[SOLVED - FITV] 3rd Gen - Revving at idle?
Posted: Thu Oct 12, 2017 2:38 pm
Hi guys, how you all doing?
So I apologise if this seems like a n00b question, I'm pretty sure it's normally something to do with vacuum lines but I've replaced most of them (run out of hose, need to buy more) and it's still doing the same thing. Basically, when cold it idles ~1200/1500 rpm, which is normal due to automatic choke and whatnot. It idles smoothly, doesn't sound rough and holds a consistent speed. Normally I let it idle for a minute or 2 before driving, but I don't let it get up to temp before pulling off. Instead I opt for little smooth, gentle acceleration and low engine speeds until shes up to temp, and even then I don't ALWAYS put my foot down
She runs and drives fine, nice and smooth as expected, but if I come to a stop before the engine is up to peak temperature it starts revving up a little by itself. It only revs from normal idle (~750/1000rpm), to about 1500/2000rpm and back to normal idle again but continuously, and only stops if I put the engine under load (like putting it in gear and lifting the clutch a little with the handbrake on). This settles the idle down to normal and if I then slowly depress the clutch, take it out of gear, and release the clutch again the engine idles normally, unless I tap the throttle in which case is starts revving again.
Keep in mind it's a 26 year old car which is mostly factory parts (including original clutch and alternator), so I do expect that some things are wearing out and are in need of replacing. I'm doing what I can when I can, but the rarity of these cars makes new parts hard to come by and expensive, and I'm strongly against "in-house refurbs" because, let's face it, these idiots don't know our cars (one actually told me on the phone that they "don't replace regulators because they don't normally go on these cars").
What I'm wondering is, aside from vac lines, what could this be? I have noticed that the radiator has been swapped for one off an auto and has the built-in oil cooler (so likely not the correct capacity for the car) and that my alternator is kinda naff, could either of these be the problem? My logic on the radiator is that if the engine is heating up faster than it's supposed to maybe it's misfuelling or something? And in theory if the clutch in the alternator is gone maybe there isn't enough resistance on the engine which explains why lifting clutch to the biting settles it down.
Btw what I mean by my alternator is "kinda naff" is that the tensioner kept snapping on the old owner, and ever since I fixed it I get flashing battery light at random points in the rev range (sometimes it just flashes continuously) and recently it's stopped correctly charging the battery if I go over 2000rpm. Really weird, I know, and I'm looking for a replacement. Also might be worth noting that I did recently discover that my main relay was suffering the common cold-solder joint issue and have repaired that.
If it's not cooling system, alternator, or one of the vac lines that I'm yet to replace then I really don't know what else it could be.
Car is a 1991 3rd Gen Prelude with B20A7 and manual gearbox (pretty rare as far as I understand it). Any help/advice is greatly appreciated. Really want to fix these little niggles and get back on with the bodywork as she desperately needs a respray so I can start showing her off
So I apologise if this seems like a n00b question, I'm pretty sure it's normally something to do with vacuum lines but I've replaced most of them (run out of hose, need to buy more) and it's still doing the same thing. Basically, when cold it idles ~1200/1500 rpm, which is normal due to automatic choke and whatnot. It idles smoothly, doesn't sound rough and holds a consistent speed. Normally I let it idle for a minute or 2 before driving, but I don't let it get up to temp before pulling off. Instead I opt for little smooth, gentle acceleration and low engine speeds until shes up to temp, and even then I don't ALWAYS put my foot down
She runs and drives fine, nice and smooth as expected, but if I come to a stop before the engine is up to peak temperature it starts revving up a little by itself. It only revs from normal idle (~750/1000rpm), to about 1500/2000rpm and back to normal idle again but continuously, and only stops if I put the engine under load (like putting it in gear and lifting the clutch a little with the handbrake on). This settles the idle down to normal and if I then slowly depress the clutch, take it out of gear, and release the clutch again the engine idles normally, unless I tap the throttle in which case is starts revving again.
Keep in mind it's a 26 year old car which is mostly factory parts (including original clutch and alternator), so I do expect that some things are wearing out and are in need of replacing. I'm doing what I can when I can, but the rarity of these cars makes new parts hard to come by and expensive, and I'm strongly against "in-house refurbs" because, let's face it, these idiots don't know our cars (one actually told me on the phone that they "don't replace regulators because they don't normally go on these cars").
What I'm wondering is, aside from vac lines, what could this be? I have noticed that the radiator has been swapped for one off an auto and has the built-in oil cooler (so likely not the correct capacity for the car) and that my alternator is kinda naff, could either of these be the problem? My logic on the radiator is that if the engine is heating up faster than it's supposed to maybe it's misfuelling or something? And in theory if the clutch in the alternator is gone maybe there isn't enough resistance on the engine which explains why lifting clutch to the biting settles it down.
Btw what I mean by my alternator is "kinda naff" is that the tensioner kept snapping on the old owner, and ever since I fixed it I get flashing battery light at random points in the rev range (sometimes it just flashes continuously) and recently it's stopped correctly charging the battery if I go over 2000rpm. Really weird, I know, and I'm looking for a replacement. Also might be worth noting that I did recently discover that my main relay was suffering the common cold-solder joint issue and have repaired that.
If it's not cooling system, alternator, or one of the vac lines that I'm yet to replace then I really don't know what else it could be.
Car is a 1991 3rd Gen Prelude with B20A7 and manual gearbox (pretty rare as far as I understand it). Any help/advice is greatly appreciated. Really want to fix these little niggles and get back on with the bodywork as she desperately needs a respray so I can start showing her off
