good morning and thank u for allowing me to join, apologizes in advance for the long post but i am stumped with the following issue.

i have a 2003 pathfinder, it was sometimes difficult to start but if u pumped the gas it started, anyway the horn didn't working so i replaced it. However immediately after replacing the horn the eccs2 fuse blew, i replaced it and it blew again, i checked all the wiring with nothing obvious and replace the fuse again this time it didnt blow but the car wont start, this was 3 weeks ago.

after much testing the following is where i am at:
engine turns over well
cam position sensors are new
crank position sensor is new
spark plugs are new ( replaced before the issue)
fuel pump and filter are new ( replaced within 3 months)
i have spark when cranking, but no fuel. have power at the injectors but ecu isnt sending the negative pulse to open them
sent ecu for testing and the said there was a fault, ( they repaired it and returned it)
after reinstalling the ecu i still have the same issue, if i manually ground the injectors they work and the car fires up.
immobilizer is working as it should.
wiring from the ecu to injectors is good
no fault codes are showing

its clearly an electrical issue but i have spent 3 weeks trying to work it out and am still in the same position that i started at
any advise at this point would be greatly apreciated
thanks in advance
andi

Are the new sensors OE or aftermarket? One way to check if the cam sensors are causing the issue is to disconnect both of them and see if the engine starts after a long crank. If one is inop or malfunctioning it will cause a no-start, but if both are flatlined then the ECM will usually quit looking and start the engine using the crank sensor only. So if disconnecting both starts the engine, you know at least one of them is bad.

If you have a good scanner, look at the cam angles (both should be around 0 deg when cranking) and RPM reading (should be steady around 200 when cranking). If you get way-off or jumpy readings from any of them then that sensor is probably bad. Same for the MAF, it should read fairly steady at something north of 1 g/s.

If that all pans out, given what you said about the fuses blowing, I'd say there's a good chance you have a short in one of the injectors or wiring which is blowing up your ECM's injector driver. Personally, I've never had much luck with ECM "rebuilders", they seem to miss stuff frequently. There's no overload protection built into the driver, so a short circuit to power across an injector coil will smoke the driver chip. I'll assume you ohmed all the injectors, but ohm across all of your injector connectors too. You should read infinity or at least large ohms on all six, if any of them read near 0 then there's a short between the wires or a melted FET in the ECM. To find out which, repeat the test with the ECM disconnected. If it still reads low then the wiring is short, if it doesn't then the ECM is shorted internally.

Sorry for the delayed response.
The sensors are original parts, anyway i sent the ecu back to the repair guy as he gave me 6 months warranty he said that the injector drive was fried again and has replaced. He advised to check that the injectors weren't shorting direct to ground before reinstalling the ecu.

I reinstalled the ECU and the car started up first turn of the key, turned it on and off several times starting first time every time, i then re-taped all of the engine harness back up ( we had removed all of the tape to check the wiring for breaks or shorts) tried the car again several times after this and it started first time every time again.

I then ran the car for approximately an hour ( not driving ) when i noticed that one of the ignition coils was smoking and red hot, i replaced it as i have a spare again the car started first time repeatedly. Then 30 mins later when i went to actually test drive it DEAD, exactly the same as before!

i contacted the ECU repair guy and explained what happened ( left out the coil burning ) he says as expected that its something in the car frying the ECU. Tried a few more times to start it and noticed that now another coil is red hot ( other side of the engine not the same location as last time )

I never found the cause of the initial fuse blowing and it hasn't blown again since, i have gone through the wiring several times and removed all the tape with nothing obvious showing, i have power and grounds in all the right places. I am at a loss as to where to start next, the ECU guy suggested that maybe an injector is breaking down under load and shorting out, unfortunately good mechanics and auto electricians in Dubai are had to find, they have a tendency to guess at stuff and just replace parts until it works, i've even seen them replace the entire engine just for a head gasket as they don't know how to replace it.

Thanks in advance
Andi

Check your engine grounds end-to-end, when coils blister and cook-up it's almost always a grounding issue. Smoking coils will blow fuses and make a mess. Once you're sure all the grounds are good, I'd replace all of them. Even the ones which are still working may have damaged driver FETs.

Ok so the main battery ground was in fairly poor condition, so replaced the whole cable and the terminals from battery to suspension strut housing and then down to the engine ( have to be honest its in the strangest place on the engine, bolt point onto the steel water pipe? I've never seen a engine ground in such an odd place normally its directly to the block or the gearbox, is this right or has someone put it there prior to be buying the car? )

Anyway figured i might as well turn the key and see even though i hadn't replaced the coils yet, car started pretty much straight away although clearly not running on all 6 maybe 3 or 4 and if u touched the accelerator it died. it was late and i knew i needed coil packs so i left it for the night thinking i had won!!!!

Coil packs purchased and installed this afternoon now its firing but wont even idle!!! At this point i am starting to loose my s**t with this car the temptation to burn in and claim on the insurance is rapidly increasing. I tried adding a good quality jump cable from the battery to the block just in case that helped but no difference.
Thanks in advance
One very frustrated Andi

The engine ground on an older VQ Pathy should be direct to the block at the right front, someone must have relocated it. There should also be a lug in the center of the cable for the body ground, that does attach to a bracket. Make sure you didn't get any coil plugs swapped, see EC-679~680 for the trigger wire colors:
https://www.nicoclub.com/service-manual ... 2%2Fec.pdf

Morning,

Sorry for the delayed update but have been waiting to get my ECU back from the shop.

I moved the main ground directly to the block and added an additional ground to the engine as well. I sent the ECU back to the repair shop, this time he said both the injectors and the coils circuits were fried. He replaced both under the original warranty ( have to say I'm impressed he has repaired it 3 times now) unfortunately he had run out of parts so had to wait for the parts to come in.

