Rev Cut Too Early

[speeddemon]

Greetings...

I am new to this forum and this is my first post.

I have a 1997 model Toyota Corolla (AE100). Earlier, it had a 1.3 litre carby engine which I swapped about a year ago with a 1.8 litre 7afe Lean Burn (distributor less ignition, twin coil packs). The lean burn mechanism also controls butterflies in the intake runners which switch the vehicle from 12 to 16 valves (kinda like TVIS on early 4age).

Ever since the engine swap, the car will not rev beyond 5500 RPM. Whether it is stationary or in any gear, 5500 is the max it will go. I get no check lights and the wiring that came with the engine is original and uncut.

Can anyone help me identify the problem???

Thanks

[soozukisteve]

Oh..also

if you use a strobe with an rpm readout you can double check that it isnt your guage thats out as i imagine there being diffrences in the wiring of the rpm signals from distributor to DIS.

Make sure you have no massive air leaks in the inlet side(again unlikely to cause you such an obvious problem but you never know!!).Use some aerosol carb cleaner or equivalent and spray it around the manifold and throttle body area with the engine running.A rise in rpm signifies an air leak.

Lastly from me,check all of your inlet pipes for blockages as well as exhaust(catalytic converters are prone to failing and can break into pieces blocking the exhaust up:-have come across this several times but only just remembered.Doh!!)

[soozukisteve]

Greetings...

I am new to this forum and this is my first post.

I have a 1997 model Toyota Corolla (AE100). Earlier, it had a 1.3 litre carby engine which I swapped about a year ago with a 1.8 litre 7afe Lean Burn (distributor less ignition, twin coil packs). The lean burn mechanism also controls butterflies in the intake runners which switch the vehicle from 12 to 16 valves (kinda like TVIS on early 4age).

Ever since the engine swap, the car will not rev beyond 5500 RPM. Whether it is stationary or in any gear, 5500 is the max it will go. I get no check lights and the wiring that came with the engine is original and uncut.

Can anyone help me identify the problem???

Thanks

Hi mate.I had a similar problem when i did an engine swap on a fiat cinquecento (900cc to 1246cc).How relevant this is,is neglagable as i ended up selling the car before i got to the route of the prolem....

However,there are a few things you could check that are generic to most EFI systems...

Did you replace the fuel pump for the 7afe(the 1.3 may not be able to flow enough even though you should theoretically be able to hit the limiter with no load on it)!

Does it feel like a rev limiter (does the engine feel like its backing off in order not to over rev or does it just feel like there isnt enough power to pull it past 5.5k)

If you dont mind revving it with no load (not recommended if it has reasonably high mileage) and you have a strobe or ignition timing light,you could connect it up,rev it and

see if you are getting an ignition cut.I dont know how the toyota rev limit works but try it on all four leads just to be sure.

If thats ok you could try checking the timing as you get around 5.5k and make sure the timing isnt being retarded drastically.

if you can get access to a fuel system pressure tester you can check for correct fuel pressures and make sure your pressure isnt dropping off at high rpm.

You could check also that your lean burn 'flaps' are behaving themselves and opening fully at higher rpm(iirc they should start opening at about 3k and be well open by about

4.5k) I guess the techies might be able to be more precise....

p.s.Hope i dont sound too patronising as you obviously have some technical knowledge if you did the swap yourself.This is my first post so i dont want to p*** anyone off already!... :-)

steve

[soozukisteve]

ooops.dont quite know how i managed it but my last 2 posts are the wrong way around.....

[speeddemon]

ooops.dont quite know how i managed it but my last 2 posts are the wrong way around.....

Thanks for the responses. The butteflies work fine, and switch over at around 4K rpm. I checked the rpm on a number of devices and they do stop at 5.5K. The vehicle pulls very strongly till that point and you can feel the rev limit cutting in very softly. However, keep it there and there seems to be a total ignition kill (I have experienced a similar rev cut on a lot of toyotas, however at the specific redline of the particular engine).

Although I put in a brand new fuel pump of recommended capacity, I have a doubt on the fuel flow due to the size of the fuel delivery pipes.

Secondly, could it be a faulty crank position sensor? These engines are prone to this problem, since the way they are transported often lends to damage, the engines either don't start or misbehave.

I am also experiencing some hesitation at low rpms and also some popping sounds from the exhaust on the over run.

Cheers

[soozukisteve]

ooops.dont quite know how i managed it but my last 2 posts are the wrong way around.....

Thanks for the responses. The butteflies work fine, and switch over at around 4K rpm. I checked the rpm on a number of devices and they do stop at 5.5K. The vehicle pulls very strongly till that point and you can feel the rev limit cutting in very softly. However, keep it there and there seems to be a total ignition kill (I have experienced a similar rev cut on a lot of toyotas, however at the specific redline of the particular engine).

Although I put in a brand new fuel pump of recommended capacity, I have a doubt on the fuel flow due to the size of the fuel delivery pipes.

Secondly, could it be a faulty crank position sensor? These engines are prone to this problem, since the way they are transported often lends to damage, the engines either don't start or misbehave.

I am also experiencing some hesitation at low rpms and also some popping sounds from the exhaust on the over run.

Cheers

If you can get access to a fuel system pressure tester ,see if the pressure drops off when your having the early rpm cut.I imagine that if the fault occurs

both when driving and when revving stationary at the same rpm,its probably not a fuel delivery problem as there is virtually no load when revving freely as opposed to with your foot down

driving along,therefore a much lower fuel delivery rate requirement.

The crank sensor is a posibility but whenever i have come across them they have shown up mostly when starting and periodically when driving rather than at

a specific rpm.

I intend to shoehorn a 7afe into my ep91 starlet after xmas so im interested in trying to get to the bottom of your probs incase i come across it later.....

If you know anyone with a OBD handyscan,they can do some live readings while the fault is occuring on the road and atleast help point you in the right direction!

Out of interest,where abouts do you live?(im no proper expert(anymore!?!) but i used to work for toyota and I now lecture at a motor vehicle college in Retford Notts

and we have an OBD tester although if the 7afe is OBD1 im not sure we have a card for it!!!!)