Hi there
I've recently bought a 'spares or repair' 2001 MR2 Roadster as a project for a charity challenge European road trip I'm doing with a friend this summer.
The car hasn't been on the road for a couple of years and but is reasonably structurally sound, decent bodywork and has a good interior and roof
First job on the list of many is to get the engine running.
We charged the battery and turned the ignition and it started first time, much to our delight. However whilst tickover was fine once we tried to rev the engine it got a bit lumpy and wouldn't rev above about 2500/3000 rpm. It kind of feels like the engine is being starved of fuel or air once you try and rev past this point. Tick over is smooth, no smoke or nasty knocks.
There was an EML light so we plugged in a OBD reader and got P0120 which is throttle position sensor. We ordered a new one on eBay and fitted it today. Whilst the fault code has now gone the engine still won't rev past 2500
At one point we had P300 to 305 - engine misfire on all cylinders fault code but when we last cleared it it didn't come back.
Today we have tried the following based on reading this forum:
Cleaned MAF
Pulled all contacts, cleaned with contact cleaner and refitted
Checked vacuum pipes for leaks
Removed, cleaned and refitted crank position sensor earth bolt
Disconnected battery for 20 mins to reboot the ECU.
For info the battery keeps running flat so we suspect the alternator isnt charging properly but don't think this is connected with other issues.
Currently we have no fault codes showing but the engine still won't rev above 2500 and gets lumpy and dies when you try.
Any ideas what to try next?
Anyone know a good specialist in or near Birmingham who could come and have a look? (Car is not road legal so can't drive anywhere)
Many thanks
Hello and welcome.
Have you checked the air filter?
Mr twos Willenhall?
Quote from: Ardent on March 2, 2024, 16:55Hello and welcome.
Have you checked the air filter?
Yep, used but fine, tried with it out too and no improvement.
Mr twos Willenhall?
Thanks, will google
@LozB Hello and welcome.
While my car will ( has since 2011) start on 6 month old fuel I doubt 2 year old fuel will have the same volatility, but then maybe you have made sure all is well in that department?
I have read of petrol filter blockage/ problem, so maybe worth a search .
In order of likelihood:
A bad MAF will not throw a code, but cleaning may have been insufficient. The only way to know with the MAF is to put a known good one in.
If the alternator is dragging the voltage down, that could well be the problem.
You don't mention spark plugs or air filter, both things to consider.
Bad crank sensor.
Unlikely, but possible: Sometimes this can be a symptom of a blocked catalytic converter. This can be caused by the break-up of the pre-cats in the exhaust manifold. It's worth removing the two oxygen sensors in the manifold and checking the condition of the matrix it should have a regular flat surface and the honeycomb should be easily visible. If the matrix is worn, that could be your problem.
@Carolyn It's sometime since I read about a blocked cat on here, but now you mention it the inability to rev was a typical symptom.
I recall the same, but thought let's start at the cheap easy end 1st
+1 on the petrol filter and lines
Quote from: Joesson on March 2, 2024, 18:52@LozB
Hello and welcome.
While my car will ( has since 2011) start on 6 month old fuel I doubt 2 year old fuel will have the same volatility, but then maybe you have made sure all is well in that department?
I have read of petrol filter blockage/ problem, so maybe worth a search .
Thanks, hadn't thought about fuel but your are right it could well have been in there for a few years, will try that next. Anyone know the best way to drain a fuel tank?
Quote from: LozB on March 3, 2024, 16:32Thanks, hadn't thought about fuel but your are right it could well have been in there for a few years, will try that next. Anyone know the best way to drain a fuel tank?
I don't know the "best way" but a certain/ quick but not so tasty Way is with a length of tubing/ garden hose and a suitably sized container/s and syphon it out:
Hose long enough to reach the tank bottom at one end and the ground , or lower if possible at the other.
A good suck on the open end and then straight into the container on the ground, (the open end Must be lower than the tank end) just before you get a mouthful.
It is all in the timing. This probably should come with all sorts of health warnings, but I have survived several such procedures.
Quote from: Carolyn on March 3, 2024, 08:38In order of likelihood:
A bad MAF will not throw a code, but cleaning may have been insufficient. The only way to know with the MAF is to put a known good one in.
If the alternator is dragging the voltage down, that could well be the problem.
You don't mention spark plugs or air filter, both things to consider.
Bad crank sensor.
Unlikely, but possible: Sometimes this can be a symptom of a blocked catalytic converter. This can be caused by the break-up of the pre-cats in the exhaust manifold. It's worth removing the two oxygen sensors in the manifold and checking the condition of the matrix it should have a regular flat surface and the honeycomb should be easily visible. If the matrix is worn, that could be your problem.
