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700/900 Series General Forum for the Volvo 740, 760, 780, 940, 960 & S/V90 cars |
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New problem. Engine stumblesViews : 1977 Replies : 55Users Viewing This Thread : |
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Jan 16th, 2020, 14:29 | #41 | |
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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.
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Jan 16th, 2020, 15:47 | #42 | |
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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 |
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Jan 16th, 2020, 16:28 | #43 |
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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
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Volvo 940 19T, Charge cooled, Chipped. |
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Jan 16th, 2020, 16:34 | #44 |
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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
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Volvo 940 19T, Charge cooled, Chipped. |
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Jan 16th, 2020, 17:18 | #45 | |
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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.
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Jan 17th, 2020, 11:27 | #46 |
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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!
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Jan 17th, 2020, 11:48 | #47 | |
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https://www.atpelectronics.co.uk/ Fingers crossed they show up a fault and the repair is a sensible price!
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Cheers Dave Next Door to Top-Gun with a Honda CR-V & S Type Jag Volvo gone but not forgotten........ Last edited by Laird Scooby; Jan 17th, 2020 at 11:49. Reason: Adding link |
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Jan 18th, 2020, 11:29 | #48 | |
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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. Last edited by TonyS9; Jan 18th, 2020 at 11:45. |
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Jan 18th, 2020, 11:58 | #49 | |
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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.
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Jan 18th, 2020, 12:10 | #50 |
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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.
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