poor running, misfire?
Discussion
It's probably glad of any petrol in the tank! As it stopped raining I just subbed in my spare ECU and then AFM, but no difference, so it's looking likely to be a poor connection. My spare AFM has a breakout of all the connections so I'll use that with honest John the second's pdf's to check the various voltages and connecting wires. This is a pain after busting a gut to get the second bearing sorted out (more on that anon).
This all sounds familiar to the problem I had earlier this year. Replaced everything, spent a fortune and hours under the bonnet with an Avo and scope. My problem turned out to be the Fuel computer (ECU)and was easily identified by borrowing and testing from Lee's parts pool on this forum. Got mine replaced (exchange) from BBA in Gillingham http://www.bba-reman.com/ very reasonably and quick jobs a good en!
Good luck - Chris
Good luck - Chris
Well as I said I just tried spare ECU and AFM - same problems. I had a poke around this morning in the drizzle and debugged:
1. Coolant temp sensor wiring is all good
2. AFM wiring good
3. TPS wiring is good.
That's most of the sensors. I suppose it could be genuinely too much fuel pressure but I haven't got a pressure gauge handy. I'll take a look at the injector mark/space ratio with the oscilloscope, that should be fairly narrow on tickover, and will narrow down what's going on.
1. Coolant temp sensor wiring is all good
2. AFM wiring good
3. TPS wiring is good.
That's most of the sensors. I suppose it could be genuinely too much fuel pressure but I haven't got a pressure gauge handy. I'll take a look at the injector mark/space ratio with the oscilloscope, that should be fairly narrow on tickover, and will narrow down what's going on.
When I first got the 400 in 2006 it had a similar problem, and that turned out to be timing, plus I think possibly rotor arm. Some wear in distributor shaft was also mentioned. Only cost 75 quid for complete diagnosis and set-up including parts, and that was a pukka racing place .
I always go to someone with a Crypton type machine before replacing stuff.
I always go to someone with a Crypton type machine before replacing stuff.
When I last had the car at RTracing (for clutch)3 months ago, upon picking her up she wouldn't start or run properly at all...over-fuelling. She'd been ok before.
Richard Thorpe thought some of the (brittle) EFI wiring had been damaged internally during the engine removal, and so it was. He kept the car back and fixed it. Can't remember the exact bit (he might remember). Back to normal running now. Worth a close look.
Richard Thorpe thought some of the (brittle) EFI wiring had been damaged internally during the engine removal, and so it was. He kept the car back and fixed it. Can't remember the exact bit (he might remember). Back to normal running now. Worth a close look.
Well I was out there this afternoon and the saga continues. I couldn't even start if this time plus my battery charger hadn't charged up the battery - grrr. So I spent a good couple of hours getting it going - had to change the plugs in the end. I checked the fuel pressure at 2.7 bar seems OK.
Anyway the car was up to its usual tricks, then suddenly cleared itself and ran normally. I got readings from all the ECU multiplug conections in ignition on, running rich and running ok scenarios.
There are a few differences, but not that many.
Pin 6 is 1.2V stopped / 1.4V running rich / 0.2-0.9V running good.
Pin 12 is 3.6V / 2.2V / 2.5V
(pin 12 is an output for setting up the mixture, apparently)
I wonder if Pin 6 - the AFM reference voltage - is being compromised by an intermittant short or something like that? I've been wiggling around the various wiring harnesses but couldn't make it go wrong. The trouble is that I don't know why the condition is coming and going, yet! Investigations continue.
Anyway the car was up to its usual tricks, then suddenly cleared itself and ran normally. I got readings from all the ECU multiplug conections in ignition on, running rich and running ok scenarios.
There are a few differences, but not that many.
Pin 6 is 1.2V stopped / 1.4V running rich / 0.2-0.9V running good.
Pin 12 is 3.6V / 2.2V / 2.5V
(pin 12 is an output for setting up the mixture, apparently)
I wonder if Pin 6 - the AFM reference voltage - is being compromised by an intermittant short or something like that? I've been wiggling around the various wiring harnesses but couldn't make it go wrong. The trouble is that I don't know why the condition is coming and going, yet! Investigations continue.
