mx5cartalk.com

So I took the car out for a drive last-night. Then the car started idling at 2000rpm when I pulled up at my first set of traffic lights. Well it eventually settled to 1500rpm and I let it go. Continue on figuring I'll look at it later. Reached my destination, turned off the car. Few hours later get back in to go home, turn it on and now the cars idling at 2500rpm and blipping itself to 3000rpm every second...... makes for an interesting drive home when the car is driving itself below 3000rpm and constantly blipping itself at every traffic light.

I get the thing home about 2am and I wouldn't be able to sleep without looking at it, so I start checking every sensor on the intake manifold is plugged in, unplugging it and re-seating it incase. Everything seems fine, reset the ECU by disconnecting the battery for 30 seconds and turn it back on. Car still idles at 3000rpm, then drops to 2500rpm and now idles continues blipping the throttle upto 3000rpm..... so I take off the intake and have a look, notice a slightly bend fin on the MAF. I touch it with my finger to see how solid it is and it instantly falls off....... now the car won't start.

So have I finished off an expensive MAF sensor and am likely to have other idle air control issues (couldn't find any vacuum leaks so assuming it was that) or have I just found a likely canditate for my interesting ilding problem. On full-throttle the car did feel fine I should add. I'll email mania and see if they've got a MAF too....

I've actually got the car booked with them for Fri-day for a tune and it'd be nice to get the car up there.

Let us know how you go.

Jules

Well I've done a little more research and Irwin8er came round on saturday. It looks like I killed the centre electrode on the MAF, no idea why it was brittle and most likely already cracked but I never found the centre again. Took the MAF off Irwin's NB8A and the car started straight away...then proceeded to continue idling at 2500rpm and blipping the throttle to 3000rpm. Reset the ECU again and still the same.

We then spent about an hour unplugging and re-pluggin in every sensor, gave around the butterfly a clean. Took out the Idle screw and cleaned behind which dropped a decent amount of carbon. Then started the car again and exactly the same idle problems. Even with things like the TPS unplugged it still ran the same....

Only solution to stop it blipping itself is to turn on the A/C. This drops the idle to 1600rpm and it's constant. This still implies to me that the computer is doing freaky things to my IAC valve.

The car is a 2001 NB8B with the racing beat 4-1 power pulse extractors, K&N filter straight on the airflow meter which is sitting behind the driver side headlight(relocated the coolant overflow bottle). Then Rod Clarke's old ECU pushing the buttons. This setup had been running fine (albeit quite rich) for the last week.

Now, I've been in contact with Mania since. A replacement MAF is $180. However seeing as in the long-term I plan to be turning this into a mock SP I thought I'd check how viable swapping to a MAP sensor is. This became doubly viable due to me annihilating my old MAF...... So it turns out Rod's ECU is relatively custom and one of the first mania ECU's. To run a MAP it needs to be modified, then completely re-tuned. Irwin's going to lend me his MAF for the day and the car goes up on Fri-day for the work.

Due to the A/C reducing the idle significantly (idle is controlled by the standard ECU) I'm hoping it fixes itself when everything is reset....still worries me that it did it after I disconnected the battery for a whole minute... If I had a MAF to use I'd disconnect the new ECu and just have the standard one to test it. I don't atm though.

Alright car is back and working great, well actually it feels like it has even more torque over a bigger range and no longer back-fires or bogs off throttle.

So lesson's learned, to get the car upto Mania Daniel did me a big favour and offered to let me drop the car off at his house, then he'd drive it to work so it could be at mania all day as opposed to risking having it only available from 2pm in the afternoon and it possibly needing quite a bit of work/tuning. I need to give 3 months notice for leave...so that wasn't an option short notice. I'd already had to work an extra 5 hours overtime to get off work at midday to drop it off..when I only wanted a tune with the MAF sensor. So this helped me out a lot, big props for going above and beyond.

Irwin8er gave me his MAF to use on wednesday night, so I got it home, disconnected the positive terminal on the battery and installed the MAF. I figured this would %100 guarantee the computer was reset well and truly. Installed the MAf again, idle went to 2500rpm and kept blipping. So I turned the car off, disconnected the positive terminal again and removed the piggyback. Reconnected the battery and started it again, it immediately goes upto 2000rpm and start blipping the throttle again....*sigh*....then surprisingly while I walk round the car to move the current knocking pod air filter..the idle settles itself. Now I'm half-way between a faulty IAC valve and the mania ECU giving the factory ECU weird signals. Anyway it's late wednesday night, car seems drivable and my idle problem has magically dissipated. So I take it out of the garage, turn on the head-lights so I can see where to put my garage key...and the wipers start. Didn't remember actually hitting the stalk at any point so I reach in and lift the stalk...it's already lifted the whole way. Flick the stalk to fast and back up to off....wipers still on. Joy..... So now I have a random electrical problem to boot. Anyway just wanted to fill the tank up for thursday nights drive , on the way to the servo I turn on the highbeems because someone coming the other way had theirs on. Wipers stop..... highbeems go off, wipers come on. Next test, turn off headlights and just to go parkers and behold...wipers stop. It's midnight though, I have to get up for work in 5 hours so I just pull-over and disconnect the wiper motor. Really can't be bothered playing with it. Also the car feels like crap with the standard ECU, while the mania one was causing some major back-firing and bogging down off throttle, to the point of nearly stalling it....I had torque from 4k-6k....this simply vanished on the standard ECU. Not a good drive...

Thursday night I get the mx5, it's bad weather , been raining on and off so I need to reconnect the wipers. 10 minutes in I cant' stand the wipers and we stopped at northgate Macca's and got supplies while I disconnected the wipers. Thankfully it didnt' rain on the drive up. The funny part is we pull up, find Daniels and the moment I go to show him the wipers going when the headlights turn on....it doesn't happen XD

The important things I learned though, are that even if a car is the same model with the same mods, swapping an ECU doesn't work. The car feels smooth and feels like it has more torque now(starting at about 3800 and lasting to about 6700 according to the butt dyno, doesn't feel like it tapers off nearly as much). If I recall correctly it made 92kw atw.

My Idle problem is likely gunk, Daniel said there was a decent amount of carbon around the IAC plunger and likely it was getting blocked from closing completely and the computer kept trying to close it by retracting and moving forward. So on the agenda is a full intake manifold clean. A piece must've random dislodged when I went to take it up thurs night.

The light+wipers problem never re-occurred, I'm sure it'll come back to harass me next time I get problems.

Also before I forget, Irwin8er drove my old death-trap the camira upto Daniels in convoy so I could get home, now that I am home I think I'll go give him his MAF back.

Hey Hellum,

Sounds like you've lost an earth connection somewhere and drive signals are causing earth lift in a line they shouldn't. From what you're saying re lights and wipers, sounds like it's somewhere in the dash loom. So, what might sound like an odd question - was the idle blipping up in time to what the wipers would normally do on intermittent?

No the wipers were on normal speed, it would take anywhere from instant to 10 seconds for the wipers to start. I'm more inclined to think it's the stalks, most likely the normal beam. Still it hasn't re-occurred yet so I'll leave it be.