Strange Engine Powerloss

K

kalibwenm

Member +
Hi guys,

I've been noticing how my engine would loose some power, compared from before i had it overhauled, especially in 4th gear, at higher rpms. I've also noticed a vibration through the floor and steering wheel, while decelerating from a high speed pull, from 5th to 4th to 3rd gear, as well as a big increase in fuel consumption. lastly i've noticed that on idle, (when parked) my rpms could sometimes have a sudden drop to 500rpm, but if i switch on the headlights, it will get back to normal.

(NOTE) : My mechanic says there's 3 ignition timing stages:

-Stage 1= The stock 4efte timing.
-Stage 2= The improved from stock, but piston friendly timing.
-Stage 3= The advanced timing for racing nights only.

but right now i'm set on the stock timing, which is 10 degrees i think.

What's causing this change:

- could it be an ignition issue? (it does have a very light backfire at times)
- Could it be a loss of compression problem? (having to rebuild the engine again)
- could it be a transmission issue? (slipping clutch, or loose components)

I'd really appreciate your honest feedback on this one, before i make any investments.

Thanks in advance...cheers :rockon:
 
dac69er

dac69er

Super Moderator
you can advance the base ignition timing, but the ecu will probably pull it back over time anyway if there is any knock detected. i assume you are running stock ecu?

what condition is your ignition system in? it is probably worth replacing the serviceable bits if you havnt already.

test the compression to see what is happening there. no other way of checking it really.

is the vibration there when you brake or just decelerating?
 
K

kalibwenm

Member +
dac69er said:
you can advance the base ignition timing, but the ecu will probably pull it back over time anyway if there is any knock detected. i assume you are running stock ecu?

what condition is your ignition system in? it is probably worth replacing the serviceable bits if you havnt already.

test the compression to see what is happening there. no other way of checking it really.

is the vibration there when you brake or just decelerating?
Click to expand...

Yes i'm running the stock ECU, but i'm still using the same ignition system since i brought in the engine from malaysia, 3 years ago. It came with 8mm ht leads, and right now i'm using a set of irridium heat 6 plugs, which has been gapped to 0.08mm.

As for the vibration, it starts as soon as i start decelerating and and applying the brakes, but then it keeps on vibrating for a while when i start accelerating again. However, if i park the car, switch off the engine, start it up and drive off again, the vibration would stop.
 
K

kalibwenm

Member +
Rev said:
If compression is ok looking at injectors would be good to rule out.
Click to expand...

I haven't checked the injectors yet, but i'm sure there's no fuel leak, as there's no smell of fuel, except maybe some clogging due to the poor fuel we have here...(btw i'm using unleaded fuel, is that good?)

One other thing i forgot to mention, i've noticed some very fine cracked lines on the stock CT9 manifold, would that help in causing this problem?
 
R

Rev

Member +
kalibwenm said:
I haven't checked the injectors yet, but i'm sure there's no fuel leak, as there's no smell of fuel, except maybe some clogging due to the poor fuel we have here...(btw i'm using unleaded fuel, is that good?)

One other thing i forgot to mention, i've noticed some very fine cracked lines on the stock CT9 manifold, would that help in causing this problem?
Click to expand...

Having high temps, poor fuel and the car sitting for while is not injector paradise as this link explains:
http://www.jaguarfuelinjectorservice.com/WebStore/Fuel%20injector%20problems.htm

For stockish boost unleaded 91fuel should be ok but bad fuel in the tank will take the 91 to a lower ron which takes many good tanks to come back to 91 again.
@dac is spot on if your compression is up a bit from the rebuild that can mean the ron needs to be higher. But many things reduce the need for higher ron having a good cooling system and maybe a slightly higher pressure radiator cap in some instances.

Manifold leaks I think you test for leaks with wd40 if leaking revs go down not sure if it works for hairline cracks as you describe.
 
