Stumbling/surging

[12lepler]

Ok so I checked my fuel pressure and I have 30 psi when I cycle the key, and 30 while at idle and it shoots up to 35+ when I get in the throttle. So I don't think it's a fuel pressure issue. By the way, could lower octane gas be causing this problem?

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[Nascar83Fan]

What octane is in the car and what octane is the chip for? Your fuel pressure is actually low, it should be at least 38 Psi @ idle with line on and stay at or be higher than the idle fuel PSI reading is. even with key on it should read higher than 30 PSI.

 

[12lepler]

What octane is in the car and what octane is the chip for? Your fuel pressure is actually low, it should be at least 38 Psi @ idle with line on and stay at or be higher than the idle fuel PSI reading is. even with key on it should read higher than 30 PSI.

Well that's the problem, I don't know what tune it's running. The receipt I have for that only says "street chip". it has mid grade gas in it, plus it's old so I was thinking that could be some of the problem. So do you think it's safe to up the PSI some?

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[Nascar83Fan]

What you need to do is see what chip the car has and see if it has a label on it with numbers written on it if it's a turbo tweak or other type of aftermarket chip. The old gas isn't gonna help it run too good, it probably has a 91, 93 or 94 octane chip in it. But you need to see what the chip in the ECM on the passenger kick panel is, to know what octane, boost, and timing it was burned for. Once you know what octane it needs as a minimum, you can put fresh gas in it. How full is the gas tank currently if the needle is accurate? I would baby it, also would put some fuel system treatment stuff in to help clean the fuel system & injectors and put fresh gas in the tank. Then you need to verify the fuel pressure reading with the line off and since you have a fuel pressure regulator that is adjustable, have to set it to at least 43 PSI. Then once you done that, put the line back on and should see at least a minimum of 38 PSI with the line on.

 

[12lepler]

What you need to do is see what chip the car has and see if it has a label on it with numbers written on it if it's a turbo tweak or other type of aftermarket chip. The old gas isn't gonna help it run too good, it probably has a 91, 93 or 94 octane chip in it. But you need to see what the chip in the ECM on the passenger kick panel is, to know what octane, boost, and timing it was burned for. Once you know what octane it needs as a minimum, you can put fresh gas in it. How full is the gas tank currently if the needle is accurate? I would baby it, also would put some fuel system treatment stuff in to help clean the fuel system & injectors and put fresh gas in the tank. Then you need to verify the fuel pressure reading with the line off and since you have a fuel pressure regulator that is adjustable, have to set it to at least 43 PSI. Then once you done that, put the line back on and should see at least a minimum of 38 PSI with the line on.

So set it to 43 with the line off? The vaccum line?

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[12lepler]

This here says "street 93" so I'm assuming it's a 93 octane chip. My idea was to drain the gas out of the tank with a hose on the schrader valve, and then hot wiring the fuel pump to just pump all the gas out of the tank

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[Nascar83Fan]

Yeah with the vac line that goes to the fuel pressure regulator off, get it set to at least 43 PSI.
Yeah you need to put 93 octane in it, but still would run a bottle of fuel system cleaner through it when you put the gas in just to make sure the injectors aren't clogged.

 

[earlbrown]

Ok so I checked my fuel pressure and I have 30 psi when I cycle the key, and 30 while at idle and it shoots up to 35+ when I get in the throttle. So I don't think it's a fuel pressure issue. By the way, could lower octane gas be causing this problem?

You got problems. The 30 KOEO is low as it is. When you were idling, it should have been less than 30. You are getting some sort of reference signal since the pressure jumped when you gave it gas UNLESS it was a result of a voltage change just from revving the engine up.


the lower octane will cause other problems like blown head gaskets, pounded out bearings and a crankshaft shaped hole in your oil pan.


You HAVE to have a stable fuel delivery system in place before doing anything with these cars. Period.

 

[12lepler]

You got problems. The 30 KOEO is low as it is. When you were idling, it should have been less than 30. You are getting some sort of reference signal since the pressure jumped when you gave it gas UNLESS it was a result of a voltage change just from revving the engine up.


the lower octane will cause other problems like blown head gaskets, pounded out bearings and a crankshaft shaped hole in your oil pan.


