poohbear Posted July 7, 2012 Share Posted July 7, 2012 Hi all, I have a '95 P38 running on lpg that wont return more than 10 - 12mpg and is also sluggish and down on power. It starts and runs fine and pulls off ok but has no acceleration over 40 - 50 though when it does get there it will sit at 70+ fine, in fact it wont do over 50 going up hill. It kicks down and sounds like it's trying but just doesn't pick up. I'm also struggling to get above 10mpg on both lpg and petrol. Hawkeye shows a bad O2 sensor on bank A which I guess could explain bad mpg if it's running rich but would it also cause the other symptoms? Anybody got any ideas - come across this before? Thanks, Dave. Quote Link to comment Share on other sites More sharing options...
duncmc Posted July 7, 2012 Share Posted July 7, 2012 When was it last serviced? Old worn out spark plugs maybe, how is the air filter? How many miles has the engine done? Is the camshaft worn? What is the compression like? What type of LPG system have you got, and does that need servicing? Is your timing correct? My 3.9 isn't that bad on fuel now (14mpg), but I am still down on power like you, and I have worked through all the above. And it has got better, but now I just have to do the camshaft and timing chain. Oh yes, and which engine is it, 4.0 or 4.6 and GEMS or THOR? Might help other more knowledgable people than me. Quote Link to comment Share on other sites More sharing options...
poohbear Posted July 7, 2012 Author Share Posted July 7, 2012 It's a 4.0 GEMS - last service at 151K now at 153K, Sequential LPG system fitted in 2010 - it was done abroad so I can't give any more details until I've translated the certificate! I have only had it a week and so haven't had a chance to give it a thorough going over yet - oil looks clean and supports recent sevice. I have cleaned the MAF and both O2 sensors (using isoprop) and will pull the plugs today to see if they point to anything obvious mixture wise - however one of the Lambdas was well sooty so I expect it's over fuelling on that bank. I am just trying to work out if it's worth keeping and working through the niggles or whether I'm going to end up chasing my tale and digging into my pockets. After all it's fine up to 40 and it will cruise at 70 easily - it just takes forever to get there and at 10mpg I can't justify the running cost. Thanks, Dave. Quote Link to comment Share on other sites More sharing options...
Tanuki Posted July 7, 2012 Share Posted July 7, 2012 Do a compression test. Check that the catalysts have not collapsed internally: if the engine's been overfuelling at any time it's easy for the cats to get overheated and melt themselves into a useless mass. Check that you've not got a displaced baffle in one of the silencer-boxes that's restricting the flow of exhaust-gases. If the products-of-combustion can't get out easily, the engine's bound to be lethargic and inefficient. --Tanuki Quote Link to comment Share on other sites More sharing options...
poohbear Posted July 7, 2012 Author Share Posted July 7, 2012 Thanks for the pointers. Blocked/restricted exhaust had crossed my mind - both cats are rattling which points in that direction. Can I bung a multimeter on the lambda sensors to see if one is dead - any ideas of good values Quote Link to comment Share on other sites More sharing options...
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