Misfire intermittent / coolant leak

[H2zzMRA]

Hi everyone- desperate need of help-

Mr2 2zz swap- recent purchase!

Has been misfiring, losing power intermittently for 24 hours. I noticed the coolant was low, so topped up and bled it- now there is an engine light on and very rough idle + misfires. Coil packs are dry/ engine appears to be heating up. Then I noticed when the car was warming up (?? On closed loop) started misfiring badly. Noticed a radiator leak/ pipe leak.

Could this cause the symptoms? Possibly an  airlock?

Help! I'm hoping it's not worse than that?!
How would people suggest trouble shooting this?

Thank you 🙏

[Carolyn]

Get an OBD dongle and Torque Pro and see what gives in terms of codes and sensors.
.
I'd also be pulling spark plugs for inspection and (I'm afraid) I'd run a compression test for possible head gasket issues.

[H2zzMRA]

Thank you Carolyn -

What's strange is that it runs perfectly fine when cold, but v rough and misfires when hot

I'll run the checks you suggested

[Ardent]

As is the way here.

Always start at the simple (cheap) end of the wedge.

Air filter?
Maf clean
Plugs?

You get the jist

[Joesson]

Thank you Carolyn -

What's strange is that it runs perfectly fine when cold, but v rough and misfires when hot

I'll run the checks you suggested

Symptomatic of that which @Carolyn suggests!

[H2zzMRA]

Throwing up a DTC P0410 code - a malfunction in the secondary air injection (SAI) system

Cleared code and running fine?! Any ideas? Haven't yet checked plugs/ compression test- will do so today.

Could a coolant leak in radiator cause this? Sizeable leak going on

[Gaz mr-s]

Throwing up a DTC P0410 code - a malfunction in the secondary air injection (SAI) system

Cleared code and running fine?! Any ideas? Haven't yet checked plugs/ compression test- will do so today.

Could a coolant leak in radiator cause this? Sizeable leak going on

I can't give you chapter & verse, but that code is only pertinent when in the original car. The secondary system is not used when fitted in an MR2. I don't know if it can be prevented, but I have seen owners saying it comes on periodically & they clear it.

Where's the coolant leak from & have you asked the previous owner if they knew about it?

[Gaz mr-s]

The misfires, - are the coilpacks Denso?   The 2zz's coilpacks are prone to cracks down them,  & it's sometimes a sign of internal failure.

[H2zzMRA]

Toyota coil packs - not sure if they have been replaced ever but I doubt it - denso are v dear but I may have to buy some.
Thank you - I'll change em out

[Gaz mr-s]

Toyota are made by Denso.  I think they own the company.  Don't change without knowing, - as you say they're not cheap.

The reason I asked is because usually if a coilpack is faulty the OBD can pick up misfires, but I've heard it said that non o/e will not show.
If you have misfiring but no codes suspect the maf.  Shop carefully, the same maf is used in loads of Toyotas.
 

[Ardent]

Is this a case where if you pull the lead from a coil pack and does not change the engine note, that  indicates a duff pack - then if you swap the the pack with another and the fault moves...

[H2zzMRA]

having run the car / cold start approx 15 degrees ambient temp the total fuel trim is -8 (approx 3 mins after starting engine)
Read outs from MAF= 5-6 g/s
Engine load 20% at idle of 1500
Does that seem about right for closed loop?
Seems to be leaning the engine out after starting? I suppose that would be the case if the MAF was dirty/ undereading?

Would you bother cleaning or just swap? I've read cleaning can deliver poor results

[Gaz mr-s]

Cleaning it doesn't do harm.  A quick-drying alcohol is what you need.  Protect the sealing o ring from the alcohol.
You may not have done it before....the sensor is not the visible 'blob' (but clean it too). The main one is up inside the plastic.

[Ardent]

/  I've read cleaning can deliver poor results

Where have you read that

[Carolyn]

There is no way to know how well the maf is working short of trying a known good one and observing any difference.

[H2zzMRA]

I read it on an MR2 chatroom- one person option I guess

[Gaz mr-s]

I read it on an MR2 chatroom- one person option I guess

If that means f/book be wary of a one-off opinion, - there is a lot of guff on the groups, - people spouting uninformed stuff.
Having said that I'm on them more than I am here, - just the way car-groups have gone.

[H2zzMRA]

That's why I joined this chat room- it seemed the only sense I could find was on here
Thank you for all the help btw- it's a great community
Can't wait to get this car running smoothly again

[Ardent]

That's why I joined this chat room- it seemed the only sense I could find was on here

Yep.

[H2zzMRA]

Having cleaned MAF- all readings seem consistent with a working MAF.
Still backfiring/ misfiring when in closed loop-
When I unplugged the upstream o2 sensor the backfires stopped?
Voltage swings from 0.01-0.8 on sensor.
Runs fine with sensor unplugged- with sensor I'm running  rich scenario and combined fuel trim is -8 to -10% during and after warm up
1)Gonna replace the sensor
2) only issue it doesn't solve is a 'bounce' when letting off throttle (in neutral) at 1500rpm before setting at 800rpm

Any ideas regarding the bounce? Is this  normal dashpot behavior ' or am
I missing something here?

Thank you again everyone!

[Ardent]

Not got the answer, but if sensor is outputting a variable voltage (swinging) that suggests to me it is working. If a flat 0 or flat 1, perhaps not.

Are these readings all done stationary?
Just wondering if temp or circumstances are enough to allow system to switch from closed to open loop.

[Gaz mr-s]

Fluctuating idle is usually caused by the Idle Air Control Valve in the throttle body.  Removing the t/b is a PITA.
Idle problems can also be caused by air in the system.  The radiator bleed valve is top left as you face looking-in.
Definitely worth trying that first.

[H2zzMRA]

Not got the answer, but if sensor is outputting a variable voltage (swinging) that suggests to me it is working. If a flat 0 or flat 1, perhaps not.

Are these readings all done stationary?
Just wondering if temp or circumstances are enough to allow system to switch from closed to open loop.

Yeah done stationary. Thanks for the advice

[H2zzMRA]

Think I've found the culprit - intermittent misfire on 1 cyclinder from coil pack. Usually occurs only after 55/60 degrees coolant temp.
Sheesh
Bit of a mine-field finding a place that sells genuine denso 0104 coil packs?

Where is 'safe' to buy these?

Onlinecarparts.co.uk have them on for £65 each- seems like a counterfeit price

[Gaz mr-s]

Online car parts are in the same group as Autodoc.....probably just a different website taking you to them.