Will improper cam timing cause any trouble codes? I think I've got the cam timing out of wack, but, there aren't any trouble codes, except for emissions crap that we took off (EGR, pressure sensor and fuel temp). The car pops and backfires still, even after replacing all of the cam/crank sensors, beefed up the grounds, checked the MAF voltage output to the ECU, checked TPS output, IACV, new o2 sensors, checked injectors/coils, new plugs, and checked for vacuum leaks. ECU pins look fine.. and I've checked everything all the way back to the ECU. I've tried another ECU, with the same result.. just to rule out a bad unit.

So, I'm going to check the cam timing.. but, I don't have any crank/cam sensor codes.. Is this normal if the engine is out of time?

Travis

 

In my experience, it won't set off a crank/cam sensor code.

 

K.. well, I guess I'm going to pull the valve cover off tomorrow and see what the cam lobes look like at TDC.. It's got to be cam timing.. I don't see how it could be anything else at this point. I've gone over every electrical part in the system. It's backfiring through the intake, and out the exhaust.. it'll rev occasionally, but, won't idle and doesn't respond to throttle input until a second or 2 later. Has to be cam timing..

Travis

 

Any last minute ideas/opinions before I yank the motor?

 

Timing light.

 

Car won't stay running to check it.. it will spit/sputter, but has a huge delay in throttle response and won't idle at all.

 

Compression test in that case. The numbers will change invariably in some way or other. There's usually a significant bank-to-bank variance when it jumps time.

 

I remember back when I had backfires, both normal and through the intake ( http://forums.maxima.org/showthread....468&highlight= ).

End result? Two failing coils. Kinda sad, how things turn out to be the easy problems.

 

Pulled the valve covers and plugs..

At TDC, the number 1 lobes are pointed towards each other like this.. / \

The number 4 lobes are pointed like this.. \ /

I checked with a timing light, and number sparks between 10-15 degrees.. so I don't think it's the timing.

Compression on all cylinders is 150-160 (motor has low comp. pistons).

All coils fire, so it's not the coils..

So, it looks like the cam timing is good.. Next thing will be to put stock injectors back in, and a stock MAF with stock ECU to rule out my JWT ECU and/or Z32 MAF.

Travis

 

When you installed the larger injectors, were new o-rings used? Lubed before install?

 

Yeah.. and I double checked them today when I pulled the upper intake manifold off.. No leaks..

I'm trying to track down some stock injectors to swap in.. I have a stock ECU/MAF to try out.. I just need the injectors to see if it'll run.

 

Found a set of stock injectors.. should be here Monday/Tuesday..

 

maybe its backfiring because the egr is deleted...? just a thought since all that remaining fuel still stays in the exhaust stream

 

The EGR function is not active at idle.

 

What's up with the fuel pump driver module? I don't have that installed, but I don't see that being a problem.. ? I have a Walbro 255lph pump in the car.. Pressure with the key on is 43psi (engine not running).

 

I know the fuel pump is only on for a few seconds when the key is in, maybe w/o the driver it is always on causing a problem?

 

The fuel pump control module is only there to reduce voltage to the pump during light throttle conditions. The ECU still has complete control over when the pump is on or off.

 

Right.. I see that in the FSM.. The reduction in voltage shouldn't reduce the pressure though, right? Just reduces the load on the pump, because it doesn't need to spin at full speed to provide light fuel flow.

 

Well.. I finally got the car fired up and running perfectly.. The JWT ECU was the culprit, apparently.

With stock injectors, MAF and ECU, the car fires right up and idles/revs just fine. So, the JWT ECU went back to JWT today for repair.. It may be a problem with the hardware, though, so I may be purchasing another core to send to them.