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5000 RPM cutout

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zerorecall

Probationary Member
4
0
Aug 29, 2005
Monroe, Washington
Hey Guys,
My car pulls real nice all the way to 4500-5000 then cutsout really badly....... pulls,pulls then 4500-5000 bam!!!! WTF just like hitting a wall. then once RPMs are down it pulls hard again. I tried searching, but all I was able to come up with was need a new ECU or a speed sencer...... any help would be great, I am new to DSM's LOL! , I have been a supra guy for so long. :thumb:
 
Souds like your experiencing "Fuel Cut" Research it, learn it, fix it. If your still all stock, its probly caused by a massive "boost leak" . Research that too.
 
I have thought about that too, and I did check all the lines. it happends even when I turn down the boost to 9Lbs. It happends no matter what boost setting I have. I did a test to see if that was it by blocking off the boost senser... AKA FFCD, but that didn't work.... I know turbo cars like the back of my hand, I have owned 2 MKIII supras and 1 MkIV supra all turbo, so I know that would be a easy fix but that was not what is happening here. but thank you for your input. :) :rolleyes:
 
I'm having the same problem on my tsi. i'm also on 9 lbs . I hit 5,000 and i get hard fuel cut.
I'm going to get a compressor and everything to do a leak test. I tried using soapy water while the car was idling. It's too hard to hear exactly where the hiss is coming from with the engine running.
when i hook up the compressor i'm hoping it should be easy to find it. The hiss seems to be coming from around the injector area.
 
zerorecall said:
I have thought about that too, and I did check all the lines. it happends even when I turn down the boost to 9Lbs. It happends no matter what boost setting I have. I did a test to see if that was it by blocking off the boost senser... AKA FFCD, but that didn't work.... I know turbo cars like the back of my hand, I have owned 2 MKIII supras and 1 MkIV supra all turbo, so I know that would be a easy fix but that was not what is happening here. but thank you for your input. :) :rolleyes:
I bet you it's easier than you think it is.....

bkblazen2003 said:
I'm having the same problem on my tsi. i'm also on 9 lbs . I hit 5,000 and i get hard fuel cut.
I'm going to get a compressor and everything to do a leak test. I tried using soapy water while the car was idling. It's too hard to hear exactly where the hiss is coming from with the engine running.
when i hook up the compressor i'm hoping it should be easy to find it. The hiss seems to be coming from around the injector area.

Injector seals and insulators....


For both of you:
What kind of spark plugs are you using, what are they gapped at?

Your problem is either one of two things. Spark plugs, or a boost leak. I betcha :thumb:
 
Any of the guys with problems test/check there map sensors? Its possible there stuck in the open loop mode (or bad) and giving you the "feel"of fuel cut at around that rpm range. Just a thought.
 
that could be true about the loop deal I know I had a similar looping issue with my 94TT but I fixed that with a new ECU.
 
does the rpm keep goin but the car isnt pulling anymore? it might be because of the stock turbo that past 5k doesnt boost anymore and you feel like you engine isnt pulling anymore.
 
madhatter210 said:
Any of the guys with problems test/check there map sensors? Its possible there stuck in the open loop mode (or bad) and giving you the "feel"of fuel cut at around that rpm range. Just a thought.
That's possible.

But first check for boost leaks using THIS link.
Fuel Cut is caused not by lack of fuel, but to much air/un metered air.
If the boost leak test doesn't work, then check the MAS.

Also, update your vehicle profile so we can actually relate to your car.
 
ddavisaf said:
That's possible.


Also, update your vehicle profile so we can actually relate to your car.

I was thinking the same thing after I posted I guess I should of said mas/map and covered both.
 
madhatter210 said:
Any of the guys with problems test/check there map sensors? Its possible there stuck in the open loop mode (or bad) and giving you the "feel"of fuel cut at around that rpm range. Just a thought.

yea i changed my maf. the old one had no lower honey comb and silncer. with the new one if only made the idle better. still had fuel cut
I will buy everything i need for the leak test next week. for zerorecall do a full tune up changing plugs,wires if needed. cheack timing belt, timing marks, base timing. i hope that solves the problem for the both of us.
if not i'm gonna look into getting a fcd. i'm also going to look into a safc . maybe with that i can trick the ecu from ever thinking that the maf is maxed out.

Aye Zerorecall are you also getting bad idle?
 
bkblazen2003 said:
if not i'm gonna look into getting a fcd. i'm also going to look into a safc . maybe with that i can trick the ecu from ever thinking that the maf is maxed out.
The simple answer is that because fuel cut is pre-programmed into the ECU, there is no method of disabling it. There are no modifications that can do so, aside from an ECU upgrade that eliminates fuel cut. Upgraded fuel pumps, injectors, and fuel pressure regulators do nothing to avoid or eliminate fuel cut. NOTHING.

That being said, there are some methods (some cheap, some not) of postponing fuel cut. All the methods work on one principle: fooling the ECU into thinking there is less air entering the engine than, in fact, there is. This can be done by adding unmetered air, or by changing the sensor inputs used by the ECU to determine air mass. Of course, these methods usually mean the engines run leaner than stock. Again, read this section of the ECU primer for details.