You HAVE to have a stable fuel delivery system in place before doing anything with these cars. Period.

Ok then what should my pressure be? I have one person telling me 38 at idle and you saying that it should be less than 30 at idle which is it? And I'm trying to get stable fuel delivery that's why I'm asking questions here. And what about a reference signal? Why does that matter on a vaccum operated FPR?

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[Nascar83Fan]

http://ihadav8.com/forum/VortexBuicks/basics.htm
Going off of what was said from here under this section:

Fuel Pressure Regulator

The cars originally came with a non adjustable fuel pressure regulator that put out about 40 psi of fuel pressure when the hose was disconnected from the engine. The TTA cars came with another regulator that was also non adjustable, but, it had a bit more pressure when the hose was off and typically showed 42-43 psi when the hose was disconnected.

When the hose is attached as is normally the case, the vacuum created by the engine will pull up on the diaphragm in the engine and the fuel pressure will drop to about 33 or so in the non adjustable factory regulator on the Regals, and, to about 36-37 on the TTA's.

Note that in all cases that I discuss, the engine is running. Also note that the vacuum created by the engine will vary due to engine condition, engine combination, and the load on the engine at the time. My numbers above are in Park, engine idling after being warmed up.

When boost is applied thru the hose to the regulator, then the fuel pressure rises. A properly working regulator with an adequate fuel pump will increase the fuel pressure by one pound for each pound of boost applied to it. That means if the fuel pressure is 43 psi with the hose disconnected, then the fuel pressure should rise to 63 psi if one is running 20 psi of boost at wide open throttle.

Note that chip makers specify a fuel pressure for their chips. A very common number is 43 psi and this number refers to the "hose off" pressure with the engine running. Be very sure that you reattach the hose before driving the car or very bad things will happen if you bring the boost up.

If your fuel pressure is set too low, the car may run too lean. If it is too high, then the car will run too rich. It is very important that the regulator provide consistent fuel pressure if you expect the car to perform consistently and safely. A properly working regulator and a fuel pump that can meet its demands are one of the basic requirements on a turbo car.

 

[12lepler]

http://ihadav8.com/forum/VortexBuicks/basics.htm
Going off of what was said from here under this section:

Fuel Pressure Regulator

The cars originally came with a non adjustable fuel pressure regulator that put out about 40 psi of fuel pressure when the hose was disconnected from the engine. The TTA cars came with another regulator that was also non adjustable, but, it had a bit more pressure when the hose was off and typically showed 42-43 psi when the hose was disconnected.

When the hose is attached as is normally the case, the vacuum created by the engine will pull up on the diaphragm in the engine and the fuel pressure will drop to about 33 or so in the non adjustable factory regulator on the Regals, and, to about 36-37 on the TTA's.

Note that in all cases that I discuss, the engine is running. Also note that the vacuum created by the engine will vary due to engine condition, engine combination, and the load on the engine at the time. My numbers above are in Park, engine idling after being warmed up.

When boost is applied thru the hose to the regulator, then the fuel pressure rises. A properly working regulator with an adequate fuel pump will increase the fuel pressure by one pound for each pound of boost applied to it. That means if the fuel pressure is 43 psi with the hose disconnected, then the fuel pressure should rise to 63 psi if one is running 20 psi of boost at wide open throttle.

Note that chip makers specify a fuel pressure for their chips. A very common number is 43 psi and this number refers to the "hose off" pressure with the engine running. Be very sure that you reattach the hose before driving the car or very bad things will happen if you bring the boost up.

If your fuel pressure is set too low, the car may run too lean. If it is too high, then the car will run too rich. It is very important that the regulator provide consistent fuel pressure if you expect the car to perform consistently and safely. A properly working regulator and a fuel pump that can meet its demands are one of the basic requirements on a turbo car.

Ok I'll set my FPR when it isn't midnight haha. And by the way, I asked earlier what is the proper vaccum readings at highway speeds? Sometimes when this is happening I'm at like 20-25+hg of vac. Is that normal for cruising at 65?

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[earlbrown]

Ok then what should my pressure be? I have one person telling me 38 at idle and you saying that it should be less than 30 at idle which is it? And I'm trying to get stable fuel delivery that's why I'm asking questions here. And what about a reference signal? Why does that matter on a vaccum operated FPR?

