Likely that most of you have already read this drama on the other forum, but had heard there may be additional technical expertise hidden over here at My350Z - so I'll roll the dice and see what happens.

Self-installed the APS ST, and after resolving a little issue with the scavenger pump wiring, I was under boost and rockin' out all over Phoenix. She pulled hard, and had a great couple days, though I was having some minor concerns with driveability (some fluctuating idle and under continuous throttle), so I took her into DynoComp in Scottsdale for a tune.

Enter: Dark clouds overhead

During the first couple dyno runs and some quick adjustments, idle A/F was 14.6 (ideal status, so I am told). However, under boost, the A/F jumps to max reading (30+). DynoComp spent a few hours with her trying to fix the issue:

• Checked fuel pressure at pump - good (don't have #'s for you on this, sorry. Also failed to ask if pressure was increasing under boost or not).

• Checked for kinks in fuel delivery - notta.

• Checked for vacuum leaks at manifold, vac lines, BOV, turbo, etc. - notta

• Checked MAF - reading 7v input signal. Changed the MAF - problem persisted. Changed entre wiring loom. Same effect.

DynoComp called me this afternoon with the ominous warning, "JoeDirt - after 30-plus dyno runs, at this point we simply don't know. We're looking more closely at the input signal on the MAF, but everything else checked out fine. The best that we are able to do at this point is start tearing it down and working backwards..."

That sounds expensive.

So - quite simply, the car is getting no additional fuel under boost. I tore apart the Internet the past 4 days, and find a fairly consistent resolve in either a faulty fuel pump/regulator or MAF. Other options include bad programming, crapped out wire somewhere, etc. The kit included upgraded pump, a regulator, and injectors that, in my opinion, were installed properly - tho at this point I would welcome self-blame if it meant getting her fixed.

Therefore, I solicit other opinions as to why the Z gets no gas under boost. Thanks in advance for your time...

 

Sounds like fuel pressure is not rising with boost. Check the pump and bucket assembly. After that it could be the map sensor on the Unichip. That's all i can think of. Do you have a way of checking the injector duty cycle. That will tell you alot about what is going on in the fuel system.

 

Is the A/F meter calibrated and reading correctly??? Those sensors are sometimes very flaky. May be worth looking into before going too far.

 

I imagine DynoComp's sniffer is right on so I'll assume those A/F numbers are dead on. Not using the #'s from my gauge - my wideband isn't working as of late.

No access to injector duty cycle - I'm just a simple shadetree guy - car is currently at DynoComp awaiting a blessing from God or something similar. Was thinking that maybe someone has had a similar experience that could throw me a bone as what to look for or pass on...

 

I had the same thing happen on another car (EVO). It was a bad fuel pump. I don't know if this is your problem, but it certainly can be.

By the way, 14.7AFR is simply the point at which the car burns the cleanest. Some cars idle better when they are a little richer. You can also run leaner than that when cruising in order to increase milage. Every car is different though and some will give you more room to work than others.

 

Bad fuel pressure regulator???

 

Dunno - one of my 3 guesses as well (in my post above: MAF, pump or reg.). APS said they were talking with DynoComp to find a mutual resolve and attempted to emulate the problem on their end. I have two 14-hour shifts tomorrow and Thurs to rid my mind of the Z... LOL Maybe Friday will yield better news.

Will let everyone know once I do!

 

I am not sure why they would checking MAF input voltage. What is the MAF voltage at idle. Shoudl be 1.1v.

When the AFR is that far off (30+, really hard to believe, the best wideband reads up to 22.4 afr), it's something extreme. I would seriaously not trust their wideband meter at all at this point. You might really want to think about investing into a wideband gauge...but i digress.

1) first, i would check the MAF voltage. I belive the input voltage needs to be 12v. just hinkign out loud, but if you tapped (for the oil scavenge pump) the same power rail as that provides the MAF voltage, than it could be screwing things up. This is a REAL long shot.
2) fuel pump check. Connect the pressure gauge to the hose that comes out of the housing. Take a pair of pliars, wrap some cloth around the hose and pinch it to completely close it. Read the pressure. This is the maximum pressure that the pump can flow; make sure that the pressure is at least in the 70's (will probably be higher). This is the procedure that's usually used to test for adequacy of the pump, according to cartech's instructions. I would call APS before doing this one though.
3) do NOT tear down the turbos as it's unlikely to be anything mechanical at this point with the turbos.
4) check that you are actually developing boost (but please don't blow your motor in the process)
5) fuel pressure check. I would get a handheld pump and connect it to the vacuum reference port. While at idle, build up the pressure and see what happens to the fuel pressure as you do that (I am assuming t's one of those pumps with it's own pressure gauge).

 

As an update - issue was resolved by APS and DynoComp - simple fix - APS turbo running VERY nicely at the moment. Can't complain about the performance or the customer service

 

What was the problem and the solution?

 

spill it man, what was the problem?

ahm

 

How are you going to ask for help/suggestions on what could be wrong with your ride, then find out what the problem was and not tell everyone so it may help someone down the road that runs across the same problem!

 

Would be nice to know what the simple fix is.

 

My guess is it was a kinked vac line running back to the FPR, or the hoses at the fuel pump were hooked up incorrectly. What do I get if I'm right?

 

bump for resolution...

 

The suspense is killing me!

 

Well

 

Get a rope!!!!!!!!!!!!!!!!!!!

 

Come on Dirt, put down the pills for 5 min and post, FTLOG!

 

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