Idle Issue 3400 V6

[blckgagt]

Hey guys first post here so please bare with me. If i fail to provide any information important to this issue just let me know and I will provide.

Anyways, I have a 99 Grand Am with 3400 V6. My engine and transmission mods are as follows: MMS Race Block w/ 8.5:1 comp ratio, Forged pistons , Eagle H-beam rods and ARP rod bolts, ARP head studs. MMS Stage 2 heads, Turbo Cam, chromemoly pushrods, GM gaskets. MMS 65 mm Turbo Kit w 60lb/hr injectors, Walbro fuel pump. MMS 3.29 4t65eHD conv., 3500 stall TC. The engine has been completely balanced.

The car seems to have a hard time idling when the car is in drive. To avoid stalling, I have to keep my foot on the accelerator.
While the car is parked however, it idles ok; When i rev the engine, the rpms increase; as soon as i let my foot of the accelerator, the rpms drop pretty low causing the car to nearly stall or stall out completely.
I have a fuel pressure gauge in the car and have tried a series of tests to determine if it is fuel related.

At key on the fuel pressure reads 48psi
While idling, the pressure jumps down to 43psi
With vacuum hose removed from AFPR, the pressure increases back to ~48-49psi.
When revving the engine, the fuel pressure increases then quickly drops <40psi.
I have noticed that if i turn the car to the ON position the fuel pressure starts 48psi, then bleeds down much faster then it should.

The last part is probably attributed to the hard start I am also encountering.

Ill post the last two logs I created since some of the PIDs are not available in one as they are in the other. Both logs are while the car in park. Sorry if they are rather long. I hope someone can help narrow down my problem which i believe to be fuel pressure related. Thanks

[MMGT1]

Need to post your tune to go with this. Add IAC and delivered trans torque to your scanner if you could as well. Then get another scan and post your file along with it.

If it is really bleeding down fast you may have no choice but to pull the manifold and fuel rail. Leave injectors attached to rail and key on, inspect them and see if you have a bad one in there somewhere.

[Bucky]

I had a very similar problem, when in D the car wanted to stall at idle.

I ended up changing the TC and Transmission and it fixed it. Not sure what it was but it never threw any codes.

[blckgagt]

Alright i uploaded the Tune as well as an updated log file.
You will notice that after i rev the engine, the car really bogs down. I put the car in drive for maybe 10 seconds and didn't notice any abnormal.
I also noticed a moderate fuel smell while sitting in the driver's seat or even from under the hood.

Would the INJ. Pulse Width Avg. Bank 1 and 2 indicate any issues with the fuel injectors? They seems like they follow each other pretty well, but i wasn't sure if they would catch a leaking injector by showing one bank slower/faster than the other.

At this point, i thinking either leaking injector/bad o-ring/bad check valve.

I planned on checking the injectors by the method you described, but i figured i would wait to hear what others could detect from my logs first.

[MMGT1]

The tune looks good. I cannot see where its the cause. The only change Id really make it the target idle. It is a little low for that cam, but that's my preference. Your in the 220 range and I would have that cam idle 725-750rpm at operating temp. Your IAC counts are not too high either but this is a cold engine still. You may be able to fix a lot of this with OL commanded AFR and target idle speed. You cant trust any trims you see in that set up with a cold engine. Do you see the same thing when engine is at full temp?

[blckgagt]

Thanks for taking a look at this. Still new to this software, but I am slowly picking up on it. I may take your advice and raise the idle rpm, but Id like to figure out this possible fuel issue. The fuel pressure should not be dropping as fast as it is. Even when key is in the on position it losing fuel pressure too quickly. I haven't brought up the car to full operating temp since I got this tuner. Car used to produce white smoke even at idle, but that seems to have disappeared. Also the tags are expired so driving on the roads is out of the question. I'll try to let it get to full operating temp in the next week or two and see what the scanner tells me.

[Dr. Nopps]

Every 3.1 or 3.4 I've ever seen has the stupid FPR hiccup upon starting at least some of the time, might even go away for a while. I've got to say (thank you) this is my first look at quantified data showing what's happening instead of my damn car starting the first two or three attempts. On some vehicles it will get bad enough to seriously affect running, but not often. I would say with those staged out heads adding a little idle would make a lot of sense, good advice there. Thanks again but for turning me on to Milzy Motor Sports. After reading your post I checked out their site which has all the actually serious aftermarket parts for a 3.1/3.4 that you wish everyone else was selling all along. Good for them, I always thought these motors were a little overlooked/neglected. And good for you too man, that sounds like one kick ass motor, I wonder if MMGT1 is more jealous than I am over here!

