420a (turbo) car stalls when stopped and bucks when taking off in 1st and 2nd

[gsgoingturbo]

Ok, I did the search and didn't find anything quite what I'm looking for.

I have a 420a and it's been turbo for almost a year. Recently I ran through some water on a rainy night (made the belts squeal) and since then the car has wanted to stall at stops. It has improved slightly, but now instead of stalling at stops, it bucks when taking off. I'll take off and it will buck hard, shift into 2nd and it'll continue, 3rd is fine. When I'm slowing down I can also hear my exhaust popping. I get some smoke from under the hood at times, don't really know why that is... I haven't really had time to check it, thought I'd ask for help.

What I have checked
:fuel pressure - 55psi
:no water in intake piping
:checked battery connections


Car has ran fine with no problems till the rainy night... any help would be greatly appreciated

 

[LD25Delta9]

First off, do you have a CEL on? If so, scan it. If not, check your terminals on the alternator and also check for the resistance of your sensors on the back. Something could be cracked but not throwing a code. Not likely, but possible. Also, since you have a 99 fuel system and you may have mounted your FMU in the back, check your vaccum reference line for any cracks that may have sucked up water. I'd be pointing my finger hardcore at that being a possibilty.

 

[95'RS-T]

what do you mean your "exhaust pops" Do you mean Like a back fire?

 

[gsgoingturbo]

No, not backfiring... like when I'm drifting down a hill letting the car hold itself back, my exhaust sounds real throat. I have noticed that when I push my brake pedal hard my rpms will drop from around 700-800 to something like 300-400. This problem has gotten better since it started but still not fixed. Vacuum lines are ok, doesn't seem to be anything else noticeable that is wrong. Do have a CEL but haven't found time to get it read

 

[GofaST4life]

Go to your local auto store and get that CEL checked, it should take not even 5 minutes.

 

[95'RS-T]

the backfire from the compression when going down hill kinda sounds like your either running rich or bad down stream o2 sensor im leaning more towards the o2 sensor because of the CEL like stated above get it checked at your local autozone EDIT is it a 5 speed or automatic?

 

[rstare]

That "real throat" sound you're talking about, when you let your foot off the gas while it's still in gear is because the AFR is really lean. When you let your foot off the throttle in gear you get a really high vacuum and that spot in the table the ecu knows to run the AFR much leaner. Basically, the ecu knows you want to decelerate. That's what produces the "throat" sound.

 

[gsgoingturbo]

the backfire from the compression when going down hill kinda sounds like your either running rich or bad down stream o2 sensor im leaning more towards the o2 sensor because of the CEL like stated above get it checked at your local autozone EDIT is it a 5 speed or automatic?

manual

 

[96TurboGS]

Try cleaning the crankshaft connector harness by the oil filter on the back side of the oil pan. It may have picked up some water while passing though the puddle. Its famous for getting debris and water in them creating a intermittent signal to the PCM.

 

[gsgoingturbo]

Sorry for the very long wait before I got back to this... Got my car codes read and I got two: 1. System too lean 2. EVAC (which he told me was o2)

The guy reset the codes and when I left the car seemed to be okay. Then about half a mile down the road my CEL came back on and when I stopped at lights my car stalled out twice. I made it home, parked the car and it didn't stall out this time. Turned the car off and had no trouble starting it right back up, again no stall. Does this seem normal? I am glad my first guess was right about the o2 sensor. But my new concern is that it said system too lean. That's because my o2 is probably shot right? My fuel pressure is reading at 58, and when boosting between 3-5lbs it goes up to about 68-70.

 

[dsm9]

my car did the same thing... i checked for boost leaks, and replaced my map sensor and it went right away.

 

[gsgoingturbo]

really? is that it? can you give me more info? i'd like to know about what happened with yours. if it is the same thing you can really help. thanks in advance

 

[dsm9]

well i didnt run trhough water, i did some work to my fuel system. when i would drive everytime i began to come to a stop my car would stall out. i went to advance to get them to do a check and it came back bad map sensor. i replaced it and its been fine since. i would also check your ic pipes too tho.

 

[gsgoingturbo]

Had to replace timing components. The bearings fell out... replaced belt, tensioner, idler, and timing gear. No bent valves. replaced spark plugs and wires.
now asking if turbo setup could have been the reason behind this. I do have some boost leak but other than that no leaks. What should the fuel pressure be set to? (i've asked and seen answers before just want confirmation) and what should it be when boosting? (quick reply, I can update better later)

 

[#40Fan]

Should be around 49 psi if you are completely stock on the fuel system.