K

kalibwenm

Member +
Rev said:
Having high temps, poor fuel and the car sitting for while is not injector paradise as this link explains:
http://www.jaguarfuelinjectorservice.com/WebStore/Fuel%20injector%20problems.htm

For stockish boost unleaded 91fuel should be ok but bad fuel in the tank will take the 91 to a lower ron which takes many good tanks to come back to 91 again.
@dac is spot on if your compression is up a bit from the rebuild that can mean the ron needs to be higher. But many things reduce the need for higher ron having a good cooling system and maybe a slightly higher pressure radiator cap in some instances.

Manifold leaks I think you test for leaks with wd40 if leaking revs go down not sure if it works for hairline cracks as you describe.
Click to expand...

Thanks Rev...i'll take a look at the injectors, as well as try the WD40 technique when i get home.

Cheers mate :rockon:
 
G

gorganl2000

Lifer
kalibwenm said:
Hi guys,

I've been noticing how my engine would loose some power, compared from before i had it overhauled, especially in 4th gear, at higher rpms. I've also noticed a vibration through the floor and steering wheel, while decelerating from a high speed pull, from 5th to 4th to 3rd gear, as well as a big increase in fuel consumption. lastly i've noticed that on idle, (when parked) my rpms could sometimes have a sudden drop to 500rpm, but if i switch on the headlights, it will get back to normal.

(NOTE) : My mechanic says there's 3 ignition timing stages:

-Stage 1= The stock 4efte timing.
-Stage 2= The improved from stock, but piston friendly timing.
-Stage 3= The advanced timing for racing nights only.

but right now i'm set on the stock timing, which is 10 degrees i think.

What's causing this change:

- could it be an ignition issue? (it does have a very light backfire at times)
- Could it be a loss of compression problem? (having to rebuild the engine again)
- could it be a transmission issue? (slipping clutch, or loose components)

I'd really appreciate your honest feedback on this one, before i make any investments.

Thanks in advance...cheers :rockon:
Click to expand...

hail, in addition to what the others have said and based on what you said above, first off do a diagnostic check

imo there is only one correct timing setting...10 degrees BTDC as dictated by Toyota with the ecu in diagnostic mode---this works well for daily, racing, pistons friendly, snow, summer, high/low octane, etc when using the stock ecu....it just works....so that's where i'd suggest you keep it...if you want to play with ignition and fuel, i'd recommend you get a piggyback or standalone....i've seen people play with timing in the past, it usually just moves the power curve either forward or backward (you gain top and lose bottom rpm power OR you gain bottom and lose top rpm power). as well, if you use proper 100 octane gas with a reset stock ecu (give it a few kms to adjust), you may be able to benefit from a few bhp as it is.

now, was the vibration there before you reinstalled your engine?..but id suggest you need a wheel alignment as suspension is usually moved when removing/installing an engine and may not be aligned as it was before...you can also check for your tires, balance and air pressure,,,check for brake rotors if warped...checked to make sure all suspension and steering parts (rod ends, ball joints, lower arms, drop links) are properly tight and nothing worn.

for the intermittent drop in idle, i'd suggest you check for vacuum leaks on the hoses and that all ore hooked back up correctly..may be check TPS

on the matter of higher gas usage, check your o2 and MAP sensors are hooked up properly
 
rage

rage

Lifer
plugs gapped to 0.08mm? typo? or else thats way way too little.
The low ron fuel isnt the best for this type of engine. the engine was built for ron100 fuel in japan and all the ecu settings expect this fuel aswell.
setting the ignition timing on 10 degrees should have the engine running just fine on idle and on boost. the vibrations concer nme a little bit. that should only happen when something is out of balance. what was done with the engine rebuild? any parts replaced? like crank, rods, pistons?

and you lost the power right from the start when you got the engine back?
might check the timing belt markings if they are correct. if something is off 1 tooth the engine will still run but runs lumpy, loss of power etc.
 
