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Discussion Starter #1
Hi there,
I just baught a 98 mr2 NA.

For the first 20-30 mins the car is absoloutley fine, redlines and all.
However once the engine “warms up” i start to occasionaly have lack of power if i put my foot down.
After about a hour of motorway driving I start to have terrible problems and i cant get anywhere above 3k revs. If i try to increase the acceleration whatsoever or the car is under any load (slight hill) the engine bogs down, rumbles and makes little power.
I practicaly have to limp it home at 50mph.
Sometimes the power comes back for 20s and sometimes when at idle the engine will bog down and stall.
It only happens after the car has been driving for a while.
And even in neutral it wont rev past 4000.

My thaughts are that it could be fuel pump/filter as car has been sitting around for a while with prev owner. Seems like fuel might not be getting to where it needs to go. Mabye temp sensor+ecu as happens when the car is warm.

Getting no error codes.

Any help would be fantastic.

thanks a ton
Harry
 

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I would start by checking the coolant temp sensor and the air temp sensor in the intake manifold.
 

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I would start by checking the coolant temp sensor and the air temp sensor in the intake manifold.
The GEN3 3SGE doesn't have an air temp sensor in the intake manifold. Only the airbox. (y)
Hi there,
I just baught a 98 mr2 NA.

For the first 20-30 mins the car is absoloutley fine, redlines and all.
However once the engine “warms up” i start to occasionaly have lack of power if i put my foot down.
After about a hour of motorway driving I start to have terrible problems and i cant get anywhere above 3k revs. If i try to increase the acceleration whatsoever or the car is under any load (slight hill) the engine bogs down, rumbles and makes little power.
I practicaly have to limp it home at 50mph.
Sometimes the power comes back for 20s and sometimes when at idle the engine will bog down and stall.
It only happens after the car has been driving for a while.
And even in neutral it wont rev past 4000.

My thaughts are that it could be fuel pump/filter as car has been sitting around for a while with prev owner. Seems like fuel might not be getting to where it needs to go. Mabye temp sensor+ecu as happens when the car is warm.

Getting no error codes.

Any help would be fantastic.

thanks a ton
Harry
Unfortunately I can't offer any further advice on what to look at. Very odd symptoms.
 

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Sounds fueling related. I would change fuel filter and see if it gets any better. Unfortunately, rusted fuel tanks usually clog the fuel pump sock which means dropping tank.

Could be coolant temp sensor, but it’d get to operating temp well before 20 mins. That makes me think not a sensor issue.
 

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Discussion Starter #8
Done some more research and im pointing towards the cranshaft sensor having a few problems. (also potentialy feul related, however it is temprature dependent so seems unlikley)
I coudlent realy find anyone with an MR2 with the same problem, however i have found soem analogous problemes with ceilicas.
eg. celica with crankshaft problem (different engine), Another celica, didnt say it solved it but mentions cracked crank sensors casuing a similar problem on 5S-FE
It seems to be some sort of limp mode, however no error codes show.
Im realy at a loss to what is ahppening.
What would be the best way to check fuel pressures/ if the pump is working?

The engine runs beautifly when cold. But after 20 mins i start getting power outages.

Thanks everyone btw
 

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Done some more research and im pointing towards the cranshaft sensor having a few problems. (also potentialy feul related, however it is temprature dependent so seems unlikley)
I coudlent realy find anyone with an MR2 with the same problem, however i have found soem analogous problemes with ceilicas.
eg. celica with crankshaft problem (different engine), Another celica, didnt say it solved it but mentions cracked crank sensors casuing a similar problem on 5S-FE
It seems to be some sort of limp mode, however no error codes show.
Im realy at a loss to what is ahppening.
What would be the best way to check fuel pressures/ if the pump is working?

The engine runs beautifly when cold. But after 20 mins i start getting power outages.

Thanks everyone btw
If it's a UK 98 then it won't have a crank shaft sensor, only the distributor but if it's a JDM import then it does have a crank and cam shaft position sensor.
 

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Discussion Starter #10
If it's a UK 98 then it won't have a crank shaft sensor, only the distributor but if it's a JDM import then it does have a crank and cam shaft position sensor.
Prety sure its a uk 98, so is your best guess fuel related then. Ill do a few tests on fuel pressure
 

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I assume being a 98 it has OBDII right? USA mandated OBDII in 1996, did the UK?

If so Toyota Techstream can pull live data so you can watch the sensors and it will log the data.

I have seen codes in computers that don't set the Check Engine Light off.
Years back I got a aftermarket USB to OBDII Cable like this and got a slightly outdated copy of Toyota Techstream off the web....
I tossed it on an old laptop and now I can pull live data from my 2002 SC430. I assume it would work with a 1998 too


As to the fuel, I wouldn't suspect that this would be the problem but my 1991 MR2's and I assume yours has a drain plug on the bottom of the tank so you could drain any stuff sitting in the bottom of the tank pretty easily. Replacing the fuel filter is never a bad idea but I don't think this is your problem.
 

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Discussion Starter #12
I assume being a 98 it has OBDII right? USA mandated OBDII in 1996, did the UK?

