Sporadic loss of power while boosting

[And_44]

Howdy ya'll. Got a random problem that doesn't happen very often maybe once a day and quickly fixes itself, just want to get a idea as to what it is and take care of it and hope it improves performance some. I have a 1990 Talon AWD TSi 5speed. Mods done to it are a tubular exhaust manifold, have stock O2 housing and DP with 3"exhaust (no cat), free mod'd intake, and was told by previous owner that the 14b has upgraded larger internals...(havn't confirmed).

Well the problem has happened when in 3rd most of time and only maybe 2-4 times while in 4th or 5th starts at about 2500 when the turbo starts or should be spooling but instead of getting the boost it feels like the car is a 1.8liter and has no power. If I let go of the gas completely while in gear and try again to accelerate problem goes away and pulls like a mofo. It almost seems like the WG or BOV is staying open after the shift from previous gear and letting go of gas creates a back pressure or what not to close it. Also it gets the boosted LOUD not a bad loud but like the turbo is boosting at max. BoV is recirculated and almost new. Not sure if a boost leak would be this sporadic. Any input would be greatly appreciated.

I'm already aware of a exhaust leak between turbo and head just havn't found exact location, but don't believe that to be the cause as it would be more common for problem to happen. Car idles ok at 600-800 rpms when stopped, no dying problems just bogs down like a spark blow out. Though it does burn rich, so rich sometimes makes eyes water some;( Also my EGR sensor's wire has been fried since i bought car almost a month ago + longer puts up a CEL check it weekly and only that one code (43).

No other noises besides the exhaust tick, loud exhaust, whistle from moon roof, and a annoying rattle sometimes from the back half of car. Smells are only from the rich exhaust, and absolutly no smoking what so ever (very happy about that) Also burns no oil, and has a small coolant leak but nothing big.

Thank you in advance for any input and advice.

 

[Calan]

From what your saying (in one REALLY long run-on paragraph ), it sounds to me like you have some tuning issues. The loss of power after shifting could be a lot of things, but I'm thinking it is due to knock and your ECU pulling boat loads of timing.

Letting off the throttle and then getting back on it, and then seeing the problem disappear is common for knock (either real or phantom) in that area of the power band.

If it's running as rich as you say...well there's a big part of your problem. Throw a good tune on it!

EDIT:

You definitely need to fix all boost and exhaust leaks ASAP. If you don't, you'll be running in circles trying to chase down other issues.

 

[And_44]

WoW, Phantom knock or regular knock is not what i was expecting but yea, could be a very good probability. I'll do a search for it in the morning and see what I can find. Thank you much for the input that wasn't something I was even considering. .

Exhaust leak well previous owner got lazy and didn't install all the bolts into the exhaust manifold to head and believe it's missing a bolt on the exhaust manifold to turbo, gonna go to Tacoma bolt and screw to get replacement, part stores don't carry bolts or studs;( With fans off and engine running I can feel the pufts of exhaust hitting my hand as I hold it over exhaust manifold, hope it's not cracked;( Boost leaks well I'll give it try, but believe it's pretty solid.

And tuning I'm new to that word. I've usually kept my cars stock, this is the first car which I got a month ago in this condition (well worse "wasn't running") and with these mods. If it involves an upgraded ECU well I believe there's a DSMlink in car but it doesn't have the chip installed. Gonna check the timing this weekend though had to replace the CAS so timing may be off some.

If exhaust manifold is cracked would the 2g Exhaust manifold be a downgrade from the tubular exhaust manifold? Would probally be for the better downgrade and close the gap though I would think between the 14b.

 

[And_44]

Well, I believe I may of gotten this problem hammered out. I thought what the f*** and put in new plugs and as I was removing old ones I was checking the gaps and was shocked to see .04-.045 gaps..... So put in some new NGK gapped at .028-.03 and also checked the timing was at almost 20BTDC adjusted it back to 5BTDC and took it out for a spin, drove it all day probally 100miles city and freeway, and couldn't get it to do what it was doing once. Adjusting the timing though did raise my curb idle speed from 650rpms to a nice 850-950rpm's. Not complaining about the higher idle, but now looking to replace vacuum lines with new and remove the emission hoses discribed in mod. Hehe got car registered as emission exempt so no worries with those. I'm getting extremely happy with my results on working on this car. Every time I do something it runs nicer, smoother, and better. Next is to replace that annoying putting cracked tubular exhaust manifold. Already got the purchase of a 2g exhaust manifold arranged for tomorrow. Diffently not going back to tubular seem way to fragile, few months down road after getting supporting mods will get the 16g with a FP manifold or Evo III manifold, but a 2g should do until then.

 

[Calan]

Cool deal! I figured it was some sort of tuning issue.

A ported 2G manifold is practically the same as an E3 manifold, and either one can take you a long way. The FP race manifold is a nice piece from everything I've heard about it, but I think there are a lot better ways for you to spend your money for a while, assuming you get a decent 2G mani.

I believe there's a DSMlink in car but it doesn't have the chip installed.

Other than the cable, DSMLink is just an eprom inside the ECU. It either has it, or it doesn't. Open up the ECU and look at the chip...if it says DSMLink (or ECMLink, ECM Tuning, etc.), then you are in business. Just call up Tom or Dave at ECMTuning and talk to them about a new cable or whatever you need. They are good people over there.

***************

Just keep doing the little things and learning how to tune, and stay on top of the maintenance; it will just get better.

 

[And_44]

Thank you calan, your input has been extremely motavating and helpful Took a look again at my current manifold and thought it was just missing some studs;( Well it wasn't previous owner busted off the studs right near the outer surface of the head, so the new 2g manifold install is gonna have to wait until I get the proper tools to remove the studs. Drill and Heli-coil kit. Not gonna bother with the E-Z out way, prefer to have the steel threads from heli-coil. Since I'm waiting gonna also invest in a die grinder and carbide bits and go ahead and port with it out, and when I uninstall current manifold go ahead and take out the turbo and o2 housing and port those as well. I feel comfortable doing the drill out and heli-coil do it all the time at work on aircraft. Porting though will be a new experience Seems pretty straight forward though. Thanks again, and glad I have this forum to bounce stuff off Will pull ECU this weekend and crack it open to see about chip too There's a shop here locally that does Link tuning for like 60-85 bucks. So may just have them do the initial tune, and then work off that.

 

[And_44]

Well an update about my exhaust. Yesterday I used this stuff called Thermosteel on the crack, and oh boy does it work wonders, car no longer has that loud putting noise. Seems that the turbo spools up a heck alot faster too. While waiting for the thermosteel to dry i went ahead and did the 0$ emission vacuum line removal, and replaced the other remaining vacuum lines with new. Car now spools faster, idles smoother, and I noticed the engine compartment wasn't as hot as it once was. Probally was hotter before b/c of the exhaust gas's making their way into the engine compartment instead of flowing through turbo and exhaust like it's supposed to. Found out though that I'm missing the boost control selonoid, and I don't have a manual boost controller yet. Previous owner removed selonoid and had a MBC set up, but he removed it and sold it on CL Now I'm stuck at 8psi for now. Can't wait to get my BCS back and running, or investing in a MBC to get that 15psi back. After getting the boost back to stock next is the wideband AF gauge then the link/logger for the ECU. And working from there.

 

[And_44]

An update Thermosteel is crud. It held up for about a week and started falling off.

My recommended fix is to get a new manifold or have someone reweld it.