Car falls on it's face under WOT/full boost

[uniuno]

So I've never had a car act like this before and it has me stumped.

When I accelerate hard and hit 10-11 psi sometimes it feels like I jabbed the brakes as hard as I could.

Besides that it runs good. It started doing it when it got cold, coincidence? up for debate...

What is wastegate pressure supposed to be? I wouldn't think it would be 10 psi... it's 6.5 on my mitsubishi.

It's pretty much stock, the previous owner put a POS THUNDER manifold on that cracked all to hell so I had to have it welded.

I zip-tied the active intake runners in the low rpm setting to make sure it wasn't them flopping around or something like that. I replaced the spark plugs and wires as well.

I'm now leaning towards bad coil or maybe even something EGR related. Like I said, stumped...

Thanks for your help!

 

[hornsfan10609]

Sounds a lot like fuel cut, especially if it is more prominent in cold weather

 

[Spiced MSP]

Car needs to be tuned more than likely

 

[uniuno]

Hmmm, Plausible.

It's been flashed, supposedly, the dealership in Livonia (Detroit suburb) that did it was horrible. I had to take the thread from here in to show the service writer that adamantly denied that there was a flash available for it.

I have a spare walbro 255 laying around that was intended for my other car, would it drop right in? Would it help?

Thanks for the ideas!

 

[shane02pro5]

Stock boost is closer to 7psi...and as rich as the stock ecu runs your stock injectors are probably maxing out causing fuel cut in colder weather with the boost TOO HIGH unless you are fully bolted with ems and a knocklight for safe measure. Make sure the wga is holding pressure by blowing into the vac line. I'm guessing you dont have a wideband to know your afrs when this is happening.

Check for more cracks in your thunder mani too...I welded mine 5x.

 

[Outlawstar98]

What temp is it outside for you right now? Anything lower then 35-40 degrees makes me get the fuelcut. Just dont gun it and you will be fine.

 

[Wagonbacker9]

+1 to all above, its fuel cut... my car cuts at as low as 4 psi if it is cold enough.

 

[uniuno]

I wish I had a wideband to watch... I need to get a pump so I can pressurize the wastegate. I'm wondering if dropping the in the walbro would richen it up enough to make a difference. Or would the O2's just see it rich and compensate by decreasing the pw?

I put a oem gasket back on the turbo flange, I wish I had used an aftermarket MLS or one that crushes,,, the stock one is sucking... my lean code is back as of my drive home from work tonight....

I'm going to try cleaning the vacuum ports on the intake, one of them wasn't working well enough to operate the boost gauge.

 

[uniuno]

hmm, not a fan of not being able to gun it ahahhaa

 

[Wagonbacker9]

I think you're misunderstanding. Its not that the car is actually running out of fuel, the ECU is going into a protection mode which (for better or worse) is overly sensitive.

Upgrading the pump wouldn't do anything unless you altered the pressure, and if you did, the ECU would learn around it. The only way to avoid it is to either get a fuel cut defender (bad idea) or improve the tune with a piggyback.

as for cleaning it out.... getting all the things on the car working correctly will do wonders, so I'd focus on that.

 

[uniuno]

Ahhh, I see, so all of these cars drive like this when it's cold out? It started happening when it was in 40-50 degree range

 

[Wagonbacker9]

Ahhh, I see, so all of these cars drive like this when it's cold out? It started happening when it was in 40-50 degree range

to one degree or another, yes. We've all had the pleasure. mine didn't do it NEARLY as bad on the stock intercooler. Last winter I was overboosting so I figured that was why... this winter I figured out, its just how it is.

 

[uniuno]

Wow, awesome! Thanks everyone!

 

[uniuno]

So the vacuum port that goes to the active intake solenoids has vacuum, but when I rev the engine the vacuum gets a little stronger instead of going towards 0 like it should... What's going on in there? Has anyone had the intake apart?

 

[Wagonbacker9]

So the vacuum port that goes to the active intake solenoids has vacuum, but when I rev the engine the vacuum gets a little stronger instead of going towards 0 like it should... What's going on in there? Has anyone had the intake apart?

Never messed with that. just use the port on the top of the mani... the ones on the back have a lot of valves and controls

 

[uniuno]

yeah, I put everything vacuum related back to stock configuration and it got worse.

How can this be intake related!?

I'm seriously considering getting the intake from a 626, what year is best to go with?

 

[uniuno]

Aaaaaaand fixed! It was exactly what I thought it was to begin with. Apparently my zip tie fix on the intake runner valves wasn't cutting it. I took the vacuum line off of where the solenoids went to and T'd into the one in the middle and temporarily put my boost gauge back on the suspected bad port. Went out and did a couple runs to redline with no issue! She's running great, we'll see how long that lasts... Thanks for your help everyone!!!