Yeah it's a flapper. I was looking at all my voltage measurements last night in detail (and in the warm!) and it looks like the AFM has some peculiarly high voltages - around 12V - on pins 8 and 9 of the ECU, so that's where I'm going to check this morning. It might be a short in the wiring.
I'd be interested in some definitive figures for the monitor port - pins 12 and 26 of the ECU - it looks like a useful diagnostic tool - potentially.
I'd be interested in some definitive figures for the monitor port - pins 12 and 26 of the ECU - it looks like a useful diagnostic tool - potentially.
D'oh! D'oh and triple D'oh!
When reading the ECU multiplug pinout I got the sense reversed, so all my readings are in the "mirror image" on the plug, so to speak. I even changed the little diagram I had made on my 'diagnostic ECU' yesterday - now I've changed it back again!
So the real readings with corrected pins for above are:
Pin 13 is 1.2V stopped / 1.4V running rich / 0.2-0.9V running good.
Pin 7 is 3.6V / 2.2V / 2.5V
Pin 13 is the coolant temp sensor input - so that's the culprit, then. I had previously checked the wiring, so time to fit the new one which arrived the other day (although it's intermotor - yuk!). Pin 7 is the AFM wiper - under the rough running it's taking in less air, so that's normal then.
I had previously checked the coolant temp sensor readings and they seemed OK under various engine temps, but perhaps it behaves differently when connected to the ECU and a fault is showing up.
When reading the ECU multiplug pinout I got the sense reversed, so all my readings are in the "mirror image" on the plug, so to speak. I even changed the little diagram I had made on my 'diagnostic ECU' yesterday - now I've changed it back again!
So the real readings with corrected pins for above are:
Pin 13 is 1.2V stopped / 1.4V running rich / 0.2-0.9V running good.
Pin 7 is 3.6V / 2.2V / 2.5V
Pin 13 is the coolant temp sensor input - so that's the culprit, then. I had previously checked the wiring, so time to fit the new one which arrived the other day (although it's intermotor - yuk!). Pin 7 is the AFM wiper - under the rough running it's taking in less air, so that's normal then.
I had previously checked the coolant temp sensor readings and they seemed OK under various engine temps, but perhaps it behaves differently when connected to the ECU and a fault is showing up.
adam quantrill said:
looks far too rich
Adam, theres got to be more to it than that? No reference to condition of plugs, plug colour, sooty deposits inside tailpipe, smell of fuel at engine bay or that nasty smell of unburned fuel in the exhaust?Lets assume it IS running rich because some of the above check out, then which components might cause the system to do that? Taking no account of what you have already done/tried, this is the full list.
o Temp Sensor/associated wiring with erroneous resistance readings.
o Throttle Pot/ditto above, inducing random erroneous firing of acceleration/full load enrichment circuits.
o AFM maladjusted or pooped.
o CSI pooped/leaking due to filter problem leading to crud in the fuel rail
o Injectors - one or more, leaking due to - ditto above - or being pooped.
o TT switch - is NOT part of the CSI issue in this particular case as it function on during cranking.
o FPR pooped with a damaged membrane OR there is a (small) split in the vacuum control pipe from plenum thus never allowing the FPR to fully reduce pressure to 26 psi when needed.
o ECU - possible, but not so likely as a fault in the output circuits usually stops the engine dead with gross overfuelling.
Like I said none of the above takes into account what you may have already tried. Its just a list and all the likely solutions can be found in your fav ref archive.
Next, dont overlook possibility that intermittant ignition fault may cause misfiring and therefor incomplete fuel combustion so the next good spark ignites a richer mixture in any particular chamber making it seem like there is an overfuelling issue, particularly plug colour.
Look for intermittant spark tracking (on a dark night), a faulty plug, plug gaps too wide, weak spark generation, damaged suppression condenser, damaged spark plug lead, what have you? WD40 everything and checkout the plugs and leads. Hope this help? Cheers.
