Ah! 5k RPM = NO FUEL *Not fuel cut*

[kraka]

EDIT EDIT EDIT: PRoblem is not 5k fuel cut anymore....Please direct me to a diagnosis on the Misfire/hesitation/leaning out issue, not the 5k cut out
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Oh man, what did I do now

For the past month or so I've been having an awful misfire in my top end power range.....At 6000rpm or so, I get a slight jerk and I go hella lean for exactly 1/2 a second, which I mistaked as a bad timing retard from High Knock counts....

Nope.....Everyday I chose to ignore this and tune around it, trying my best to add LOTS of fuel at the 6k setting....This ended up with no luck, so I just went on with my life trying to avoid the sensation of the slight top end jerk...

Today, I hit rock bottom!!! I hooked my largely neglected Datalogger back up for the first time since the Misfire started.....As I began doing 2nd-3rd gear pulls, I noticed that my 6k misfire now turned into a 5000rpm complete Fuel Cut!! My car has a Huge Jerk and the needle bounces off the 5 on my tach just like my studderbox does!!

So, I quickly pull up the log....What does it say? 4500rpm = 85% Injector Duty Cycle.....4800 = 60% .....5100 = 0.0% <---- Yikes !!!!!

Yes, my car completely cuts out fuel at 5k, and there is no reason behind this....My wideband used to read 13.0-16.0 during the slight hesitation, now at 5k rpm my wideband goes COMPLETELY LEAN, past 17.9a/f because my injectors are not flowing any fuel at that point....

But why, ladies and gentlemen? Please help me solve my problem....This has been an ongoing problem that has puzzled the best of my DSM wiseman friends.....

Background/Important Need-To-Knows:
-------------- EvoIII @ 20psi = Same 'misfire'/fuel cut at any boost level
-------------- 560cc injectors/walbro 190 = Stock wired walbro might be the culprit? Stock wiring = Bad voltage when pump needs lots of voltage to avoid going too lean?
-------------- Eprom w/ chip = Eliminates Fuel Cut as a feature....This only eliminates fuel cut enduced from MAS readings too high

My problem went from Tuning Hiccup to Fuel Cut disaster in a month, and I cant stand driving the car with this behavior.....I noticed this problem started only when I hooked my logger up, but I can't see that being an issue...Just stating.....

Please Help
-Josh

 

[andymoraitis]

Josh,

There's a few things that may be culprits so perhaps you can give these a shot. I'd start by pulling the ECU and checking for any leaking caps or a rotten egg smell. I'd also swap the stock FPR with another known working unit and check the MAF to make sure it's not dropping airflow counts.

It almost sounds like starvation to the rail, so don't rule out the 190 or the stock FPR. A voltage check on the 190 will tell you if you're getting decent supply. My inclination is to say it's a fuel volume issue, but I'm also wondering if this isn't somehow tuning related. I know you keep adding fuel with the AFC, but it would be great if you could post your correction values. My point in having you do this is that we may see that you're adding too much fuel and running the injectors out of IDC since the richer your tune is, the more fuel you ask the injectors for. This may result in IDC's that are simply too much for them to handle and they basically "shut off" as they run out of steam.

A complete log of a 3rd gear pull showing timing, knock, O2 voltage, IDC and IPW would help. Jeez it could even be something as simple as your injectors being faulty and not having enough fuel supply to deal with the correction values.

Get us some more info and I'm sure we'll get some more tuners involved.

Andy

 

[kraka]

Awesome...Thanks for the response....Unfortunately, its not as simple as a few of those suggestions would entail.....

First, an UPDATE:

------ FUEL CUT OFF AT 5k RPM is not the issue anymore!!! This was due to the logger somehow causing the studderbox to be in full effect when the cable was connected...Odd right?

BUT, My misfire is still there and is KILLING ME! I now can't log the misfire b/c the logger causes that problem...Sucks right?

