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Mysterio
03-30-2008, 12:56 AM
I'm using a stage5 calibration on my 87 dodge shelby charger from you guys. I am having a problem hitting a HARD fuel cut at the top end of 4th gear at around 5000-5500 rpm. Power loss light comes on, it dies completely like a HARD fuel cut.

I'm assuming it's got to be a computer related fuel cut. If it was just the pump lacking on pumping ability it wouldn't turn the power loss light on and cut out that hard for a second and then drive fine right afterwards.

So my question is. Can one of you guys tell me EXACTLY what the possible causes are for the computer causing fuel cut?

iTurbo
03-30-2008, 07:16 AM
Have you checked the codes and verified you are actually getting 45 (overboost)?

Mysterio
03-30-2008, 12:24 PM
Have you checked the codes and verified you are actually getting 45 (overboost)?

I never have gotten a code 45, and I never said it was overboost.. It's the same type of fuel cut like when you hit overboost. But it only happens at 5000-5500 rpm in 4th gear when I've already been at full boost for like 15 seconds already. And I'm runnin a 3 bar map so 15 lbs of boost shouldn't be overboost. And it holds 15 lbs of boost steady according to my gauge.

MiniMopar
03-30-2008, 01:33 PM
Does the tach drop to zero when the cutout happens? If so, then it's the HEP signal being lost. Otherwise it sounds like the rev limiter or overboost. What is the overboost cut out set to in this cal and how are you controlling boost? Being a custom cal, it may not quite behave as a stock cal as far as code are concerned depending what has been done to it. I've seen some weird stuff in Blueberry mods for example.

Mysterio
03-30-2008, 04:31 PM
Does the tach drop to zero when the cutout happens? If so, then it's the HEP signal being lost. Otherwise it sounds like the rev limiter or overboost. What is the overboost cut out set to in this cal and how are you controlling boost? Being a custom cal, it may not quite behave as a stock cal as far as code are concerned depending what has been done to it. I've seen some weird stuff in Blueberry mods for example.

I'll have to do it again and watch the gauges a bit better and see exactly what happens. I'm controlling the boost w/ a manual controller which is set at 14-15 lbs. The cutout should be like what? 24 lbs with a 3 bar map right? The HEP is BRAND NEW. And it was doing it w/ the old HEP before that one went bad. So it's not the HEP itself causing it if that is the case it would have to be something in between the hep & LM.

MiniMopar
03-30-2008, 04:53 PM
The 3-bar can read up to 29psi or so, but that has nothing to do with where the overboost cutout is set in the cal. This is a key thing they should have told you when you got it.

turbovanmanČ
03-30-2008, 06:55 PM
And thats why he's asking here, to find out what Cindy sets them at, :clap:

MiniMopar
03-30-2008, 07:00 PM
Oops...sometimes I forget to look at which forum I'm in...:bolt:

turbovanmanČ
03-30-2008, 07:07 PM
Oops...sometimes I forget to look at which forum I'm in...:bolt:

Well if you quit touching your noodly appendage, :confused: ;)

Mysterio
03-30-2008, 08:09 PM
Haha. I posted here figuring Cindy or someone could give me a little breakdown of exactly what things can cause the computer to fuel cut so I know where to look at can narrow things down.


Correction though. I am running a stage4, not a stage5. Sorry. But according to their website max boost on the s4 cal is 29 psi

Mysterio
03-31-2008, 08:48 PM
FWD Performance can't contribute at all with this situation??

turbovanmanČ
03-31-2008, 08:52 PM
FWD Performance can't contribute at all with this situation??

Probably best if you call them.

Mysterio
03-31-2008, 09:35 PM
Probably best if you call them.

Yea I figured but I didn't want to :P I guess I'm going to have to though.

moparzrule
03-31-2008, 09:43 PM
Does it do it in fifth gear? Any other codes?
And you are running a 3 bar MAP sensor correct? Because if you are still using a stock 2 bar that would explain this. In fourth gear you have a higher load, so it will make a touch more boost, maybe just the right amount to trigger overboost.

Mysterio
03-31-2008, 09:53 PM
Does it do it in fifth gear? Any other codes?
And you are running a 3 bar MAP sensor correct? Because if you are still using a stock 2 bar that would explain this. In fourth gear you have a higher load, so it will make a touch more boost, maybe just the right amount to trigger overboost.

