Welcome to the North American Subaru Impreza Owners Club Wednesday April 1, 2015
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Normally Aspirated with bolt-on Forced Induction Powertrain

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 11-02-2001, 10:07 AM   #1
Jewbaru
Scooby Specialist
 
Member#: 1994
Join Date: Jul 2000
Location: "Teh Hebro Town"
Vehicle:
2013 Impreza WRX
WRB

Default Stuttering, possible fuel cut, and ideas?

Here's the details:
Ludespeed Stage II turbo
RRFPR
J&S Safeguard
upgraded fuel pump
A/F guage with it's own O2 sensor mounted in the header collector.
Zener Diode (4.7)

At the onset of boost, the car bucks, the A/F guage goes totally lean, then it starts to pull normally, and the A/F guage shoots up to rich (where it should be).

I've noticed it for a while, and my J&S isn't registering any detonation, so I thought it might be excess fuel. Untill I hooked up the A/F. I dug around and noticed people saying their Diode isn't clamping correctly, resulting in the same condition, only a little worse. I have another diode that I'll try out, but I'm just curious if anyone else has had this problem recently.

The only reason I suspect my car wasn't detonating was due to the fact the car was at low boost, and a fairly light load, plus the car runs stupid rich off boost.
* Registered users of the site do not see these ads.
Jewbaru is offline   Reply With Quote
Old 11-02-2001, 10:20 AM   #2
blaster88
Scooby Specialist
 
Member#: 1109
Join Date: Mar 2000
Chapter/Region: MAIC
Location: Reston, VA
Vehicle:
1999 Suzuki Samurai
Blackish

Default

That sounds similar to the problem I was having with the zener diode.

If you have a multimeter, hook it up to your map sensor wire, and see what you are getting.

What you might be getting, if you are using a 4.7v diode, is that it is actually clamping off too low, and not getting a good fuel dump at first.
blaster88 is offline   Reply With Quote
Old 11-02-2001, 12:14 PM   #3
Jewbaru
Scooby Specialist
 
Member#: 1994
Join Date: Jul 2000
Location: "Teh Hebro Town"
Vehicle:
2013 Impreza WRX
WRB

Default

hmm, I don't have a multimeter, so I can't test voltage. However, I swapped on the other Diode (5.1) and I THINK it's still doing the same thing. The O2 sensor isn't heated, and I only went up the street, so I couldn't be sure on the readings.
Jewbaru is offline   Reply With Quote
Old 11-02-2001, 12:53 PM   #4
HndaTch627
Scooby Guru
 
Member#: 6551
Join Date: May 2001
Chapter/Region: MWSOC
Location: Carol Stream, IL
Vehicle:
'01 GC8 Dinged STM
'09 Concours 14 ABS Black

Default

well the only time 8complex's car did something like this was when it detonated and the piston shattered. Sounds like you are clamping hte voltage to low at first and teh ECU doesn't like that and the the voltage to high(which the ECU REALLY doesn't like) Try getting a 4.8V zener diode.

Otherwise who know.

jeremy
HndaTch627 is offline   Reply With Quote
Old 11-02-2001, 02:04 PM   #5
Jewbaru
Scooby Specialist
 
Member#: 1994
Join Date: Jul 2000
Location: "Teh Hebro Town"
Vehicle:
2013 Impreza WRX
WRB

Default

heh, mine hasn't detonated yet (knock on wood), so I'm counting my lucky charms, hehe.

Ok, after a better drive, with the 5.1v it pulls smoothly up to 3psi, then bucks a little. If I'm close to WOT it doesn't buck, and regardless it doesn't buck in 1st gear.
Jewbaru is offline   Reply With Quote
Old 11-02-2001, 03:33 PM   #6
STiShawn
Scooby Specialist
 
Member#: 2348
Join Date: Sep 2000
Chapter/Region: MWSOC
Location: St.Louis
Vehicle:
2006 WRX TR
Steel Grey Metallic

Default

Joel, I have a multimeter...you can borrow it if you'd like.
STiShawn is offline   Reply With Quote
Old 11-02-2001, 04:51 PM   #7
Jewbaru
Scooby Specialist
 
Member#: 1994
Join Date: Jul 2000
Location: "Teh Hebro Town"
Vehicle:
2013 Impreza WRX
WRB

Default

Shawn, I'm gonna have to take you up on that offer.