No, I said 30 was too low and it should have dropped when you were idling. When you turned the key on it should have jumped to about 45ish. When you start the car it should drop to around 38 or so depending on our idle vacuum.


And the reference signal in important on a 'vacuum operated FPR' because it's also boost referenced. If the pressure doesn't track your manifold PSIA across the board, you're fueling is screwed even if you have a good pump.

 

[87-WE2]

OK - I'm getting confused on this too!!
As far as your original issue with the bucking at highway speed - I had the same issue. Thought it was the TCC solenoid. I unplugged it and no change, just like yours. I decided at that point to live with it and focus on other issues. I bought a new TT chip & injectors and BINGO - problem solved. My old chip was an old ATR Pitbull chip and I have no idea why, but it makes the car "hunt" for a place to lock the converter in 3rd & 4th gear. With the TT chip - no such issue. I'm no chip expert, but I don't recognize the chip you're running. If I ever have another one of these cars and don't know what chip is in it, that will be the FIRST thing that gets tossed and replaced. I would rather play it safe than sorry since the chip controls

As far as fuel pressure goes, you need to have it set at about 43 psi with engine idling and the vacuum line removed from the regulator. While not EVERYONE runs this base fuel pressure, it has kind of become the standard base pressure that everyone starts from. If you have a stock regulator (Bosch brand with PN that ends in 233), you may not be able to get there. The old school way around this was to use a regulator from an 89 TTA (Bosch brand with PN that ends in 237) and most would get about 43 line off. My 237 provided me with about 45psi line off, but it is long gone.

As far as the vacuum goes, it's hard to say. If there's an aftermarket cam in it, it may not pull as much vacuum as a stock cam. My stocker pulls about 18-20 inches of vacuum at idle if memory serves correctly. Your vacuum reading is going to vary during driving based on engine speed and how far your right foot is pushed towards the floor. For example, if you're doing a WOT pull and have the card in "D" and run it up to 100mph, during the run up to 100mph your gauge should be showing boost. If you then let off the throttle and leave it in "D", your gauge should go WAY down to below the idle reading. If you have some vacuum lines that are leaking, your readings will vary. BLM's can be a good indicator of vacuum leaks; high BLM #'s indicating vacuum leaks. The benchmark reading for BLM's is 128 +/-10.

 

[12lepler]

OK - I'm getting confused on this too!!
As far as your original issue with the bucking at highway speed - I had the same issue. Thought it was the TCC solenoid. I unplugged it and no change, just like yours. I decided at that point to live with it and focus on other issues. I bought a new TT chip & injectors and BINGO - problem solved. My old chip was an old ATR Pitbull chip and I have no idea why, but it makes the car "hunt" for a place to lock the converter in 3rd & 4th gear. With the TT chip - no such issue. I'm no chip expert, but I don't recognize the chip you're running. If I ever have another one of these cars and don't know what chip is in it, that will be the FIRST thing that gets tossed and replaced. I would rather play it safe than sorry since the chip controls

As far as fuel pressure goes, you need to have it set at about 43 psi with engine idling and the vacuum line removed from the regulator. While not EVERYONE runs this base fuel pressure, it has kind of become the standard base pressure that everyone starts from. If you have a stock regulator (Bosch brand with PN that ends in 233), you may not be able to get there. The old school way around this was to use a regulator from an 89 TTA (Bosch brand with PN that ends in 237) and most would get about 43 line off. My 237 provided me with about 45psi line off, but it is long gone.

As far as the vacuum goes, it's hard to say. If there's an aftermarket cam in it, it may not pull as much vacuum as a stock cam. My stocker pulls about 18-20 inches of vacuum at idle if memory serves correctly. Your vacuum reading is going to vary during driving based on engine speed and how far your right foot is pushed towards the floor. For example, if you're doing a WOT pull and have the card in "D" and run it up to 100mph, during the run up to 100mph your gauge should be showing boost. If you then let off the throttle and leave it in "D", your gauge should go WAY down to below the idle reading. If you have some vacuum lines that are leaking, your readings will vary. BLM's can be a good indicator of vacuum leaks; high BLM #'s indicating vacuum leaks. The benchmark reading for BLM's is 128 +/-10.

