Turbo issue identified, now how to fix it?

[jmatyas]

I have been banging my head against the wall trying to figure out why my car is bucking and loosing all power at 4k rpm under heavy load. Replaced sensors and adjusted timing and done everything I could think of, yet the problem came down to the wastegate not actuating.

How would I be able to check to make sure it is not working correctly and what do I need to do to replace it?

The turbo is a MHI Evo 3 16g hooked up to a Punishment Racing FMIC. It is an internal wastegate. Thank you for any advice you can give me. Really wanting to get this monkey off my back finally.

 

[LarryJoe]

This really sounds like a boost leak symptom. Have you done a leak test?

 

[H@xtGSX]

Check the actuator with a vacuum tester... I don't think the wastegate not opening would cause that though, unless you're fuel injectors can't keep pace with the additional psi.

If it isn't a boost leak, I would be looking at you're AFR on a wideband, or at least looking at the fuel trims with a OBD scanner.

 

[jmatyas]

4 boost leak tests and not a single one found. That was the first of many things on the check list. Also 1g crushed bov holding strong, no crappy 2g plastic pos. We tried to move the actuator arm with a long screwdriver and it did not move a bit.

Things that we have tried already:
1. Boost leak test
2. Sensors replaced
3. Maf inspected
4. Spark plugs and wires replaced
5. Many many more haha

Also its running stock boost. Thought id add that.

 

[H@xtGSX]

If the wastegate isn't opening, youre not running stock boost... And unless you have larger than the stock 450's, your might be exceeding your fuel capacity and going lean enough to make it run like crap. Do you have a boost gauge and any way of watching either the injector dead times, Air/Fuel ratio, or at the bare minimum the fuel trims?

 

[jmatyas]

I wish I had a wideband or a scanner but have not had the money to put into getting one. The car is running rich and not lean which is a odd thing with the issue it is having. Obd scan is not showing anything irregular, besides that it runs a bit rich. No CEL codes or anything either. Stock injector's and fuel pump.

 

[jared98gst]

sounds like hes hitting fuel cut
if you cant make the arm move its stuck shut or open, in your case sounds like shut
the 16g spools up and bam 4k under load is more than enough to spool that thing up and hit cut

 

[jmatyas]

Im 100% sure its not fuel cut. Fuel cut makes you feel like you hit a brick wall, this is more of a bucking and kicking, getting power losing power kind of a feel. Boost stays at 12psi when it is doing this as well. Fuel cut was my first thought but we have ruled that out completely.

 

[kchaazz]

This sounds like fuel cut to me, Im 99% sure of it. If you dont have a wideband to see AFR at wide open throttle, or a scanner/logger to look at fuel trims, how do you know whether your rich or lean? If you dont have an aftermarket boost gauge, how do you know where the boost is going? 16G will easily creep 7-8 psi over stock regardless of whether or not youve got the wastegate hooked to the stock BCS or to an MBC. I dont understand how you attempted to manually actuate the gate with a screwdriver, and I highly doubt the gate is bad, but to properly check for correct operation is to hook a regulated air supply(10- 25 psi is fine) to the nipple on the gate and see if the arm pushes out and retracts on its own, OR, remove the small retaining clip and pull the arm off the pin on the gate lever and pull the arm by hand and with some effort, the arm will come out and retract on its own. How much pressure did you put in when you performed the boost leak test? You should take it to 20 PSI at least.

 

[H@xtGSX]

http://www.dsmtuners.com/forums/bolt-tech/9593-turbo-flow-rates-here.html

http://www.dsmtuners.com/forums/articles-tuning-ecu/366003-injector-fuel-pump-supported-airflow.html

I would initially guess you are topping out your injectors and it is bucking because it is cutting... Cut isn't always a solid stop. It can just jerk around a lot too.
...and I forgot to mention, as stated above, you would use the discharge port on the vacuum tester to pressurize the actuator, not create a vacuum. As said above, you're guessing without a way to look at the exact psi, afr, timing, and trims. He is right... That 16g can creep up a lot on a 2g O2 housing, even ported. So if you think your running 12 psi (which would still be high for the 450's), it could very well be 16+ psi at full throttle and 4k rpm.

I would highly suggest you not floor it until you get the wastegate working, a way to watch your actual fuel situation, and larger injectors with a tuning solution.

 

[LarryJoe]

It's possible you're creeping and going to high of boost. They are known for that. Is your boost gauge digital? If so it probably can't show you what it's really hitting before you hit fuel cut.

 

[jmatyas]

A lot of great info, thank you all for the help/suggestions so far.

The boost leak tests were done at 20psi, the boost gauge is an AEM mechanical gauge, I reason that I feel that it is running rich is because after a test run the spark plugs will be coated in fuel and you can smell the fuel when Im on the throttle hard. I would love to check for a boost creep but since the car will not let me push it a bit I dont know for sure. If I slowly get on the gas and hold it out it stays right at 12psi, but if I launch it 3/4 to WOT it will buck. As for fuel cut it looks like Ill have to put that back on my list of possibilities, bummer.

It looks like I have no choice but to get a wideband with a logger to go any further, or just go the EPROM route since I have one and get ecmlink. Really disappointed that after two years of owning this car it has never run right, looks like its time to save money and fix this car before I can sell it.

