[Mk2] [NA] Where to start?

[Rhyswh]

So I'm new here......I don't actually own an MR2! So brief background, I'm into cars and own a mk1 Mx5 (not sure if that's a swear word here lol). My friend decided to buy himself a car that would be more fun than a Ford Focus. I obviously suggested an mx5 but he wasn't keen. So second suggestion was the MR2! He just bought one that needs a lot of work, he isn't mechanically minded so will be relying on me to do a lot which is great because I would classify myself as an enthusiastic bodger

I have some knowledge of cars and happy to work on them. So on to the problem.

I think the engine is the 3sge. I'll double check that when I get a good look at it. It's a 1990 Rev1.

The car idles a little high, this was in the ad. Previous owner said he'd put a clamp on the intake pipe as a temporary fix....not sure what he even means by this. Idle is currently around 1200rpm. My friend reported on the drive home that it felt sluggish and definitely slower than my mx5. My understanding is the MR2 should be slightly quicker.

So symptoms are currently; High Idle and possibly down on power.

I've got a feeling there might be a vacuum leak. Had a very quick look the other day and could hear some hissing coming from the Air Intake pipe when touched. Anywhere else I should look at first?

I'm sure there will be many more questions!

[pbmr2]

Hi,

Could be loads of things but top things to look at are:

Idle control valve sticking or cracked. They get clogged up with old oil vapour and stop moving enough. Carb cleaner can sort them out but will need to remove to do this, new gasket needed at this point.
The plastic also cracks which creates an air leak. replace at this point.

tvis system. it's a valve the changes the intake path at higher rpm. the small hoses for it can crack, the vacuum chamber under the intake can crack, the actuator diaphragm can split creating an air leak.

ecu temp sensor. they fail slowly over a long time. can be tested with a multimeter. cheap to replace is needed.


throttle body or other intake joint gasket. creates an air leak.

missing blanking plug on an intake take-off.

vacuum sensor on rear firewall, the hose can split with age and if knocked the hose attaching point can snap, creating an air leak and failing the sensor to read vacuum.

ignition timing. simple enough to check.

There is also a way to ask the ECU if it think there is any sensor problems. can do a fault code check using a paperclip.
link from the other site..
http://www.mr2oc.co.uk/know-your-2/mk2. ... bartid=162

if all that doesn't solve your problem then there are other things to look at. they are sensitive to poor ignition servicing or something else could be at play.

good luck

[Rhyswh]

Thanks for that. Loads of things to check. Will have a look over the next week and let you know how we get on!

[Rhyswh]

So had a chance to have look last night. I think the issue is definitely around the throttle body and intake pipes.

Took the whole intake off the throttle body and found out what the previous owner meant by "restrictor" on the intake. Just before the intake pipe attaches to the throttle body there's a pipe that comes off and attaches to the bottom of the throttle body (I've taken a picture but can't post it yet). Whilst with the car I couldn't figure out what this was for. I was thinking afterwards when I was checking the throttle body over the flap inside was fully closed with no throttle so I'm going to assume this little pipe somehow feeds air into the throttle body (through the ISC valve) for when the car is idling, would this be correct?

Anyway, the previous owner had stuffed a smaller tube into the metal elbow that comes off the intake pipe to restrict airflow down this pipe. After taking this out idle went up from 1200rpm to 2000rpm, it then dropped about 300rpm and climbed back up every 5 seconds or so which I think is normal if the car is idling too high. I could squeeze the pipe that connects to the bottom of the throttle body to drop the idle right down to 700rpm so there's definitely an issue here.

Next step will be to clean the ISC valve. If the the ISC valve is playing up could this result in loss of power when on the go? In my head that wouldn't make sense.

I tried to do a diagnostic check as well but couldn't get the CEL to do anything, it wouldn't even flash to say everything is ok, just stayed solid.

[Rhyswh]

As a side note, the car might feel under powered because it could be the 119bhp version

I'll have a look for the engine code but is there any other clear signs that would suggest the lower power model, like trim level? Spoiler? etc

[Ben]

What's the red-line on the rev limiter?

[Rhyswh]

I'll have to check. After looking at pictures of the 3sfe and 3sge I'm pretty sure it's not the 3sfe.