 

[gsgoingturbo]

Ok, so after the timing work was done... the brake booster was loosing vacuum and causing the car to stall when the brake was pressed. That is fixed. The new problem is that the car will still stall when coming to a stop, but not all the time. I'd say about 35% of the time. And even with a low battery I can still start the car everytime it stalls. When I got the car back I disconnected the turbo (meaning I left everything set up, just I unhooked it from the intake and put a pipe and filter off it, like NA) The conversion was never completely dialed in since I've had so many problems with the car.

Setup:
Treadstone manifold
t3 garrett turbo
tial wastegate (6lbs spring)
FMIC
Apexi blowoff
aeromotive fpr
10:1 vortec fmu
FCD not hooked up (but not currently boosting)

Pretty basic setup I think. Fmu and Fpr are under the hood... I believe all lines are hooked up correctly. If anything the vacuum lines are a spiderweb of hoses.

I also notice that when letting the car hold itself back it will backfire. The gas pedal feels real stiff as well. Dunno why...

Sometimes I can hear the car misfire... at least that's what it sounds like to me.

Any advice here would be great. Thanks

 

[bagged420a]

Why are you runnning an Aeromotive fpr and a FMU? Does the car idle rough?

 

[rstare]

When I got the car back I disconnected the turbo (meaning I left everything set up, just I unhooked it from the intake and put a pipe and filter off it, like NA)

Don't do that. Unless you've removed the turbine from exhaust stream you'll still cause the turbo to spool, just not create any boost. You will ruin your turbo this way.

Also, I want to know the answers to the above posters questions. As well as how you have it setup.
Have any vacuum leaks?

 

[LD25Delta9]

I know this sounds like it would have nothing to do with it, seeing as how it's the main part that catches water when you go over a puddle on the passenger side, but I've seen some really funny things happen when the alternator starts to go bad. It caused bad problems in the upper RPMs with my friends car until he replaced it and I've had problems at idle with two different failing alternators.

 

[gsgoingturbo]

Why are you runnning an Aeromotive fpr and a FMU? Does the car idle rough?

Yes idles rough... falls on it's face often and stalls. Got the aeromotive thinking I needed it... I removed the stock fpr and replaced with aeromotive fpr

 

[rstare]

Yes idles rough... falls on it's face often and stalls. Got the aeromotive thinking I needed it... I removed the stock fpr and replaced with aeromotive fpr

Vacuum leak.
You don't need it, now you have two rising rates. The FMU and the Aero AFPR. I'm not sure if having to rising rate regulators will screw things up...
What is your idle fuel pressure set at?

Also, please note my prior post about your turbo.

Unless you've removed the turbine from exhaust stream you'll still cause the turbo to spool, just not create any boost. You will ruin your turbo this way.

Just trying to save you some headache and money.

 

[Locke]

Vacuum leak.
You don't need it, now you have two rising rates. The FMU and the Aero AFPR. I'm not sure if having to rising rate regulators will screw things up...
What is your idle fuel pressure set at?

Also, please note my prior post about your turbo.

Just trying to save you some headache and money.

AFPR's are 1:1. While it is unneeded, if he left the vac line disconnected it won't raise fuel pressure, and won't hurt anything. With it hooked up he will be adding more fuel than needed; It could possibly be detrimental to performance, but wouldn't be dangerous.

OP: Proper diagnosis can save you from purchasing unneeded parts, saving money.

edit: Just seen you were running a 10:1 FMU. This won't provide enough fuel when boosting. If you must use the 10:1 (laziness?) then keep the vac source on the AFPR hooked up, this will help bring the fuel supply nearer to requirements. It'd be best to keep the AFPR vac source disconnected, and replace the 10:1 with a 12:1. Also, the parts guy that told you the EVAP code was related to the o2 sensor is an idiot. These are unrelated systems.

You also mention that when boosting 3-5psi, your pressure goes from 58 (static) to 68-70. This is horribly wrong. With a static fuel pressure of 58psi, your odd choice of a AFPR and a 10:1 FMU, at 3-5psi your fuel pressure should be at 91-113psi.

Your fuel pressure should be about 50psi, and with your goofy fuel setup you'd expect to see 83-105psi at 3-5psi of boost.
With a 12:1 and 50psi static fuel pressure, we'd like to see 86-110psi at 3-5psi boost.

You DO have a 255HP fuel pump, right? This would be required for boosting with a FMU.

 

[bagged420a]

You need to check all your vacuum lines, and make sure everything is hooked up properly. Sounds like there is a bad leak, or something got connected wrong.

 

[gsgoingturbo]

Yes, I do have the 255 fuel pump. And I was told on this site, on another thread, that with running the AFPR I should use the 10:1 FMU... I do have all the vacuum lines connected. also my fuel pressure is set to 50 at idle.

 

[bagged420a]

I do have all the vacuum lines connected. also my fuel pressure is set to 50 at idle.

It still think that you have a vacuum problem, even though they are connected. Are you 100% sure that they are correctly connected?