Last edited:
K

kalibwenm

Member +
gorganl2000 said:
hail, in addition to what the others have said and based on what you said above, first off do a diagnostic check

imo there is only one correct timing setting...10 degrees BTDC as dictated by Toyota with the ecu in diagnostic mode---this works well for daily, racing, pistons friendly, snow, summer, high/low octane, etc when using the stock ecu....it just works....so that's where i'd suggest you keep it...if you want to play with ignition and fuel, i'd recommend you get a piggyback or standalone....i've seen people play with timing in the past, it usually just moves the power curve either forward or backward (you gain top and lose bottom rpm power OR you gain bottom and lose top rpm power). as well, if you use proper 100 octane gas with a reset stock ecu (give it a few kms to adjust), you may be able to benefit from a few bhp as it is.

now, was the vibration there before you reinstalled your engine?..but id suggest you need a wheel alignment as suspension is usually moved when removing/installing an engine and may not be aligned as it was before...you can also check for your tires, balance and air pressure,,,check for brake rotors if warped...checked to make sure all suspension and steering parts (rod ends, ball joints, lower arms, drop links) are properly tight and nothing worn.

for the intermittent drop in idle, i'd suggest you check for vacuum leaks on the hoses and that all ore hooked back up correctly..may be check TPS

on the matter of higher gas usage, check your o2 and MAP sensors are hooked up properly
Click to expand...

Thanks Gorganl200...i guess i'll leave the timing as it is, and as for the vibrations, it was there before i had the engine rebuild, but it wasn't as persistent as now. I'll check out the o2 sensor, Map sensor, and TPS, and have them replaced if needed...the vaccum lines, i'll just replace them with new silicone hose, i have a roll laying around.

Cheers mate...:rockon:
 
K

kalibwenm

Member +
rage said:
plugs gapped to 0.08mm? typo? or else thats way way too little.
The low ron fuel isnt the best for this type of engine. the engine was built for ron100 fuel in japan and all the ecu settings expect this fuel aswell.
setting the ignition timing on 10 degrees should have the engine running just fine on idle and on boost. the vibrations concer nme a little bit. that should only happen when something is out of balance. what was done with the engine rebuild? any parts replaced? like crank, rods, pistons?

and you lost the power right from the start when you got the engine back?
might check the timing belt markings if they are correct. if something is off 1 tooth the engine will still run but runs lumpy, loss of power etc.
Click to expand...

Hahaha...sorry rage, that was a typo, it's actually 0.8mm...The purpose of the engine rebuild was to replace all the seals, bearings gaskets, timing belt and rings (basic stuff)...Idk haven't really payed much attention to the suspension setup, but i did balance out my tyres, and the handling seems alright, there's no vibration at all, except when i'm decelerating from a high pull (for example: it does this after accelerating to redline in 4th gear onwards, and letting go of the gas)...note that this only happens during a highway pull, uphill seems fine.

I really don't know why i'm loosing power...however i've seen some smoke out of the exhaust on rare occasions, aswell as a little oil leak on the CT9 turbo,but it pushes fine, it spools faster than before, (you can hear the turbo spool up almost as if i'm running an open downpipe, but there's no leak in the exhaust)...Could this also contribute to all these problems?

Cheers mate...
 
R

Rev

Member +
kalibwenm said:
Hahaha...there's no vibration at all, except when i'm decelerating from a high pull (for example: it does this after accelerating to redline in 4th gear onwards, and letting go of the gas)...note that this only happens during a highway pull, uphill seems fine.
Click to expand...

Maybe this is lift off knock related. I have seen 70 lift of knock on the flat and noticed the ecu reducing knock on restart after exceeding 30 lift off knock while boosting uphill.


What about air in the engine cooling system causing raised knock levels and effecting power?
 
Last edited:
K

kalibwenm

Member +
Rev said:
Maybe this is lift off knock related. I have seen 70 lift of knock on the flat and noticed the ecu reducing knock on restart after exceeding 30 lift off knock while boosting uphill.


What about air in the engine cooling system causing raised knock levels and effecting power?
Click to expand...

air in the cooling system?...i'll check for bubbles in the radiator, but please do explain the lift-off knocks, cuz i have no idea what this is.

