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Discussion Starter · #1 ·
As i'm getting into boost, no matter what gear, engine feels like it's on rumble strips, and at least half the power is gone.

Cam sensor is suggested by a friend. Almost everything underhood is new oem stuff.

I'm thinking fuel pump relay or knock sensors. My catalytic converter is stock, no rattling.

Vacuum is at 15-22 on the boost gauge. Idles fine, gradual throttle is fine, moderate boost is fine.
Only happens when under full boost.

Heading to the jy after work tomorrow to hopefully diagnose.

I've spent at least 1K within the last month on maintenance/exhaust, i'm sore
 

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Sounds like detonation, double check boost controler vac hoses for correct routing. Then check all related boost controlers/waste gate.
 

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Had a similar issue recently, the car under full boost would stumble and shake. Found some broken vac lines and that cleared it right up. If that doesn't work, how about the basics, plugs, cap, rotor, wires.

Just out of curiosity, where did you get your exhaust done?
 

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Discussion Starter · #4 ·
20K on all oem cap,wires,plugs have ~10K.

fuel filter is 20K, i'll order a new fuel pump relay.

got a jy cam sensor, problem still persists.

I will say this, car started to run weird after a 145mph closed course run earlier in the day.

Exhaust is just a 2.5" cat back, 2.5" resonator, 2.5" magnaflow muffler, BUT a 2', 2.25" crush bent rear section . They supplied the piping and did the welding. A shop down by 595 in Davie, FL.
 

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There are a couple hidden vacuum elbows under the manifold that may be the culprit. Check to make sure the MAF is clear too. Thanks for the piping info. I am thinking of making up my own exhaust.
 

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Discussion Starter · #6 ·

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No worries man, good that those things are done :). Check the ones by the turbo vac tree too. Maybe PCV nipple got some crap in/on it, from the high speed run....hehe nipple
 

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Discussion Starter · #8 ·
I'm going to scan it, and check/re-gap all plugs tomorrow after work.
 

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no problem with having a new fuelpump relay lying around, but it definetely isnt your problem. its either on or off, got nothing to do with boost. if you're persistent, pull the relay and insert a jumper in the top an bottom connectors of the relay socket (closest to and furthest away from the windscreen), this way you bypass the relay function, pump gets uninterrupted power. see if that solves your problem, before shelling out on a new relay.
 

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no, I mean a straight jumper cable. about 10cm with a male cable connector in each end. discovered this when my relay went and died on me, in the middle of nowhere. front and rear connectors are the main power going through the relay, to the pump, so if you connect these two, you bypass the relay function. not something Id reccommend driving wih permanently, it MIGHT draw power from the battery even when keyed out and turned off, but for troubleshooting its a great way to determine uf the relay is the issue, or the pump.

for your issue in particular, it COULD be (note the capital letters, not saying it is) your fuelpump, or the fuelpressure regulator. the latter is not very likely, its basically just a vacuum clock. if your pump is getting tired, it might not be able to keep the prescribed 3bars fuelpressure up, which could result in rumbling and uneven running when all that pressure is needed, eg on high RPMs.
 

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Discussion Starter · #12 ·
Alright I understand, that's kinda iffy for me to try out but I scanned it and got no codes.. FPR is new, fuel pump is old.

I'll get a walbro 255 and a new fuel pump relay. Goin gto pull and check plugs/cap&rotor today.
 

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Discussion Starter · #13 ·
So... I pulled all five plugs, they are grayish-brown, according to Haynes that is normal. What is not normal is one of the plug wire shafts are light brown, and the plug looks a little beat up (the cylinder closest to the intake box)

There is a couple hairline cracks on the disty cap cover, but no cracks inside. The rotor looks good. The wires look good.

BUT there has been a slight "blurp" at idle every 10 or so seconds, not sure if always been there or more noticeable since exhaust.

I'll see if any better on the way to work. Have pics but photobucket site is down, will upload shortly.
 

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Discussion Starter · #14 ·
Well after a drive the problem's not as bad, but still there. Also overboosted to 17lbs at one point which is a first after exhaust, I don't like that.

Plugs were at .29-.30 which I regapped to .28. I think new plugs, wires(ipd)?, oem cap/rotor would cure the issue. There have always been a sputter since 2010 so I also think a new fuel pump relay is in order.

Pics below:
The wire closest to the intake is brown, i wonder why.
 

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Hmmm...I mean that all looks relatively normal, from my experience. Maybe run some injector cleaner through before you replace the plugs and wires. Also, are you using premium or mid range fuel?
 

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Discussion Starter · #19 ·
I've ran injector cleaner right before i put these in, and i ONLY use 93
 

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Good, just checking!!!
 
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