MAF - interesting comment - had assume no code meant it was ok - engine dies when we pull connector so it's definitely communicating with ecu - might give this a try after fuel check as new ones seem quite pricey
Alternator - interesting comment too, hadn't thought of that - problem still occurs when battery is fully charged though - does this mean less likely?
Plugs and coils done by previous owner, look new.
Air filter is ok, even tried without it installed and problem still occurs so can't be that.
Crank sensor - we checked the earth which is ok, again assumed faulty sensor would throw a code but maybe not? Do you need to remove oil to remove sensor? Does it just pull out once screw removed?
CAT - will check via o2 sensor holes. Currently struggling to remove heat shield due to bolt corrosion. Disk cutter in the post.
Thanks for all your advice
You don't need to drain the oil to remove the crank sensor. You're right about how it comes out.
The maf might be working-ish, but not well enough.
The alternator not working is a common cause of failure to rev. This cropped up with another member fairly recently. As it's bad, you have to replace it anyway. If it's dragging the voltage down, sparks can struggle even if the battery has been charged. The more I think about it, I'm thinking this is the most likely culprit, as we know it's malfunctioning.
Fuel filter and pump problems are unusual.
Quote from: LozB on March 3, 2024, 17:04CAT - will check via o2 sensor holes. Currently struggling to remove heat shield due to bolt corrosion. Disk cutter in the post.
Don't confuse pre cats with actual cat.
Don't need to remove heat shields to check pre cats.
Quote from: Ardent on March 3, 2024, 20:29Don't confuse pre cats with actual cat.
Don't need to remove heat shields to check pre cats.
But do really need a special cut away socket spanner to remove the sensors while the heat shields is in place/ or not.
Quote from: LozB on March 3, 2024, 17:04MAF - interesting comment - had assume no code meant it was ok - engine dies when we pull connector so it's definitely communicating with ecu - might give this a try after fuel check as new ones seem quite pricey
Alternator - interesting comment too, hadn't thought of that - problem still occurs when battery is fully charged though - does this mean less likely?
Plugs and coils done by previous owner, look new.
Air filter is ok, even tried without it installed and problem still occurs so can't be that.
Crank sensor - we checked the earth which is ok, again assumed faulty sensor would throw a code but maybe not? Do you need to remove oil to remove sensor? Does it just pull out once screw removed?
CAT - will check via o2 sensor holes. Currently struggling to remove heat shield due to bolt corrosion. Disk cutter in the post.
Thanks for all your advice
Had a bad crank sensor on a VW 1.8t once, no codes but same symptoms in that it refused to rev past 2500rpm or so.
Just in case, - MAF cleaning, the sensor is not the easily-visible blob, - it's up inside the plastics.
Spray, don't touch.
Ok today's latest update.......
First we tried running the engine with battery fully charged. Still wouldn't rev past 2500.
Then we removed as much fuel as we could but not much as tank was almost empty. Added 20 litres of shell's finest and ran for 20 mins and still no improvement
Then we fitted a replacement MAF out of a working Toyota, still no improvement
We have now removed the alternator ready to replace next weekend
Also started to remove crank position sensor, removed sensor itself and bracket holding wiring in place, but currently struggling to work out how to get to the connector on the other end of the wire - the cable seems to disappear above the AC compressor/fuel pump (not sure which it is) and can't see it or get to it. Any ideas what I need to remove to get to the connector?
Current plan is to fit recon alternator and new crank position sensor next weekend. Also check the o2 sensor holes for pre cat degradation - sensor removal tool in the post.
If all that doesn't work then we are pretty much stumped and will have to phone a friend at a local MR2 specialist.
Unless you lot have any other thoughts or advice?
Still leaves the blocked cat option.
Never done it myself, but does the crank sensor not just unplug from the wiring.
The wire for the connector you seek is clipped to a small bracket on the dip-tube. It is, as you suggest above the A/C compressor. (The fuel pump resides inside the tank). My money is still on the alternator.
Quote from: LozB on March 9, 2024, 22:32Ok today's latest update.......
First we tried running the engine with battery fully charged. Still wouldn't rev past 2500.
Then we removed as much fuel as we could but not much as tank was almost empty. Added 20 litres of shell's finest and ran for 20 mins and still no improvement
Then we fitted a replacement MAF out of a working Toyota, still no improvement
We have now removed the alternator ready to replace next weekend
Also started to remove crank position sensor, removed sensor itself and bracket holding wiring in place, but currently struggling to work out how to get to the connector on the other end of the wire - the cable seems to disappear above the AC compressor/fuel pump (not sure which it is) and can't see it or get to it. Any ideas what I need to remove to get to the connector?
