Over fuelling and misfire... Place your bets
Discussion
I've had my Chim for 16 years and it's been very reliable with only the odd glitch mostly down to bad new parts.
I've taken this car to Italy and Southern Germany (twice) and it's been great.
Due to pandemic and circumstances I've only managed a couple of thousand miles over the last 3 years of which 300 was last year.
On it's first longer run this year I started to get a misfire on the ay to an event and was hoping it would clear but on the way back it git worse to the point it was shunting so I pulled in and played with the HT leads and found the king lead might have been a bit loose (It wasn't hanging out but wasn't fully home either) into the coil so pushed it fully home and it behaved.
However, what I'd begun to notice was the the sell of unburnt fuel whenever I reversed. Now I know they over fuel on startup but it seemed like it was continuing when running. A friend followed me last night and said it was "blowing crap out the exhaust when you hoof it) . Looking back at my app that records fuel usage it seems it was using a lot of fuel (averaging15 mpg instead of 22) for the last year but I'd put that down to multiple start ups to do shorter runs but looking back over previous data 15 seems low even for when I'd been doing similar in the past.
The ignition system is original spec.
Today I started to investigate and found the following :
One of the LT leads was a bit loose: Tightened
The Stepper motor was quite loose (Could have undone it by hand): Removed, cleaned and refitted with PTFE tape
7 of the plugs were black (turned off last night after I came back from a spirited drive but not restarted today) but number 6 cyl is grey:
Any thoughts from the collective of the cause for the over fuelling, the one grey plug and any other things I should be checking.
The dizzy cap and rotor arm are known good and the leads are a couple of years old from Powerspark.
Thanks for any thoughts and advice.
I've taken this car to Italy and Southern Germany (twice) and it's been great.
Due to pandemic and circumstances I've only managed a couple of thousand miles over the last 3 years of which 300 was last year.
On it's first longer run this year I started to get a misfire on the ay to an event and was hoping it would clear but on the way back it git worse to the point it was shunting so I pulled in and played with the HT leads and found the king lead might have been a bit loose (It wasn't hanging out but wasn't fully home either) into the coil so pushed it fully home and it behaved.
However, what I'd begun to notice was the the sell of unburnt fuel whenever I reversed. Now I know they over fuel on startup but it seemed like it was continuing when running. A friend followed me last night and said it was "blowing crap out the exhaust when you hoof it) . Looking back at my app that records fuel usage it seems it was using a lot of fuel (averaging15 mpg instead of 22) for the last year but I'd put that down to multiple start ups to do shorter runs but looking back over previous data 15 seems low even for when I'd been doing similar in the past.
The ignition system is original spec.
Today I started to investigate and found the following :
One of the LT leads was a bit loose: Tightened
The Stepper motor was quite loose (Could have undone it by hand): Removed, cleaned and refitted with PTFE tape
7 of the plugs were black (turned off last night after I came back from a spirited drive but not restarted today) but number 6 cyl is grey:
Any thoughts from the collective of the cause for the over fuelling, the one grey plug and any other things I should be checking.
The dizzy cap and rotor arm are known good and the leads are a couple of years old from Powerspark.
Thanks for any thoughts and advice.
eric450 said:
When mine was intermittently running rough and massively over fuelling it turned out to be knackered lambda sensors.
This was confirmed by using rover gauge.
Had them both changed and it has been fine since (about three years)
Worth a look.
Cheers .... Eric
To OP. The clue here is "confirmed using RoverGaige" get RG and give it a go before you proceed scatter gun replacing things in hope it fixes it. Common stuff is engine temp sensor, maf sensor and lambdas. All of which can be seen woth RGThis was confirmed by using rover gauge.
Had them both changed and it has been fine since (about three years)
Worth a look.
Cheers .... Eric
second post here click on. the v8 register.net link and have a look at page 7 for a rough guide of values to expect.
https://www.pistonheads.com/gassing/topic.asp?t=18...
https://www.pistonheads.com/gassing/topic.asp?t=18...
Edited by Belle427 on Thursday 8th June 18:40
Tyre Tread said:
I have Rovergauge
Will need some help with knowing what values to look for.
start .Will need some help with knowing what values to look for.
I can help with that.
Over the last few years I've been analysising "poor running" chims and griffs using statistical techniques. With that said I can tell from data which sensors are not only working but working correctly and normally in comparison to other good and bad running cars.
What I need you to do (to get the data I need to make the comparisons is as follows.
