Fuxl Posted July 12, 2010 Share Posted July 12, 2010 Hello I'm completly new here, and I couldn't find anything helpful for me with the search engine. Maybe somebody has an idea whats the matter with my 3,5l V8. This board was recomended in a german board. They told me that here are some real technical cracks around! Now the story of the last weeks. its a little bit complicated, and my english isn't really good ( I beg your pardon) but hopefully you can follow it. some weeks ago, I transfered a body of an 1985 RRC (manual shifting) on the chassis and the engine of my 1987 RRC (automatic). No real problems here, after some modifications to the starter relay. The engine was running without problems! good idle, good power, no smoke Then a friend of me told me, that every ecu is a little bit different because of some resitors which got old and changed there resitance. and maybe the engine got more power with a other ecu. Doesn't sound so implausible to me, and I still had the second ECU from the other car. - So I Pulled the connector off of the ECU and connected the other one. - started the engine - It was running, but very rough, and I think not on all 8 zylinders - I turned the engine off - changed the ecu back - started again - and again, the engine was running, but very rough and only with a lot of throttle. after some tries, I found a broken wire in the connector. It was the PIN4. this is the +12V from the ignition-key Happy that I found the reason for the mess, I repaired the broken wire and checked all other wires as good as possible by seperating the whole cable harness. I didn't find anything else. - tried to start - same **** again! - engine doesn't run smooth In a german board I got the hind to: www.roversd1.nl There I found a good diagnose manual I checked everything step by step, and found 2 strange things: - Test 7 Voltage of airflow potentiometer There should be a voltage of 3.7V between Pin 6 and Pin 7 But I only got 0,6V By opening the airflap the voltage should drop to 1,6V, but in my case its increasing to 2,6V Ok, I thought I got the problem again, and changed the Airflow potentiometer to that one from the other engine. But after the change, its all the same! Same Voltage as before. I checked the resitance of the airflowmeter, and there everything is ok.........strange to me the second strange issue was the throttle potentiometer - Test 9: Voltage of throttle potentiometer There should be a reading of 0,325V between the yellow and the red wire. I checked this Voltage after the assembling of the new body, and it was correct. But now there are 4,2V at red and yellow when the throttle is closed. and the voltage drops by opening the throttle. This should be complety in the other direction. The Voltage should be low when closed, and increase by opening. A change or the potentiometer to a different one, didn't change anything! Ok, these are my problems. As far as I could check, all elektrical parts are OK. I excahanged: - the ECU - the airflowmeter - the throttle potentiometer - the resistor pack I checked: - the ground connection of the ECU - the ground connection of every black wire at the ECU - I checked every wire, I could identify, if it has an ground connection, and if it has a connection with the sensor on the other end. - I checked the main relay - I checked the fuel pump and the fuel pump relay - I exchanged the red thing which looks like a relay and is lockated under seat between the two relays So, thats the status! And I have absolutly no ****ing idea what I should do next! PLEASE!!! HELP!!! YOu are my last hope!! with friendly greetings Fuxl Quote Link to comment Share on other sites More sharing options...
NigelM Posted July 13, 2010 Share Posted July 13, 2010 Hi, My first reply so go easy. This is probablt to simple but have you checked the coolant temp sensor? They are known to fail and tell the ECU that it is -40C so the ECU puts too much fuel into the engine - it runs but very rough. Change the sensor (very cheap) or in your case check the wiring - it is easy to mix up the coolant temp sensor for the ECU and the temp guage sensors as they are next to each other. Good luck NigelM Quote Link to comment Share on other sites More sharing options...
Fuxl Posted July 13, 2010 Author Share Posted July 13, 2010 Hi, My first reply so go easy. This is probablt to simple but have you checked the coolant temp sensor? They are known to fail and tell the ECU that it is -40C so the ECU puts too much fuel into the engine - it runs but very rough. Change the sensor (very cheap) or in your case check the wiring - it is easy to mix up the coolant temp sensor for the ECU and the temp guage sensors as they are next to each other. Good luck NigelM Hello Thanks for the tip, but its not the sensor and its not the temperatur switch. I checked both, and they are OK. with friendly greetings roland Quote Link to comment Share on other sites More sharing options...
