Boost leak? Ignition? ECU? WTF?

[jtalton626]

Ok, I'm officially pissed off at my car. And I'll tell you why. I have owned my DSM for three years now. I have dropped over $12,000 into this build over the years. Throughout an entire motor swap, new internals, etc. the same problem has occurred. After my car warms up (ie. 0.5 miles of aggressive driving, or maybe 1 mile of normal driving) it will not get any more than 5psi of boost before falling flat on it's face.

I am going to list the starting date of this particular problem, and repairs I have done.

5/2007-Have car stereo system installed by local stereo company (should have done it myself). Upon leaving the parking lot under WOT and hitting a nice sharp curve, my entire cars shudders and cuts off, all electrical systems in the car flash on and off as if struck by lightning, and I pull off to the side of the road less than 300 feet from spending my last $300 on an unnecessary upgrade. Started the car up, drove it home and noticed what seemed to be fuel cut. Upon inspection of the car, discovered the friggin 17 year old noob they had in the installation bay had forgotten to put my battery strap back on. The short was my battery post terminal BURNING a 1.5 inch hole into the underside of my hood.

Shortly after this happened, I blew out my #3 piston ring and sideline the car for a while. Decide that I would be better off with an all new build, and hopefully lose the "boost leak" problem at the same time.

I buy a new block (7 Bolt), 7 bolt crank, H-Beam rods, ARP connecting rod bolts, stage 2 head, new valves, ECU, ignition coil pack, new power Trans unit, walbro 255, 650 cc injectors, bigger lifters, larger radiator, slimline fans, prothane mounts, cross drilled and slotted rotors, and CAS.

So, I fire this bad boy up and WOW!!! Feel the power!!!! 15lbs! I make it a mile, and 5 lbs later it falls on it's face. I can't tell if it only does it under load or if it's pressure related but 5psi seems to be the limit. I can push it past 4,500 if I don't let the boost come in (letting out the throttle).

I got an AF gauge (not a wideband) and it says I am going lean when the car starts to cut out. But why would it run at the 380-400 horse range all the way up to 7000 on the tach at 15 lbs when it's cold and then fall on it's face a mile later at 5 lbs? It can't be mechanical or it would be all the time. Timing is amazing right now, until the problem starts. I'm thinking a boost leak somewhere that expands when it gets hot. If it's a cracked manifold I'm gonna be ticked ### that will be 3 in a month that I have bought and they were bad.

What is the EASIEST and BEST way to do a boost leak test? Can I do a test while it's hot in case the leak is only present then? I'm about tired of this shit, but if I give up and sell the car my wife will be telling me "I told you so, that thing was a piece of crap from the day you bought it. Just a big pile of money pit". And she's right...but she doesn't understand. You guys do. I need some help. I feel like a mitsu engineer just by OWNING this car especially after going to the dealership only to find out I knew more about the car than they did...but apparently I don't know enough.

 

[Shortstuff]

I would suggest ECU be your problem, because i have heard of peoples battery jumping up and grounding out on the hood and frying the ECU, but you did list that you replaced it, only thing i could suggest would be a short or cut in a wire somewhere near your ECU. Possible when they installed your radio they cut some wires they wasnt supposed too. I hope you figure it out and let us know what you find. Also we do understand and they are money pits but dont get discouraged you will find the problem...

 

[ramsack]

sounds like a boost leak, running out of fuel, knock, or a coolant temp sensor issue. i know my car (9:1) likes to boost better when it's cold, and when it warms up it knocks. 2 reasons for that, the combustion chamber heats up, and it runs leaner when warm. i have no idea if a narrowband gauge will tell you what you need to know under boost for the afrs you usually go for, but if it is leaning out, then that also sounds like a fuel supply issue. either a clogged filter, too small of a fuel supply line, or time for bigger injectors. at the near 400hp range you should have had a wideband for a long time now. i would get one. i feel ya, cars are money pits and not everyone understands that.

 

[jtalton626]

Well, I honestly hope that the wiring was not cut during the radio installation. I have since installed numerous electronic goodies and I really hope I don't have to dive through all that mess to find a wire with a tenth of an inch crack in the insulation. That would be my luck though.