[MMGT1]

What he's got over me there is the Trans/stall. Would have loved to stall the one I had, it was the only thing missing from the package. I ran a Vortech V9 where he's turbo, other than that we pretty much had the same build there...lol Milzy is the way to go IMO with the 31,34 and 3800's. I don't know if 60* is around anymore either, but Milzy is going strong, just spoke with him a few days ago actually

[blckgagt]

Every 3.1 or 3.4 I've ever seen has the stupid FPR hiccup upon starting at least some of the time, might even go away for a while. I've got to say (thank you) this is my first look at quantified data showing what's happening instead of my damn car starting the first two or three attempts. On some vehicles it will get bad enough to seriously affect running, but not often. I would say with those staged out heads adding a little idle would make a lot of sense, good advice there. Thanks again but for turning me on to Milzy Motor Sports. After reading your post I checked out their site which has all the actually serious aftermarket parts for a 3.1/3.4 that you wish everyone else was selling all along. Good for them, I always thought these motors were a little overlooked/neglected. And good for you too man, that sounds like one kick ass motor, I wonder if MMGT1 is more jealous than I am over here!

I'm not so convinced its the FPR is my situation. I am running an Aeromotive adjustable FPR instead of stock. I've disassembled it and didn't notice anything funky. The diaphragm looked fine, and i don't notice any signs of fuel leaking past it or the vacuum tube.

Milzy has a lot of products for these engines. Another option, if you haven't heard of them yet, is WOT-Tech. Both offer quite a bit for us.

What he's got over me there is the Trans/stall. Would have loved to stall the one I had, it was the only thing missing from the package. I ran a Vortech V9 where he's turbo, other than that we pretty much had the same build there...lol Milzy is the way to go IMO with the 31,34 and 3800's. I don't know if 60* is around anymore either, but Milzy is going strong, just spoke with him a few days ago actually

I planned on running a superchager, but the options were nill and most people were not willing to let part with theirs at the time. Either way, I am happy with my choice. I have wondered what a more aggressive cam option would do though, but that's in the future.

Anyways, I haven't messed with the idle just yet; however, I ran a leak-down test with the fuel rail off, then reinstalled for 10 minutes to test out other theories and came up with nothing. No leaking whatsoever from the rail, injectors, afpr or anywhere from underneath the car.

In both cases, within ~2 to 2.5 minutes the fuel pressure decreased from ~43psi to 30psi.
After 10 minutes, the fuel pressure had run down to around 22psi.
Maybe it is me, but that seems to be an awfully bad leak.

I think i may have narrowed the issue down to a bad check valve unless there are other theories...
On these cars, i believe the check valve in the gas tank, is that correct?

[Boostfridge]

I'm not so convinced its the FPR is my situation. I am running an Aeromotive adjustable FPR instead of stock. I've disassembled it and didn't notice anything funky. The diaphragm looked fine, and i don't notice any signs of fuel leaking past it or the vacuum tube.

Milzy has a lot of products for these engines. Another option, if you haven't heard of them yet, is WOT-Tech. Both offer quite a bit for us.



I planned on running a superchager, but the options were nill and most people were not willing to let part with theirs at the time. Either way, I am happy with my choice. I have wondered what a more aggressive cam option would do though, but that's in the future.

Anyways, I haven't messed with the idle just yet; however, I ran a leak-down test with the fuel rail off, then reinstalled for 10 minutes to test out other theories and came up with nothing. No leaking whatsoever from the rail, injectors, afpr or anywhere from underneath the car.

In both cases, within ~2 to 2.5 minutes the fuel pressure decreased from ~43psi to 30psi.
After 10 minutes, the fuel pressure had run down to around 22psi.
Maybe it is me, but that seems to be an awfully bad leak.

I think i may have narrowed the issue down to a bad check valve unless there are other theories...
On these cars, i believe the check valve in the gas tank, is that correct?

I would try clamping off the feed line if you can after key on to see if it still drops. if it doesn't drop the same you know its the check valve.