Fuel cut is cessation of fuel delivery and spark generation by the ECU. It is a pre-programmed response designed to save the turbocharger from utter destruction in the event of a catastrophic wastegate malfunction. For more details, read the ECU Primer, specifically the chapter on fuel cut. Also read Todd Day's Diagnostic Port issue on fuel cut, and the answer to "How do I prevent fuel cut" in this FAQ.

When the ECU detects a condition that the factory didn't intend the engine to experience, it will try to save the engine using something commonly known as "fuel cut". All of the injectors are shut off as well as all the spark plugs, effectively shutting down the engine. When the condition has passed, the ECU will go back to running spark and fuel as normal. You might experience this as a violent bucking sensation.

What conditions will cause fuel cut?

There are three conditions under which the DSM ECU will chop fuel.

Engine speed higher than 7500 RPM. This is overrev protection. If your engine rotates faster than the valve springs can pull the valves back up into the head, the pistons could smack into them, causing major damage. Note that simply chopping fuel will not stop the overrev condition if you misshift and the transmission rotates the engine past the revlimit. (The author did this to his friend's M3.)
Engine air flow greater than a certain amount. If the airflow into the becomes too great, the phenomenon by which the MAF counts the air entering the engine starts to break down, missing counts. The factory ECU sets a very conservative limit here. It doesn't need to be as conservative as it is to prevent missing counts. After we removed this limit, we were only able to hit the MAF counting breakdown problem on a first generation DSM with a 20G set to 19 psi on a 3" exhaust.
Engine under high vacuum for more than a couple seconds. This is not a matter of engine safety, but of smog control. Some of the worst smog can occur during engine deceleration. If you are coasting down a steep hill using the engine to help slow you, the ECU will turn off all fuel to the engine to both aid in engine braking and smog production.
What does fuel cut feel like?

Like you hit a brick wall, if it happens when you have the throttle to the floor. Typically, the ECU thinks too much air is entering the engine, the engine shuts completely off, the air amount decreases to under the limit, and the engine goes back on again. This can be quite jerky.

Some days I get fuel cut, some days I don't, even running a consistent boost pressure.

Fuel cut does not depend on boost pressure - it depends on air flow. Remember the gas laws from high-school chemistry? If you keep the pressure constant, you can pack more of a gas when it is cold into a given space than when it is hot. So even if you keep your boost pressure the same, more air will be flowing into your engine when it is cold at night or in winter than when it is hot during the day or in summer. Thus, you might start experiencing fuel cut at night or during winter that you don't experience at other times.

How can I prevent fuel cut from happening?

Of course, we recommend the Stage II ECU modification, which removes the air flow limit imposed by the ECU. There are other methods that use MAF modifications to "fool" the ECU into thinking less air is entering the engine ("Dime Store Fuelcut Remover", MAF gutting). There is a danger with these "fool-the-computer" mods, however. The ECU might not provide as much fuel as the engine requires - possibly running lean. With our modification, the ECU still knows exactly how much air is entering the engine.

I am getting something that feels like fuel cut, but the car only has a slight hesitation, not a dramatic on/off.

Here are three possible reasons for fuel-cut like hesitation. Keep in mind that none of these involve the ECU directly.

Lack of spark. Under high boost conditions, if the spark is weak due to dirty plugs, it can be completely blown out. If the spark plug wires are old, the insulation might be breaking down, letting the spark arc to the engine instead of firing in the cylinder.
Lack of fuel. Fuel filter or fuel injectors could be clogged. The fuel pump might not have enough output to handle your fuel load. Sometimes, simply running an extra heavy gauge wire to the fuel pump can overcome voltage drops that occur when the pump is drawing a lot of current.
Modified MAF. If you have removed the honeycombs (they produce a laminar airflow) from a DSM MAF, you can disturb the phenomenon by which air flow is counted. If the MAF is missing air counts, the ECU will not put out enough fuel to properly match the air the engine is getting. This can cause a lean condition.
A possible fourth reason for this sort of fuel cut might occur if you have our Stage II fuel cut removal and you are running a modified MAF on a 1st generation DSM. The vortice field that the MAF uses to count the air might be breaking down if there is air disturbance due to honeycomb removal. At this point, you will want to step up to the large MAF used in the Stealth and the 2nd generation DSM. Technomotive will has been running two daily driver cars with a 95 MAF with great results. Look for the 2G MAF upgrade soon.

Chapter 7: DSMs and fuel cut

Turbochargers are positive feedback devices - the faster they spin, the more air they push into the engine. The more air they push into the engine, the more exhaust gases are produced. The more exhaust gases that are produced, and the faster the turbo spins. The faster they spin....

See the problem? The faster they go, the faster they go! Eventually something would have to break. To prevent this situation from occuring at all, turbos have a device on them called a wastegate that limits the turbo speeds to manageable levels. This is a pressure-activated valve that opens at a preset pressure and vents additional intake pressure either to the atmosphere or back into the exhaust stream.

