No Bs I Will Pay The Person Who Finally Diagnoses This Problem Correctly

[rabenne]

I have a 2g with a 6 bolt. I have t3 t4 50 trim with turbonetics manifold, victory performance o2, megan racing downpipe, 550 cc injectors, walbro 255 fuel pump, aermotive fpr, fmic, dejon tool intake pipe, new ngk wires, and new ngk plugs bpr-7es with .028 gap. Im only running 12 psi right now, and under light throttle the car is running AWESOME. Once i break about the 60% throttle mark, after boost builds to 12 (3500 RPM), around 4200-5000 rpm the car loses its power, and jerks around, and misses hard... its killing me trying to figure it out. I just did a boost leak test and it held pressure to 20 psi no problem, and after i removed the air source, it continued to hold pressure for 25 seconds. I have a Zeitronix zt2 with pocketlogger zt (SICK SHIT 59 samples/second) and according to that I am running a nice solid 11.5-12.2 AFR. This doesnt really change when car misses... .the problem is I let off the gas when it happens so its hard to tell whats goin on. Im really lost on this one, and so is everyone else Ive spoke with. I am running 43 psi fuel pressure at idle with vac line off, and it goes to around 38 psi with it on.

My guesses,

1. bov is opening early and dumping all the volume of the boost, but still maintaining enough to read 12 psi at the autometer c/f boost pressure gauge. It feels like a boost leak kinda, but I have tested it two times, nothings leaking.

2. FUEL CUT? it doesnt feel like i hit a brick wall at all... more like the crank missed some power strokes, then got itselt together agian, then misses again.


I am willing to pay $50 via paypal to anyone who can give me a no bullshit answer, that actually proves to fix my problem.

THANKS
William Powell

 

[toybreaker]

It almost sounds like a fuel supply problem.

Is the filter reasonably new? Might want to throw in a quality replacment.

I've seen a couple of issues recently with aftermarket pump setups. It's not really so much the pumps as what happens when the hardware is loosened/tightened back at the fuel tank. I've seen a couple where the hard line gets twisted/bent/kinked, and it creates a restriction at higher flow rates, such as what you're describing.

Because you're lifting (as you should!) when the problem occurs, you may not see a fuel starvation from your datalogger/electronics, the average voume that the o2 sees may minimize the effect.

The ignition coils/secondary circuit are another choice. Are the plug ends basically all burning the same?

Good luck, let us know what you find.

I'd love to throw $50 more at the tsunami fund...

 

[PieEyedPiper]

It almost sounds like a fuel supply problem.

Is the filter reasonably new? Might want to throw in a quality replacment.

I've seen a couple of issues recently with aftermarket pump setups. It's not really so much the pumps as what happens when the hardware is loosened/tightened back at the fuel tank. I've seen a couple where the hard line gets twisted/bent/kinked, and it creates a restriction at higher flow rates, such as what you're describing.

Because you're lifting (as you should!) when the problem occurs, you may not see a fuel starvation from your datalogger/electronics, the average voume that the o2 sees may minimize the effect.

The ignition coils/secondary circuit are another choice. Are the plug ends basically all burning the same?

Good luck, let us know what you find.

I'd love to throw $50 more at the tsunami fund...

^^^
coils and fuel filter.

 

[lasertim]

Have you pulled the plugs after this happens? What do they look like. Have you done a spark test with an actual spark tester?

Too many people check for spark by just holding the plug close to a ground. To mimic the cyliner pressures you need to make sure the coil is providing enough "juice" to jump a pretty decent gap(like 3/4") when outside the cylinder. This can be tested with a spark tester.

Here is a very simple and cheap one if you dont know what I am talking about.

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http://www.thetoolwarehouse.net/shop/THE-404.html

 

[phillabaum03]

Wow do i need some money. See if the throttle positoning sensor is pushed on all the way.

 

[blackGSX2g]

Wow do i need some money. See if the throttle positoning sensor is pushed on all the way.

A TPS sensor will not cause a misfire like that.

I've had the same problem several times with different causes.

