Some more S3 diagnostic questions - help!
Discussion
OK, after spending all evening trying to diagnose a problem of general lack in power (until reaching about 4000rpm) and running a little rich, I have a few questions:
Firstly, just out of interest, I've noticed a small cylindrical in-line unit on one of the vacuum pipes running from the plenum chamber. What's this for?!
I also have a 'spare' connector floating around which I guess should really be connected to something?! There are 2 connectors close together one of which goes to a sensor unit on the bulkhead which is connected to a vacuum pipe from the fuel regulator (I assume this tells the ECU about fuel supply based on the vacuum), but would be interested to know more!, the other isn't connected to anything as I've said which seems strange (perhaps an optional extra shich mine wasn't fitted with?!)
Finally, for the general lack of power, I've checked the timing, compression & everything else I can think of all which loooks good. I'm thinking perhaps this is an ECU or MAP sensor problem. Any thoughts???
Cheers,
Rob
Firstly, just out of interest, I've noticed a small cylindrical in-line unit on one of the vacuum pipes running from the plenum chamber. What's this for?!
I also have a 'spare' connector floating around which I guess should really be connected to something?! There are 2 connectors close together one of which goes to a sensor unit on the bulkhead which is connected to a vacuum pipe from the fuel regulator (I assume this tells the ECU about fuel supply based on the vacuum), but would be interested to know more!, the other isn't connected to anything as I've said which seems strange (perhaps an optional extra shich mine wasn't fitted with?!)
Finally, for the general lack of power, I've checked the timing, compression & everything else I can think of all which loooks good. I'm thinking perhaps this is an ECU or MAP sensor problem. Any thoughts???
Cheers,
Rob
Hey guys. Please!!!
I've now learnt that the gadget on the bulkhead is a MAP sensor & checked the vacuum tube ot it is OK. It doesn't like it when you disconnect the vacuum so I assume it's working OK.
The same vacuum pipe then goes to what I assume is a fuel regulator (looks a little like an vacuum advance). restricting the vacuum to this has a little difference, but not much. How much difference should this make?
It has been suggested that I try cleaning the injectors, but I don't think this would have such a drastic reduction in performance do you?
???
Rob
I've now learnt that the gadget on the bulkhead is a MAP sensor & checked the vacuum tube ot it is OK. It doesn't like it when you disconnect the vacuum so I assume it's working OK.
The same vacuum pipe then goes to what I assume is a fuel regulator (looks a little like an vacuum advance). restricting the vacuum to this has a little difference, but not much. How much difference should this make?
It has been suggested that I try cleaning the injectors, but I don't think this would have such a drastic reduction in performance do you?
???
Rob
robculm said:
Hey guys. Please!!!
I've now learnt that the gadget on the bulkhead is a MAP sensor & checked the vacuum tube ot it is OK. It doesn't like it when you disconnect the vacuum so I assume it's working OK.
The same vacuum pipe then goes to what I assume is a fuel regulator (looks a little like an vacuum advance). restricting the vacuum to this has a little difference, but not much. How much difference should this make?
It has been suggested that I try cleaning the injectors, but I don't think this would have such a drastic reduction in performance do you?
???
Rob
I've now learnt that the gadget on the bulkhead is a MAP sensor & checked the vacuum tube ot it is OK. It doesn't like it when you disconnect the vacuum so I assume it's working OK.
The same vacuum pipe then goes to what I assume is a fuel regulator (looks a little like an vacuum advance). restricting the vacuum to this has a little difference, but not much. How much difference should this make?
It has been suggested that I try cleaning the injectors, but I don't think this would have such a drastic reduction in performance do you?
???
Rob
I am sure someone will give you the tech info you need , but why not get yourself a copy of 'The Bible' the 'S' series manual by Steve Heath it tells you everything you need to know about running and maintaining these superb cars , it is available thro' the TVR car club , or do a search on this forum.
Guy
Or there is this one [url] http://cgi.ebay.co.uk/TVR-S-Series-Bi but I think it's the first version and not the second version. Not sure what the difference is ?
ChrisGadd said:
Or there is this one [url] http://cgi.ebay.co.uk/TVR-S-Series-Bi but I think it's the first version and not the second version. Not sure what the difference is ?
Steve greatly expanded the original. The second edition is twice the size of the first.
Hi. Thanks for your feedback, I was feeling a bit lonely there for a minute.
I've got the 2nd edition of the Steve Heath book, but it really isn't much help for post air flow meter models, there's nothing about the MAP sensors etc.
Anyway, I managed to check the fuel pressure on the rail today thanks to my friendly local garage & it shows up fine (about 3bar), also checked the manifold pressure which was again good.
They are pretty convinced it is the MAP sensor. Unfortunately my ECU doesn't give any fault codes (ever), but even though the MAP sensor seems to do something (i.e. when you disconect the vac pipe to it the engine barely even idles), apparently they can sometimes tell the ECU that there's a vac present, but not do a good job at adjusting for variation in it.
They think a new one could only be £30 - £40 so it may be worth getting one anyway, at least that rules it out.
Any thoughts?
Thanks again, Rob.
I've got the 2nd edition of the Steve Heath book, but it really isn't much help for post air flow meter models, there's nothing about the MAP sensors etc.
Anyway, I managed to check the fuel pressure on the rail today thanks to my friendly local garage & it shows up fine (about 3bar), also checked the manifold pressure which was again good.
They are pretty convinced it is the MAP sensor. Unfortunately my ECU doesn't give any fault codes (ever), but even though the MAP sensor seems to do something (i.e. when you disconect the vac pipe to it the engine barely even idles), apparently they can sometimes tell the ECU that there's a vac present, but not do a good job at adjusting for variation in it.
They think a new one could only be £30 - £40 so it may be worth getting one anyway, at least that rules it out.
Any thoughts?
Thanks again, Rob.
Sorry, me again!!!
OK, now I'm seriously pissed off!!!
This damn MAP sensor. It has 3 pins, Live (5V), GND & the centre pin which gives a variable output from 0.5 - 4.5V depending on the vacuum. Mine was giving a constant 2.5V at the ouput pin, so assuming the sensor was duff I replaced it today & ******* still the same problem! I have now discovered that the centre pin (output) also has a 5V supply running to it when it is unplugged!!! I'm sure this is the problem, surely if it's an output it should be at 0V when it's not even connected! Can one of you guys with a MAP sensor check the voltages across the plu while it's not connected just to confirm my suspicion??? Please!!!
So, assuming this is not right, I guess my ECU is to blame. Does anyone know much about this or can recomend a really nice chap that does who I could contact for some advice?
Many thanks & have a great weekend in this lovely sunshine!
Cheers,
Rob
OK, now I'm seriously pissed off!!!
This damn MAP sensor. It has 3 pins, Live (5V), GND & the centre pin which gives a variable output from 0.5 - 4.5V depending on the vacuum. Mine was giving a constant 2.5V at the ouput pin, so assuming the sensor was duff I replaced it today & ******* still the same problem! I have now discovered that the centre pin (output) also has a 5V supply running to it when it is unplugged!!! I'm sure this is the problem, surely if it's an output it should be at 0V when it's not even connected! Can one of you guys with a MAP sensor check the voltages across the plu while it's not connected just to confirm my suspicion??? Please!!!
So, assuming this is not right, I guess my ECU is to blame. Does anyone know much about this or can recomend a really nice chap that does who I could contact for some advice?
Many thanks & have a great weekend in this lovely sunshine!
Cheers,
Rob
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