 

[H@xtGSX]

Ok, so it stays at 12, even as your rpm is climbing? That would sort of suggest the wastegate is working, and if you have that boost gauge, are you SURE it isn't creeping? It can spike up real fast, and by the time you have a chance to look down, you may already be cutting, which would drop boost psi immediately... Based on the injector size and stock pump, you can support 32lbs of flow, but that B16g can kick out 36lbs of flow. That would definently cause some bucking if you are passing that 32lb threshold.

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[jmatyas]

On the few dyno runs we ran it stayed at 12 once it spooled up (we ran it on the dyno to watch things closer than we could have on the road, not for power of course). Maybe climbed to 14 once but never higher than that. There is no mbc its hooked directly from the IC pipe to the wastegate, not sure if thats the correct thing to do but thats what I have been told by a few others to run it to keep it at stock boost. I do have a mbc but have yet to install it.

 

[kchaazz]

So, you do have a boost gauge, thats good, I just didnt see one in your profile so I ASSumed you didnt . Well, if you dont have any intake tract leaks, and youre on the stock fuel system, Im not sure what would cause your issue just yet. I noticed you said you had an OBD2 scanner telling you its running rich. Where were your STFT and LTFT sitting? Is it only rich at wide open throttle? If so, I suggest checking for weak ignition at this point because it will definitely cause this. When were the wires replaced last? Is there oil on the wires due to a leaky oil cap or oil in the spark plug wells due to leaking valve cover gasket set? Are you running the correct plugs- NGK BPR6ES, gapped to .028- .032??

 

[H@xtGSX]

If you're really running rich, you'll have negative trims, and probably a negative adjusted LTFT. I haven't ever run so rich it caused bucking, and I have run it really rich when I first started tuning it... Like 8:1 on boost, shooting flames out the fart pipe and smelling like an oil refinery driving by. It still ran fine without jerking around, just not very powerfully. Plus, if you have no tuning device, the ECU isn't going to run it rich by default... It is already tuned to the stock fuel system. It should be bang on from the second you hit closed loop. Unless, you're in open loop constantly, which would suggest an O2 sensor giving the ECU no info. Something else to check... Is it cycling?

The way you have your boost reference run to the wastegate is gate pressure... What ever that is on a B16g. Someone else can chime in here with that figure. I'm sure you can find it in less than a minute searching "16g wastegate pressure".

 

[jmatyas]

Ill have to call the shop for those sittings, I dont have them on me at this moment. The spark plugs and wires were replaced 2 weeks ago, ngk's with correct gap (double checked). It was showing it running rich at higher rpms yet at the same time I have fuel coming out my exhaust even at idle which I have no clue what could be causing that?!?! Unless it was excess from the test runs. This car is just one big headache.

 

[H@xtGSX]

The headache goes away once you understand how the parts interact. You only have a few possible culprits here. It shouldn't be too hard to fix... Another possible scenario could be the fuel pump is taking a dump and not keeping up anymore. Then, your fuel pressure dips when you need it most, and viola! Lean bucking and jerking and running like poop. Though, this would not be consistant with fuel dumping out the back end... It can cause similar symptoms.

Running rich with no tuning device on a stock system usually means you're stuck in open loop. Look up the criteria for closed loop operation, and look into those possible offenders. There aren't that many.

OR the MAF itself is not reading correctly... But again, in order to know what it is doing, you need to be able to see the readings on an OBD2. What I don't get is that if you had it on a dyno, the people running it SHOULD be able to see this stuff, and it should be immediately obvious where the problem is coming from... Every dyno I have ever used had full telemetry, from fuel pressure, to afr's, to boost, to EGT's... Including all of the ECU info, and the Karman sensor frequencies. That is how they can tune it so well, because the can see everything the car is doing in real time with logging. If that dyno shop is not getting full telemetry, and can't pick out where that bucking is coming from, I think I would take it somewhere else...

That about runs the entire spectrum of possibilities, from fuel cut to this.

 

[jmatyas]

Well even more bad news. I just went out and took a look at the turbo again for the fun of it and I noticed a large amount of oil inside the housing, almost no play on the turbine though. I started it up and revved it up a bit and it seemed to chirp and chatter a bit, starting to think the new turbo is bad already. I really hope not since I have only put in about 120 miles on this turbo, but with the noises and amount of oil im starting to think it may be toast. Another pain in the butt to add to the list.

 

[H@xtGSX]

Get a rebuild kit or send it to Justin and have him sort it out properly. I have never had a blown turbo and driven it, so I don't know if that is a possible contributing factor, but I am sure it isn't helping.

 

[pauleyman]

Oil in the intake side? Check your intake pipe. Stock setup sucks in some oil. Coats your IC inside also. Double check those plug wires and make sure they are seated.

 

[H@xtGSX]

True, the PCV does suck a lot of the blown by oil down the intake if you still have it connected. I blocked that port on the intake so long ago, I forgot about it.

 

[DuricsmitGST]

Check your vacuum lines. I've had a small hole in one and my car hada similar bucking problem. swapped for new line instantly fixed the problem.