1. I would lose power on sweeping right hand turns. I thought it was the pump going dry, but it ended up being a loose battery pinching the fuel feed hose right above the fuel filter. I doubt this is your problem as yours occurs all the time. It wouldn't hurt to check that out as well as the condition of your filter.

2. I would lose power on high g straight line acceleration. The cause of that was an improperly aligned fuel pump. I've found that if I don't have the pump aligned to the exact position it should, I run into fuel starvation problems. Check that and make sure that its perfectly centered inside the baffles in your tank.

3. When oil from my old dead turbo hit the wires on my GM MAF, I had the same symptoms you describe. You didn't list that as one of your mods, but I figured I'd throw it out there anyways.

Pull each one of your plugs to verify that they are roughly the same color. What we are looking for here is the overall burn color of the plug, and to rule out a stuck/clogged injector.

 

[PSI NRG]

What are you running to control fuel? AFC, dsmlink, AEM?? I would say its most likely fuel related... probably a bad tune my friends car was doing pretty much the same thing but it only did it when it was colder out and he was running AEM.

 

[rabenne]

when i replaced the spark plugs last week (thursday) they were not only uniform brownish tan color, but they didnt show any signs of carbon buildup or oil leakage. they looked like i could have put them back in, but i threw a new set in at 8 bucks a set.


as for the fuel pump, im really liking this idea a lot. I ran my car out of gas about a month ago, and this means the pump was running dry... It could just be burnt up and having trouble at high flow demands.

HOW can I verify that it is in fact a fuel shortage?


ALSO, which coil pack is best on a 6 bolt 2g? If im going to buy one, better be the best one.


Fuel filter is probably equally possible, that is the cheapest place to start, so that my first guess, next its a new walbro 255


Thanks for your help, $50 if your right!

 

[rabenne]

Sorry.... Duh... Safc-2

 

[blackGSX2g]

HOW can I verify that it is in fact a fuel shortage?


ALSO, which coil pack is best on a 6 bolt 2g? If im going to buy one, better be the best one.


Fuel filter is probably equally possible, that is the cheapest place to start, so that my first guess, next its a new walbro 255


Thanks for your help, $50 if your right!

Good to hear about your plugs, that helps narrow down the problem.

Any 4g63 coil pack will work the same on your car, the only real difference is the plate it is mounted to.

Did you do the injector re-wire for the 6-bolt swap?

Start with the fuel filter and verifying that the pump is aligned and pumping as it should. Since your running really low boost, you could try swapping in a stock pump if you still have it to rule out a faulty pump. I doubt thats the case as I ran my tank dry the other night on my 190 and it still works fine. I was anticipating that our local track had race gas available so I planned my drive to the T, but they ended up not having the pump going so I got screwed. I ran a 13.1 at like 93 because I ran completely out of gas in the middle of 3rd gear and I had to coast the rest of the way. The fuel pump didn't sound any different and it still works fine to this day.

Its worth a shot if you are bored and just want to make sure.

 

[rabenne]

WHAT AM I GETTING MYSELF INTO???

I have never heard of the injector rewire... or im not sure exactly what your talking about. Please elaborate. Also, I will probably buy a new fuel pump since they are only 85 on dsmparts.com. I am going to get a 1g coil pack.


OK that all said, I just got back from logging some runs with the pocketlogger zt....

I have been looking over them, and trying to figure out whats going on, I CANT.... PLEASE LET ME KNOW IF YOUR GOOD AT UNDERSTANDING LOGS, ITS PRETTY SIMPLE ONLY RPM, AFR, AND THROTTLE POSITION.


My rpm signal seems to go up and down during high throttle accelleration. could it be a bad cas or is this totally normal for rpm to jump up and down slightly within a few hundredths of a second. I ask because according to the ZT the rpm signal dances around a bit more when the problem hits...

 

[rabenne]

this is impossible to tell on the computer graphs, but in data table form its clear as day, and i can export it to excel for anyone who wants to take a guess....

