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#1 |
Scooby Newbie
Member#: 240903
Join Date: Mar 2010
Location: Park City, UT
Vehicle:92 Corvette Red |
![]() This is going to garner all the typical replies, likely, but I'm stumped, so here goes:
Changed the timing belt, WP, pullies, etc as part of PM. All went well. Car started right up, runs well....until you "get after it" and from about 3500 RPM up, it lacks power. The higher you rev it, the worse the power deficit is. I have "poor man's dyno's" all around me; mountains + speedometer and I have 6-7 years of experience with this car, doing "dyno pulls" on these hills. One hill, in particular, I can climb at 50 mph in third gear...every day. Now, won't crack 40. The other hill, 80 mph and accelerating(if I want to push it), in 4th gear, now won't barely get to 75. Barely. Or it might not even get there. I'm convinced the cam timing is off (advanced), but the marks all line up. I triple checked 'em when I did the belt swap, spun the engine over and re-checked, all was good. Still, it ran weak so I pulled it all apart last night and checked again....ALL lines up as they should. There is however, a distinct loss in power over night, from the previous 6-7 years of 'dyno testing' to work and back, every day. Thoughts that I haven't thought of?
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#2 |
Scooby Guru
Member#: 30669
Join Date: Dec 2002
Chapter/Region:
Tri-State
Location: USA, North NJ, 07456
Vehicle:1998 Legacy 2.5GT Silver Sleeper BK, 5MT |
![]() Things I can think of quickly.
When I check timing marks (especially when radiator is installed) using a small mirror so I get a "head on" view of the marks. This removes parallax looking just from the top. Granted, more of an issue on DOHC's than SOHC. Crank timing mark, I remember some engines/years had 2 marks, IIRC, one was front of the gear, the other was rear gear flange. Either one would work, only one was correct. Otherwise, what else got disconnected/removed when doing the work? Any CEL's, either pending or active? |
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#3 |
Scooby Newbie
Member#: 240903
Join Date: Mar 2010
Location: Park City, UT
Vehicle:92 Corvette Red |
![]() Good point on pending codes. Went and checked, none.
What other work? Changed WP, tensioner, coolant, idler pulleys, and both serp belts. That's it. Here is what I touched: belt guards Belts Rad/fans damper plastic covers tensioner pulleys/belt water pump/t-stat. Re-assembled. I don't "get it". At this point, I'm considering advancing the crank one tooth. During my inspection last night, I actually tried that last night to verify actual timing; once I moved the crank one tooth, it was totally obvious that then, the timing was off a tooth. I put it back and it once again looked to be spot on. I used the timing mark on the reluctor wheel behind the crank sprocket. I talked to a staff of mine this AM who is an ex Subi dealer tech, he mentioned that I should be using the timing mark on the crank sprocket face, not the reluctor wheel. I rejoiced. "That's the problem!"...but then I checked on ProDemand, and that is not the case; they say to use the mark on the reluctor wheel that I used. I did look and not see any mark on the crank sprocket, either, so.... ![]() |
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#4 |
Scooby Specialist
Member#: 80465
Join Date: Jan 2005
Chapter/Region:
RMIC
Location: Denver
Vehicle:2001 2.5RS Black Diamond Pearl |
![]() Overtighten the accessory belts too much? Reset the ECU after this work? Bad tank of gas? Clean the MAF sensor? Check/clean all grounds? It sounds like your timing is fine. Maybe you're feeling the new bearings that aren't loose anymore.
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#5 |
Scooby Specialist
Member#: 283429
Join Date: May 2011
Chapter/Region:
South East
Location: Down yonder.
Vehicle:2016 Crosstrek Silver |
![]() Having done more than my fair share of those belts I can assure you something is one tooth off. Even with a mirror I have gotten one off - and I am sure I will still do it which is why I triple check and even use a short straight edge of some kind.
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#6 | ||
Scooby Newbie
Member#: 240903
Join Date: Mar 2010
Location: Park City, UT
Vehicle:92 Corvette Red |
![]() Thanks for posting and trying, guys.