Current plan is to fit recon alternator and new crank position sensor next weekend. Also check the o2 sensor holes for pre cat degradation - sensor removal tool in the post.
If all that doesn't work then we are pretty much stumped and will have to phone a friend at a local MR2 specialist.
Unless you lot have any other thoughts or advice?
Hope you get to the bottom of it. These kind of problems are frustrating in the extreme and often due to something simple.
This is a proper hail Mary, but is the throttle fully opening? It seems highly unlikely but just thinking if the cable is reeeeeeally stretched or has become dislocated it might mean the throttle isn't fully open even if the pedal is flat to the floor. Easy to check by opening the throttle by hand?
How tight is the throttle cable? It would be amusing (in a way) if it's a case of the throttle cable being too slack...
Thanks for responses again folks. You are brilliant.
Re the throttle cable I'm 99% sure it's not that as I rev by manually rotating the actuator on the throttle body. Good thought tho.
It's really strange, initially the revs rise but then once you get to a certain point the revs flatline and the more you open the throttle the more lumpy it gets. It's like the air volume is increasing but the fuel volume isn't......or vice versa.
Crank sensor and alternator next weekend along with inspection of pre cat.
As a matter of interest whilst thinking about sensors do you think it's worth changing the camshaft position sensor at the same time? Do these ever fail without a fault code?
Thanks
Sorry naggin about fuel. Fuel pressure ?
I don't now if Gasoline cars work's the same way as Diesel.
Correct me if i am wrong (Wife say's it happens time to time)
Driving one of our diesel car's it was as if you turned of the key over 2000rpm when the fuel filter was clogged. Computer "shuts off" to save the engine when the amount of fuel isn't enough.
Quote from: LozB on March 11, 2024, 15:22Thanks for responses again folks. You are brilliant.
Re the throttle cable I'm 99% sure it's not that as I rev by manually rotating the actuator on the throttle body. Good thought tho.
It's really strange, initially the revs rise but then once you get to a certain point the revs flatline and the more you open the throttle the more lumpy it gets. It's like the air volume is increasing but the fuel volume isn't......or vice versa.
Crank sensor and alternator next weekend along with inspection of pre cat.
As a matter of interest whilst thinking about sensors do you think it's worth changing the camshaft position sensor at the same time? Do these ever fail without a fault code?
Thanks
If you change too many variables at the same time, you risk learning nothing useful, Get the alternator and crank sensor done (seeing as you've already spent that money) and see what gives. I bet it will run fine.
I used to work on older Mercedes and BMWs and in most cases the cause was a weak fuel pump, not supplying enough fuel to go pass certain revs.
Replace the fuel pump always solve the problem.
Maybe this is the case?
I think it's a testament to these cars' normal reliability that we are all just kind of clutching at straws here.
Hope you fix your issue.
Sounds fuel related to me. Pump, injectors maybe
I'm going with pre cat failed gone on holiday to the main cat. Blocked won't rev...
My apprentice MR2 has done the same.
After a couple of weeks delay we are into alternator and crank sensor this weekend. Anyone ever replaced a crank sensor? I've removed the sensor itself but the wire disappears behind the engine and I can't see how you get to the connector on the other end. Looks like you have to remove the whole intake manifold assembly? Any tips?
Quote from: LozB on April 6, 2024, 12:55After a couple of weeks delay we are into alternator and crank sensor this weekend. Anyone ever replaced a crank sensor? I've removed the sensor itself but the wire disappears behind the engine and I can't see how you get to the connector on the other end. Looks like you have to remove the whole intake manifold assembly? Any tips?
https://www.mr2roc.org/index.php?msg=822676
The above may be helpful, includes a photo of the complete unit with wiring.
The crank sensor has been troublesome on other members cars and I found this using the Search Function and Crank sensor.
Ok so today's update.........
We couldn't find out how to disconnect the crank sensor despite checking search engine on here and fishing around with an endoscope. The wire just disappears into the engine and no clear route to getting to connector. I think you would have to remove the whole intake manifold and assembly to do this. Happy to be corrected. Anyhow I cleaned up all connections and the old sensor itself and re fitted.
We then fitted a new alternator and belt..........which was tricky but we did it in the end. YouTube is our friend particular 'Ottos Garage' channel.
