Hesitation on idle and throttle, revs needle bouncing (SOLVED)

[GreddyMR2]

Hi,

need a little (or maybe a lot) help from you. Just tell me what might cause this and where should I start looking at.

Here is the problem, I will try to describe it as goog as possible.

First of all, I have Adaptronic ECU with a base map. I just setup that under 60 celcius or over 99 celsius revs would not go higher than 3k. Other than that is not touched.

OK so I was driving without problems before, all seemed good. Some time later it started to do this: when the car is cold, revs are ~2k (in ECU it is adjusted to be 1,2k when cold) and they only drop when I rev a car a bit more or just after some time. Also, the vaccum is fluctuating when the car is cold and revs are going up and down a bit. Once the car warmed up, rev hold at 800rpm and vacuums stays solid.

Then I went to a tuner and he found a boost leak. It was leaking through the 2 o-rings in T-VIS. We thought it migh cause cold car problems, so yesterday we fixed a leak by eliminating T-VIS at all. Note that we removed intake manifold and all the earths from it and the attached them where they were.

I started the engine and unfortunately vacuum was still bouncing. I started to drive home and suddenly revs started to bounce. But only revs needle, not the engine. I put in neutral and suddenly engine stalled. Started it again and slowly drove home, but the idle was very rough and hesitating when revving. I thought like an electronical problem or bad earth?

Now this morning I started the car and revs again was at around 2k. I turned on the lights and revs needle jumped to 3 or 4k (only the tacho, not the engine). Then I disconnected IACV and revs dropped to 800. Thought the IACV might be fauly, but why tach is bouncing?

Next, I reconnected a battery and tacho jumping dissapeared. Unfortunately just for a while. I started to drive to work, all seemed well (just IACV was disconnected), but then again tacho started bouncing and car started to hesitate at throttle. After some miles it stopped and was working well again. Then, after some more miles, it started to do the same. Also, rev limiter at 3k turned on (note that I have ECU setup to limit revs when water temp below 60 or higher than 99). Also, one time engine suddenly stalled at idling and then somehow started itself again. I slowly managed to drive to work. I put a car in a parking, I heared very rough idle and when I tried to rev a bit, I heard some pops through the exhaust and engine stalled again.

Anyone can help me with ideas where to look at?

Rev limiter at 3k rpm - faulty temperature sensor or loose connection?
Tacho bouncing - bad earth?
Hesitation - bad water temperature readings?
Why revs go up too high when IACV connected?
Maybe we damaged some wires when taking off and on intake manifold?
Anything else?

Thanks in advance!

[2mad]

I would rule out the aftermarket ecu by plugging in the stock ecu and see if you still have problems mate .

[GreddyMR2]

I would rule out the aftermarket ecu by plugging in the stock ecu and see if you still have problems mate .

Not sure if it's possible as the AFM is already removed and sold...
Or can it read from IAT sensor?

These hesitations started only from yesterday, when we took off and on intake manifold. So maybe we moved a wiring and some connections became loose.

[2mad]

Ow that is a shame .. have a good look over what you last adjusted/moved see if you can find something out of place ..


As a ps when i swopped over to speed density , running lean at idle made it bounce ... just a thought but is sounds like you problems more server than that


Hope you sort it mate

[GreddyMR2]

Ow that is a shame .. have a good look over what you last adjusted/moved see if you can find something out of place ..


As a ps when i swopped over to speed density , running lean at idle made it bounce ... just a thought but is sounds like you problems more server than that


Hope you sort it mate

Thanks, will have to check everything over today
I hope we will find something and fix it as I have some racing event next weekend...