New discovery, if I'm around 1/4 throttle or more, the car pulls normally, and the A/F reads steady rich. I put the 4.7v back on, and it doesn't cut at 3psi anymore. Under light throttle it bucks however.
Jewbaru is offline   Reply With Quote
Old 11-02-2001, 04:57 PM   #8
8Complex

Moderator
 
Member#: 922
Join Date: Feb 2000
Chapter/Region: MWSOC
Location: Schaumburg, IL
Vehicle:
04 FXT
Red

Default

Actually... you're throwing a CE light, right Joel? Have you checked what it was for? Mine had been for MAP Voltage spikes, which caused the car to boost just as you described. I ended up getting rid of the zener diode and getting a Split Second VC-1 voltage clamp (in 5v/4.8v clamp flavor, IIRC). Thing works great and no problems since then.

The only other possibility is that your RRFPR is set to kick in slightly too late and you are leaning out at the 1psi mark and it kicks in like 2psi (guess). I had a pretty hard time getting mine set right, so I think it's a possibility.
8Complex is offline   Reply With Quote
Old 11-02-2001, 04:58 PM   #9
8Complex

Moderator
 
Member#: 922
Join Date: Feb 2000
Chapter/Region: MWSOC
Location: Schaumburg, IL
Vehicle:
04 FXT
Red

Default

After reading that last reply, it sounds pretty normal, actually.
8Complex is offline   Reply With Quote
Old 11-02-2001, 05:34 PM   #10
stimpy
Homicidal Maniac
Moderator
 
Member#: 1612
Join Date: Jun 2000
Location: Austin, TX
Vehicle:
2008 STI

Default

From what a local tuner has said, zener diodes will bleed some voltage and cause a lean-run on throttle tip-in. You may be seeing just that.

-Jon
www.nothingserious.net
stimpy is offline   Reply With Quote
Old 11-02-2001, 09:33 PM   #11
the Dabbler
Scooby Newbie
 
Member#: 4540
Join Date: Feb 2001
Vehicle:
MY00 2.5RS Sedan
Abnormally Aspirated

Default

My car behaves almost identically to yours, Jewbaru. Lean on throttle tip-in, then okay when things start going. Others have had similar problems.

Originally, I had a 5.6V, 1W zener in there, which was recommended from a post way back. I thought this might be clamping too high (or too low, even -- zeners are not very well characterized in this region of operation), so I swapped it out for a 1N4688, which is a 4.7V zener with a very low rated zener current of 50uA (also mentioned in that earlier thread). It still does it.

The problem is, the zener isn't really meant for this application, at least not in as simple a circuit as this. It may work fine for some people, but it doesn't seem to be an entirely repeatable thing.

I have one more thing to try on the DIY voltage clamp side of things, then I'm springing for the Split Second device.

I haven't had a chance to hook up a multimeter, but plan to this weekend.

Nick: I forget -- do you have a plain Vortech FMU? Super FMU? Bell unit?
the Dabbler is offline   Reply With Quote
Old 11-03-2001, 05:28 AM   #12
8Complex

Moderator
 
Member#: 922
Join Date: Feb 2000
Chapter/Region: MWSOC
Location: Schaumburg, IL
Vehicle:
04 FXT
Red

Default

Ryan - I have the Bell adjustable.

BTW, I believe when I had that problem, it went away after I got the Split Second voltage clamp... let me drive my car with the kit on again before confirming that though (arghhh!).
8Complex is offline   Reply With Quote
Old 11-03-2001, 02:41 PM   #13
Sauginius
Scooby Newbie
 
Member#: 277
Join Date: Sep 1999
Chapter/Region: SCIC
Vehicle:
98 Not a Subaru
BRACK

Default

Wow...it seems that a lot of us are having this problem. Here's my setup:

Vortech 4:1
JnS
Walbro 255lph
SS Voltage clamp (5V)
Running 5lbs

I used to have the zenier (1N4688), and yes, I was still getting MAP voltage spikes (as shown by the CEL code). After I switched to the SS voltage clamp, things got a little better. But......