 

[Talesin]

1) Do you just have Zeitronix logs, or do you have a proper datalogger as well? It would be useful to see your timing advance during the trouble spot. Could just be knock and pulled timing if nothing else. Speaking of which, is your timing properly set to 5 BTDC?

2) I'm not sure if it would cause any issue with a six-bolt swap, but weren't the 95-96 CAS signals inverted? Supposedly just makes it run a little rough when you swap a 95 ECU into a 97+, but brainstorming possibles.

3) Standard 1G fuel pressure is approximately 36-38psi without vacuum, 26-28 with. It likely wouldn't cause a problem with the larger injectors, but could over-vaporization possibly contribute to increased chance of knock? (Point 1, above)

4) Have you checked your vacuum system for leaks? A boost leak test will check up to the throttle body, but if you have something like a leak in your brake booster line that only leaks under positive pressure, it could be contributing.

5) If your BOV/CBV is leaking, it would just result in a bit of slowdown, not rougher running if you're properly recirculating. The only time you'd run into trouble with a BOV leak is if you were venting without switching to a blowthrough setup first. Is your boost gauge tapped at the compressor outlet, or the intake manifold?

6) Might seem silly/obvious, but have you had a compression test and/or leakdown run on the engine?

 

[rabenne]

I can provide either, or both.... timing stays high throughout.... i dont know much about timing, what should the min and max be?

Yes its set to 5 timing advance at idle.

I will try to replace the brake booster vacuum line tomorrow.

I have not done a compression test, but I will do that tomorrow as well... Do you really think its compression related? swapped motor has less than 50,000 miles and was rebuilt when it had 40,000 bought from ###. I will test it anyway.

 

[Talesin]

Provide RPM, (front narrowband) O2, TPS and Timing logs from the ODBII datalogger. The Zeitronix is well and good, but if it's keeping a good AFR, there's no reason to look that over too hard. Its tacho wire also might be getting confused... we need to see what the ECU thinks is going on.

Is that measured with a timing gun, or what the datalog is telling you? Was the timing set/checked correctly, after putting the car into diagnostic mode, with a timing gun? The ECU will likely read MUCH higher timing advance when revving in neutral.

Check your vacuum system first, don't just go off and replace the hoses. They could still be good.

It's always good to occasionally do a comp test, just to check on how the engine is doing, and to catch any problems early. Once a month is good enough for me, but I like keeping records like that to spot trends.


Does the car still exhibit the problem when revving to 7000 in neutral? Can you run it smoothly all the way to 7K if you do NOT hit boost? That should at least narrow it down some.

 

[rabenne]

JUST took it out again and it BUCKED HARD.... Probably the worst time since it started a long time ago.... it jerked so hard the tires chirped... it seemed like the motor stopped running and the tranny locked up the wheels... but it was only maybe a quarter of a second, and then it cam right back on.... if it werent for the locking up during the jerk i wouldnt have guessed it stopped the motor... this sounds way more like fuel cut now that it jerked hard... it was like i slammed the brakes with the gas on the floor.... Could this have been fuel cut the whole time? how can i verify fuel cut... im sorry but a nice link would be great!

 

[rabenne]

yes i can rev smoothly and with decent power at half throttle, which gives me partial boost... or without boost... pulls fine to the redline 7000

 

[Talesin]

Sounds like fuel cut to me, but there's little reason for that, if you did the boost leak test correctly, unless your SAFC is hosing something horribly. And if the AFR is good on the WBO2, then that's unlikely.

Please post the datalog from the ODBII logger. I have a couple of suspicions, but they're premature until I get a look at what the ECU thinks is going on. Also, just re-read the initial post... 12.1-11.5 is a little rich, just by the way.

 

[andymoraitis]

12.1-11.5 is a little rich, just by the way.

If that's on pump gas, then I think you meant to say it's a little lean.

