3sGTE Intermitant 30-40% power loss

[worldwalker]

Car: 91 SW20 GT 3sGTE
Problem: (Please read the lot as it requires a detailed description)
Car starts perfect every time, idles perfect, revs perfect and smooth, it just has its moments when it has no power.

When the car is cold the car has little or no power off boost, it struggles to drive, however it will free rev fine and smooth but wont take any loaded freerev (as in if you go to WOT in free-rev it wont meet the load as instantaniously as it should). When boost increase power will sharply increase (excessivly compared with the off boost performance) then it seems to pull OK. As the engine warms the problem is less noticable down low below 2500 however it becomes more noticable above 2500, especially above 3000. At times the car will drive great and produce full power, but at other times (more increasingly as time goes on) the car will just lose its power all the way through the revs. On some occasions and origonally this is how I first noticed it, the power will be ok, hit 3000RPM and then it cuts back.

Now the car will rev ok when it loses power, its simply as though someone has reduced the power output across the rev range. Again when this crops up blipping the throttle (as when downshifting) has almost no effect because the engine wont react to a sudden jab of throttle like it should.

There are no error codes on the ECU, however reseting it seemed to have an effect But i dont know if that incedental or not. The engine is preoducing normal boost and there doesnt seem to be any change in boost, however becuase this problem is across the rev range I hardly see how that would even be a consideration.

The car seems to be gusseling fuel too, but I have no real expereince with these engines, so I dont know if thats normal.

Possible solutions:
Airflow meter...
O2 sensor...
Boost leak..?
Injectors???
Coil pack???
Something else?

Replaced so far:
Leads
Rotor
Dizzy Cap
Iridium plugs

also car only runs on ultimate. And I've put an injector cleaner additive, although I know that its not much cop.

Please any help would be great, I'm back to work tommorrow and wont be able to solve this until next week now.

Thanks

Nick

[timbosaurus]

It's not running rough when it's down on power is it? Like it's running on 3 cyls?

I don't know the first thing about MR2's, but maybe if a valve is intermittantly sticking or something???

Do you know if the engine has ever been dismantled/rebuilt? If not it could rule out the "something put back together wrong" idea some might have?

Just some suggestions, and gets you back up the top

[timbosaurus]

seriously retarded spark could also drop power right back. Not sure what can do that on these engines. Faulty knock sensor?

[Roundy]

if the knock sensor is faulty it will take the power right out of the motor, i had never really driven anything so slow

But when it happened on mine the CEL came on and was on constantly.

i would check the ignition timing, even tho you replaced the dizzy cap etc i would still double check, as it sounds like it could be the knock response going off its head!

other then that i would check all the inlet to make sure there isn't a leak in amongst it all.

Cheers
Nathan

[timbosaurus]

Where is the pressure sensor on these engines? Is it possible that its making, and reading boost, but the leak is after a restriction like the cooler so got boost before cooler, no boost after?

[The Real Roadrunner]

it not an injector leaking is it as running to rich will kill power aswell as cause excessive fuel consumption.

[gee120]

has anyone adjusted timing recently or just prior to when this started? Just off memory to adjust timing i think you had to put the ECU in test mode for these engines otherwise you wont get a true static timing reading

[Roundy]

has anyone adjusted timing recently or just prior to when this started? Just off memory to adjust timing i think you had to put the ECU in test mode for these engines otherwise you wont get a true static timing reading

indeed, join TE1 and E1 in the diagnostic plug, a reconfigured paperclip does the job nicely

[gee120]

yup that the 2 you need, i been lazy about trying to remember that of late as i tend to just plug up the Launch X431 scanner

[abently]

Firstly, do a Compression Test to make sure the Bottom-end is still holding pressure / and or the Valves are seating perfectly. Warm the car up to temperature before shutting it off and testing it.

If the results come back good, then it'll have to do with your Fueling, so Injectors, AFM, Fuel Regulator, Fuel Pump or Vacuum hoses......

[-GT-]

My 2c is it sounds like timing; as it's intermittant i agree it sounds like the knock retardation is coming in frequently and severely. It may be a faulty knock sensor, but also double check your base timing, as said above, if it's advanced a fair bit it will be causing pre-detonation on a pretty regular basis.

[gee120]

i dont think it would be the knock sensor as i have had 2 fail on me and when this happens you get the engine check light come on and every time you go above 3K rpm under load the check light will reappear

[Roundy]

indeed a dodgy knock sensor kills all the fun all the time.

but what -GT- and I are saying is that the knock sensor is working exactly as it is intended to and retarding the ignition when it senses detonation, which it sounds like it is doing all the time.

So first stop there would be to check the ignition timing.

Cheers
Nathan

[worldwalker]

so how do I adjust the timing then?

[Mr Revhead]

plus one for knock issue...

what fuel are you running it on?
seems odd that it just started doing it.

you dont want to adjust the timing, maybe.
you need to check it.
timing light and an idea on how to use one is what you need