Car pulls hard from a stand still. But, say I'm crusing at 2K in 3rd....if I punch it, the car bucks a couple times while boost builds up to 5lbs. If i keep on it, the car bucks a few more times, then goes like hell at 5 lbs.

JnS isn't retarding....so I'm not sure if I'm dett'ing. Am I getting too much fuel? A/F reads stoich if not a little lean so I'm not sure about too much fuel.

One thing that I've noticed though. When the car has been started in the morning after sitting a while (after the oil gets up to temp), if I go for a few boost runs, this enitre condition is non-existant. The car runs REALLY well to full boost, no bucking, no hesitation, just pure boost. I can punch it in any gear and it goes. There was a thread a while back about the ECU giving the engine more fuel during the initial few mintes after warm up. You guys might wanna try this to check it out.

Oh yea, the Dabbler, I'm also in So. Cali (West LA). I'm interested to check out your setup...maybe we can get together to figure this out.

Francis
Sauginius is offline   Reply With Quote
Old 11-04-2001, 01:03 AM   #14
DammitBevis
Scooby Newbie
 
Member#: 3569
Join Date: Jan 2001
Chapter/Region: MWSOC
Location: Murphysboro, IL, USA
Vehicle:
2006 STi
AW

Default

As my usual disclaimer goes, I'm NOT A SUBARU MECHANIC.
But... I love working on this stuff, and can't help throwing ideas at people.
If the diode and RRFPR checks OK, the next thing I'd check is the......
Throttle Position Sensor?
Easy to check, and a common problem across all makes of engines. It's especially noticable on forced induction. What happens is that the little wiper will wear a 'notch' in the resistive material. Then whenever it goes over that spot it will skip for just a moment, but enough to momentarily confuse the computer. To test just hook a voltmeter to the wiper, or tap, or center, or whatever you want to call it, then ground the other probe of the voltmeter (usually ign has to be on). Slowly open the throttle, and the needle should move steadily. The reading isn't as important as the smooth movement. You'll need an analog meter to check this, or a VERY good digital meter with a bar readout. Modern computers are programmed to apply a certain amount of smoothing to this signal to prevent marginal TPS's from throwing codes. But when measurements start getting critical (such as turbo motors), a little goes a long way.
Good Luck!
DammitBevis is offline   Reply With Quote
Old 11-05-2001, 01:11 PM   #15
the Dabbler
Scooby Newbie
 
Member#: 4540
Join Date: Feb 2001
Vehicle:
MY00 2.5RS Sedan
Abnormally Aspirated

Default

Quote:
Originally posted by Sauginius
Wow...it seems that a lot of us are having this problem. Here's my setup:

Vortech 4:1
JnS
Walbro 255lph
SS Voltage clamp (5V)
Running 5lbs

I used to have the zenier (1N4688), and yes, I was still getting MAP voltage spikes (as shown by the CEL code). After I switched to the SS voltage clamp, things got a little better. But......

Car pulls hard from a stand still. But, say I'm crusing at 2K in 3rd....if I punch it, the car bucks a couple times while boost builds up to 5lbs. If i keep on it, the car bucks a few more times, then goes like hell at 5 lbs.

JnS isn't retarding....so I'm not sure if I'm dett'ing. Am I getting too much fuel? A/F reads stoich if not a little lean so I'm not sure about too much fuel.

One thing that I've noticed though. When the car has been started in the morning after sitting a while (after the oil gets up to temp), if I go for a few boost runs, this enitre condition is non-existant. The car runs REALLY well to full boost, no bucking, no hesitation, just pure boost. I can punch it in any gear and it goes. There was a thread a while back about the ECU giving the engine more fuel during the initial few mintes after warm up. You guys might wanna try this to check it out.

Oh yea, the Dabbler, I'm also in So. Cali (West LA). I'm interested to check out your setup...maybe we can get together to figure this out.

Francis
Oh, great. You have the SS Voltage Clamp, and you're still having the problem?!? That's not good. I was holding out for this as a last-resort fix. Did the MAP Voltage Spike CEL code go away, at least?

Shouldn't the A/F read a bit rich, if anything, at WOT? Stoich seems too lean under those conditions. I know other people run 4:1 successfully, but some calculations suggest that might not be enough.

