87' 3.5 efi cold engine rough running

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rojbarker

rojbarker

New Member
Posts
544
Location
Handover, 'Ampshire
Hi,

I've got an 87' 3.5 efi. In the mornings when started for the 1st time of the day, it runs rough for 2-3 minutes. If you give it any gas, it pops back and stutters. You can't drive it for a few minutes. It will run perfect if left alone idling. It idles alright but the revs do hunt a bit at first.

After a few minutes, it normally runs fine and gets progressively better.

I've done plugs, leads, dizzy, rotor and it's had a new coil so I guess it's on of the temp sensors or cold start injector. What should I check first?

I puchased a fuel temp sensor (on a whim) but not sure I really need it so haven't fitted that yet.
 
Hunting at idle is often a sign of the 4CU engine ecu packing up,so subbing over a known good one is a good idea if you can.The irritating thing with them is that they dont support self diagnosis live data etc,so you are stuck with checking values with a multimeter with info from the workshop manual.Disconnecting the cold start injector is a good idea too,as long as its not minus 40 outside.Coolant temp sensor issues would be second to look at,if the ECU is OK.
Dont forget that Rover V8's dont take kindly to cheap ignition components,so genuine or Lucas are the only way to go really.
 
I saw one on Ebay for not much money - might be worth having a spare..

I read somewhere else that the cold start injector only kicks in at some ridiculous temp! Wasn't sure if it was true or not.

I'll check them out - it's got to be something pretty easy to fix.

Thanks for the info!
 
Still haven't had chance to look into this (too busy!) but now the frosty weather is coming, it's getting worse!
Cold morning, I start the car, it runs for 3 seconds before revs drop too much and it dies. I have to do this 3 times and then it will idle low like it's going to die then picks itself up. I still have to leave it running for a few minutes to warm up before driving it.
Weird thing is it will idle perfectly in this state but as soon as you touch the throttle, it bogs down, pops back, misfires, and the engine pretty much quits until you let off.
 
As eightinavee said. It's the ECU under the drivers seat giving u probs. On my 3.5 (now departed) I had the same trouble with rough starting in the morning plus a lot of black smoke.
I took the ECU to the Lucas Repair Center near Lichfield and they repaired it while I waited, well it was 3 hours so I spent my waiting time in nearby Burton on Trent. I watched them test it before I left they put the ECU on a test rig and look at a scope and found lots of problems and probs about to happen soon, not only the one that was caursing the bad starting.

Anyway they replaced the bad componants on the ECU's PCB, the charge was £100 and well worth it as I found out when every thing was put back together the difference to the engine was dramatic better starting, more responsive etc etc.

Lucas won't be there now but I would recommend getting a refurb ECU from a reputable supplier and yes the cold start injector dosent work in our UK climate. The ECU takes care of cold starting by controlling the other 8 injectors to stay open longer allowing more fuel into the combuston chamber..

Regards
 
I'll see if I can find another ECU then - I tried to get one off ebay but for some reason, I can't find any on there now. Must be people stocking up for the cold weather!
Thanks for the info guys, I'd have ended up replacing everything BUT the ECU trying to sort it out.
 
rojbarker said:
ECU LRZ170 is that the Lucas part number I need? What PN's should I look out for? Mine doesn't have ABS if that makes a difference. And it's a manual.
Click to expand...

LR pt.no's. I still have my RR parts manual 1986 to 91 and the number in there is PRC7440 upto vin GA and RTC6497 vin GA onwards.

The LR number should be on small a Land Rover label stuck on the ECU, that is if u have the original ECU fitted.
These ECU's have always been hard to get hold of even when they were a stock item at LR dearlers thats why I went to Lucas, so if there are still any Lucas agents that's the place to try first u may have to leave your ECU with them.

Also I've been there as well.. replacing all other bits and bobs first.

Regards
 
discool said:
RTC6497 vin GA onwards.
Click to expand...

Which is the ECU for 3.9 hotwire FI-system without the cold start injector. Usually the rough running when cold-issues are related to the ECU being knackered. I fixed my old 3.5 EFI Rangie for a while by re-soldering the ECU myself. It worked fine for few months but then it started again and I was forced to get another ECU from Fleabay.
 
The guy with the Lucas Lord of Darkness ECU for sale said his came off an '87 efi so might as well go for that one. He who dares!

Thanks people, hopefulyl that will sort it out. The auction runs for another few days so will have to wait to see what happens. I've put up with it for this long, few more days won't hurt.
 
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