V8david Posted July 16, 2010 Share Posted July 16, 2010 Hi Roland I have no idea about electrics but was the battery disconnected when you were swapping ECU's? How long was it disconnected for? Have you tried disconnecting the battery for half an hour or so, letting the ECU 'reset' then re-connecting and trying again? Two more points: 1: Don't worry about your English, it's much better and clearer than most English people I know! 2: The 'friend' who suggested the ECU swap in the first place... When this is all fixed are you going take the spare ECU and insert it as far up his arse as your arm will reach?! Hope you get it fixed. Good luck. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted July 16, 2010 Share Posted July 16, 2010 Have you tried disconnecting the battery for half an hour or so, letting the ECU 'reset' then re-connecting and trying again? This makes no difference on Flapper (14CU) systems as they don't have a memory. Quote Link to comment Share on other sites More sharing options...
errol209 Posted July 16, 2010 Share Posted July 16, 2010 Hello This board was recomended in a german board. They told me that here are some real technical cracks around! my english isn't really good ( I beg your pardon) but hopefully you can follow it. Hallo gibt in Österreich! (Verzeihung mein Deutsch, Google hat es für mich) Yes, we are a bunch of cracks on here (I think you mean Verrückte, not Risse?) but we're harmless . Your English is plenty good enough, welcome to LR4x4.com! Quote Link to comment Share on other sites More sharing options...
V8david Posted July 16, 2010 Share Posted July 16, 2010 Have you tried disconnecting the battery for half an hour or so, letting the ECU 'reset' then re-connecting and trying again? This makes no difference on Flapper (14CU) systems as they don't have a memory. Told you I didn't have a fu#king clue. Sorry... Quote Link to comment Share on other sites More sharing options...
Fuxl Posted July 19, 2010 Author Share Posted July 19, 2010 hello again I was really fustrated with this very strange fault. My last conclusion is: - I broke the +12V Ignition wire by the first disonnection of the ECU - when I connected the spare ECU, this one got ****ed up because it was missing the +12V when I was starting the engine. - by reconnecting the old ECU, even this one got destroyed. so, I needed a good idea how to repair this mess of an engine! option 1: buy a new ECU and hope that this is really the fault. this means round about 200 bucks option 2: buy a new used engine. And I found a really good 3,9 liter mashine. this one would cost me 500€ including the complete hotwire sytem. because of an old german saying: Hubraum statt Wohnraum! (cubic capacity instead of living space), I will invest in the bigger, better, greater engine! And hope that it is done with it! Hallo gibt in Österreich! (Verzeihung mein Deutsch, Google hat es für mich)Yes, we are a bunch of cracks on here (I think you mean Verrückte, not Risse?) but we're harmless . Your English is plenty good enough, welcome to LR4x4.com! Hopefully my english is better than the german from Mr. google! "Crack" is in austria a very common word for people who are real experts. it's something like a "nerd", just a little bit cooler! thanks for attention! with friendly greetings Roland Quote Link to comment Share on other sites More sharing options...
Quagmire Posted July 26, 2010 Share Posted July 26, 2010 Roland, If you think that both your ECU's are now toast you could try Megasquirt? Check the sub forum for it here: Megasquirt forum Quote Link to comment Share on other sites More sharing options...
g&t Posted August 3, 2010 Share Posted August 3, 2010 Hi Fux1, I won't even try to reply in German I personally would'nt swap the 3.5 for a 3.9 as, having owned both, I did'nt find any significant difference in performance when I used the RR's over the same journeys & the later 94mm bore engines can develop block problems that will make your current troubles seem minor by comparison. Other than saying that the early EFI system is the most simple of all I'm afraid I can't add anything that has not already been posted by others, sorry Quote Link to comment Share on other sites More sharing options...
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