Hi, I have a 340 1.4 which I use for drifting. Recently after giving it a thrashing it runs very poorly unless it's on full throttle. On Full throttle it appears to run fine but anything less than full throttle makes the engine speed decrease and eventually stall. Once it's in this "mode" where it only runs on full throttle it still idles fine and the only way to cure the problem (that I have found) is to turn the engine off and leave it to cool so that the next start is a cold start. I've tried running the interior fan and driving at 50mph to cool the engine but this doesn't help, it seems like it needs to be shut down and left to rest.
Does anyone have any ideas as to how to stop this from happening? (Other than to stop abusing it)
Cheers, Sam.
1.4 only runs on full throttle
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Alex Laidlaw
- Posts: 230
- Joined: 10 Nov 2009 01:54 pm
- Location: Oxford and Worcester
Re: 1.4 only runs on full throttle
If it will idle and run at revs only it is probably a problem with the primary choke on your carb. It will idle because that bypasses the primary choke and will run fine at full revs when the secondary choke has opened (I guess, I've never had to take a Volvo carb apart but had similar issues with other cars 
). Check any vacuum hoses are good (including the connection to the Renix ignition unit). If they're good then check for leaking gaskets by spraying a bit of WD40 over the edges of the carb with the engine running, if there is a change in the engine note then you've found a leak. Otherwise take the carb carefully apart clean it all out check the floats are ok and jets are clear and put it back together, you should really get an overhaul gasket set (its a Weber 32 DIR) but can sometimes get away without. There's not a lot to adjust on the later factory sealed generation carbs, just cleaning them out and putting them back together usually cures most problems, do this before attempting any adjustments.
). Check any vacuum hoses are good (including the connection to the Renix ignition unit). If they're good then check for leaking gaskets by spraying a bit of WD40 over the edges of the carb with the engine running, if there is a change in the engine note then you've found a leak. Otherwise take the carb carefully apart clean it all out check the floats are ok and jets are clear and put it back together, you should really get an overhaul gasket set (its a Weber 32 DIR) but can sometimes get away without. There's not a lot to adjust on the later factory sealed generation carbs, just cleaning them out and putting them back together usually cures most problems, do this before attempting any adjustments.Re: 1.4 only runs on full throttle
Cheers, you were right. The first gasket you come to when taking the carb apart from top to bottom needed replacing and some of the carb bolts were loose. The problem seems to be sorted now!