New problem. Engine stumbles

[Laird Scooby]

Originally Posted by mhuk

I removed the k tronic ecu. Nothing bad inside. Don’t know where to go now really.

https://www.volvoforums.org.uk/showt...298517&page=21

Took a while but i found the bit about testing the ECU, think the contact etails for the place he used are in there somewhere, if not pst a reply asking for the details.

Testing the ECU is almost certainly your next step, some secondhand ECUs can fail when transferred to another car (or even removed and replaced in the same car) for some unknown reason, worth getting your checked and/or repaired, it comes back with a lifetime warranty anyway.

[mocambique-amazone]

Originally Posted by mhuk

Ok I need to read that thread. Thank you.

So this ecu called jetronic controls the fueling ie injectors.
And this might be diff and need sending away.

I have two chips from the old owner.
Maybe I could plug it in and test it’s. It the mapped chip?

984 is with integrated anti-theft device.
You can't use this without chipping or with the riight anti-theft system
Propably the best ECU Volvo did use with LH2.4

good luck, and check if the TPS stay closed, Kay

[mhuk]

Not sure what you mean Kay. I stuck the old chip in and it fired up but i guess its the original chip.


With the old chip it still runs crap.

So to make sure no bad wires which is doubtful. I connected my led negative side to pin 18 on the fuel ecu. I got a live from the battery. Ignition off im getting a light. Ignition on and its off. Turn engine one and its flashing. Revs drops lights out. Same as injector plugs.


Looks like ecu. Ill get it sent off.



Massive thank you Dave and everyone else who has supported me. Ill keep you updsted.updated.

Martin

https://youtu.be/nza_WVBtMmc video

[mhuk]

Guys

Note the massive vacuum issue is rubbish. As I said I using my cheapo gauge. it's clearly crap.

draper shows a good reading!!!

cheers

[Laird Scooby]

Originally Posted by mhuk

Not sure what you mean Kay. I stuck the old chip in and it fired up but i guess its the original chip.


With the old chip it still runs crap.

So to make sure no bad wires which is doubtful. I connected my led negative side to pin 18 on the fuel ecu. I got a live from the battery. Ignition off im getting a light. Ignition on and its off. Turn engine one and its flashing. Revs drops lights out. Same as injector plugs.


Looks like ecu. Ill get it sent off.



Massive thank you Dave and everyone else who has supported me. Ill keep you updsted.updated.

Martin

https://youtu.be/nza_WVBtMmc video

What Kay means is that the ECU ending with "984" ahs the built-in immobiliser for use with the Volvo security system and the keys with the chips in although i can't remember which came first.

By using what appears to be the original chip and getting the same results, it proves it's not a firmware problem but seeing that latest video, it's almost identical to the symptoms ANDTWENTY was getting on his n/asp car - injectors are injectors and injector drives are injector drives, i think (although we never had confirmation) that the injector drives were the problem on his.

[mhuk]

OK Thanks.


I just posted the ECU with all the information. It's gone to ecutesting.com I think that's where the other chap sent his.

Fingers crossed it's OK on it's return! Failing that i'll think about scrapping and selling the fun parts. I have a mark 1 Audi TT on SORN with all sorts of fun parts added and runs just fine. However the 940 is much better for taking children and bikes around!

[Laird Scooby]

Originally Posted by mhuk

OK Thanks.


I just posted the ECU with all the information. It's gone to ecutesting.com I think that's where the other chap sent his.

Fingers crossed it's OK on it's return! Failing that i'll think about scrapping and selling the fun parts. I have a mark 1 Audi TT on SORN with all sorts of fun parts added and runs just fine. However the 940 is much better for taking children and bikes around!

That name rings a bell, he did tell me but i can't find the link. Managed to find the name, ATP Electronics, £45 for testing and £225 for repair. Don't know how that compares to what you've been quoted but probably similar.

https://www.atpelectronics.co.uk/

Fingers crossed they show up a fault and the repair is a sensible price!

[TonyS9]

Originally Posted by Laird Scooby

The trouble is it's not revving Tony, the revs die for no apparent reason.

Sorry, I've come into the thread occassionally and maybe skipped over the fix for that, but the first post says its constantly reving at 1500rpm.

Other symptoms are ignition cutting on high rpm, are you sure this wasn't the limiter coming in?

So the main problem is rpm dropping. I very much doubt such a regular drop would be caused by a dodgy fuel pump replay, fuel pump or injector relay. It seems more like a missing/incorrect input and the ECU is doing it deliberately.

You have confrmed the injectors are being cut, the only way for this to happen IMO is;

1. It thinks the throttle is closed and you are in fuel cut mode slowing down.
2. You have exceeded the air flow limit voltage
3. It isn't getting rpm signals from the ignition ECU.

Now we are suspecting the ECU, but I would have checked out the above items first.

The first one ties up with the weak mixture theory and the fact that it takes a little while to go at 2000rpm.

The second one seems unlikely but you have heavily modded the engine, without chipping the ECU? However you have tried an aftermarket chip which should eliminate this.

The last one would just not start, there is no reason for it to kick in, and if revs are shown on the rev counter in the fault condition then the ignition seems fine.

For theory 1 does this not happen above 2500rpm? If not then I'm thinking we are in slow down fuel cut terratory, and your throttle closed signal is stuck on.

[Laird Scooby]

Originally Posted by TonyS9

Sorry, I've come into the thread occassionally and maybe skipped over the fix for that, but the first post says its constantly reving at 1500rpm.

Other symptoms are ignition cutting on high rpm, are you sure this wasn't the limiter coming in?

So the main problem is rpm dropping. I very much doubt such a regular drop would be caused by a dodgy fuel pump replay, fuel pump or injector relay. It seems more like a missing/incorrect input and the ECU is doing it deliberately.

You have confrmed the injectors are being cut, the only way for this to happen IMO is;

1. It thinks the throttle is closed and you are in fuel cut mode slowing down.
2. You have exceeded the air flow limit voltage
3. It isn't getting rpm signals from the ignition ECU.

Now we are suspecting the ECU, but I would have checked out the above items first.

The first one ties up with the weak mixture theory and the fact that it takes a little while to go at 2000rpm.

The second one seems unlikely but you have heavily modded the engine, without chipping the ECU? However you have tried an aftermarket chip which should eliminate this.

The last one would just not start, there is no reason for it to kick in, and if revs are shown on the rev counter in the fault condition then the ignition seems fine.

For theory 1 does this not happen above 2500rpm? If not then I'm thinking we are in slow down fuel cut terratory, and your throttle closed signal is stuck on.

Everything you suggest has been checked Tony, even the aftermarket chip. If you look at his signature line, it says "Volvo 940 19T, Charge cooled, Chipped." so he has tried replacing that chip with the original that was supplied when he bought the car. No change.

If you refer to that extremely long thread i linked to, you'll see the symptoms are exactly the same and the ECU was proven to be faulty after i had diagnosed it based on asking the OP of that thread to perform certain tests and checks via WhatsApp which of course didn't appear in the thread.

The MAF voltage on this one has been checked and appears satisfactory as have the inputs from the TPS - in other words the ECU is getting the right signals but still misbehaving, even with the OE chip installed. As i understand it now, the ECU is winging its way to https://www.ecutesting.com/ so i suspect we'll have an answer one way or t'other in a few days time.

[TonyS9]

Yeah I was just going over it again, summarising, but I couldn't see where the TPS had been checked other than disconnecting it. If it was stuck on by a shorted wire in the harness, then disconnecting wouldn't make any difference. However it could also be a blown chip transistor on the signal input also shorting it.