Adaptives jumping around?
Discussion
Something is wrong with my cerb sp6. I have been trying different solutions to get it to run good during a couple of weeks now. The engine doesn´t deliver power as it should, around 4000 rpm it loses power completely. First I thought it was a ignition problem but now I think it is something with the fueling that is wrong. The feeling when I drive the car is like it isn´t getting enough fuel.
I have checked:
- Compression, all cylinders between 12.7 and 13.0 kg/cm2.
- All valve clearenses are within the tolerances.
- Fuel pressure, 3.6 bar and drops to 3.4 bar for 0.1 - 0.2 secs at hard acceleration.
- Running the car with open tank to eliminate any problems with tank ventilation.
- Throttle balance is OK.
- There are no fault codes in the diagnostics.
- Leaks on the throttles by spraying ether around the connection between the throttles and the head.
- Voltage on the fuel pump 12.7V at the same time the fuse box (measured on the fuse for the fuelpump) has 14.1V and the battery 14.4V. This looks as a big voltage drop to me, so tomorrow I will try to check where the problem is.
- Routing of the HT leads and sensor wires in the engine bay, they are about 3-4 inches or more apart.
- The lambdas work as they should when looking at the curves with the diagnostics, mostly on 0 volts and do spikes up to 1-1.2 volts about every 0.7 to 1 second (On full throttle the lambda values are steady on 1.3 to 1.4 volts).
- The throttlepots give a nice steady reading over the whole range.
- The ECU connector is dry and doesn´t have any signs of corrosion, there are no signs of corrosion in any connectors on the engine.
Since I first thought it was an ignition problem I have put in new:
- HT leads
- Spark plugs
- Ignition coil
When I started to check the fueling I also changed the fuelfilter. All cylinders show the same problem so I think the injectors work as they should.
Tonight when I was trying to find out what could be wrong, I thought that I should balance the throttles once more. I had the diagnostics hooked up at the same time and I saw something that I do not know if it is OK or not, the adaptives are moving up and down about 5% rather rapid when the car is idling. I do not remember if this is normal or not so I hope some of You could help me out. I would also appreciate if somebody could post or send me a xxxx.RTL file of recording from the dignostics during hard acceleration on a car that works OK.
Any ideas what more to look for to solve the problem is appreciated.
I have checked:
- Compression, all cylinders between 12.7 and 13.0 kg/cm2.
- All valve clearenses are within the tolerances.
- Fuel pressure, 3.6 bar and drops to 3.4 bar for 0.1 - 0.2 secs at hard acceleration.
- Running the car with open tank to eliminate any problems with tank ventilation.
- Throttle balance is OK.
- There are no fault codes in the diagnostics.
- Leaks on the throttles by spraying ether around the connection between the throttles and the head.
- Voltage on the fuel pump 12.7V at the same time the fuse box (measured on the fuse for the fuelpump) has 14.1V and the battery 14.4V. This looks as a big voltage drop to me, so tomorrow I will try to check where the problem is.
- Routing of the HT leads and sensor wires in the engine bay, they are about 3-4 inches or more apart.
- The lambdas work as they should when looking at the curves with the diagnostics, mostly on 0 volts and do spikes up to 1-1.2 volts about every 0.7 to 1 second (On full throttle the lambda values are steady on 1.3 to 1.4 volts).
- The throttlepots give a nice steady reading over the whole range.
- The ECU connector is dry and doesn´t have any signs of corrosion, there are no signs of corrosion in any connectors on the engine.
Since I first thought it was an ignition problem I have put in new:
- HT leads
- Spark plugs
- Ignition coil
When I started to check the fueling I also changed the fuelfilter. All cylinders show the same problem so I think the injectors work as they should.
Tonight when I was trying to find out what could be wrong, I thought that I should balance the throttles once more. I had the diagnostics hooked up at the same time and I saw something that I do not know if it is OK or not, the adaptives are moving up and down about 5% rather rapid when the car is idling. I do not remember if this is normal or not so I hope some of You could help me out. I would also appreciate if somebody could post or send me a xxxx.RTL file of recording from the dignostics during hard acceleration on a car that works OK.
Any ideas what more to look for to solve the problem is appreciated.
You have tried most of the things I would have suggested...
Could you try a quick drive either wihout an air filter of without the airbox.. just to make sure there is no blockages.
Try early in the morning before the air gets too warm..without an air filter you'll suck some warm engine bay air..
Could you try a quick drive either wihout an air filter of without the airbox.. just to make sure there is no blockages.
Try early in the morning before the air gets too warm..without an air filter you'll suck some warm engine bay air..
I have tried with and without airbox and it doesn´t make any difference.
I have also changed the wire between the fusebox and the inertia switch so the voltage on the fuelpump is now 13.8 volts with the engine running. The car picks up a little better after that I changed the wire and the problems with loosing power has now moved up in the rpm register. I do not know if it is the fuelpump itself that isn´t working as it should or if there is something disturbing the fuel feed that I haven´t thought about.
