Notchback5.3

Hello, this is my first post on this forum so I apologize if this is in the wrong section.

I have looked through many, many of the forums attempting to solve an issue I have had for several months, but now I am out of ideas and need to post my own question.

The issue: The engine is cutting in and out at 5500 rpm. The car will rev to 6500 while sitting still, but will not rev out while driving. The ecu has no way of telling of the car is in gear or not. Below is a link to YouTube of the car showing this issue. Map sensor is reading the same as my boost gauge (7psi), afr at WOT when the issue occurs (5500 rpm) is 12.8. I have it tuned for 11.0 afr, 14 degrees timing, and 14 lbs of boost at 6250 rpm. The car currently is at 7 psi of boost until I get this issue solved.

Youtube link:
Setup: 150k mile Gen 3 5.3, ss2 cam, btr .660 springs, stock everything else. Fitech ultimate LS tuning, 7psi wastegate spring, T56 magnum. Tuned on 93. Bosch 044 fuel pump, 3/8” fuel line, deka 80’s at 58psi. Tr6 plugs gapped to .026”. 70mm turbo.

What I’ve done to attempt to fix the issue:
New cam and crank sensors
Played with crank shims
Checked fuel pressure (stays at 57-58psi) and filter
Made sure there’s no limits in the tune
Tightened plug gap all the way to .015”
Checked all wiring and added more grounds
Swapped coils
New MSD plug wires
Swapped valve springs
Checked pushrods
Free flowing exhaust, 2.25” on each bank into 3” into turbo

I have found none of these to be the culprit.

One odd thing I have found is if I unplug the cam sensor, it runs exactly the same. I find that odd, but I don’t really know what the purpose of that sensor is. The car runs absolutely perfect and has great power up until 5500 rpm and then it cuts out. Afr and map sensors appear to be working as they should. TPS only reads up to 96.5% but I find it hard that it would cause an issue like this.

To me, it feels like a computer issue due to how sudden and repeatable it is, but honestly don’t know, it could be anything.

I am absolutely out of ideas at this point and I’m tired of blindly throwing money at it to make it run right. Any input is highly appreciated. Thank you in advance.

wannafbody

iTrader: (2)

Speed density or MAF? Maybe a bad MAF?

Notchback5.3

There isn’t a MAF sensor in this system.

LLLosingit

iTrader: (4)

Actually it does, It senses load. Free revving has no load so it's easy get it to rev. Putting a load on the engine is where problems if there are any will show themselves.
You seem to have covered most of the possible fixes and I can't think of anything else to replace. Does the Fitech log cam and crank signal?

Notchback5.3

Great input, and the Fitech system does not have the ability to log the cam and crank sensors.

Chemical Tuner

0.025 gap is too good if you will not exceed 14lb. what the log shows on the run you make did you log the fuel pressure all the run , the injector duty and the wideband .

Old Geezer

iTrader: (3)

There's a tune/diagnostic forum, for these types of issues. Also a forced induction forum.

Che70velle

iTrader: (6)

I’m not a FI guy yet, but I have to question the fuel pump. Might be fine, but I wonder if you have enough fuel volume, not necessarily pressure. You run that pump inline, or in-tank? How are you filtering your fuel?

Che70velle

iTrader: (6)

Also this^^^^^^^^^^^^^^^^^^^^^^^^....

Notchback5.3

So you’re saying open the gap up more? Fuel pressure pulls down to 56 psi (set to 58 psi), injector duty cycle hits 41% and wide band is around 12.8:1.

Bocsh 044 inline, 3/8” line. Should be 300 lph at 58psi if I did my math right. Filtering inline with jegs inline fuel filter. I had the same wonder if the pressure is there, but there isn’t enough flow. I find it hard to believe that it would hold 56 psi of fuel pressure if there wasn’t enough flow. You’d think it would pull the fuel pressure down a lot more if the flow was insufficient.

Chemical Tuner

12.8 afr too lean for boost. Try to target your wideband to 11.5 afr after 105 kpa.

Notchback5.3

I’ll richen it up and report back.

Ls7colorado

iTrader: (3)

So you are already commanding 11.0 afr and it is leaning out all the way to 12.8???
That defiantly seems like it could be the problem

Notchback5.3

It’s tuned for 11.0 at 14 lbs. On 7 lbs, it’s hitting its target of 12.8. I’m going to richen it up some more per the advice I’ve received.

Also, I got to thinking more about what it’s doing, and I wonder if my injectors aren’t clogged up. Maybe it has enough injector to run well in low boost, but once the boost comes on they can’t keep up. I’m going to pull the injectors hopefully today, but maybe tomorrow and give them a good cleaning and see if that changes anything.

Ls7colorado

iTrader: (3)

If duty cycle was higher I would say dirty injectors but even that is highly unlikely.
What do the plugs look like?
What is battery voltage when under load?

Notchback5.3

Ladies and gentlemen, boys and girls of all ages, I done got it fixed. I was thinking the same thing about the injectors so I took them out and cleaned them. Sure enough, tons of gunk came out of them. I didn’t realize my post filter was only a 40 micron and wasn’t filtering out the small stuff.

I took it for a rip and it still studdered ever so slightly in first and almost non-existing second gear on. Definitely progress. I’m going to pull them out again and give them another thorough cleaning and I’d guess my issue is going to be fixed.

I also lowered my injector LB/Hour rating on the Fitech. I read somewhere that the deka 80’s at 58 psi flow 94 lbs. At WOT my fuel pressure is pulled down to 56 psi so I adjusted them down to 90 lbs to ensure I’m not running lean. I might bring that down a little more to be on the safe side.

Also, I richened up the tune per the input I’ve received here. I think that’s a great idea and I didn’t notice any adverse affects.

Overall, I am tickled to death with the help I’ve received from you guys. There’s nothing quite like a turbocharged LS screaming at 6500 rpm and just asking for more. I’m looking forward to making the switch to E85 and turning it up. Thank you guys for your help!

G Atsma

Don't forget the 10 micron filter.....

Notchback5.3

So the issue came back, so I looked at a few more things:

I verified my timing with a piston stop. Sloppy mechanics has a great video on how to do this and how to do it correctly, worth the watch. My timing came in 5 degrees ADVANCED on top of what I was commanding. My timing table is really conservative and I never saw any knock from the sensors. I don’t think that was my issue, and my octane is actually around 100 (unleaded race gas). I would think it would have blown up by now if it was detonation, but who knows.

Secondly, I switched to BR7EF plugs. Currently on the stock gap (around .027”) and I truly believe that was my issue the whole time. For what ever reason my car didn’t like the TR6’s no matter what the gap was. I took it for a rip and it ran better than it ever has out of the boost and flat rips in the boost all the way to the rev limiter.

So if your having a cutting out issue at high rpm, I’d swap over the the BR7EF’s and see if there is any change before dumping a bunch of money on things like I did.

Ls7colorado

iTrader: (3)

Awesome glad you got it fixed, thanks for letting us know what it was!

Zrillian

Installed new maf, fuel pressure regulator, both evap canisters, and then a k&n fuel filter. Same issue but mine is 4500 @wot. Perfect pressure at the rail and pump will dead head almost 115psi at the pump before filter. Could we both have a restricted fuel filter?