I haven't noticed the difference in operation depending on how hot/cold the engine is. But then again, I haven't been looking. I'll pay more attention tomorrow morning.
the Dabbler is offline   Reply With Quote
Old 11-05-2001, 01:32 PM   #16
Jewbaru
Scooby Specialist
 
Member#: 1994
Join Date: Jul 2000
Location: "Teh Hebro Town"
Vehicle:
2013 Impreza WRX
WRB

Default

In response to Sauginius, it sounds like your FPR isn't dumping enough fuel on the onset of boost, check the regulator.

Now, with my car, the RRFPR is set to start dumping fuel WAY before boost, and I can watch the AF go off the chart when I start to go on boost. Here's my theory:

The Zener is designed for computer electronics and the like, things where voltage is usually all or none, not gradual like in our situation right? I noticed that if I'm high in the RPMs, and I romp on it, no cut, car stays steady rich, and pulls like a mofo. However, if I'm LOW in the RPMs, it'll stutter at the onset of boost.

I'm wondering if it's working properly when the signal "spikes" and it bleeds like it's supposed too, but just doesn't work up to par when the signal is gradual, and is clamping sporatically...

Anyway, how much was the SS Clamp? Says almost $80 on their website. Also, where can I find out more about the J&S clamp?
Jewbaru is offline   Reply With Quote
Old 11-05-2001, 01:34 PM   #17
stimpy
Homicidal Maniac
Moderator
 
Member#: 1612
Join Date: Jun 2000
Location: Austin, TX
Vehicle:
2008 STI

Default

Contact Trey Cobb or Christian (www.moderngarage.com) and they can give you more information about it. Basically, its a fully adjustible version of the Split Second unit.

-Jon
www.nothingserious.net
stimpy is offline   Reply With Quote
Old 11-05-2001, 01:51 PM   #18
Jewbaru
Scooby Specialist
 
Member#: 1994
Join Date: Jul 2000
Location: "Teh Hebro Town"
Vehicle:
2013 Impreza WRX
WRB

Default

oh yea, one more thing...

it's entirely possible there are slight differences in the MAP sensors from car to car, causing the smallest diff in signal to be sent to the ECU, small enough to where the ECU doesn't care and the voltage is the same, but big enough to where the Zener will clamp at different levels.

BTW, Thx stimpy for the info.
Jewbaru is offline   Reply With Quote
Old 11-05-2001, 04:30 PM   #19
Sauginius
Scooby Newbie
 
Member#: 277
Join Date: Sep 1999
Chapter/Region: SCIC
Vehicle:
98 Not a Subaru
BRACK

Default

Dabbler, ya, I'm still having the problem with the SS VC although it's not as prominent. I was also looking for the VC as a last-ditch-problem-solver too but I guess that didn't work out. It was $70 ish shipped. Ordered direct from SS.

I still have the CEL but this time I'm not sure whether or not it is MAP voltage spike code (since I don't have the scan tool). It just might be a lean-run code since something seems to be up with my fuel delivery.

With regards to my fuel though, I'm pretty sure something else is up....either my FPR is bad, there's some clog in the line or something else. My idle fuel pressure seems to be WAY low (~25 lbs)....even for stock (and I have the Walbro!). But, when boost kicks in, it shoots up to 75-80 lbs and I'm like ***?! When fuel press rises, should it rise smoothly and gradually, or should it stutter when it rises? (cuz that's what mine does). I'm thinking it should be smooth hence a problem with the fuel delivery.

Anyhow, Jewbaru, I think your theory is right about the zenier. The current is too small for the ecu but definitely big enough for the zenier to change things. All I know is I can definitely feel a difference between having the zenier and the VC.