Quote:
Quote:
No, the timing belt wasn't off, although the symptoms could have matched that problem; no top end power. But, I knew the marks were on, and I knew the pulleys hadn't moved when I changed the belt. So.....what else kills top end power? I had a hunch, so I ran a quick test; one that I've done before with conclusive results. I pulled the front O2 sensor, and screwed a compression tester hose into the bung, then slipped a long rubber hose over the end of that hose, and ran it into the car....and I hooked a fuel pressure gauge to it. Fired it up, matted the throttle in neutral....saw a peak of 22 PSI. BAM. THAT is the problem, and it was pure coincidence that the symptom started at the same time that I did the timing belt. |
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#7 | |
Scooby Specialist
Member#: 283429
Join Date: May 2011
Chapter/Region:
South East
Location: Down yonder.
Vehicle:2016 Crosstrek Silver |
![]() Quote:
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#8 | |
Scooby Newbie
Member#: 240903
Join Date: Mar 2010
Location: Park City, UT
Vehicle:92 Corvette Red |
![]() Quote:
Cat disintegrated, plugged up the outlet. I tried to go to the "Images" page, so I could post pics, but the page never sent the supposed emailed instructions. This is the hardest car forum to post pics on, that I've been a member of. I'd guess that the Cat failed from 226,000 miles of vibration, heat cycles, and possibly, just the way I drive it. It's driven WOT probably 30% of it's life? Since I've had it. My commute since I bought the car involves driving down a canyon about 3000' vert....then typical highway and 2ndary road for about 10 minutes, then up a canyon 6 miles long, 3000' up, where it's WOT the entire time. Going home? Repeat but going the opposite direction. I joke that I just keep the car WOT all the time, and use the "Speed lever" (that would be the shifter) to adjust my speed. I'd think that had an impact on the Cat, and heat cycling over the last 30 years, 220+K miles. |
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#9 |
Scooby Newbie
Member#: 240903
Join Date: Mar 2010
Location: Park City, UT
Vehicle:92 Corvette Red |
![]() Test drove it a few minutes ago....got my ~30? hp back!
I ended up punching out the remainder of the primary cat. This problem/fix is going to prompt me to do something I've already wanted to do for a while. First, I'd like the car to have a little sound to it. Second, I want to get two fully functioning cats on it again. While R&R'ing the exhaust, the flanges for the two cats were super rusted/pitted. So much so that I had to use three gaskets on the flange between the two cats to get it leak free. I don't think that'll last, so I think my "fix" is basically temporary. I think that a Subaru with dual exhaust, a couple Flowmaster muffs could sound pretty sweet, and make the driving experience, a little more interesting...if not any faster. ![]() The next weekend that I have free, I'll have to start laying out pipe and see what I can come up with..... |
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#10 |
Scooby Newbie
Member#: 240903
Join Date: Mar 2010
Location: Park City, UT
Vehicle:92 Corvette Red |
![]() Maybe this will work (hosting pics on a user/pic friendly forum)?
My pic timing wasn't perfect; matting it in neutral and grabbing a perfectly timed pic as the RPM is soaring is tough, but it tells the story: ![]() I dropped the exhaust and separated the cats. ![]() Got that front cat apart and found this on the inlet side.... ![]() DOH!! ^That^ don't look right! Here is the outlet side.... ![]() ...and there was my "timing belt problem". |
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#11 |
Scooby Guru
Member#: 30669
Join Date: Dec 2002
Chapter/Region:
Tri-State
Location: USA, North NJ, 07456
Vehicle:1998 Legacy 2.5GT Silver Sleeper BK, 5MT |
![]() Welp, glad you found it.
![]() Thanks for posting the resolution. I HATE dead end threads! ![]() I have had a CAT fail before, but it took several weeks with slight loss of power and gas mileage slowly dropping. This was in a 1989 Toyota Camry Alltrac 4 cyl. |
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