A work mate of mine is having grief with his N reg 620 Ti.
Once it has warmed up (but sometimes whilst it is still cold) it will miss fire badley once it gets above 3500RMP (just as it is coming onto boost). It pops and bangs and once you change up it runs on three until it has cleared the unburnt petrol so it is definatly and electrical cut out.
Things all ready changed
Actuator pipe
plugs, leads, dizzy cap and rotor arm
coil
He has even tried removing the outlet pipe from the turbo, but it still does it. It will do it consitantly evan in neutral.
The car is standard apart from a stainless exhaust. He has run out of ideas (and fast running out of cash!) but does have another mate with a Ti who he can swap most bits with to eliminate them as the cause.
Any ideas?
Edited by Webmaster on 24/03/2008 at 07:30
|
Sorry if this sounds like a plug for our profession but dont just chuck bits at it get a pro in to diagnose and fix the problem.
Andrew
Simplicate and add lightness!!
|
Hi,
Just to contradict Andrew, and not wanting to cause a fight, I had a very similar sounding problem on my 220 Turbo (same engine) and got a pro to diagnose it. New MAP sensor, they said, costing about £400 (as it's part of the ECU and can't be replaced seperately).
Actual problem was the rotor arm (which was new only a couple of months earlier), cost £8.
This was not the first time a "good" garage had "diagnosed" a sub £10 problem for a several hundred £ problem on this car. (Loose suspension bolt confused for two warn driveshafts. £700.) Some garages confuse diagnosis for replacing bits until it starts working. Unfortunately you don't know which ones until you've thrown your money away on a misdiagnosis.
Anyway my point is that new rotor arms can fail!
And get a second opinion before you open your wallet.
Good luck!
Mark
|
Thanks Mark
He tried the rotor arm off of a fully functioning Ti as part of the eariler swap the obvious, easy to do bits. Other areas that have been sugested is the actuator diafram might of split, but I wouldn't have thought it would give the ignition cut and/or massive over fueling. Someone else thought that it may be down to the cam postition sensor and advised that to test this you should disconect it. This just made it miss from cold above about 1500 RPM! (so it was quickly reconected!!).
This is a wierd one, as when it is cold you can rev it cleanly through to the redline (not that you should do this on a cold engine mind). Could a faulty temperature sensore be at fault and not turning off the 'choke'?
Thanks
Craig
|
Craig,
Is there any black smoke coming out the exhaust ?. You could try putting a piece of wire across the connector to the temperature sender. Then you will know whether it's running on the 'cold map' when it's playing up.
|
It doesn't smoke upto the point of missing, but I'm not sure if it smokes when it does. Where is the teperature sender on these things? and would running a wire between the 2 connectors make it think it has warmed up?
We have checked the pipe gpoing to the ECU for blockages and it was OK, I'll have to see if it has a pipe to the dizzy. I wouldn't have thought it would be down to to that mind, I had the vacume advance blanked off on my Mini when it was rolling roaded recently, but its something quick and easy to check.
Cheers
Craig
|
Not sure of the exact location on these engines but you could try looking in the thermostat or water outlet to radiator area. Easy to mix these up with the sender for the temp gauge so check the gauge hasn't gone to cold with the connector removed.
Senders are thermistors so resistance reduces with temperature. So bridging the connector across tells the ecu the engine is hot. Should give you a clue whether the motor is over fueling or it's an ignition problem.
Best of luck
|
|
|
|
Could be wrong but sounds like a timing fault ie advance retard
not working correctly.not certain about the car but may have a pipe connected to ecu from inlet manifold and some were from distributer if the pipe is cracked or split would cause it.
Just a thought but one to look at.
|
|
|
Check the pipe to the MAP sensor to see if it is blocked with oily gunge. make sure you remember which end of the pipe is which and check to see how far down the pipe the gunge has got. If it has got all the way to the sensor itself you will have to remove the ecu and clean out the sensor (carefully).
If it's popping and banging then you may have already destroyed the cat. Budget for a new one at the next MoT and prepare to rejoice in your good fortune if it survives.
|
|
He's allready done that and it was all clear. Hadn't thought about the damage to the cat, that'll chear him up!
|
I know. i only realised that after reading the thread a second time.
Unfortunately, it only takes a single misfire to destroy a cat in some circumstances. luckily, Rovers cats are more robust than many out there.
The temp sender is below the thermostat housing, front left of the engine as you look at it.
Does the engine get up to normal temp okay? the MEMS ecu only gives full temp fueling above 82C, so if you've fitted an 82C stat instead of the specified 88C (or if the stat is sticking open) you will have fueling problems.
Could be you've got a faulty injector - do you have access to a good-old-fashioned dwell meter (in a Gunsons Test-Tune for example)?
|
Are you sure it's over fueling? could it be fuel starvation? Blocked fuel filter or line? Leak in the fuel lines somewhere preventing full delivery? Dodgy elec connection to the pump allowing it to cut out?
I'm tempted to agree with Andrew in this case.
|
This is a wierd one, as when it is cold you can rev it cleanly through to the redline (not that you should do this on a cold engine mind). Could a faulty temperature sensore be at fault and not turning off the 'choke'?
Had another think and i reckon Cyd has the right idea suggesting fuel starvation. The fault Craig describes could be caused by the MAP sensor not increasing fueling with boost pressure. Running from cold the extra fuel enrichment would maybe be sufficient to stop the engine missfiring.
Would seem to be a good idea to try bridging out the temp sensor and if this doesn't make an improvement check and clean the map sensor and pipework.
|
I still think it's an overboost problem - the fuelling is cut back when overboosting is detected.
--
groups.msn.com/honestjohn - Pictures say a thousand words.....
Reply |
Report as offensive
| Link
|
|
|
|
i had the same problem.ive sust it .put a new thermoste in and put original spark plugs back in it should work it did for me
|
it should work it did for me
Hopefully after 4 yrs they've managed to sort the problem out!
|
Mind you, it would be nice if they could report back on their "progress"
--
groups.msn.com/honestjohn - Pictures say a thousand words.....
|
|
|
|