However i did realise that my dumpvalve was way too soft, an air was leaking out from it, so i fixed it last night and it helped a bit, but it still doesn't fix the fuel efficientcy, and vibration issue.

cheers.
 
R

Rev

Member +
Good you found the leak that accounts for a lot of what you have been experiencing.If you keep the radiator cap high on a gentle slope the air can bubble out.Lift off knock occurs when there is little fuel in the cylinders with throttle being closed this condition with no spark can result in knock from exhaust heat (and other factors) that make the ecu remove timing unnecessarily from the whole map.Some standalone ecus let you adjust the knock sensitivity at throttle liftoff so timing is preserved.

I see the vibration was there before but is now worse, suggest checking you have no metal on metal rattles the knock sensor would pick up and also look at the intake air temp sensor wiring as if disconnected this can increase fueling.
 
Last edited:
K

kalibwenm

Member +
Rev said:
Good you found the leak that accounts for a lot of what you have been experiencing.If you keep the radiator cap high on a gentle slope the air can bubble out.Lift off knock occurs when there is little fuel in the cylinders with throttle being closed this condition with no spark can result in knock from exhaust heat (and other factors) that make the ecu remove timing unnecessarily from the whole map.Some standalone ecus let you adjust the knock sensitivity at throttle liftoff so timing is preserved.

I see the vibration was there before but is now worse, suggest checking you have no metal on metal rattles the knock sensor would pick up and also look at the intake air temp sensor wiring as if disconnected this can increase fueling.
Click to expand...

Hi Rev,

I managed to check every wiring etc, but all seems fine, although i haven't had the chance to do a compression test, as well as testing the sensors.
 
R

Rev

Member +
A lot of areas already covered but I would mention the pcv valve can contribute to weak vacuum if stuck. Also you mention electrical is better after restart alternator loading the engine say with poor battery can pull revs down and cause vibrations.
You have changed components so lots of possibilities eg Re fuel consumption is there special oil for running in new piston rings?
 
K

kalibwenm

Member +
Rev said:
A lot of areas already covered but I would mention the pcv valve can contribute to weak vacuum if stuck. Also you mention electrical is better after restart alternator loading the engine say with poor battery can pull revs down and cause vibrations.
You have changed components so lots of possibilities eg Re fuel consumption is there special oil for running in new piston rings?
Click to expand...

Hi rev,

No need to worry about the vibrations anymore, as lastnight after i almost crashed, i found out what was the real culprit, it was a weak lower arm, whereby the rust was slowly eating it up from the inside...i still can't beleive how i didn't see this coming...anyway, it broke lastnight while i was speeding on my way home, luckily it was uphill, so i managed to stop the car with little effort, but i did some crazy shit on the higway, and tight bends, thank god it broke up hill on a straight road.

But still, after i get it fixed tonight, i will take it for a spin and see if the vibration still remains.

However, i will keep in mind the things you've said, i find it very educational, as i didn't know half of them, and it's worth taking a look anyway...so thanks bro.

Cheers.
 
R

Rev

Member +
Glad your ok looks like rust with vibration is the one to watch for.
After you said ' I've also noticed a vibration through the floor and steering wheel ', made me think of larger vibrations but these appeared to be covered , thankfully your luck has held, smooth driving bro.
 
Last edited:
K

kalibwenm

Member +
Thanks guys, and yes i have to start going to church soon...lol

The car is back on the road, i went for a test drive last night and there's still some vibrations, but i think a good wheel alignment will fix it...also the tyre surface rubbed onto the road when the lower arm broke, wearing it off a bit, but we'll see how it goes after the wheel alignment is done.

Fuel-wise, i'm really trying my best to keep it off boost when not needed, by shifting at 3000rpm, or 2800rpm, as i feel this could be contributing to the high fuel consumption. (correct me if i'm wrong)

Anyway, if anything comes up, i will let you know.

Kind regards.

cheers :rockon:
 
You must log in or register to reply here.
Top