[2mad]

If you cant find anything take it to a mapper and have them plugin to the ecu and do a diagnosis .. ecu's a pretty smart now .. should get the answer


Hope you make it to your meet buddy

[GreddyMR2]

If you cant find anything take it to a mapper and have them plugin to the ecu and do a diagnosis .. ecu's a pretty smart now .. should get the answer


Hope you make it to your meet buddy

I will go to a mapper today, so maybe he will do some logging and will see where the problem lies

Will post some news at the evening

[2mad]

Hope he sorts it for your event .. dash cam vid of it please

Seen a vid of you, your a good driver mate

[GreddyMR2]

Hope he sorts it for your event .. dash cam vid of it please

Seen a vid of you, your a good driver mate

Thanks for complimets! I got a gopro this year, so I will definitely make a video! It will probably be posted to my build page at 25th or 26th of april

[2mad]

Really do hope everything works out for you, cant wait to see the vids

[GreddyMR2]

I am a bit impatiant and upset about a car, so went outside again to make some checkings
I checked the TPS wires, because they were cut and connected to make them longer, thought that maybe there might be a problem. But everything seemed ok there.

Then I reinstalled some connectors, like one under the distributos, water temp sensor and TPS of course. Also, connected ISCV.

And guess what, car started and revs holded nicely at 1.2k and vacuum stayed solid.

So I am 99% sure that the problem is related with a bad contact, either in wiring or connectors. I hate electrical works

[2mad]

Sounds like your on the right path , keep plugging away, you'll get there

[GreddyMR2]

Did some work today, but have not managed to solve main problem.

We checked the values of water temp sensor. At one time it shows normal 80-90 celcius and suddenly it starts jumping to 120 and so on. At this point car starts hesitating and stalling.

We mapped it a bit so it started to run well at throttle, but it still does not hold normal idle, stalls when not revving and sometimes tacho bouncing. Tomorrow we will try to find faulty ground wires as we suspect that some of them might be faulty.

Also my speedo is not working, but the ecu shows bouncing speed. from 0 to 250kmh and so on. But this might be bad cable or bad connection at speedo. I changed speedo gear in the gearbox yesterday, but it did not solve non working speedo.

[Scott Barton]

Have you checked here? Might be something useful.
http://www.imoc.co.uk/forums/viewtopic.php?t=24011

[GreddyMR2]

Have you checked here? Might be something useful.
http://www.imoc.co.uk/forums/viewtopic.php?t=24011

I know these usual servicing things, but I don't think it would cause my symptoms.
Water temp bouncing can't be related with ignition, right?
I see two options. It is a bad sensor or wires have no good contact somewhere.

[GreddyMR2]

I'm finally at home with some good news!
We did a lot of wires checks with bad luck (I mean we found that all wires are good) and finally we decided to check a ground on intake manifold. We took it off and car didn't start at all. Then we made an extension and bolted a ground wire to the clean part of body. And looks like all the problems are gone! The problem is that manifold is covered with paint and it did not get a good ground. Also, when ground wire becomes warmer, the resistance becomes higher and so it even loose a connection sometimes.

The mapper was very surprised all the ecu is grounded by only one wire.

Anyway, finally we can map the car
Hope to do it next friday and have some great time at saturday's event.

Conlusion is that I realised how important is to have a perfectly clean ground points. That's my job for this weekend. To clean all the ground points.

[2mad]

That is great news buddy .. good luck at the event



As a ps. I fitted 2 zero gauge cables to earth my mr2 , one from the alternator bracket to the body and one grearbox to the body .. never had any problems after that



Kev.

[GreddyMR2]

That is great news buddy .. good luck at the event



As a ps. I fitted 2 zero gauge cables to earth my mr2 , one from the alternator bracket to the body and one grearbox to the body .. never had any problems after that



Kev.

Thanks for the advice
By the way, do you mean you connected a new wire from alternator bracket to body? Because originally it's not supposed to be there?

[2mad]

Yeah I added them (bit of a punt) but worked for me .. the earth iirr from the throttle body to the cars body stopped burning out after this that was my earth problem

[mr2magic]

A point to note is that the manifold ground is a common ground for lots and lots of systems. The terminal takes 4 wire ends from wires that in turn are also spliced

That this faulty ground caused so many problems is therefore no surprise....but I wouldn't have thought it was at fault from the description. You learn something new every day I guess