I hooked it up fired her up, she ran much much better, still not right but way better.

 

I checked for a CEL and there was none, I checked the voltage coming from the ECM to the temp sensor and it was 2.2v. Perfect.

 

So I unplugged the fuel pump relay and BAMB!!! Perfect idle, 600rpm smooth, it's been weeks since it's idled without stumbling.

 

It would rev all the way to 5000rpm super strong, then it slowly ran out of gas, started stumbling, then died.

 

When the fule pump was plugged in it ran a little rich (like before it was F@#$ed up) and was missing.

 

So I know the injectors and timing are good thanks to that great 5 min of strong engine, but maybe the regulator or fule pump are messing up.

 

I have 93 400cc Nissan 300zx injectors with my 94 pathfinders fuel reg.

 

I havent checked the fule line pressure yet but I'll post pictures of that soon.

 

Maybe an aftermarket ajustable fuel reg??

 

Thoughts??

Edited November 7, 2011 by robertjame

[sewebster]

Could just be your fuel pressure regulator is busted... it's only like a $50 part, so I would test the pressure with a gauge (procedure in the FSM for the specs with the regulator vacuum plugged in and not) and replace it if it's broken.

[robertjame]

FSM for the pathfinder says 43psi is the correct pressure for the pathfinder injectors, i have 300zx injectors and the FSM for the ZX says the rail should be kept at 36.3psi.

 

The correct mixture depends on the pressure and the pulse, if the pressure is to high the pulse will put out more gas then the ESM requested.

 

I think this must be it, either I need a 300zx regulator or an After Market Ajustable one to get me in the market of 36psi.

Edited November 8, 2011 by robertjame

[sewebster]

Sounds like you're on the right track!

[JamesRich]

If you want to continue running the larger injectors you will have to tune your ECU for them. The stock pathfinder injector is 180cc. As for as your ECU is concerned you still have the stock injector so it sends a pulse for a metered amount of fuel to come out of a 180cc injector. Since you have 400cc injectors they are probably dumping almost twice the amount of fuel it should. The ECU can adjust some to lean it out but not as much as needed.

For now you should try putting your stock injectors back in and it should run right so you know you have solved your problem. Then look up nissan ECU tuning.

James

[robertjame]

I ordered an ajustable fuel regulator to bring me back to the fuel pressure I need for the 300zx injectors, now as you said the computer will lean them out a little but not enough.

 

But cant I also lean them out a little more as well by reducing the line pressure farther then the stock spec for the 300zx injectors?

 

If the computer is running off 180cc @ 43psi and I currently have 400cc @ 43psi and need to take it down to 36.3 psi to run the spec psi on the 300zx injectors.

 

Cant I go farther still and drop the fuel pressure to 20-30psi??

 

Just till I can afford to get my ECM mapped for the new fuel capacity.

 

Thoughts??

Edited November 8, 2011 by robertjame

[JamesRich]

Should work but you might not get a good atomizing spray if you go to low. I remember a guy on a titan forum got more fuel by raising his pressure with an aftermarket regulator.

James

[robertjame]

Thanks, its merrily a tide over till I can map the ECM, thanks for the search tip by the way, ton of info out there about how to map Nissan ECM yourself,

 

although I probably will still mail it off to get it mapped.

 

Its very extensive to do yourself. Im going to have an upper intake modified to have a larger air well + a Q45 throttle body.

 

I'll have my commuter mapped to include all of that + a new exhaust by summer next year.

 

Ill try and post pictures of stuff as I go.

 

Thanks a lot for your help guys, I'm new to posting on here but been a daily reader for over a year now.

 

Great to be a part of the forum.

 

Robert Johnson

Edited November 9, 2011 by robertjame

[robertjame]

Fixed, new ECM and ajustable fuel regulator set to 5psi. This approach works but dosent offer any increase in performance from the injectors with out the ECM being remapped. Once I do that I can crank the PSI up in the 30's. Thanks again guys.