I really need to see someone's setup. I wanna make sure I haven't crossed my fuel lines or anything.....anyone got pics?
Sauginius is offline   Reply With Quote
Old 11-05-2001, 04:56 PM   #20
stimpy
Homicidal Maniac
Moderator
 
Member#: 1612
Join Date: Jun 2000
Location: Austin, TX
Vehicle:
2008 STI

Default

Sauginius, I am seeing similiar fuel pressure problems. Up until I converted to a parallel fuel rail system, my fuel pressure was a little above 50psi. This was with a Walbro 255lph pump and the stock FPR. After the parallel rails, my pressure went down a couple psi, but that was expected. However, over the next couple weeks, my fuel pressure has gradually gone down to about 37psi. At that point I swapped for the SVX fpr in hopes that the stock fpr had just given up the ghost. That dropped my fuel pressure only slightly, but it did bring back the pressure boost under WOT. Over the past couple days, my fuel pressure has now dropped down to 25psi. I am at a loss as to why this has happened. There are no fuel leaks that I can see and my pump hasn't been in my car for more than 8 months (not ever under boost either). I went for 7 months without a single dip in fuel pressure and now it has dropped drastically...

-Jon
www.nothingserious.net
stimpy is offline   Reply With Quote
Old 11-05-2001, 04:56 PM   #21
ImprezaRS dot com
over boosted again
Moderator
 
Member#: 1458
Join Date: May 2000
Chapter/Region: RMIC
Location: Colorado Springs CO USA
Vehicle:
2015 Forester 2.0 XT
2005 2.5 RS, 2013 Tribeca

Default

All of you guys with this problem - solved with a Torque Chip II.

Post here if you would buy one if I had a group buy on these?

I have them on my site for $279 + S&H, but with 5 buyers would drop to $229, and with 10 buyers would drop to $209 + S&H. Over 15 buyers would go to $189 + S&H.

Larry
www.SubaruPlanet.com

Last edited by ImprezaRS dot com; 11-05-2001 at 05:17 PM.
ImprezaRS dot com is offline   Reply With Quote
Old 11-05-2001, 05:19 PM   #22
Jewbaru
Scooby Specialist
 
Member#: 1994
Join Date: Jul 2000
Location: "Teh Hebro Town"
Vehicle:
2013 Impreza WRX
WRB

Default

Larry, your site says zero about the chip. I'm VERY picky about electronics I buy, so you better be able to fork out some real good details, or point me to someone who can. Sounds cool tho, but I don't have $250 to drop on something like that right now.

Joel
Jewbaru is offline   Reply With Quote
Old 11-05-2001, 05:23 PM   #23
stimpy
Homicidal Maniac
Moderator
 
Member#: 1612
Join Date: Jun 2000
Location: Austin, TX
Vehicle:
2008 STI

Default

stimpy is offline   Reply With Quote
Old 11-05-2001, 05:28 PM   #24
the Dabbler
Scooby Newbie
 
Member#: 4540
Join Date: Feb 2001
Vehicle:
MY00 2.5RS Sedan
Abnormally Aspirated

Default

Quote:
Originally posted by ImprezaRS dot com
All of you guys with this problem - solved with a Torque Chip II.

Post here if you would buy one if I had a group buy on these?

I have them on my site for $279 + S&H, but with 5 buyers would drop to $229, and with 10 buyers would drop to $209 + S&H. Over 15 buyers would go to $189 + S&H.

Larry
www.SubaruPlanet.com
Larry --

I don't want another JCS and/or TCII flame war to start here... Me personally, I want to investigate all other possibilities before I spend that kind of money, JCS or not.

Like I said, I have one more shot at the DIY voltage clamp (not involving a zener diode). If that doesn't work out, I will give the TCII, J&S VC, and/or SS VC consideration.

Thanks.
the Dabbler is offline   Reply With Quote
Old 11-05-2001, 05:32 PM   #25
Jewbaru
Scooby Specialist
 
Member#: 1994
Join Date: Jul 2000
Location: "Teh Hebro Town"
Vehicle:
2013 Impreza WRX
WRB

Default

alright, thanx Jon.

Dabbler, could you please keep me informed on your DIY task?
Jewbaru is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Hesitation, Possibly Fuel Cut (searched) Black_Sun Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 2 02-03-2009 11:57 PM
Possible fuel cut problem?? IlovemyRex Factory 2.5L Turbo Powertrain (EJ Series Factory 2.5L Turbo) 5 03-08-2006 08:41 PM
Hitting Fuel Cut and Boost cut at 18 PSi HELP!! ChrisV-FL Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 5 08-11-2002 10:36 AM
Fuel cut and CEL from 15.5 psi ?? pace Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 23 10-27-2001 04:14 PM


All times are GMT -4. The time now is 02:38 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2015 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.