[Ben]

OK. I nearly fell for one years ago before buying my first MR2. If the red line is at 6k, it's a 3SFE. 7 is the magic number IIRC

[Rhyswh]

Managed to find a picture from the advert and the redline is at 7000rpm

[Ben]

Disco!

[pbmr2]

yep the pipe you describe is the intake for the idle valve, it takes it from there as it's after the air filter so clean. the restrictor you found isn't stock, sounds like an attempt to fix the problem with a simple bodge.

The idle valve being sticky could cause loss of power during normal driving also. the pulsing idle is the system trying to correct the air flow error. it's not normal to keep reving up and down like that, is shows an issue.
Remove the ISCV to clean and inspect for leaks. Once removed you'll need a new gasket before proper fitment again.

really would test the temp sensor also, if these are at fault then the ecu uses the idle system to set the idle according to the temperature reading it's getting.

once all that is done you need to set the idle speed, which isn't just turning the idle speed screw. you need to put the ecu into a mode where it stops trying to correct the speed. see the BGB.

Here is a link to the workshop manual (BGB, big green book). it's a bit clunky to read though but all the information about fault fixing etc is in there and how to test each sensor or system.
you will prob need to skip to the FI section. the 3sfe engine works the same way as the 5sfe so follow the parts for that engine.

busy weekend coming up good luck

[Rhyswh]

What I meant by normal for the idle to dip is that because the idle is so high it's normal for it to dip like that, I didn't mean it being normal for the idle to dip in general

First thing I did yesterday was to try and reset the idle speed just incase (bit of wishful thinking lol). Bridged TE1 and E1 in the diagnostic box. Idles at around 1200rpm but the screw is as far right (I think it's that way round) as it will go so can only increase it.

Will have a proper look at the ICSV and test it. If that doesn't work then I'll check the Temp sensor next. Is there a way of testing this sensor and which temp sensor are we talking about? Is it the one in the airbox?

I've looked at that manual a lot already, it's very useful!

[Rhyswh]

Found how to test the intake temp sensor as well so will give that a go.

[Rhyswh]

When I'm checking the ISCV should the valve open and close fully or should there be a slight gap when closed?

[Rhyswh]

Had the ISCV off last night and tried testing it. The valve itself wouldn't budge until I put some pliers on it and forced it round! It's much looser now but when testing (connecting sensor to battery) nothing happened. Valve just stayed in same position. Could it be a faulty sensor? If that stopped working I guess eventually the valve would seize in place. The valve is all mechanical as far as I can tell so as long as it turns freely (which it does now) then I can't see how this would be the problem.

Any advice on where to get another ISCV? Seems hard to find parts for the mr2!

[pbmr2]

sounds like you have found the fault.

for testing the temp sensor see my previous post, there is a picture directly from the workshop manual on how to test the temp sensor. it's the multi pin one in the water elbow that you need to test.

Get some carb cleaner in the idle valve and search youtube for a video on cleaning it. it may just be clogged up with crud but it could also be end of life and need replacing.
you will need a new gasket also.

The little vent inside should be able to close fully when working normally.

The idle screw being wound all the way in is a sign of someone before you trying to sort this out and not getting as far as you just have.

Nearly there!

[Rhyswh]

Ok, my friend has a part cleaner at work (high pressure water cleaner) so he's going to give the valve a good blast through. There was quite a bit of oil in there.

Any advice on where to get a replacement gasket? Can't seam to find anywhere to buy parts like this for the Mr2.

As a side note, worryingly the coolant that runs through the valve was brown and gritty Have a feeling someone might have used tap water so there's rust somewhere in the system.

[pbmr2]

try tcbparts.co.uk, they are old school so you have to call them but very helpful, good prices and very fast delivery.

otherwise you might have to get a gasket kit. I'm sure you can get the one gasket though, even if you have to go to toyota for it. just need the part number.

change that coolant now! do a good flush through and then refill with the correct type of coolant. Also change the thermostat as they age and stick which can cause overheating issues.

good luck

[pbmr2]

just had a hunt but I don't have a link for an EPC to find the part number. hope someone else can help

[Rhyswh]

I have contacted them already but had no response yet. Will try ringing them as well.

I've found a solution to getting an ISCV, most throttle bodies on ebay come with the ISCV and sensor attached to them. Just need the gasket.

Is a rev2 throttle body the same as the rev 1. I can see a visual difference on the rev3 but the rev 2 looks exactly the same?

Will replace the thermostat as well.