Rocky671 Posted February 21, 2017 Report Share Posted February 21, 2017 I was on my way home from work on the freeway and i felt my gas pedal sink in.It was verry sensitive.I pulled over come to find out the bracket on the throttle cable broke.I replaced it But,Now In neutral and in gear my rpms shoot up to 3k+ and my gas pedal is not alighned with the brake and clutch pedal like before.Only way to get the idle down is to put it in gear and hold down the brake and hold the clutch half way. Quote Link to comment
datzenmike Posted February 21, 2017 Report Share Posted February 21, 2017 Throttle cable isn't adjusted properly to let the carb close at idle. 1 Quote Link to comment
Rocky671 Posted February 21, 2017 Author Report Share Posted February 21, 2017 its as back as it'll go.Ill try it agaian.And gas pedal has resistance again but still looks back more then brake and clutch pedals. Quote Link to comment
datzenmike Posted February 21, 2017 Report Share Posted February 21, 2017 This is the bracket at the card? Then what you replaced it with is not the same. Quote Link to comment
Stoffregen Motorsports Posted February 21, 2017 Report Share Posted February 21, 2017 Pics would help a ton on this one. Without pics, I come up with 4 possible problems. Pedal assembly Cable Bracket Carb linkage 1 Quote Link to comment
wayno Posted February 21, 2017 Report Share Posted February 21, 2017 Return Spring? 1 Quote Link to comment
shacks510 Posted February 21, 2017 Report Share Posted February 21, 2017 You're going to roast your clutch if you use it to bring the RPMs down. Don't do that. 3 Quote Link to comment
Rocky671 Posted February 21, 2017 Author Report Share Posted February 21, 2017 just did that to at the lights just to get it home.iys parked now until i figure the problem out. 2 Quote Link to comment
sebpv Posted February 25, 2017 Report Share Posted February 25, 2017 the pedal has an adjustment too. The more tension you give the more readily it gives gas to the carb Quote Link to comment
Rocky671 Posted March 10, 2017 Author Report Share Posted March 10, 2017 ok guys.Sooo i went out and got a new weber 38 carb.Buuuut,still Everytime i start my truck my rpms sky rocket past 2k almost 3k.I checked the pedal,my throttle cable is not to tight,hose from distributor to carb is hooked up.Any ideas??? Quote Link to comment
datzenmike Posted March 10, 2017 Report Share Posted March 10, 2017 Well there is a fast idle on cold engines. On the Hitachi it's ,.800-2,200 RPMs at the start and reducing as the engine and choke warms. The choke will be on and the mixture very rich. Extra air is added to increase the engine RPMs and speed the warm up. So what happens when the engine is warmed up???? The hose from the distributer has no bearing on this. It's ported vacuum from above the throttle plate and not intake vacuum. On a warm and properly set up engine I have NEVER see RPM go up if an intake hose is off or there's a vacuum leak. ALWAYS the RPMs drop. 1 Quote Link to comment
Rocky671 Posted March 10, 2017 Author Report Share Posted March 10, 2017 Honestlt this is my 3rd 720 and is the 1st time dealing with this issue.Never had a high idle like this.i have to press the gas a couple of times for idle to drop and the keep pressing it until its warmed ao it doesnt die out.once its warmed up a little bit it idles at about 15 Show quoted text Quote Link to comment
Stoffregen Motorsports Posted March 10, 2017 Report Share Posted March 10, 2017 Again, check the basics first. Since it had this problem before you installed the new carb, I'm guessing it's either in the linkage or you have a massive vacuum leak. The fact that you have to keep pressing the pedal after it warms up tells me that it's probably a vacuum leak. Could be timing too, but if this was ok before, then probably not. If those check out, then it could be the electric choke adjustment. I don't know where to go with a question like this. There are so many possibilities and so many variables, it's hard to give a simple answer. If I had a feel for your mechanical capabilities or some more history on the car/truck, those would both help guide us to a solution. Quote Link to comment
datzenmike Posted March 10, 2017 Report Share Posted March 10, 2017 If you 'kick' the gas the rpms will drop because the choke unloader is activated. Give your truck a chance to warm up. Once warmed up, adjust the idle speed up to keep it going. Possibly a vacuum hose is leaking.... or the idle is just too low to begin with. 1 Quote Link to comment
wayno Posted March 11, 2017 Report Share Posted March 11, 2017 This is a Weber now, does it have an adapter plate? If everything else is good check your PCV valve, I had one go bad once, it run up past 2000rpms, when I put my finger over the hole it dropped to normal idle. 1 Quote Link to comment
