The Lack Of Power Over 3000rpm

[Brendy]

Thanks I'll check it out

[Hoovie]

Prob off-topic but maybe relevant ... These Pre-cat boxes have given lots of problems on the MR2 Roadsters and there have been cases of bits disintegrating and going back into the engine and wrecking it!

Fix seems to be to get rid of the material entirely with a removal tool (aka Screwdriver to break it up I to small enough prices!) and there was some kind of extra warranty in place to cover damage from disintegration.

Above is from memory when I was looking at MR2 vs MX5 purchase early last year in readiness for top-down motoring in the predicted scorching summer (lucky I didn't get either in the end !! )

[Brendy]

Hi All

checked the pipe connections as per yyaann post and they are in correct order.

Am i right in thinking that the vacuum pump increases vacuum pressure as rpm increases and that the vsv on receiving a signal from the ecu shuts off the vacuum to the turbo actuator at around 3000rpm to prevent turbo overboost? if so i'm thinking that the vsv closing device is shot (I've checked electrical side of the vsv and i can hear a click when 12v is applied to the connectors) or that there is a problem with the ecu sending the cut off signal to the vsv.

I'm thinking of hooking up a long hose from the vsv into the cabin and checking if the vacuum is shutting off whist driving at 3000rpm+ as picked up from other articles. Any advice? (apart from watch where you are going, could be 3 pts on the license if caught!!)

[anchorman]

Interesting experiment. I think it will be a combination of revs and load. Perhaps you could find a steep hill rather than chase around at warp speed!

[Brendy]

Hooked up the hose and vacuum pressure did not seem to change and certainly did not shut off at high load. Swapped the vsv off another rav from a scrap dealer mate and it made no difference. Possibility that it is faulty too but what's the probability? Now thinking the ecu is not sending the signal to the vsv to shut off the vacuum. Other than that I'm at a loss!

[anchorman]

If you do all the touchy feely mechanical bits that you can do, you sometimes need to run it into somebody who can actually read what these electrical bits are doing. Am I right in saying yours runs fine with the vac pipe off? If so, leave it off and stop worrying!

[slowboarder]

"It also has the exhaust noise that has been described in the other posts. To me its the turbo blowing off the pressure as its over boosting. Its like a steam train "chuffing” away."
"This is the sound produced when the front exhaust box (containing a ceramic honeycomb) has become badly blocked. My 2003 D4D 4.2 suffered all this some time ago. Replace the box (expensive) or remove its contents (not universally approved, but effective).
A blocked box strangles power at high throttle/revs, and the chuffing noise is the turbo letting off excess pressure.
To test all this out, simply remove the exhaust system from the front box onwards (leave the downpipe from the turbo), and test-drive the car. (It will be surprisingly quiet.) If power returns, then the front box is the culprit.
Chris"

We had similar symptoms on our 2003 Previa D4D with 115k mileage. No MIL light, no errror codes, just sluggish and lack of power with a real struggle to get through 3000rpm uphill. Important for us as we live in the Alps and the hills are big!.

Cleaned the turbo vanes via fuel treatment, cleaned the EGR, checked the VSV, linkages, pipes, replaced air filter, fuel filter, cleaned MAF sensor and many of the checks recomended on this forum. I replaced the SCVs as a separate fault. Finally came across the above, undid 2 exhaust bolts (5-6mins) to allow the exhaust gases to escape by wedging open the joint just before the catalytic converter and ..............result! The car was transformed with loads of power. Could even hear the turbo spooling up and down. Now booked in to see if we can get the inners of the cat removed. A BIG THANKYOU to Chris!

Update Sept 15 2014 - the mechanic cut the pipe just after the cat and removed the broken inners which were causing the exhaust gases to back up under load, welded the pipe back together and the job was done.

We took the Previa up and over the Col du Petit St Bernard for lunch in Italy at approx 2100m altitude . Drove faultless and with loads of power. Previously we would not have even considered taking the Previa up any of the mountain passes as it would have been a rolling road block. No noticeable increase in exhaust noise. Cost €85 / £68 (including a brake fluid change).
Fuel consumption has also improved.

[Brianlewis]

Check the air flow meter on top of the air filter, this proved to be my problem on my Previa, same engine D4D. Try cleaning, if no good swap it out or disconnect to prove it (you will get an engine management alarm).

Hope this helps.

[TRAIN DRIVER]

Had the same problem problem with 03 registered Rav 4. Heard a thud at speed on motorway then would not pull past 3000 revs. Dealership changed air filter and said "try that" and we did, going well past 3000 revs up to about 4000 and the Turbo exploded, whining then rattling and blowing smoke. Limped back using oil.

Turns out the dealership had fitted a reconditioned turbo 3 years ago. before we bought it. That failed under our warranty and then they fitted another recon' again. We did not know this at the time.

We are not happy and hope that sharing this info might help others.

TRAIN DRIVER