Stalling/Bucking...HELP

3731 Views 21 Replies 5 Participants Last post by BluAero, Aug 25, 2010

BluAero

Discussion Starter · Aug 6, 2010 (Edited)

Hey guys need some help here. Here's the background on my car:

It's a 97 900 SE with the AC compressor and middle idler pulley deleted. The car has Green giants, a Walboro 255, T28 Turbo, full 3 inch, Gensaab 6 puck/viggen pp, and tuned for 30 psi.

Here's whats going on: I put a new serpentine belt on because my last one was getting chewed up on the edges. When I hit big bumps or when I'm at the same speed for a while, it bucks and wants to stall. I can feather the throttle to buck it back so it doesn't stall out. It's beginning to get annoying because it can happen whereever, whenever. Thing is, the car will start back up after if stalls. It just happened to me when I was pulling into the parking lot. What could cause this stalling?

I put a 71 inch belt on in. PK1805 Dayco from advanced auto. I've read that the length is actually 71.06 inches, which shouldn't make a huge difference, but it seems like the belt I put on is very taught. Tight to the point that the belt is bowed out and not flat between the ps pump and the idler pulley...Like ( as opposed to | ... I'm thinking that the tensioner may be pulled too tight because the belt is too short. So upon deceleration I think that the tensioner is detentioning or something?? Could this be possible?

I know that with the deleted AC compressor and middle idler it was up in the air as to whether it was 1805 or 1815... Could 1805mm be too tight? It seems that the tensioner is further forward then normal which makes sense if its too tight...

EDIT: I do not believe tensioner is the cause of the problem. Thinking about it more, if the belt is tight it shouldn't effect the tensioner detentioning unless a pulley fails.

Or Water pump starting to fail? Alternator and starter are good because I've replaced them and it starts right back up after stalling.

Idk where to go with this or what to do and definitely need help since this car is far from stock and its not a normal issue...HELP!

Thanks in advance guys

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BluAero

Discussion Starter · #2 · Aug 7, 2010

Update:

It did this to me on start-up a little while ago then I left it alone for about an hour and everything was fine. It's weird.

The boost gauge on the dash goes past full boost into the red and the car doesn't want to start or idle when this problem shows up. If I rev it up I can move it just enough to get it in the driveway from the rd. The odd thing is that I just started it back up and drove around the block and it was gone..

Vacuum leak maybe?

srp

· #3 · Aug 7, 2010

This only happen on a full tank of gas?
Can you hear the purge valve clicking on the right hand strut tower?
Do you have an actual boost guage with vacuum also?

BluAero

Discussion Starter · #4 · Aug 7, 2010

srp said:
This only happen on a full tank of gas?
Can you hear the purge valve clicking on the right hand strut tower?
Do you have an actual boost guage with vacuum also?

1. No this happens very intermittently and it does not matter where the fuel gauge is

2. I do not hear the purge valve clicking on the right hand strut tower, but I have not listened to it that closely. Could this be the problem? Sticking maybe?

3. Yes I do. It reads 0 psi/vac. When the ignition goes on, the boost on the dash goes to full, but not the aftermarket gauge. When I start it bogs and wants to stall but a rev up will move it. w/o gas it will stall.

Thanks for the reply

srp

· #5 · Aug 7, 2010

I would pop off the purge valve and clean it with some WD40.

Your not reading any vacuum on the aftermarket gauge with the car on and idling? That's not right. It should read close to 20 inches mercury(in.Hg).

The stock gauge within the instrument cluster goes to the end of the red when you first turn your car on?

Have you reset the ECU yet?

BluAero

Discussion Starter · #6 · Aug 7, 2010

srp said:
I would pop off the purge valve and clean it with some WD40.

Your not reading any vacuum on the aftermarket gauge with the car on and idling? That's not right. It should read close to 20 inches mercury(in.Hg).

The stock gauge within the instrument cluster goes to the end of the red when you first turn your car on?

Have you reset the ECU yet?