Thanks for that! I've been through most of it but will take a look at some of the less obvious things.
At the moment the TT switch is disconnected and the wires isolated, so it should be out of the equation.
The overfuelling seems to come and go, one minute it's running really well, the next it kicks into this overfuelling mode.
One experiment seemed very decisive - when in overfuelling mode I pulled the fuel relay. Almost immediately the engine started running properly. Jabbed it back in and it ran rich again. So this points to either overpressure fuel or the ECU holding the injectors open too long. Certainly not ignition.
Another thing I checked was that the fuel return line is OK - I took the line off and ran the excess into a container. There was a healthy flow, plus blowing down the line showed that it's reasonably clear. Plus the engine still ran in overfuelling mode. I'll see if I have another FPR handy - you never know, maybe it's a litle clogged or otherwise knackered? The pressure gauge I borrowed is peak hold so isn't massively useful unless I take off the valve.
The plugs I took out yesterday were very sooty indeed.
The TPS is - if anything - adjusted too low - it's on about 0.04V.
At the moment the TT switch is disconnected and the wires isolated, so it should be out of the equation.
The overfuelling seems to come and go, one minute it's running really well, the next it kicks into this overfuelling mode.
One experiment seemed very decisive - when in overfuelling mode I pulled the fuel relay. Almost immediately the engine started running properly. Jabbed it back in and it ran rich again. So this points to either overpressure fuel or the ECU holding the injectors open too long. Certainly not ignition.
Another thing I checked was that the fuel return line is OK - I took the line off and ran the excess into a container. There was a healthy flow, plus blowing down the line showed that it's reasonably clear. Plus the engine still ran in overfuelling mode. I'll see if I have another FPR handy - you never know, maybe it's a litle clogged or otherwise knackered? The pressure gauge I borrowed is peak hold so isn't massively useful unless I take off the valve.
The plugs I took out yesterday were very sooty indeed.
The TPS is - if anything - adjusted too low - it's on about 0.04V.
Well it's still a bit shafted. More symptoms include:
- seems to start OK then kick into overfuelling mode later.
- TPS is a bit knackered - probably work out at the low end, can't adjust it to the proper idle threshold. Also the wiper seems to be picking up noise.
- fuel pressure is fine, 26psi on idle, 2.75 bar on WOT (or vacuum disconnected), vacuum to FPR is working fine.
- can idle with NO FUEL PUMP CONNECTED! I wonder if one/more injectors are stuck on?
- injectors are getting 10ms on-time at idle. This doesn't really rise much on blipping the throttle. Dunno what the proper figure should be though.
- seems to start OK then kick into overfuelling mode later.
- TPS is a bit knackered - probably work out at the low end, can't adjust it to the proper idle threshold. Also the wiper seems to be picking up noise.
- fuel pressure is fine, 26psi on idle, 2.75 bar on WOT (or vacuum disconnected), vacuum to FPR is working fine.
- can idle with NO FUEL PUMP CONNECTED! I wonder if one/more injectors are stuck on?
- injectors are getting 10ms on-time at idle. This doesn't really rise much on blipping the throttle. Dunno what the proper figure should be though.
If you run the pump for a couple of seconds with the engine stopped to bring the fuel rail up to pressure, does it hold pressure? If not, leaking injectors might be one explanation. Hard to believe more than one would go at the same time though, so doesn't feel very likely but it's always a possibility.
The fact it would idle without the pump running is a little unusual, mine would definitely try to idle with the pump off but not quite make it. Perhaps the cam on yours is giving slightly more vacuum and just making the difference.
Do you have a recirculating crank case breather? If so disconnect that and see if it makes any difference. Hopefully not, but if for some reason you're getting combustible gasses blown out that might contribute to the rich running.
The fact it would idle without the pump running is a little unusual, mine would definitely try to idle with the pump off but not quite make it. Perhaps the cam on yours is giving slightly more vacuum and just making the difference.
Do you have a recirculating crank case breather? If so disconnect that and see if it makes any difference. Hopefully not, but if for some reason you're getting combustible gasses blown out that might contribute to the rich running.
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