Details I will add:
--- Ecu: Problem occured on both old non-eprom ecu and NEW Chipped EPROM...BOTH PERFECT WORKING CONDITION <---- SteveP socketed and checked
--- I have no reason to believe the FPR is bad, only that the low fuel pressure from running stock 1g pressure might have a small effect on me running so lean up top and the high Injector Duty I usually get
--- I run a Hacked 1g MAF...Working condition....I also run a 2g maf which currently is not in the car but will be coming back when I recieve a new one....My chip is set for a 2g maf...Either way this shouldnt be the issue

Tuning Wise:
--- I know a good amount as far as tuning knowledge goes...I have always tuned my car, and I know its sweet spots and A/F's it likes....Since I run a wideband, I know that I am not going too Rich...At my 5k setting, Im somewhere around -10% to get the wideband to sit in the 11- low 11 range (560cc/2g maf chip), but at 6k Im forced to move my settings to 0% because I am doing my best to richen it out with out flooding too much fuel....I guess with a No fuel cut chip I can try richening it even more, but theres no reason to have to add 20+% fuel past the set injector compensation....

On my logged runs, I suffered very little knock, only the occassional 3-4 counts which dont effect timing.....But, at 5k like I said, the car hits the artificial rev limit......Take the logger off = Back to normal.....

 

[scottsee]

We really need a log man.. I'm sitting here thinking about all the things that could cause that, and their are quite a few. Please, if you get a chance post a log of RPM, Timing, Airflow, Knock, O2 voltage, IDC, IPW. I've never used a logger, if they have the ability to log in grams/rev, that is MUCH more useful then airflow lb/min..

Curious. When you mention hitting "studderbox" at 5000rpm's with your data logger connected from your OBDI port to your palm pilot, you are under load & are above 7mph, right? Not sitting at a stand still, but actually moving in 1st, 2nd gear without the clutch pressed in?? 2-step and 3-step studderbox use only 2 sensors to control their operations. Speed sensor, and clutch engagement sensor (can't remember what the hell its called right now). Their has to be something wrong with one of these 2 sensors, or/and with ecu control functions of these sensors.

Unless you have an NLTS ability it makes no sense at all why you would be hitting a rev limiter at 5000rpms, unless if you have an "auto default" option set on your pocket logger set to activate via the logger software whenever the logger sees a connection through your OBDI port to your ECU.. And somehow changing the stock rev-limiter to a different value. That sounds far off, but nothing else makes sense. NLTS (3-step) only works when the clutch is pressed and you are moving faster then a user-set value.

Test if it is in fact a rev limiter, just log IPW, IDC, RPM, wideband. IPW should jump between off/on very rapidly, IDC 0%, RPM substation rpm within a couple hundred rpms, wideband should lean out to it's max value.

Can you change your basic studderbox in your palm software to 7000RPM's or actually rev that high while not moving? Knowing If you can free-rev past your problem point while not under load will help..

Like Andy said, it could be something as simple as low fuel pressure, from a dieing pump, relay, shorting pump wires, old FPR, dirty injectors, exc. If you have any way to check BFP and/or replace it with an AFPR, or have the ability to test the voltage to your pump that would greatly help with diag the process. Sometimes when dieing pumps start showing them selfs they disguise themselves in abnormally low front o2 voltage. As fuel pressure demands go up, the dieing pump cant keep up, creating low pressure in the rail, lowing pressure in the regulator, causing 02 voltage to goes down. It's typically followed by a lot of knock from lean mixtures. Remember, the ECU always assumes BFP, It's not monitored..

Simple plugs/wires cause major break-up, sometimes from just the wrong warm/cold styler plugs, or incorrect gap. Coil packs/CAS/Fuel pumps are largely connected. without feedback seen from the cas, the fp relay wont turn on. If the ECU was loosing the signal from a failingCAS the relay would be cutting out causing a similare flow issue.. It could very well be the ECU too.. Check it! When CAS get old/wet they can cause weird misfire issues, but I've never heard of anything like that, but you do have an over 13 year old car... I would just try and spec/test the coil/cas/plug/wires just to be 110% sure its not something off the wall. If you don't know how we will help you..

Seriously, it could be just way to many things, but as Andy said, its probably something in your fuel delivery system, ECU feedback, or sensor failer... I don't think you are going to find away to tune around this. But I hope I'm wrong..

Post that log..

 

[kraka]

Thanks Andy for the phone call....We basically narrowed it down to a fuel delivery issue, but I should at the same time test my new 2g maf to see if it solves this as well as rewiring the walbro if it is voltage dropoff....I'll answer some of scotts problems, even tho I explained most of them earlier....

