Fuel Cut Help!

[DontStartModdin]

I just sold my daily driver and am now forced to drive my '90 Plymouth Laser RS-T everyday. I'm in Wisconsin where the average temp has been around 20*. My car is faily stock, but I have a Slowboy Racing boost controller that I cannot set lower than 14psi. With that being said, I have to keep the rpms under 5k or I'll hit fuel cut. And even lower at night where it drops close to 0*.

My question is, would throwing some evo III 510cc injectors in there solve this problem?

Thanks a lot for your help in advance,

-Keith

 

[silver bullit]

No not unless you have the mods for it or you dont mind walking when your motor blows.

Just tkae out the mbc and set the car back to stock boost till you can afford to modify it

 

[DontStartModdin]

No not unless you have the mods for it or you dont mind walking when your motor blows.

Just tkae out the mbc and set the car back to stock boost till you can afford to modify it

Why would my motor blow? Wouldn't it just run a little rich?

I've seen people throw a 2g mas on with some 550's and there running fine. Wouldn't this be a little more safe than that?

 

[silver bullit]

Why would my motor blow? Wouldn't it just run a little rich?

I've seen people throw a 2g mas on with some 550's and there running fine. Wouldn't this be a little more safe than that?

Yes it will compensate but you dont have any way off telling what your motor is doing.

Ironic that your name is DontStartModdin maybe you should read up on why.

Running rich or lean excessively for periods of time can cause knock, detonation, and can cause the pistons, turbo wheels to melt if it gets way to rich or lean.

But mainly i have been there done that, but hey its your wallet not mine.

 

[HighBoostLaser]

You have boost leaks check for them then are you venting you Blow off Valve in the air aka taking you tube off the blow off valve for sound if so plug you bov tube back on!

 

[DontStartModdin]

Yes it will compensate but you dont have any way off telling what your motor is doing.

Ironic that your name is DontStartModdin maybe you should read up on why.

Running rich or lean excessively for periods of time can cause knock, detonation, and can cause the pistons, turbo wheels to melt if it gets way to rich or lean.

But mainly i have been there done that, but hey its your wallet not mine.

I have a logger.

My main point is since the weather is so cold out, wouldn't that take care of some of the fuel burn up? I know i'll be running fairly rich at idle, but when driving it should balance out decently.

 

[DontStartModdin]

You have boost leaks check for them then are you venting you Blow off Valve in the air aka taking you tube off the blow off valve for sound if so plug you bov tube back on!

I have no boost leaks.

And no i'm not venting my bov.

The reason i'm hitting fuel cut so fast is because of the cold weather being so cold.

It was fine in the summer while running 16psi. And I was getting absolutely no knock at all.

 

[HighBoostLaser]

Ok Hmmm

 

[kenamond]

The quickest fix I can think of is to use your foot to control boost; just don't floor it, and you can easily control boost. The next-simplest fix is to remove the MBC and run a vaccuum line straight from the j-pipe to the WGA. I'm not sure what the stock WGA pressure is, but it's like 9psi on a 2g.

I wouldn't recommend increasing your injector size without a fuel controller. Your fuel economy will go to hell, you'll run rich, but it won't do anything at all about fuel cut (fuel cut is based on excessive airflow, and larger injectors won't tell the MAF to decrease its airflow signal, right?).

If you've got the cash for an AFC and 510s, you could go that route, but (didn't check your profile), you might end up running out of fuel due to stock FP which would be worse than fuel cut.

And it might be that you have some boost leaks. If so, fixing them will buy you more headroom with fuel cut. Perhaps you know this, but a leak while under boost will leak air that's already been metered by the MAF, so the ECU thinks its getting more air than it actually is (it's not getting the leaked air, but it doesn't know that; it only knows what the MAF tells it). Since fuel cut is based on airflow, a boost leak, no matter how small, would put you closer to fuel cut.

 

[HighBoostLaser]

Well how do you know you dont have boost leaks? Also then well my car runs fine annd daily its -15 out so I dont know why your car would be running rich if its hitting fuel cut your running lean.

 

[HighBoostLaser]

The quickest fix I can think of is to use your foot to control boost; just don't floor it, and you can easily control boost. The next-simplest fix is to remove the MBC and run a vaccuum line straight from the j-pipe to the WGA. I'm not sure what the stock WGA pressure is, but it's like 9psi on a 2g.