If so Toyota Techstream can pull live data so you can watch the sensors and it will log the data.

I have seen codes in computers that don't set the Check Engine Light off.
Years back I got a aftermarket USB to OBDII Cable like this and got a slightly outdated copy of Toyota Techstream off the web....
I tossed it on an old laptop and now I can pull live data from my 2002 SC430. I assume it would work with a 1998 too


As to the fuel, I wouldn't suspect that this would be the problem but my 1991 MR2's and I assume yours has a drain plug on the bottom of the tank so you could drain any stuff sitting in the bottom of the tank pretty easily. Replacing the fuel filter is never a bad idea but I don't think this is your problem.
Unfortunetley, from what i undersatnd only the beams models of MR2's have OBDII, which is a pain in the arse as it would be realy great to have live telemtry to see what the problem with the car is.
Im almost certain its a sensor issue too but I just have no idea how to proceed with diagnosing the problem. Is there any way I could check error codes on the run?

Also is it normal that the temp of the car only gets to about a third after about 20-30 mins of driving (this is about when the issue start happening)?
Mabye I have a coolant issue and the engine runs too hot and my gauge deosnt show it so goes into limp mode? A faulty sensor somwhere seems far more likley.
 

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Also is it normal that the temp of the car only gets to about a third after about 20-30 mins of driving (this is about when the issue start happening)?
Mabye I have a coolant issue and the engine runs too hot and my gauge deosnt show it so goes into limp mode? A faulty sensor somwhere seems far more likley.
No, your engine should be up to operating temperature within 10 minutes, if the gauge doesn't read half way by 10 minutes you have a thermostat problem or the gauge sensor is bad.
 

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Discussion Starter #14
No, your engine should be up to operating temperature within 10 minutes, if the gauge doesn't read half way by 10 minutes you have a thermostat problem or the gauge sensor is bad.
Ill change the thermostat and rebleed the system with new coolant then i think.
Engine might just be getting too hot as thermostat isnt regulating water flow properly.

Although its strange its reading too cold
 

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Usually when a thermostat fails open the engine doesn't get up to operating temperature, if it does it quickly goes back down when you increase speed or turn on the heater. The engine doesn't need 100% of the radiator's heat dissipation capacity so the thermostat regulates coolant flow to keep the engine at optimal temperature.
 

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Discussion Starter #16
Usually when a thermostat fails open the engine doesn't get up to operating temperature, if it does it quickly goes back down when you increase speed or turn on the heater. The engine doesn't need 100% of the radiator's heat dissipation capacity so the thermostat regulates coolant flow to keep the engine at optimal temperature.
Hopefully that might be the issue, but would the system beeing too cold cause the engine to not perform correctly?
 

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If the ECU thinks the engine is colder than it actually is it does change fueling to compensate. Not saying your engine not getting up to temperature is your problem but it is a problem. Start there and then see what happens.
 

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Discussion Starter #18
If the ECU thinks the engine is colder than it actually is it does change fueling to compensate. Not saying your engine not getting up to temperature is your problem but it is a problem. Start there and then see what happens.
Thanks alot mate. Ill tell you how it goes
 

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Like the fuel filter idea, the thermostat is not a bad idea to replace if for no other reason than just basic maintenance. The one thing that would make the job easier is to lift the back of the car so it's higher than the radiator allowing the air to bleed out of the cooling system.

I believe you mentioned that your car was an NA but I had a similar problem with my Turbo. the only difference is that my car will set a check engine light.

It turns out that I had a bad knock sensor and that was retarding the timing once I got up to temperature. When this happened my car would go into limp mode and I would barely get above 3000 RPMs.

Restarting the car would literally take it out of limp mode in the car would drive fine as long as I didn't get on it too hard. The knock sensor on the turbo was one of the few weak points of the MR2.

Honestly this should have been the first thing that came to my mind when I saw your problem. I think I replaced mine 10 years ago but as years go by the memories start to fade :)

The only problem with my remote diagnosis is the lack of the check engine light. Dumb question, might your check engine light be burned out?

It turns out that the knock sensor on the Toyota was essentially the same as a knock sensor on a 350 Chevy and the 350 Chevy unit was a much heavier duty sensor. The only difference I believe is that s that the 350 Chevy sensor had a different thread pitch on it so you had to rethread the sensor to match the Toyota block. Of course a 350 knock sensor is much harder to find across the pond then it is in the USA.

It is still possible to pull codes on your MR2 and a quick Google search will show you which terminals to cross on the the connector in the engine compartment to get the check engine light to blink out the codes.

If it turns out the knock sensor is bad I know one of the suppliers out there like MR2 R Us offers the upgraded GM sensor that is modified to fit the Toyota for not a lot of money
 

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I think @J.harris is on to something with the coolant temp. If it only gets to a 1/3rd temp after that long then the ECU will be in the cold running part of the fuel map meaning more fuel will be put in when not needed. My engine sometimes struggles when it's cold, it is a GEN2 3SGE but still, same idea.

See how you get on with getting a new OEM Toyota thermostat put in and go from there.
 
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