Got the ECU back yesterday car started up first time and idles smoothly but has a misfire under load but its inconsistent, one moment it's fine and the next it's like it's about to die

As previously stated, plugs are new, coils have been replaced (not genuine) cam and crank sensors are new (original) injectors are all working with good spray (also chucked a bottle of injectors cleaner in for good measure), fuel pump is new.

Could it be the duplicate coils?
Any other suggestions?

Thanks in advance
Andi

Forgot to say not getting any codes for the misfire with the scanner

andi456 wrote: ↑

Thu Apr 13, 2023 7:25 pm

Forgot to say not getting any codes for the misfire with the scanner

How do you know it's a misfire without a code that identifies it as such?

Lack of power under load, spluttering and backfiring

andi456 wrote: ↑

Thu Apr 13, 2023 9:45 pm

Lack of power under load, spluttering and backfiring

Yikes! A missed firing at ignition timing is sort of the opposite to a mistimed explosion in the cylinder or exhaust. Such a "backfire", in my experience, has been due to fuel pump or fuel pressure regulator problems, which also could explain the lack of power under load and the sputtering and no DTC codes. I have also seen the same symptoms due to a faulty alternator not generating enough power to charge the coils with enough energy to consistently fire off the ignition event. Consequently, unburned fuel is exhausted and ignited by the heat from the catalytic converters. I honestly cannot say for certain what is happening without diagnostic testing.

It appears to be backfiring in the inlet manifold, if you gently touch the accelerator it will rev and build speed but anything more that the smallest amount and it splutters and then backfires, not all the time but more often that not.

Nearly everything is new,
Battery
Spark plugs
Coil packs
Cam sensors
Crank sensor
Fuel pump
Fuel filter
Starter motor
Air filter
ECU repaired

Car idles perfectly, starts first time since the ECU came back this time. It kinda sounds like it's struggling to get air when u rev it

It's driving me insane
Thanks Andi

Check fuel pressure. Md is right, the VG33 regulators are a frequent failure point. Check for a blocked exhaust as well if it won't rev. That's most easily done with a vacuum gauge, if the reading falls way off as you increase the RPM's it means one or both tubes are blocked.

Morning,
t's definitely not the exhaust blocked, I pulled both sides down and tried it without, my car has no o2 sensors and I can see through both cat pipes into the exhaust manifolds and the same with the second cat section,
How do I test the fuel pressure regulator?
Fuel pump is new done maybe 1000 miles on it,
Fuel filter is new done 0 miles on it, I also tried removing the filter and run it direct just to check that the filter wasn't bad but no difference

Thanks Andi

The Nissan service manual has very limited fuel system pressure testing procedures on pages EC-51 and EC-52 and it requires a special adapter to be installed at the fuel damper. https://www.nicoclub.com/service-manual ... 2%2Fec.pdf
My Haynes repair manual has a very comprehensive set of inspection checks. I have written out the entire pressure check procedure below. You will need to have a fuel pressure gauge to do this.
1. Relieve the fuel system pressure.
2. Remove the fuel line from the fuel filter and install a T-fitting between the fuel filter and the fuel rail (see illustration below). Connect a fuel pressure gauge to the T-fitting. Make sure hose clamps are securely tightened.
3. Turn the ignition switch On. The fuel pump should run for about five seconds. Pressure should register on the gauge and should hold steady at 43psi.
4. Start the engine and allow it to idle. Pressure should register on the gauge at 34psi.
5. Disconnect and plug the vacuum hose from the fuel pressure regulator. The pressure should increase to 43psi.
6. If the fuel pressure is not within specification, check the following:
a) If the pressure is higher than specified, check for vacuum to the fuel pressure regulator. Vacuum must fluctuate with the increase or decrease in the engine rpm. If vacuum is present, check for a pinched or clogged fuel return hose or pipe. If the return line is OK, replace fuel pressure regulator.
b) If the pressure is lower than specified, check for a restriction in the fuel filter or fuel line. If the fuel filter and lines are OK, start the engine and slowly pinch the return hose shut. If the pressure rises above 43psi, replace the fuel pressure regulator. Warning: Do not allow the fuel pressure to exceed 60psi. If the pressure is still low, replace the fuel pump.
7. Turn the engine Off and place the ignition switch in the On position. Monitor the pressure on the gauge for approximately 5 minutes. Pressure should decrease slowly. If pressure decreases rapidly, check the following:
a) Turn the ignition key On and pinch the fuel feed line shut between the T-fitting and the fuel tank. Turn the ignition key Off. If the pressure decreases rapidly, one or more injectors may be leaking.
b) Turn the ignition key On and pinch the fuel feed line shut between the T-fitting and the fuel rail. Turn the ignition key Off. If the pressure decreases rapidly, the in-tank fuel pump check valve may be faulty.
8. After completing the testing, relieve the fuel pressure and remove the fuel pressure gauge.

Just to be sure your alternator is running well, a quick check of the voltage at the battery while the engine is running will give you some indication of how well it's operating. This is not a thorough test. Just a basic indication. Engine off, voltage should be about 12.6V. Engine running, voltage should be more than 14V and less than 15V without any load. Engine running with loads on (headlights, AC, radio, etc.), voltage should not drop below 13V.

Check for good body and engine ground as well to be sure there is no transient voltages circulating. With a voltage meter negative lead placed on the battery negative terminal, probe the body and the engine at several places with the voltage meter positive lead, while the engine is running. If you measure more than .1V anywhere, there is a short to ground problem somewhere.