I'm not sure if it does it in 5th gear or not. I'm getting a code for my o2 sensor & speed/distance sensor. I don't think either of those would cause it to fuel cut or overboost though?

I'm running a 3 bar map. Ran the wiring for it myself according to minimopar diagrams, I'm fairly confident I wired it in correctly. The overboost for the computer should be like 29 lbs though right with a 3 bar map. And I'm only running 15 lbs.... That doesn't make much sense.

MiniMopar
03-31-2008, 09:58 PM
29psi is the absolute max pressure the 3bar MAP can measure. The overboost cutout limit it set in the cal itself and generally this is something you would discuss with the vendor. If left untouched from stock, it comes out to around 21psi after the 3bar MAP refactoring.

moparzrule
03-31-2008, 10:07 PM
Bad O2 sensor would put it in limp mode, causing overboost cutout at 15 PSI no matter if it's a 3 bar MAP or not. There's your problem.

MiniMopar
03-31-2008, 10:15 PM
That also depends on the cal and which constants were scaled. Left alone, they will cutout at 21psi. It could be that, though. These don't have a staging mod, do they? If so, a bad speed sensor can trick the cal. Which O2 code are you getting? Do you have an O2 gauge? The S5 cals sometime run rich for folks.

Like Simon said, I would just call up Cindy.

WickedShelby88
04-01-2008, 12:28 AM
Yeah that could be speed sensor, O2, or a boost spike causing a boost cutout. Definitely find out by calling and seeing where your boost cutout is set. It seems to be harder and harder to troubleshoot where that gremlin under the hood is hiding the more mods you do.

moparzrule
04-01-2008, 06:50 AM
If it was the speed sensor with a staging limiter issue, it would do it in all the gears. I do not believe cindy's cal have a staging limiter anyway.

WickedShelby88
04-01-2008, 09:26 AM
Good point. Even if it were in the wiring it would do it in all gears especially. 4th gear tends to point in the direction where its when the engines at its greatest load. I might even test the alternator at this point and if an oscilloscope was available check the spark curve per cylinder.. Something is screwy somewhere. I remember having an 86 bronco with the EFI 351 and it did something similar and turned out to be the TPS.. man that was a biotch to find until we hooked the TPS to a scope and saw the glitch right away..

Mysterio
04-01-2008, 01:07 PM
51 Oxygen sensor Engine running/closed loop 84 rich/lean more than 2 min/85-88 lean more than 12 min

That's the O2 sensor code I am throwing. I think my o2 sensor is sooted up and not reading at all.

I tried to get it out the other day but failed due to it being locked in there tight as hell and having absolutely no room to work with since the o2 sensor is in a horrible spot back there.

So I don't know what I'm going to do.

turbovanmanČ
04-01-2008, 01:10 PM
Well the ox code is really irrelevant as at WOT or in boost, the computer ignores it so that won't be it. It CAN cause issues at part throttle but this doesn't seem to be the case. You can just disconnect it and see what happens.

MiniMopar
04-01-2008, 01:16 PM
Lean too long is often a fouled O2 sensor and it can make the engine run very rich. Could also be shorted to ground. Disconnecting it should eventually give you a code 21. Cindy will likely ask you to fix any sensor issues before sending the cal back.

moparzrule
04-01-2008, 01:23 PM
Well the ox code is really irrelevant as at WOT or in boost, the computer ignores it so that won't be it. It CAN cause issues at part throttle but this doesn't seem to be the case. You can just disconnect it and see what happens.

Not true. The ECU doesn't read it at WOT, but it's already throwing the code making it run in limp mode which will make it cut.

turbovanmanČ
04-01-2008, 01:27 PM
Not true. The ECU doesn't read it at WOT, but it's already throwing the code making it run in limp mode which will make it cut.

Possibly but that won't explain why it does it in one gear. If the computer is in limp mode, it will do it in all gears as the computer has no idea what gear your in.