After reading all of this, I'm leaning towards what Matt said about a misaligned pump or some form of fuel starvation. I'd get a new 255 in there and see how it reacts. Also, have you tried bumping up the fuel pressure to lower the AFR and increase the volume to the rail? If none of those work, I'd point towards some manifestation of fuel cut. With your correction on 550's, the 50 trim may still be flowing enough air at 12psi that the MAS is sensing too much at a certain point. It may not be "hitting the brick wall" fuel cut, but fuel cut nonetheless since the AFC has raised the threshold. You can take more fuel out with the AFC to raise the correction factor (and push off the onset of fuel cut) and then compensate for the lean condition this would cause by bumping up your fuel pressure (47-48 psi) to get more volume to the rail and keep you in the low to mid 11's on AFR. It's a half-assed way to see if it really is fuel cut, but if you bump the pressure and keep an eye on the wideband, you won't hurt anything.

If it turns out that this solves the issue, a larger set of injectors would be your best bet, but I would prefer to see you use something like an EPROM ECU with a custom chip (for A/F and timing) or DSM Link on a motor that'll flow that much air since too much correction on the AFC will start to skew the timing maps and put you in a tuning tail chase.

This is a tough one, so please keep us in the loop.

Andy

 

[somdturbo]

I know its obvious, but make sure you plug wires are not arching....nvm just noticed you have new wires, scratch that.

are you running a 2g maf? my bet is its bad. I had a friends/customers car that would act identical to your description.

 

[drivemusicnow]

Here are the tests, and order I would do them in. This will narrow down your problem.


1) wire the wastegate open and see if the car does the same thing. this will show you if it is airflow dependant/WOT dependant.

2) If the above test results in the car behaving the same way as before, you need to check your TPS and CAS.

3) IF the car does not buck when the wastegate is open, follow your fuel system from the rear forwards. Check for kinks in the line, check that the pump is in the correct place, replace the fuel filter. At this point I would also bump the fuel pressure up a bit like Andy said above, trying to get about a 11:1 AFR.

4) IF you don't find anything wrong with the fuel system, bump the fuel pressure up, and it is still bucking, replace the MAF sensor. I do not know of anyway to test the MAF, and replacements aren't all that expensive.

5) If you tune to a 11:1 afr, check the fuel system, MAF sensor, and still don't find anything, I would start looking into plugging in someone elses ECU and testing it.

This is all I can think of for now... Post the results to these tests and if they didn't solve it, i'm sure we'll have more info as to what is going on. Also post a log... import into excel and attach it into this thread.

 

[rabenne]

my afc read 1286 Hz of airflow when this happened.... this seems way too high... is this off or just me?

 

[rabenne]

Alright heres the deal

I think I have finally figured it all out. About 2 months ago, I blew a sensor ground, when an o2 sensor wire crossed (Always follow step one in every hanes manual... REMOVE - BAT TERMINAL) Once I figured out what had happened I was in a hurry to fix my car because I was moving the very next day. I pulled it out, soldered the small sensor ground trace back together and put it back in... The car was running just fine... It didnt occur to me until now that this is probaby the cause.... Have you ever heard of a MAF reset output transistor on the ecu? Well its the pin directly next to the sensor ground trace I blew. Apparently sometimes this transistor can be damaged, and according to DAVE MERTZ from ecmtuning.com when you reach about 10 psi of boost ( or 12 in my case), the maf readings reverse. Meaning it goes up to a point, but then starting going back down, even though there is more and more air rushing in at WOT. Once you hit that point the car shits to put it bluntly... thanks for your guesses though guys! I really appritiate the effort. Dave is getting a $50 tip when I pay him to repair my ecu and socket it for dsmlink!

 

[blackGSX2g]

If you are thinking the o2 sensor is the cause, think again. Though it still gives off readings, your ECU ignores your o2 sensor when in WOT operation.

 

[drivemusicnow]

If you are thinking the o2 sensor is the cause, think again. Though it still gives off readings, your ECU ignores your o2 sensor when in WOT operation.

It's not the o2 sensor... By shorting out the sensor, he burned a transistor in his ECU...


Just to satisfy my own ego ... My testing would have eventually solved it, but it would have shown up on the last step (ie borrow and test with a different ECU)