I wouldn't recommend increasing your injector size without a fuel controller. Your fuel economy will go to hell, you'll run rich, but it won't do anything at all about fuel cut (fuel cut is based on excessive airflow, and larger injectors won't tell the MAF to decrease its airflow signal, right?).

If you've got the cash for an AFC and 510s, you could go that route, but (didn't check your profile), you might end up running out of fuel due to stock FP which would be worse than fuel cut.

And it might be that you have some boost leaks. If so, fixing them will buy you more headroom with fuel cut. Perhaps you know this, but a leak while under boost will leak air that's already been metered by the MAF, so the ECU thinks its getting more air than it actually is (it's not getting the leaked air, but it doesn't know that; it only knows what the MAF tells it). Since fuel cut is based on airflow, a boost leak, no matter how small, would put you closer to fuel cut.

Thanks you Check For Boost Leaks!

 

[DontStartModdin]

The quickest fix I can think of is to use your foot to control boost; just don't floor it, and you can easily control boost. The next-simplest fix is to remove the MBC and run a vaccuum line straight from the j-pipe to the WGA. I'm not sure what the stock WGA pressure is, but it's like 9psi on a 2g.

I wouldn't recommend increasing your injector size without a fuel controller. Your fuel economy will go to hell, you'll run rich, but it won't do anything at all about fuel cut (fuel cut is based on excessive airflow, and larger injectors won't tell the MAF to decrease its airflow signal, right?).

If you've got the cash for an AFC and 510s, you could go that route, but (didn't check your profile), you might end up running out of fuel due to stock FP which would be worse than fuel cut.

And it might be that you have some boost leaks. If so, fixing them will buy you more headroom with fuel cut. Perhaps you know this, but a leak while under boost will leak air that's already been metered by the MAF, so the ECU thinks its getting more air than it actually is (it's not getting the leaked air, but it doesn't know that; it only knows what the MAF tells it). Since fuel cut is based on airflow, a boost leak, no matter how small, would put you closer to fuel cut.

I did a boost leak test and it came back good.

Could this be caused by my bov's (greddy type rs) adjuster is stripped and I can't adjust it? It could be possibly leaking air out that way which would cause this right?

 

[HighBoostLaser]

Yes it could be venting a little now or your bov is giving out on you under pressure.

 

[kenamond]

I did a boost leak test and it came back good.

Could this be caused by my bov's (greddy type rs) adjuster is stripped and I can't adjust it? It could be possibly leaking air out that way which would cause this right?

Only if you don't have it recirculated. You have it recirculating back to the intake pipe, right? If it's recirculated, all of that air that is metered by the MAF will stay in the intake system.

When you boost leak tested, what were the results, specifically. For example, I claim to have no significant leaks because I pressurize to 20psi and it leaks down 1psi every 4 seconds.

I'm not too familiar with the limits of the 1gs, but as a 2g owner running 15psi on stock fuel, I don't hit fuel cut at 10°F. Maybe the 1g ECU is more picky with its fuel cut limit, or maybe your car's volumetric efficiency is better than mine.

 

[DontStartModdin]

Only if you don't have it recirculated. You have it recirculating back to the intake pipe, right? If it's recirculated, all of that air that is metered by the MAF will stay in the intake system.

When you boost leak tested, what were the results, specifically. For example, I claim to have no significant leaks because I pressurize to 20psi and it leaks down 1psi every 4 seconds.

I'm not too familiar with the limits of the 1gs, but as a 2g owner running 15psi on stock fuel, I don't hit fuel cut at 10°F. Maybe the 1g ECU is more picky with its fuel cut limit, or maybe your car's volumetric efficiency is better than mine.

It is recirculated yes.

My buddy did the boost leak test for me and said I was good. Not sure what the exact results were as far as that goes.

My buddy also told be the reason I was hitting fuel cut was because of it being so cold. If that ain't it what could it be?

 

[DontStartModdin]

I am also running open downpipe. Not sure if that would matter or not.

