[Mk2] [NA] Fuel: Starved at hight revs, too much at tick over

[Fossil1970]

Hi

Hope everyone's enjoying the weather

My 1997 NA feels really flat and the 5 - 5.5k rev kick just doesn't happen these days. I took it to my trusted local mechanic and he had a look and thought it was an air leak on the induction pipe after the airflow sensor. This made it very slightly better but he said take it to Toyota. This is the 2nd Saturday they have had it on the diagnostic machine and can't tell me exactly what's the problem is as there's no stored error codes.
They tell me its over fuelling at low revs and not getting enough at anything over 2k revs according to probe in the tail pipe. They now want me to leave it with them at £90 an hour and spend a few hours on it to try and find out what's up which i can't afford really. Some time ago i had an issue where the revs would go up and down from 850rpm - 2500 rpm at tick over. It was like someone was blipping the accelerator!! That stopped and its just flat now.
The induction kit has been on 5 years and this problem only began 2-3 months ago. I changed the cone and micro filter and that made no difference.

Could someone offer me advice as to which part or sensor could be faulty please to try and reduce investigative costs at Mr T?

[Nic]

It's not something that can be easily diagnosed on here, suggestions could be given what it might be but you could end up going around in circles and at Toyota labour rates that will get very expensive very quickly!

The best bit of advice I can give you is get the car back from Toyota and take it to an MR2 specialist instead, they should be able to quickly and easily diagnose the fault and save you a whole heap of time and money.

Where are you?

[Fossil1970]

I got the car back after this second diagnostic, or too be honest lack of diagnostic check this morning. I spent £54 basically to be told the car is so old they can't read what the problem is (this is Toyota mind) and it would be back to the good old take things apart or replace everything until it stops the problem.
Bit annoyed too be honest as i thought these plug in machines were the whole point of fault tracing.

Was rather hoping someone with either technical knowledge could give me a hierarchy of things too check, or by luck someone might say "yeah i had the same - mine was cured by...."

Am in Herefordshire buddy.

[Nic]

On a new toyota yes they could plug into a diagnostic machine and it'd say exactly what the fault is. But think what a PC was like in 1997 compared to 2013, huge difference. Not sure if the 97 NA is OBD1 or OBD2 (on board diagnostic), even if it's obd2 it'll be a very basic version and their machine would only give very basic info.

You could start by doing you own diagnostic check to see if there are any stored fault codes. See how to guide here

http://www.mr2oc.co.uk/know-your-2-know ... bartid=162

[Fossil1970]

Yeah that's the problem there are no stored error codes, they could tell me that much, but that's it.
Oh well, i'll keep trawling through google hoping someone has had a similar issue and how they corrected it or how the garage did.
Thanks for being friendly and trying to help Nic, appreciated.

[Nic]

It won't make any difference if there is a fault but next thing I'd try is to reset the ECU by disconnecting the battery for a few minutes. Then take it for a test drive, it may run a bit 'lumpy' for a while and not idle, it'll take a couple miles for the ECU to 'relearn' some of the parameters.

[Nic]

I'm not that familiar with the 3S-GE engine, there'll be others on here that will be a lot more knowledgeable.

One thing in your first post you do mention is the kick at around 5K rpm, that is caused by the T-VIS/ACIS (not sure which it is on the GE), this is a valve that opens at a certain rpm to increase the torque at higher rpms. Explained HERE.

When were the spark plugs, leads, distributor cap, rotor arm and oxygen sensor last renewed? They may not be causing the issues you're having but if they haven't been changed for a while or ever (ie. they are still the factory fitted parts) then these would all be worth renewing.

[Fossil1970]

Will have a look at that link. The dizzy, spark plugs, rotor arm and fuel filter are less than 2 years old and been checked and they said they was ok.

Feel like crying, this car is the best thing ive ever driven and feel really down in the dumps as i can't keep throwing money at Toyota to try and find the problem. Wish i knew a MR2 specialist in the west midlands perhaps i could let them have a look

*edit* not sure what you mean by the oxygen sensor, guessing its that plastic bit that goes into the induction pipe after the air cone? That they say maybe the issue but at £120 i'd like to be more sure it is incase it's not and ive wasted money.

[Nic]

Will have a look at that link. The dizzy, spark plugs, rotor arm and fuel filter are less than 2 years old and been checked and they said they was ok.

Feel like crying, this car is the best thing ive ever driven and feel really down in the dumps as i can't keep throwing money at Toyota to try and find the problem. Wish i knew a MR2 specialist in the west midlands perhaps i could let them have a look

*edit* not sure what you mean by the oxygen sensor, guessing its that plastic bit that goes into the induction pipe after the air cone? That they say maybe the issue but at £120 i'd like to be more sure it is incase it's not and ive wasted money.

Forget Toyota to try and solve the problem, I don't know your area but there must be a decent tuner someone can suggest near you.

The oxygen sensor is mounted in the exhaust manifold, it reads the oxygen levels in the exhaust gasses, sends a signal to the ECU which then uses this to determine the correct fueling. An O2 sensor has a certain life span and once gone the ECU defaults to a rich mixture, this has a negative effect on mpg's and power.

[Fossil1970]

I tried cleaning the contacts in the plug that goes to the plastic bit that fits after the induction air filter, and also disconnected the battery for an hour hoping and praying it may help.

No difference. I can't see where that o2 sensor is on my Rev 4 NA, unless its under that heat shield perhaps>?. Would someone be kind enough to take a photo of its position as the Google only brings up Rev1 turbo location.

Stressed beyond belief now!

[Nic]

Stressed beyond belief now!

Get it to a specialist, they should be able to quickly pinpoint possible causes of the problems.

Come on folks, someone help this guy out and suggest a competent tuner in the Herefordshire area.

[rs007]

Obv as others have said its impossible to be accurate over a forum

But your symptoms sound possibly like a screwed or disconnected FPR on and na engine

[Nik_L]

Deffo have a good look at the TVIS/ACIS system as it sounds like the flaps could be stuck open. No low down power and no kick at 5k+ would give the symptoms of the flaps being open when they shouldn't be.

You can check by hand if they are operating smoothly, but also take the cover off and make sure they are still connected and in not broken up etc.

[Nic]

According to the thread below this is the actuator for the ACIS on a 3S-GE. Fossil1970 check the pipe to the actuator is connected and in good condition, the actuator should open at around 5.1Krpm. The actuator arm and butterfly valves should all move freely and smoothly.

Also worth doing, have a good look around the engine bay for any loose/disconnected/split hoses and any disconnected wiring connectors.

http://www.mr2oc.co.uk/know-your-2-know ... bartid=163