It could be a speed limiter that didn't get removed!

moparzrule
04-01-2008, 01:32 PM
I already expained that. The ECU has several parameters to do things if it has a bad sensor. Example is if you have a bad MAP sensor you are limited to 2000 RPM. It's cutting at stock 2 bar specs because thats what it's set to cut with a bad MAP at that point. 4th gear has the most load on the engine since he hasn't tried 5th, so it's gonna create slightly more boost which may be just enough to hit cutout.
My advice is to fix the O2, and then turn the boost up 1-2 PSI and see if it still does it.
I do not see how it could be the speed sensor at all. My daytona had a bad speed sensor the entire 4 years I had it.

Edit- OK I see you said limiter. 4th gear at 5000 RPM isn't even 100 MPH I don't think, never seen a limiter that low in fact neither of my cars ever had a limiter that I am aware of.

turbovanmanČ
04-01-2008, 01:38 PM
I do not see how it could be the speed sensor at all. My daytona had a bad speed sensor the entire 4 years I had it.

Edit- OK I see you said limiter. 4th gear at 5000 RPM isn't even 100 MPH I don't think, never seen a limiter that low in fact neither of my cars ever had a limiter that I am aware of.

I agree on the speed sensor, I've seen it cause idle issues but not driveability issues but I think I read on older cars, IE 86/87ish, it can cause cutou?

True but maybe someone had fat fingers that day and hit the wrong limits for the speed cutout, :o

Mysterio
04-01-2008, 01:45 PM
5k rpm in 4th gear is around 90 mph. It's not a speed limiter though. Because after it hits that cutout I can keep driving. I've had the car up to 100+ mph with this setup just not going full throttle / full boost. So it's not a speed limiter related issue.


I'll try to get that o2 sensor changed again. I don't know if i'm going to be able to get it out though due to how stuck in there it is and the limited work space. I'm pretty sure the o2 sensor socket actually spun on the o2 sensor a bit and rounded the nut part it grabs onto some. So that may be a problem lol.

Wouldn't unhooking the o2 sensor make it just revert to normal fuel curves/ratios and not try to edit them at all? Or will it make it run super lean and throw a code??

moparzrule
04-01-2008, 01:47 PM
I suppose it could be possible. Here's an idea then. Get up to speed on the highway, go to about 4000 RPM in 4th and shift into 5th. Now that you have lower RPM's it may not be making as much boost at the same speed you would hit 5000 RPM in 4th.
I still say fix the O2 sensor and turn up the boost 1-2 pounds.

To get the old one out you may need some heat. Honestly, you usually end up trashing them because the special O2 sensor socket is not very strong. I usually end up snipping the wires and using a regular socket with a 1/2'' air impact. I have access to a stubby 1/2'' impact so it fits, if you don't you may need to unbolt the power steering and just move it over a little out of the way. Again, you may just want to get a new sensor, take a hammer to the O2 sensor and knock off the body of it. This way just the ''nut'' of the O2 sensor is left and you can use a short socket on it (non deepwell) for better clearance. Anything you would use the ''clean'' the O2 sensor will probably damage it, and more than likely it's bad anyway because if you can't get it out it may be the original. Just better to get a new one.

moparzrule
04-01-2008, 01:48 PM
Unhooking the O2 it will run like complete crap and SUPER rich.
The O2 sensor socket flexes and gives. Break the O2 sensor, use a normal 6 point socket, heat it up if you have too, and get yourself a new sensor.
If you don't have a torch to heat it, let the car run for awhile but be careful not to burn your arm on the downpipe.

turbovanmanČ
04-01-2008, 01:52 PM
I'll try to get that o2 sensor changed again. I don't know if i'm going to be able to get it out though due to how stuck in there it is and the limited work space. I'm pretty sure the o2 sensor socket actually spun on the o2 sensor a bit and rounded the nut part it grabs onto some. So that may be a problem lol.

Wouldn't unhooking the o2 sensor make it just revert to normal fuel curves/ratios and not try to edit them at all? Or will it make it run super lean and throw a code??

Most likely as stated, you need heat, then you need a tap to clean up the threads as they will be trashed.

Disconect the ox and clear out the memory, it will be fine.


Unhooking the O2 it will run like complete crap and SUPER rich.