1. I'm going to do that now, because I'm about to drive somewhere so hopefully that will help.

2. No only when the ignition is off it reads 0. When I start it it idles around 15 in of merc.

3. Only when this problem arises. It happens whether car is started AND ignition is on. It's odd..

srp

· #7 · Aug 7, 2010

Wonder if your BPC might be acting up also. Could try disconnecting it and seeing if the problem arrises.

Make sure your wastegate actuator moves without binding.

byastremski

· #8 · Aug 7, 2010

what about looking at the "Idle Air Control Valve" off the throttle body? They can get caked up with carbon and not operate properly... take this off and use a screw driver to keep the center section open and spray some brake cleaner in... cover up both ends with your fingers and shake it around in there... then take some compressed air and clean them out... then maybe some wd-40 and re-install (maybe a little diod electric grease on the connection) and you're good

BluAero

Discussion Starter · #9 · Aug 8, 2010

srp said:
Wonder if your BPC might be acting up also. Could try disconnecting it and seeing if the problem arrises.

Make sure your wastegate actuator moves without binding.

The tune is set up without a BPC. It has a wastegate helper spring on it and the turbo only has 1 of the BPC lines going to the compressor side.

byastremski said:
what about looking at the "Idle Air Control Valve" off the throttle body? They can get caked up with carbon and not operate properly... take this off and use a screw driver to keep the center section open and spray some brake cleaner in... cover up both ends with your fingers and shake it around in there... then take some compressed air and clean them out... then maybe some wd-40 and re-install (maybe a little diod electric grease on the connection) and you're good

I've heard of these causing issues. I'll check this out too if the problem comes back. I sprayed the one way PVC valve and the car seemed to idle better than ever and start better than ever. Since I did that this issue hasn't come back... yet....we'll see

Thanks for the help guys.

srp

· #10 · Aug 8, 2010

BluAero said:
The tune is set up without a BPC. It has a wastegate helper spring on it and the turbo only has 1 of the BPC lines going to the compressor side.

That doesn't sound like a good idea...

BluAero

Discussion Starter · #11 · Aug 8, 2010

srp said:
That doesn't sound like a good idea...

Once I get the other issues sorted out, I will retune. Until then, I will run the set-up that was installed on it by the previous owner and tuned for his specific hardware.

When I retune, since I have about 3 BPC and 3 Red DIs and 1 spare T5 ECU, I will have it set up to run with a BPC valve and 1 ECU will be tuned for full power, and the other for reliability and economy.

As of now, I barely push it. Only to test whether it is running properly, which besides this problem and the oil leak, it runs pretty damn good. I stay under 10 psi and try to get on boost as little as possible.

saabkid37

· #12 · Aug 8, 2010

BluAero said:
The tune is set up without a BPC. It has a wastegate helper spring on it and the turbo only has 1 of the BPC lines going to the compressor side.

that almost sounds like a decent cause to the last motor blew up...

have you tried another ecu?

BluAero

Discussion Starter · #13 · Aug 8, 2010 (Edited)

saabkid37 said:
that almost sounds like a decent cause to the last motor blew up...

have you tried another ecu?

No, as I do not think it will run on a stock ecu due to bigger injectors and a bigger fuel pump...

And I believe it. I have to control the boost with the pedal and it's very touchy at higher Rpms. I just need to keep my right foot in check......believe me I don't want to blow it up.

The tune is a jzw tune that the previous owner asked for and works well under normal conditions. I definitely need a safer tune though, I was driving home last night and hit an on ramp in 2nd and accelerated quite briskly and the car started popping loud through the exhaust like it was backfiring and decel. I immediatedly turned the car off and back on and everything reset....... It s odd how simply resetting the ecu via restarting the car solved this.

Odd things seem to happen with this tune.

I won't be even going full boost anymore until I get that new tune. I can't a hole in the block

saabkid37

· #14 · Aug 8, 2010

BluAero said:
I immediatedly turned the car off and back on and everything reset....... It s odd how simply resetting the ecu via restarting the car solved this.