Modern turbo design notwithstanding, it is still very possible for the wastegate on the turbo to malfunction, leading to exactly the ever-faster turbo behavior described above. Recognizing this, the designers of the DSM ECU built a fail-safe limiting mechanism into the DSM ECU modules. And it goes like this:

Should the ECU ever see an intake air mass greater than a certain preset level, it will stop fuel delivery and spark to the engine cylinders. This 'critical mass' depends on air volume, temperature and pressure, as measured by the MAS sensors. The act of the ECU cutting off fuel delivery to the engine is known as the infamous 'fuel cut'.

Why'd they do this?? Well, should the wastegate ever malfunction in such a way as to allow the turbo to spin out of control, the ECU will stop firing the cylinders to save the turbo from exploding. This is not the only method the ECU has to limit the turbo operation, but it is the last and most desperate. The mass air limit at which the ECU will fuel cut was based off of the maximum amount of fuel that the stock fuel pump and injectors could deliver to the engine cylinders.

Unfortunately, those owners who purposefully modify their engines to provide greater power are deliberately forcing more air through their engines in order to produce more power. Recognizing the limitations of the stock fuel delivery system, serious modders usually upgrade the fuel pump and/or injectors in order to provide enough fuel capacity for the hopped-up engine.

However, the fuel cut limit, based on the stock fuel system, is pre-programmed into the ECU and cannot be changed. There is no method by which the ECU can be made aware of the improvements made to the fuel system, so it will blithely cease fuel delivery once the mass air intake reaches a predetermined level regardless of how much fuel capacity is really available. This characteristic of the DSM ECUs, while understandable, has been a source of nearly endless frustration for power-hungry owners.

There are solutions to this problem. Aside from reprogramming the ECU (which is sometimes possible) to eliminate the fuel cut, all of these solutions utilize the same basic principle - fool the ECU into believing there is less air entering the engine than, in fact, there is. This is often accomplished by altering one or more of the input signals sent to the ECU by the various air measurement sensors present in the MAS.

For example, a volume of air at higher temperature contains a smaller mass of air than an equivalent volume at lower temperature. The ECU determines the intake air temperature from a sensor in the MAS. Electrically altering this signal can make the ECU read a higher air temperature than actually exists. Based on this erroneous temperature, the ECU will calculate the mass air intake as being less than the actual amount.

Even expensive fuel control systems utilize this technique to keep the ECU from activating fuel cut. These systems, however, often intercept more than one ECU signal, and can provide their own monitoring equipment to allow the operator to properly observe the condition of the operating engine. This allows the owner to 'fine-tune' the car to achieve the desired characteristics while keeping the engine safe from harm.

Obviously, doing this type of modification is a relatively dangerous process. By changing the ECU inputs, the operator runs the risk of altering both open and closed-loop ECU operation to the point where the engine does not receive enough fuel. As always, it is up to the operator to monitor the engine operation to ensure that a damaging situation does not occur.
 
I just did all the hard work, all you gotta do is read up :thumb:

Test for boost leaks then come back if you're still experiencing "fuel cut"
 
zerorecall said:
yeah my idel is alittle rough.

You seem to have all my syptoms. I did find a cure for my fuel cut today. my boy also has the same problem but he got a 2g. He showed me how to use the throttle to avoid fuel cut.

Today i was able to rev till redline. You have to trick the ecu into thinking it's not getting full throttle( i guess you can only get fuel cut at full throttle). you have to press the throttle down smoothly but not 100% just about 90-95%.

It accelerates just as hard as if you had it down 100% but you get no fuel cut.
If you feel it doesn't rev as fast as you want. Up the boost pressure till your satisfied.

I'm still gonna do the leak test though.

Should of seen the smile on my face. This is the first day i took the car past 5000 since i owned it.
 
ddavisaf said:
:|
You're not fixing the problem, you're postponing it.....

Actually i'm not postoning it. with tha method i don't get fuel cut at all. I am able to reach redline. I am still going to look into whats causing the fuel cut when i put the pedal to the floor.
 
project_tsi said:
Souds like your experiencing "Fuel Cut" Research it, learn it, fix it. If your still all stock, its probly caused by a massive "boost leak" . Research that too.
:thumb:

zerorecall said:
I have thought about that too, and I did check all the lines. I know turbo cars like the back of my hand, I have owned 2 MKIII supras and 1 MkIV supra all turbo, so I know that would be a easy fix but that was not what is happening here.
Wow, with all that experience and you're looking for boost leak by visually checking the lines, perhaps you need to get to know the back of your hand better. :p Perform that boost leak test then post back.

Actually i'm not postoning it. with tha method i don't get fuel cut at all. I am able to reach redline. I am still going to look into whats causing the fuel cut when i put the pedal to the floor.
Forget about this part throttle business and fix it right, I'm sure that's why you posted in this thread. Boost leak test is step number one when dealing with fuel cut, provided that you have fuel cut.

ddavisaf, I'm not even going to comment on that long post, during working hours no less. ROFL You're now on my "do not hire list". :p
 
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