And the result was........no change....... still won't rev above 2500
We then removed the o2 sensors to check out the pre cats using our endoscope. On the left side there was evidence of partial cat breakdown around the edges, but on the right side it had gone completely, nothing there. So it looks like that may well be the problem. We also checked out the cylinders with the endoscope and they were very black and oily.
So the question now is do we look for a complete replacement engine and exhaust system or is there merit in changing the exhaust manifold for one without pre cats and changing the exhaust/main cat. When running (below 2500 rpm) the engine does sound quite good and doesn't obviously seem to burn any oil.
Advice on next steps greatly appreciated.
Will upload pics if I can work out how to do it.
The main cat will be blocked with the debris from the precat. That will stop it revving. This has happened before.
An after market manifold is a good idea. There are a couple available. If you can get a Toyosports one, they are pretty well made, ( https://www.toyosports.co.uk/toyota-193-c.asp (https://www.toyosports.co.uk/toyota-193-c.asp) They have some in stock right now and they only do them in batches so jump on that! The gaskets that come with them are bobbins - use OEM manifold to head and OEM crush rings for the connection to the cat.
A Cats2U main cat will cost around £150 and they do the job well.
Sort that before you start on engine swaps. I've seen a lot worse oil fouling than that. A bit of oil burning isn't always fatal. The spark plug doesn't look too bad.
You don't have to remove the inlet manifold to get at that connector. You could drop the AC pump (no need to disconnect it) to get a better view.
Could you disconnect the exhaust system from the manifold to see if it revs higher?
That is free to try and may give you more confidence to order new exhaust parts if it revs higher once the gases can escape.
Quote from: Topdownman on April 7, 2024, 09:46Could you disconnect the exhaust system from the manifold to see if it revs higher?
That is free to try and may give you more confidence to order new exhaust parts if it revs higher once the gases can escape.
Just be aware that what comes out will be a health hazard!
Take the cat off and unblock it?
Quote from: Topdownman on April 7, 2024, 09:46Could you disconnect the exhaust system from the manifold to see if it revs higher?
That is free to try and may give you more confidence to order new exhaust parts if it revs higher once the gases can escape.
And it'll sound WICKED
I have a spare stock manifold and exhaust system you can try if needed? I'm down near Watford.
Thanks for all the advice and offers of parts etc. We ordered the bits suggested by Carolyn above as soon as we read the post so will report back once fitted. Hoping the engine isn't too badly damaged by the pre cat debris. How will we know if it is? Rate of oil burning or could we test compression or something?
You can just see how well it runs, if there's blue smoke when you give it some beans, and see how much oil it goes through.
Toyota is happy with 1Ltr per 1,000 miles, and it will pass emissions testing at that rate of consumption.
Fingers crossed this will solve the problem ;D
I thought 1000km (621 miles) still s lot either way.
Quote from: Ardent on April 9, 2024, 12:47I thought 1000km (621 miles) still s lot either way.
So the one I have in from Chris that drinks over 2 litres from Birmingham to Swindon is probably not ok?
Def outside of spec.
So today we removed the old manifold and CAT. Bit of a nightmare job but got there in the end. Pre CAT in left leg of manifold was there but cracked and decomposing. Pre CAT in right leg was completely absent. See photos
We have new manifold and main CAT to install next weekend. Just waiting on a few new studs and nuts and for welding on subframe (see separate post)
(https://i.ibb.co/rpZSHxr/IMG-3133.jpg) (https://ibb.co/rpZSHxr)
(https://i.ibb.co/Ctp2pk8/IMG-3134.jpg) (https://ibb.co/Ctp2pk8)
Yesterday we fitted the Toyosport manifold and new main CAT and it now revs properly. Clearly that was the answer all along, the pre cat in the right downpipe had completely disintegrated and blocked the main CAT.
I guess the question now is whether bits were also sucked back into the bores giving us a car with a serious oil drinking problem. On the face of it the engine seems ok. On start up there is lots of steam but after a few minutes it seems to run clear and idles smoothly. I'm hoping the previous owner experienced a catastrophic CAT failure event which rendered the car immediately undriveable such that bore damage was limited......is that even possible?
I guess that we wont know until we get the car on a road test and we are currently a long long way off that. Suspension, brakes and power steering all need an overhaul plus misty headlights and some rust issues. I'm sure I'll be back on here asking more questions soon. You lot are amazingly knowledgeable, thanks so much for sharing your wisdom.
You might get an indication by getting the engine fully warmed up, let it idle for a minute, then BOOT the throttle, easier with a helper to see the exhaust output. Well done in persevering.
Get a borescope and poke it in through a spark plug hole.