Odd things seem to happen with this tune.

IMHO thats all the evidence you need to point to the tune as the culprit.

the ECU has a failsafe in it (i found out the hard way) that when you run outside the mapped parameters it will go to a situation of barely running and will not accelerate, power cycling the ecu resets it and it will run fine. it may be a coincidence but i also ran into this when running the green giants, which are well understood to be a crappy injector these days, and there are many better choices.

i would call john and have him write the tune on another box, and if that doesnt fix it, write a new tune from scratch.

Tweek's Turbos

· #15 · Aug 8, 2010

Jesus, dude, you are running a 30psi tune with no safeguards?

BluAero

Discussion Starter · #16 · Aug 8, 2010

saabkid37 said:
IMHO thats all the evidence you need to point to the tune as the culprit.

the ECU has a failsafe in it (i found out the hard way) that when you run outside the mapped parameters it will go to a situation of barely running and will not accelerate, power cycling the ecu resets it and it will run fine. it may be a coincidence but i also ran into this when running the green giants, which are well understood to be a crappy injector these days, and there are many better choices.

i would call john and have him write the tune on another box, and if that doesnt fix it, write a new tune from scratch.

I plan on getting a road tune from Paul and Jeff when I have some time and money to drive down to pa. Why do you say green giants are crappy?

Tweek's Turbos said:
Jesus, dude, you are running a 30psi tune with no
safeguards?

I am running the same tune that blew a hole in the block for this cars previous owner. I planned on retuning so the bpc works properly. I guess so... The tune works well usually, and under 10psi it never gives me shit, but need to have a lighter, more reliable tune while still having some nuts.

saabkid37

· #17 · Aug 8, 2010

green giants have horrible spray and atomization.

if this truly only happens over 10psi, i would lean even more towards the ecu. oh and the lack of any sort of boost control totally throwing off the maps.

BluAero

Discussion Starter · #18 · Aug 9, 2010 (Edited)

saabkid37 said:
green giants have horrible spray and atomization.

if this truly only happens over 10psi, i would lean even more towards the ecu. oh and the lack of any sort of boost control totally throwing off the maps.

Actually anything under 20 psi the car seems to do fine. It's just when I hit full boost, sometimes things start going haywire & car acts weird. The only thing controlling the boost is the wastegate helper spring basically, but I was told that the ECU in there was tuned for how this was set-up...It's odd sometimes things will act weird after or they'll be totally fine sometimes. I just want to keep it under 10 psi because when I'm easy on it and just use the power to get up hills etc, its fine.

I do agree that this tune is on the aggressive and possibly dangerous side, but as long as I don't push it nothing crazy should happen. I just have to stay off the go pedal....

EDIT: The stalling and bucking hasn't happened since I cleaned the check valve.

BluAero

Discussion Starter · #19 · Aug 20, 2010

Bam back again...

What a pain in the ass. It almost seems like the car is cutting ignition to the cylinders. Jesse did say when the car was dynoed, they used a clamp on the DI cassette wires in order to get a signal, yet the torque reading was 0,... Thats odd..

The boost gauge goes to full boost and the battery light comes on. I'll get a pic up..

BluAero

Discussion Starter · #20 · Aug 20, 2010 (Edited)

Here's what it looks like....

EDIT: this is directly from thesaabsite
FUEL PUMP ISSUES
[99]

Fuel pump failures often cause the engine to buck when going up hills or just quit completely. You can test the fuel pressure using a fuel pressure gauge. The pressure should about 40 PSI (approximately). The location of the pump depends on which car you have. The earlier 99, 9000 & 900 pumps are located under a board in the trunk and can be removed by removing the board and lifting out the pumps from the top of the fuel tank. On the later model 900, 93, 95, 97X the fuel pump is located in the fuel tank and the tank must be removed to replace it.

It does this sometimes, but starts right back up.Bliping the accelerator while this problem is happening sometimes solves it without having to restart...hmmm what you guys think?

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