Rocky671 Posted March 12, 2017 Author Report Share Posted March 12, 2017 This is a Weber now, does it have an adapter plate? If everything else is good check your PCV valve, I had one go bad once, it run up past 2000rpms, when I put my finger over the hole it dropped to normal idle. Yes it does have an adapter.Stupud question.Would not having an air filter kause this problem also Quote Link to comment
datzenmike Posted March 12, 2017 Report Share Posted March 12, 2017 The PCV valve can fail anywhere between open or closed. Specially if you have an oil burner that clogs it up. It has a valve that is pulled open against a weak spring by manifold vacuum. It is open pretty much any time the engine is running. Naturally more air is pulled in during high vacuum conditions, such as idle and deceleration. The PCV valve is technically a vacuum leak that is compensated for by adjusting the idle mixture screw. Blocking it off during idle should force a slightly rich mixture. At all other speeds this 'leak' is irrelevant as the amount of air entering is proportional to vacuum not engine speed. If the RPMs go down when blocked off, maybe the mixture was too rich to begin with and the extra air makes it rev up. 1 Quote Link to comment
Rocky671 Posted March 12, 2017 Author Report Share Posted March 12, 2017 The PCV valve can fail anywhere between open or closed. It has a valve that is pulled open against a weak spring by manifold vacuum. It is open pretty much any time the engine is running. Naturally more air is pulled in during high vacuum conditions, such as idle and deceleration. The PCV valve is technically a vacuum leak that is compensated for by adjusting the idle mixture screw. At all other speeds this 'leak' is irrelevant as the amount of air entering is proportional to vacuum not engine speed. Okay.So do i play around with the idle screw???Also the other daybj was spraying carb cleaner around the 4 corners of the base and all around everytime i sprayed rpms shot up.Is it possible for a bad gasket,to tight or to loose??? Quote Link to comment
datzenmike Posted March 12, 2017 Report Share Posted March 12, 2017 Yes. You have a vacuum leak and too much air is getting in making the mixture lean. Carb spray adds to the air leaked in restoring the air/fuel mixture and raising the RPMs. Try snugging the nuts. If a Weber there are two gaskets and there is also the risk the adapter is already cracked from tightening. Quote Link to comment
wayno Posted March 12, 2017 Report Share Posted March 12, 2017 That is a vacuum leak, you need to fix that, that is likely the reason your having issues, it should not do that. You need to remove the carb and adapter plate and start over, there should be no change in RPMs when you spray carb cleaner around the base of the carb. 2 Quote Link to comment
banzai510(hainz) Posted March 12, 2017 Report Share Posted March 12, 2017 if you have the cheaper thin carb adapter(cast) if one bolts them down to hard they may crack. theya re different versions so Im just guess which one you have . I cracked one and I gave my spare away to anoher guy and he cracked that one. I went with the tall 1 pc unit. on a L16. On a L20 or taller motor the tall aircleaner might hit the hood. They sell a 1.75 in tall aircleaner if needed Quote Link to comment
Rocky671 Posted March 12, 2017 Author Report Share Posted March 12, 2017 if you have the cheaper thin carb adapter(cast) if one bolts them down to hard they may crack. theya re different versions so Im just guess which one you have . I cracked one and I gave my spare away to anoher guy and he cracked that one. I went with the tall 1 pc unit. on a L16. On a L20 or taller motor the tall aircleaner might hit the hood. They sell a 1.75 in tall aircleaner if needed Thank u banzai510...I will change out my adapter plate. Quote Link to comment
datzenmike Posted March 12, 2017 Report Share Posted March 12, 2017 Remove and inspect it. It may just be the gasket that's leaking. Or the bolts not tight enough. We're saying that it's only possible the adapter is cracked so you know what to look for. 1 Quote Link to comment
Stoffregen Motorsports Posted March 13, 2017 Report Share Posted March 13, 2017 The two piece adapters are notorious for coming loose. To keep this from happening, use loctite on the threads of both plates. And then use lock washers on the nuts holding the carb to the adapter. Before you tear into it, put a wrench on the carb nuts and see if they are loose. 1 Quote Link to comment
captain720 Posted April 7, 2017 Report Share Posted April 7, 2017 Yeah and the gaskets are super easy and cheap, fixed an air leak on my 4wds last engine that way. Quote Link to comment
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