 

[BIRDCLAWTSi]

Do you have a logger? It could be a few things, With a logger you could see TPS value when the problem occurs, Timing , 02 voltage, Airflow , Intake and coolant temps. Check your timing marks on the pullys. Maybe , Open up the ecu and look at the caps... What exactly happens when this happens? Start from the begininig, Do you floor it? gradual acceleration?
Say you are at a stop sign getting ready to take off...What happens?

 

[jtalton626]

I do not have a logger. I do however have fully adjustable cam gears, as well as the adjustable cam angle sensor. I'll try and explain the feeling a little bit more. When I first start the car up and pull out of the driveway, there is a straightaway of about a 1/4 mile. I usually do a quick pull down this stretch. The car will hit 15lbs, and pull through every gear. After I coast in 5'th (or any gear) for a mile or so I come to another straightaway. When I push the throttle, it will go up to about 7lbs and start to sputter like it's losing fuel (air/fuel gauge goes from rich to lean) If I try to push through it by going to WOT, it falls flat on it's face, picks up back to 5lbs, falls flat, back to 5 lbs, etc. If I feel it start to sputter and I let out the throttle I can keep it going at around 4lbs. I can literally watch the A/F gauge and let the throttle out as it goes lean and as long as I keep it out of the red I can go all the way up to 5-6000 rpm. If I start to go up a hill, it puts load on it and I have to granny it up the entire hill. If I try to launch after this problem starts, it goes like a bat out of hell, builds boost to 5 lbs, and tries to throw me out the windshield. Very aggravating. I just changed my spark plugs today, gapped it all the way down to .025 (seeing if I was losing spark because of distance, high boost, etc). It made absolutely no difference whatsoever. So I doubt it's ignition related.

In the past two days I changed the coil pack, trans unit, and spark plugs. Wires are new and show no discharge in a blacked out garage. I wish i could find a MAS unit to swap out but my local junkyards have CRUSHED every car made before 95. I'm really starting to think I have a boost leak.

 

[And_44]

You figure out what was up with your beast? Having a similar issue with mine.

 

[97Boosted]

I am also having this issue after blowing a head gasket. my car runs a little rich, which is opposite yours but has the same problem.

My car runs good up until 3-4k rpm range/when boost hits.
It goes to 5 psi then stutters like crazy.
sometimes i can push through the stuttering and get boost. but the last time I did that, the turbo spooled and blew off, but it didnt seem to make me go anywhere.

my car ran amazing at first, then my hg blew and i put a MLS on and now this.

 

[schroder]

If it hasnt been solved yet, I see lots of parts, but no boost leak test. More importantly, no mention of a timing light being used to set electrical timing. I know this is an old post, but to help those in the future, heres a few things to try for similar problems:

Check mechanical AND electronic timing. Mechanical via cam gears is really easy, and something thats messed up pretty easy. Electronic is with a timing light. Make sure you ground the cas plug and you should stay at 5*.

Make sure your not leaking any fluids (i.e. gas - since his cars light show says lean)

Check fuel pressure regulator to make sure its working (again, lean)

Test fuel pump and injectors.

Perform a boost leak test (this should be a rich condition on the WBO2 sensor tho)

I doubt it, but check for wastegate tension if you have an internally gated wastegate...incase its blowing open.

Check spark plugs for gap and wear...what color are they?

Theres plenty more to do, but these should point you in the right direction

 

[casperfast]

I made a simple boost leak tester out of a 2g turbo stock intake pipe(one on turbo inlet) and an air fitting and a regulator. Works great. This wouldn't result in a lean condition but it would at least let you know the condition of your charged air pipeing. BUT I would also seafoam your engine off the bov line. When I did this I could EASILY see small cracks in my manifold, o2 housing and the wastegate. The exhaust leaks could be causing the poor spool/boost, the shuddering that feels like fuel cut. Look at you logger and see where your short term fuel trim is at when this is happening, I'm gonna geuss it is sitting around +10 or more and thus indicate a lean condition, as well as show this on your af gauge. If that is the case it is mostlikly going to be a manifold crack. Seafoam will show it!!! Good luck