1. Connect the cable to the car and RoverGauge
2. Set up the following parameters as follows. MAF Direct, Throttle=Absolute, TRIM=Short
4. In SETTINGS - OPTIONS select these setting.
5. Start logging data by clicking on Start Log button.
6. Start the car from cold and allow the engine to warm up at idle whilst continuing to capture data.
7. Allow the car to idle for approx 20 to 30 minutes.
8. Click on Stop Log button.
9. Switch the 'Lambda trim' to long and note what number is shown for both the odd and even Long Term Trim values.
10. Send me the data and I will analyse it for you.
Thank you Frank The offer of help is appreciated.
Right, I have connected Rovergauge and the light flashes orange in the lead and the Communications light is red. Trying to operate the pump or air valve through Rovergauge brings no response.
Tried starting for just a second but no activity showing.
I'm obviously doing something wrong, but what?
I have selected the items from the menu you posted but mine doesn't have the last item showing "Fuel Map Values"
Right, I have connected Rovergauge and the light flashes orange in the lead and the Communications light is red. Trying to operate the pump or air valve through Rovergauge brings no response.
Tried starting for just a second but no activity showing.
I'm obviously doing something wrong, but what?
I have selected the items from the menu you posted but mine doesn't have the last item showing "Fuel Map Values"
A mate of mine had a similar issue....the cause was really hard for him to pinpoint.
Nearly every time he gave it hard acceleration, the exhaust was very black and stank of unburnt fuel.
I followed him to Lloyds in Warminster. With the car on their hub dyno and RoverGauge running, they soon deduced that the ignition timing was not changing with revs. A check of the vacuum capsule revealed a split diaphragm. New capsule fitted and car ran perfectly.
Guess this doesn't explain (fully?) the 'normal' colour on No.8 plug on OP's car.
Nick
Nearly every time he gave it hard acceleration, the exhaust was very black and stank of unburnt fuel.
I followed him to Lloyds in Warminster. With the car on their hub dyno and RoverGauge running, they soon deduced that the ignition timing was not changing with revs. A check of the vacuum capsule revealed a split diaphragm. New capsule fitted and car ran perfectly.
Guess this doesn't explain (fully?) the 'normal' colour on No.8 plug on OP's car.
Nick
nawarne said:
A mate of mine had a similar issue....the cause was really hard for him to pinpoint.
Nearly every time he gave it hard acceleration, the exhaust was very black and stank of unburnt fuel.
I followed him to Lloyds in Warminster. With the car on their hub dyno and RoverGauge running, they soon deduced that the ignition timing was not changing with revs. A check of the vacuum capsule revealed a split diaphragm. New capsule fitted and car ran perfectly.
Guess this doesn't explain (fully?) the 'normal' colour on No.8 plug on OP's car.
Nick
I did "the suck test" yesterday (Can you tell I'm old school?) and it passed with flying colours but thanks for your suggestion.Nearly every time he gave it hard acceleration, the exhaust was very black and stank of unburnt fuel.
I followed him to Lloyds in Warminster. With the car on their hub dyno and RoverGauge running, they soon deduced that the ignition timing was not changing with revs. A check of the vacuum capsule revealed a split diaphragm. New capsule fitted and car ran perfectly.
Guess this doesn't explain (fully?) the 'normal' colour on No.8 plug on OP's car.
Nick
Boosted LS1 said:
Did you refit the plug leads correctly?
I hadn't changed them for quite some time and it runs perfectly other than rich and one plug weaker then the others. The firing sequence is etched in my brain as I have 3 RV8 engines cars but I will check anyway just for peace of mind when I go in the garage later today
Ok folks the data is in and it is quite telling.
MAF is not responding at all as its at zero constantly.
Idle control valve is also sat at Zero, ie shut, suggesting vacuum leak and base idle not correctly set.
Lambda's are working but not able to control the mixture.
Engine temp sensor is good and cooling system is controlling engine temperature perfectly.
Suggest first port of call is to fully investigate and fix the non responsive MAF
MAF is not responding at all as its at zero constantly.
Idle control valve is also sat at Zero, ie shut, suggesting vacuum leak and base idle not correctly set.
Lambda's are working but not able to control the mixture.
Engine temp sensor is good and cooling system is controlling engine temperature perfectly.
Suggest first port of call is to fully investigate and fix the non responsive MAF
blaze_away said:
Agreed. Will be chatting with op shortly
MAF is a good start point. Looking at the Main Voltage chart the voltage level from 1000 onwards is pulsing as if the alternator is dropping in and out, but it is so uniform. Wierd.If the MAF is at fault there should be an error code set? If this happens the ECU cannot calculate the load index row value, instead it uses throttle position and engine coolant temp values to adjust fuelling. For how long has the car been running like this?
Edited by davep on Saturday 10th June 09:13
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