How can I test the fuelpump? Pressure seems ok, but how do I check the flow?
Any other ideas what to look for?
Can a lambda sensor cause troubles even if it looks as it works on the diagnostics?
I have also changed the wire between the fusebox and the inertia switch so the voltage on the fuelpump is now 13.8 volts with the engine running. The car picks up a little better after that I changed the wire and the problems with loosing power has now moved up in the rpm register. I do not know if it is the fuelpump itself that isn´t working as it should or if there is something disturbing the fuel feed that I haven´t thought about.
How can I test the fuelpump? Pressure seems ok, but how do I check the flow?
Any other ideas what to look for?
Can a lambda sensor cause troubles even if it looks as it works on the diagnostics?
Have done most things i would have suggested too.
When you say lose power, what exactly happens?
Are you decatted?
I had a problem last year where around 5000rpm under hard acceleration, i would lose power - it was like hitting the rev limiter or some horrendous misfire. it was worn throttle bodies. Worn throttle pots can also cause the same issue.
How many miles has your car done and how old is it? I would suggest all pre 2004 car will be prone to this after around 25-30k miles.
Other suggestions - fuel filter? Spark plugs? (Have you done the 'tie wrap' test on each cylinder?)
I wouldnt think that fuel pump voltage is a problem?? most TVR power supoplies run the length of the car with noticable voltage losses, its one of the reasons for some people having hot start problems - i.e. voltage at the starter terminals.
When you say lose power, what exactly happens?
Are you decatted?
I had a problem last year where around 5000rpm under hard acceleration, i would lose power - it was like hitting the rev limiter or some horrendous misfire. it was worn throttle bodies. Worn throttle pots can also cause the same issue.
How many miles has your car done and how old is it? I would suggest all pre 2004 car will be prone to this after around 25-30k miles.
Other suggestions - fuel filter? Spark plugs? (Have you done the 'tie wrap' test on each cylinder?)
I wouldnt think that fuel pump voltage is a problem?? most TVR power supoplies run the length of the car with noticable voltage losses, its one of the reasons for some people having hot start problems - i.e. voltage at the starter terminals.
The car is a 1999 Cerb SP6, the engine was rebuilt by the factory late 2005 and the car has done about 10k since then. It has done a total of 32k. Last year I had the throttles rebuilt with bearings by Jason at STR8SIX. The car is not decatted.
Fuel filter and spark plugs are new, no change.
The engine goes up to the revlimiter at about 7000rpm without any signs of problems if I push the throttle down slowly in first gear, in second gear it starts to lose power around 5500 rpm.
If I hit throttle down quick in first gera it also hesitates at about 5500 rpm, in higher gears does the car feel is it picks up a lot less then it has done.
I have also had the revlimiter feeling in my car just after I bought it in the end of 2005, the problem at that time was that the garage that had put the engine back in after the rebuild of the engine had tie wrapped the HT leads together with the rest of the engine loom.
I have had the computer with me to record what happens in the engine but I am not sure of if the things I see is normal or not, such as that the timing goes from around 50 to 30 when I hit the throttle. The lambdas show 1.3 to 1.4 when hitting the throttle, is that normal? I have also seen something that made me think about fueling problems, the opening times for the injectors are higher when the adaptives are working than when the thottles open up and the closed loop control is switched off. The opening times drop with about 0.5 - 0.8ms at that point.
Fuel filter and spark plugs are new, no change.
The engine goes up to the revlimiter at about 7000rpm without any signs of problems if I push the throttle down slowly in first gear, in second gear it starts to lose power around 5500 rpm.
If I hit throttle down quick in first gera it also hesitates at about 5500 rpm, in higher gears does the car feel is it picks up a lot less then it has done.
I have also had the revlimiter feeling in my car just after I bought it in the end of 2005, the problem at that time was that the garage that had put the engine back in after the rebuild of the engine had tie wrapped the HT leads together with the rest of the engine loom.
I have had the computer with me to record what happens in the engine but I am not sure of if the things I see is normal or not, such as that the timing goes from around 50 to 30 when I hit the throttle. The lambdas show 1.3 to 1.4 when hitting the throttle, is that normal? I have also seen something that made me think about fueling problems, the opening times for the injectors are higher when the adaptives are working than when the thottles open up and the closed loop control is switched off. The opening times drop with about 0.5 - 0.8ms at that point.
Edited by Peppe on Wednesday 28th September 19:09
Edited by Peppe on Wednesday 28th September 19:10
Have also had that thought, but hopefully not. My engine is one of the more rare first version of SP6:s with the starter on top of the bellhouse and the manifolds and cats made in one piece for each bank, no clamp that makes it possible to take the cat off from the manifold. This makes it alot more difficult to check the cats, but if i can´t find another solution there will be newer style manifolds and cats during the winter.
Gassing Station | Speed Six Engine | Top of Page | What's New | My Stuff