Nope, the computer goes to limp and substitutes a value and ignores it.

moparzrule
04-01-2008, 01:56 PM
After doing a head swap on my shadow I forgot to hook back up the O2. It ran SO bad and SO rich that it was blowing black out the exhaust pipe. This helped me pinpoint the problem as I had no idea why. I only got a mile up the road and I pulled over it was so bad, and didn't have anything with me to tell me what the codes were. Thats how BAD it ran. Hooked up the O2, disconnected the battery and let the ECU reset, hooked that back up, ahh back to normal ran great.

Mysterio
04-01-2008, 03:11 PM
I actually already have a brand new mopar o2 sensor that I was planning on putting in but didn't have a chance to do yet. I was actually planning on just breaking it and using a regular socket since I was having no luck with the o2 sensor socket. I'll try getting the new o2 sensor in. Also... I noticed if I short shift 4th gear at like 4500-5000 (it cuts at 5000-5500). It wouldn't do it. But I never made it to the top of 5th to see if it did it there.

mario03SRT
04-01-2008, 03:13 PM
I hit 6500 rpms with the STG5 w/o any problems. 3bar map is on the car.

moparzrule
04-01-2008, 03:15 PM
Turn up the boost 1-2 psi and see if it does it in second or third gear.

Mysterio
04-01-2008, 04:58 PM
Ok well I turned the boost up and gave it a pull in 2nd and 3rd (turned it all the way up to 20 lbs on accident lol). No fuel cut like I'm experiencing in 4th. I took 3rd all the way to about 5000-5500 rpm so it shoulda done it by then if it was going to.

MiniMopar
04-01-2008, 05:24 PM
Maybe I missed it, but does your tach drop when the cutout happens?

turbovanmanČ
04-01-2008, 06:05 PM
After doing a head swap on my shadow I forgot to hook back up the O2. It ran SO bad and SO rich that it was blowing black out the exhaust pipe. This helped me pinpoint the problem as I had no idea why. I only got a mile up the road and I pulled over it was so bad, and didn't have anything with me to tell me what the codes were. Thats how BAD it ran. Hooked up the O2, disconnected the battery and let the ECU reset, hooked that back up, ahh back to normal ran great.

That shouldn't happen. :confused:

moparzrule
04-01-2008, 06:29 PM
Ok well I turned the boost up and gave it a pull in 2nd and 3rd (turned it all the way up to 20 lbs on accident lol). No fuel cut like I'm experiencing in 4th. I took 3rd all the way to about 5000-5500 rpm so it shoulda done it by then if it was going to.

Wow, than this is very weird.
First, fix your O2, it needs fixed anyway.
Check something for me though, check to see if your alternator connections have plenty of clearance. Heard of something once that the guys alternator connection rubbed up against the radiator causing a ground issue and it acted like a cutout. Perhaps it takes 4th gear to torque your engine enough to hit it? I dunno, just a thought though, something to check.

moparzrule
04-01-2008, 06:33 PM
That shouldn't happen. :confused:

I had to change out my plugs because they got fouled it was running so rich. Plugged it back in, no more issues.

Mysterio
04-01-2008, 06:59 PM
Wow, than this is very weird.
First, fix your O2, it needs fixed anyway.
Check something for me though, check to see if your alternator connections have plenty of clearance. Heard of something once that the guys alternator connection rubbed up against the radiator causing a ground issue and it acted like a cutout. Perhaps it takes 4th gear to torque your engine enough to hit it? I dunno, just a thought though, something to check.

Hmm... That's a possibility:

http://a116.ac-images.myspacecdn.com/images01/9/l_61cda4511f2fcc5653cee685fe871a4b.jpg


Lol....

Mysterio
04-01-2008, 07:06 PM
Now that I think about it I remember one of the bolts rubbing against my silicone coupler and actually putting a small hole in it. I don't remember if it was a bolt that actually had any use for grounding/power or if it was just a bolt holding the case of the alternator together. So maybe that is the case I'll have to fix that.

I'm actually going to buy my friend's T2 radiator so I can have a smaller radiator and mount the intercooler piping like everyone else. I ran it that way because I didn't want to move the rad mount over for the T1 radiator.

I wonder why it happens at 5000-5500 rpm everytime in th gear exactly though? You'd think if that were the case it would be more random...