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Engine boosting, but lacks power...

2K views 19 replies 13 participants last post by  ihumpvr4sforfun 
#1 ·
Car starts normally, idles fine. We've rev'd it up many times and it's smooth and sounds really good. Oil pressure is good, compression test on all cylinders is around 120 (has shown higher before). Boost pressure can reach about 3-5psi when rev'd up. Under load boost gauge reads higher than 5, but car does not seem to actually perform at that level of boost (seems sluggish). During acceleration we experience jerking, and followed by each jerking action we hear a PSHHHH, and then what also sounds like a sucking in of air. The rear exhaust manifold at the turbo gets excessively hot. We have seen it glow when nothing else has. The engine was just put back together because I had most of the gaskets and seals replaced. New clutch and flywheel aswell. New output shaft and transfer case sleeve too. Clutch and transmission feel fine. Car sounds very good. The only problem is this strange hesitation and the sound of air shooting out of some place and even what sounds like air sucking in... It just sounds like the car is almost hiccupping whenever it boosts. I will be checking rear manifold and turbo housing this week to see if the problem may lie there. Any insight into this issue will be much appreciated.

Happy new year!
 
#4 ·
To read boost levels, a mechanical autometer boost gauge.

No, I actually do not have a logger. Can somebody show me all the things I need to buy to log data? If you can give me some links to affordable loggers, I'll go buy what I need and finally get it set up. I should have done this already, but i guess now is a good time :rolleyes:
 
#8 ·
Glowing mainifold can indicate your running lean due to a major air leak after the mas, best bet is to check all the pipework and do a pressure test (as has been said already). Wrong Ignition and valve/cam timing can also produce a glowing manifold.
 
#11 ·
No, it's not adjustable, unless you have some sort of standalone or piggy back system. But that's not your problem anyways, as it's been said allover here, you have a boost leak, it may even be at the BOV since you're hearing that noise.....

When you leak out the boost, the MAF has already regestered it. So it's calculated that you need x fuel and x timing retarded. But that's been leaked out, so you're running excessively RICH and retarding the hell out of your timing (not lean like previously said). It's going to make the turbo spool hella fast with no power (just like anit-lag), casue you really should hardly be seeing any boost when reving it, it needs that load to create it (unless you rap the hell outa it). The surging you feel is the injectors flooding your cylinders, it runs it so rich that it can't even light off the mix causing a mis-fire.....

UPP
 
#13 ·
Identical problem here. Idles awesome. Cruises fine, no startup issues, no codes (other than a knock sensor code). The hesitation is most noticeable with a cold engine and right after shifting and going back on the throttle again. No aftermarket boost guage, but the stock one goes all the way up to 14. I know that is not accurate, but nevertheless, this thing IS making boost pressure. Right as the guage reads positive pressure, this hiss develops, and yes, it is a tell-tale sign of a boost leak. The neighbor has a 3 legged dog that is faster than this car. No pressure tests, but I triple checked all the hose connections, and they're all good.
Captain obvious then put his mouth up to the BOV hose and blew into it with breath pressure. Its leaking through. Good chance this is the problem. Next spring, when it is warmer and half way comfortable to work on cars again, I will plug the blow off valve and then see what happens.
 
#20 ·
Thats because the stock plastic bov's are made to leak. It has a hole in it that lets a little air recirculate into the intake even when its not open. I'm not saying its not your problem just that its not air tight. Lol@ your friend for putting his mouth on that nasty hose.
 
#14 ·
Been having a similar issue since tday, 3 months ago I got my 92 VR4 with only 48k, but a faulty ECM which I already replaced, car ran perfect since then. On friday I removed the original Y pipe that goes into the intake manifold and installed a metal one. Car ran awesome for the weekend no issues at all. When I started the car today and went out you could hear a pshhhhh sound and there was boost, but lack of power, the stock boost gauge will show boost built up to the max, however it didn't have power. Might it be a boost leak on the Y pipe I replaced?
Thanks
 
#15 ·
If it's leak after the turbos then the air meter will read air entering the turbos and show this as "boost" on the stock gauge. It's not really boost but perceived load calculated by the engine ecu.. So you have a leak somewhere after the turbos, y pipe coupler is the first suspect, then recirc valve pipe?.
 
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