 

[HighBoostLaser]

Yes possibly its called boost creep when your off the o2 but your running an open down pipe so i dont know if the same rules apply

 

[DontStartModdin]

Yes possibly its called boost creep when your off the o2 but your running an open down pipe so i dont know if the same rules apply

No boost creep at all. I have an aftermarket boost gauge and it shows that it's holding 14psi firmly until I hit fuel cut at around 5k rpm's.

 

[HighBoostLaser]

Then Dude its Deffinitely a boost leak no matter where you friend looked do it yourself and re check.

 

[My1GLaser]

My buddy also told be the reason I was hitting fuel cut was because of it being so cold. If that ain't it what could it be?

Yes, that is quite possible. Very cold air (20*) is much denser than (80*) air. If you have a stock MAF, it takes IAT into account when calculating airflow and you could be hitting fuel cut a few hundred rpm sooner because of the increased airflow.

IMO, the density difference is enough that I have a summer and winter tune. The GM MAF I run tells the ECU that the intake temp is always 81*. Which really probably doesn't matter much because the colder air will help cool the combustion chamber and reduce knock if I run a little leaner.

Do a boost leak test anyway! It should be a monthly routine.

 

[kenamond]

With a free-flowing exhaust, your volumetric efficiency (VE) will be higher. That just means that you'll flow more air at 14psi than a car with a lower VE. In that case, it might be legitimate fuel cut. Make a boost leak tester and do a BLT at every or every other oil change; they're pretty easy to do. If you have leaks, fix them. If you don't, that's great. And if you have no leaks but are still hitting fuel cut when it cools down, consider lowering boost below 14psi. I don't understand why you can't lower your MBC below 14 unless it's actually a 14psi WGA (you can't go lower boost than the WGA actuation pressure). What type of MBC? Anyway, if you put a vaccuum line straight from the j-pipe to the WGA and still hit 14psi, it's the WGA actuation pressure that's limiting your minimum boost.

So do the BLT at 20psi and fix leaks until you can leak down at 1psi every few seconds. Bypass the MBC to see if the WGA is keeping your boost at a minimum of 14psi. Post what you find.

 

[DontStartModdin]

With a free-flowing exhaust, your volumetric efficiency (VE) will be higher. That just means that you'll flow more air at 14psi than a car with a lower VE. In that case, it might be legitimate fuel cut. Make a boost leak tester and do a BLT at every or every other oil change; they're pretty easy to do. If you have leaks, fix them. If you don't, that's great. And if you have no leaks but are still hitting fuel cut when it cools down, consider lowering boost below 14psi. I don't understand why you can't lower your MBC below 14 unless it's actually a 14psi WGA (you can't go lower boost than the WGA actuation pressure). What type of MBC? Anyway, if you put a vaccuum line straight from the j-pipe to the WGA and still hit 14psi, it's the WGA actuation pressure that's limiting your minimum boost.

So do the BLT at 20psi and fix leaks until you can leak down at 1psi every few seconds. Bypass the MBC to see if the WGA is keeping your boost at a minimum of 14psi. Post what you find.

Okay, I didn't do another BLT because it's way too cold out tonight. But I will try to get it done tomorrow.

I'll give you a quick background of my car. When I bought it it was pretty stock, and running stock boost (10psi). I bought a boost controller and an aftermarket boost gauge and turned it up to 14psi. I had it like that for a few months and it ran and drove awesome the whole time (absolutely no fuel cut). Then I took the stock exhaust off because I had bought a full 3" from a guy locally. It turned out the exhast was not a direct bolt on so there will need to be some modifying of the stock mounting points. So I havent put it on yet. I took it out for a drive every once in awhile with no exhaust seeing as I had a different dd. I drove the Laser over the cousre of a month or two (last December). It was still fairly warm in December so I wasn't hitting fuel cut at all at 14psi. This pretty much all started when I sold my dd last month and now have to drive my Laser all the time. There is no doubt it my mind that the weather is playing a major role in me hitting fuel cut, because on warmer day (40* or so) it will be fine. And not hit fuel cut at all.

The boost controller I'm using is a manual Slowboy Racing ball and spring style. And it is hooked up correctly, so no problem there.

As for the wastegate actuator being set to 14psi is not possible because It was running 10psi before the boost controller.

Thanks a lot for your help. I really appreciate it.

-Keith