If new fuel and turning up the regulator doesn't work I'm gonna give Turbo Tweak a call. I wanted to do that in the first place for peace of mind anyway

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[Nascar83Fan]

It seems like the previous owner he got the car from had put the car together and once the car started doing what it was doing to the current owner, the previous owner got tired of dealing with it & decided to sell the car without resolving the underlying issues for whatever reason(s).
It's a good possibility that once the fuel pressure is correct, and they have good gas in it that the car hopefully doesn't fall on its face anymore.
I'm crossing my fingers that the car will be running good for him after the fuel issues are resolved.


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[Nascar83Fan]

If you end up having to buy a new chip and getting it matched to injectors, the TT option is a very good one. Hopefully you caught the issues with fuel pressure and old gas before anything bad happened inside.
I have an older TT 5.6 chip that was in the car when i got her almost 4 years ago and it's still working great.


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[12lepler]

Ok so here's what happened, I drained my fuel tank the other night, got 5 gallons of 93 octane for it. I turned my fuel pressure up to 43 psi with the line off. And then I took it for a drive. It still does it. BUT.. I found out that if I play with the throttle and don't let it sit in the same place, the car doesn't do it. I can maintain a speed of 65-70 as long as I'm always adjusting the throttle. Now I still want to get a good chip for it, but I was thinking maybe it's a TPS sensor that has a dead spot in at light throttle where it sits for highway cruising. So which wires do i probe to do a sweep on the sensor?

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[Nascar83Fan]

It's called a throttle position sensor ( tps ) on these cars and other vehicles that use a throttle body intake system bud. You can go buy it fairly cheap at any local auto parts store for our cars. A TPS with a deadspot can cause driveability issues and the remedy for that is replacing it with a new one. With a scanmaster it'd be alot easier for you to actually could see with key on engine off if there was a deadspot on the tps. Toggle over to tps on scanmaster and then take note of changing voltage by slowly putting more pressure on the pedal to make it sweep and as soon as you see erratic behavior can determine that it needs replacement.
Chances are that TPS needs to be replaced, as once a deadspot gets in them they're just waiting to fail after that. It's probably a really old one and they need replacing from time to time.
With key on engine off, on the TPS find the positive with a volt meter and for the ground probe find a good ground in the engine bay area to accurately test the range of the TPS. Odd that it only does it once you're at 60+ mph though, do you notice at lower speeds anything going on or only once you at 60+?
Something isnt right somewhere and without a scanmaster it's gonna be harder to trace the issues.

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[12lepler]

It's called a throttle position sensor ( tps ) on these cars and other vehicles that use a throttle body intake system bud. You can go buy it fairly cheap at any local auto parts store for our cars. A TPS with a deadspot can cause driveability issues and the remedy for that is replacing it with a new one. With a scanmaster it'd be alot easier for you to actually could see with key on engine off if there was a deadspot on the tps. Toggle over to tps on scanmaster and then take note of changing voltage by slowly putting more pressure on the pedal to make it sweep and as soon as you see erratic behavior can determine that it needs replacement.
Chances are that TPS needs to be replaced, as once a deadspot gets in them they're just waiting to fail after that. It's probably a really old one and they need replacing from time to time.
With key on engine off, on the TPS find the positive with a volt meter and for the ground probe find a good ground in the engine bay area to accurately test the range of the TPS. Odd that it only does it once you're at 60+ mph though, do you notice at lower speeds anything going on or only once you at 60+?
Something isnt right somewhere and without a scanmaster it's gonna be harder to trace the issues.

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Oh whoops I meant to say tps. I accidentally said Tire Pressure Monitoring System haha. TPS, TPMS, I say the wrong one and I look like a noob had to go back and correct myself, there are so many acronyms for sensors. But it happens when I'm at a throttle position for highway cruising. I think from years of cruising at 65, that point in the TPS has been worn out. I've seen it on other cars like my friends mid-2000s impala where it does it on the highway but nowhere else.
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[Nascar83Fan]

In that case, just get a new TPS and toss the old one aside. Then adjust the new tps accordingly.


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