Yes, I was moving when the car reset its rev limiter to 5k......This is why I cant post up a log, there is nothing useful to see, my misfire usually occurs after this...With the logger off, the rev limit goes back to normal....My logger can not change any specifics of my chip so theres no way of going around that problem....There might be a NLTS function but this happens when I am just driving above 5k, whether the clutch is engaged or nto....

Other than that, I was told to try swapping FPR's in case this one failed, swapping injectors to see if these just aren't flowing well, take out the fuel pump and check the strainer/etc for clogs, check voltage to pump....

I guess those are the main parts....As far as the electrical things you mentioned, I have heard that an electrical misfire makes you run rich for a second, whereas my misfire is cutting out fuel and leaning me out incredibly....

I will have a steady 11.0-11.3 and then when these jerks start appearing (physically jerks), the widebands jumps very quickly to a super lean a/f and then bounces back to 11 a/f

So, not sure if that makes a difference, but this is NOT a problem where fuel cuts out completely after a certain rpm anymore....These are slight hesitations where the car runs incredibly lean and backfires for a second then jumps back to normal WOT operation....

The bpr7's I have in the car are newer....I replaced them after this problem occured, thinking this was the issue....The plugs are fine....The plug wires arent very old either, they are Accel's, and the coil pack Is original for sure, but are there any other signs that those things would be going bad....I only get these misfires top end at WOT, open loop operation.....

And ECU is perfect just to clear that up again

 

[donmagicjuan]

I'm having trouble understanding how this can be a fuel supply issue if you know your IDC's are plummeting around the problem area. If your ECU is telling the injectors to stop opening, how can you suspect the fuel pump, regulator, etc.?

If the ECU is in fact perfect, then it has to be something that would make the ECU think it needs to cut fuel. The MAS was a good suggestion. Another thing that comes to mind is the TPS. It's really too bad that you can't capture a log to examine some of these things more thoroughly.

Perhaps you can connect your logger and monitor TPS voltage with the key in ON and the car not running. Hold the accelerator to the floor and watch for any irregularity in the voltage. This test won't definitively rule it out, but it's a start. I'll try to think of some other suggestions in the meantime. Best of luck, man!

 

[andymoraitis]

Josh,

Based on our phone discussion, I'd have to agree with Don that it's something telling the ECU to stop fuel delivery. I'm hoping the new MAF you have coming fixes it, but Don's also on to something with the TPS. I've seen motors do the herky jerky if the TPS voltage gets screwy at WOT.

I still think it's a good idea to check for any fuel volume issues just in case however.

Keep us posted,

A.

 

[donmagicjuan]

One more thing, Josh--

Do you have any check engine light codes? This would include any known codes, e.g. one for a removed catalytic converter, etc.

 

[kraka]

One more thing, Josh--

Do you have any check engine light codes? This would include any known codes, e.g. one for a removed catalytic converter, etc.

I have a 1g so no, altho I dont run a cat regardless.....Its pretty hard to throw a CEL on a 1g....But if the MAF I have on now was bad, it definitely WOULD throw a CEL

TPS, eh? Interesting...I'll hook up my logger 1 more time and see whats up....Its such a shame, the car pulls so hard up until a very small hesitation and then seems to pull even harder after that.....The car also seems to run better and less misfiring when my turbo-mani bolts loosen themselves every once in a while, causing a small exhaust leak....

Im using my older logger cable b/c my good one doesn't seem to be working, but I will try both cables and look for this problem again....I wish I could get a good log in also, Im usually very good at diagnosing things tuning wise but even with the wideband I feel like Im 'blind' again without this logger on

 

[kraka]

UPDATE:

Who wants to take the first guess at what it was? Cmon, this is a test to all you Wisemen...

 

[myblack98gst]

UPDATE:

Who wants to take the first guess at what it was? Cmon, this is a test to all you Wisemen...

I am VERY interested because my car started the same thing exactly.. except it would do it at stand still reving and in first after that it pulls strong to 7,500....

so come with the answer please!!!

 

[DROOPY209]

TPS....

I'm having similar issues and mine jumps around from 10.1% to 12.5% at idle.