Recovering Lost Power

WhatAmIDoing · Post by **WhatAmIDoing** » 05 Jun 2018, 11:00

My 1998 S70 T5 doesn't feel like is has the power it used to have. This is really noticeable traveling uphill. On the highway, I usually have to downshift to 4th to maintain a safe speed, A/C off. Steep grades I'm lucky to be at 45mph by the time I crest. I realize these are heavy vehicles and don't have big engines, but these are grades I travel regularly and use to be able to climb in 5th gear without dropping below 60mph.

Things I've done: compression test 165-170 on all cylinders, new spark plugs (helped with accelerating), cleaned throttle body, passed glove test, and checked for brake drag. I'm not sure what else to inspect and clean that could be sapping some beloved HP?

Post by **tryingbe** » 05 Jun 2018, 11:51

Is your turbo producing boost?
Shaft tight?
No holes in the CBV?

Post by **Kara503** » 05 Jun 2018, 13:10

To build on this, have you done the timing belt recently? Could be that you were a tooth off and have some power loss. If you havent or it is due, I may be crazy, but I feel like my 855 was more responsive and had more kick after I replaced the TB.

Do you have a boost gauge to see if you can track boost loss/gain as you fix things?

You could also try an ECU relearn just for sharts and gargles. Or if you have OBDII reading/ recording capability track your air/fuel mix to see if you are running oddly or need a new O2 sensor.

Other things: Check for vac/ boost leaks, make sure you use premium fuel, think about running some injector cleaner, check your air filter, clean your MAF, might be due for plug wires/ distributor, O2 sensors, clutch could be slipping a bit?

WhatAmIDoing · Post by **WhatAmIDoing** » 05 Jun 2018, 15:37

Turbo produces boost easy, been having some issues with overboosting. Have a boost gauge. Haven't found any boost or vacuum leaks. Did a relearn before spark plugs, honestly think it got worse, so maybe should try that again. My OBDII scanner can't read air-fuel. Running premium fuel with some Lucas injector cleaner right now. Forgot to add, cap & rotor and air filter are also new. MAF was cleaned a few months ago, so guess I can clean it again. Wires have about 30k miles on them, premium NGK. No idea on the condition of the O2 sensor. Clutch doesn't slip but is due to be replaced.

Post by **Kara503** » 05 Jun 2018, 16:21

Huh. Does it run rough at all? Is it possible you could have a misfire but aren't feeling it? Different car, but an old Ford Ranger I had, I couldn't tell it was misfiring. Had a lot of trouble with hills. No CEL, either. Turned out to be a random misfire, wiring issue.

Past that, I'm stumped. I'm still pretty new to all of this myself, hopefully someone else can help

Post by **June** » 05 Jun 2018, 16:35

Mike had a Ford that the catalytic converters started to plug up. The truck ran perfectly smooth, no lights on. Gradually over time lost more and more power on the interstate until eventually it barely would achieve 70 with the pedal on the floor. It was a V8 90s truck. There were several years where the power loss was gradual and it just felt sluggish. I know he used a vacuum gauge to diagnose it. Something to consider. June

Post by **FLXC90** » 05 Jun 2018, 17:18

Overboosting is usually a vacuum leak issue. Smoke test?

WhatAmIDoing · Post by **WhatAmIDoing** » 05 Jun 2018, 19:25

Did a smoke test in the spring, couldn't find a leak. Will try again with a better smoke tester. Runs smooth, quite well now with the new plugs actually. I was surprised when I still had no power up hills. Pretty sure there isn't a misfire. I have an aftermarket exhaust with a highflow cat and muffler. Doubt it's clogged, but I suppose it's a possibility.

Post by **jtp** » 05 Jun 2018, 20:07

I’ve had this work before:

Shift into one of the lower gears at the bottom of the shift selector plate, get it up to 4K rpms more or less continuously for several minutes on a stretch of state highway. Repeat that multiple times in the same outing.

If what I’ve read is true there is a TSB out there that is basically a more extreme version of this where you just drive at high rpm for like 10-20 minutes straight. Idea is to clean intake valves for better sealing.

I can’t personally bring myself to keep the rpms up ten minutes straight so that’s my watered down version.

Post by **June** » 05 Jun 2018, 20:34

jtp wrote: ↑05 Jun 2018, 20:07 I’ve had this work before:

Shift into one of the lower gears at the bottom of the shift selector plate, get it up to 4K rpms more or less continuously for several minutes on a stretch of state highway. Repeat that multiple times in the same outing.

If what I’ve read is true there is a TSB out there that is basically a more extreme version of this where you just drive at high rpm for like 10-20 minutes straight. Idea is to clean intake valves for better sealing.

I can’t personally bring myself to keep the rpms up ten minutes straight so that’s my watered down version.

My dealer said 5000 rpm for 5 minutes under load no ac. In my car it is second gear on the interstate. It would be interesting if you could find the TSB on that. It is for hard starting / rough running engine due to sticky valves according to my dealer. Had that problem originally with my 98 V70 2.3 many times and sure enough 5000 rpm for 5 minutes would straighten out the problem for a year or so. I have done it to every Volvo since at least once a year. June