Idle/Overheat Problems

[Dominic]

Help! During long trips, usually about an hour on the freeway, my car starts to idle weird when coming to stops. With my foot off the throttle, the idle speed increases on it's own as if I am pushing down on the throttle. I would say the idle would increase and stick to around 2-3k rpms when i'm at a full stop(approximating since my tacho doesnt work). Normally the car idles pretty low and runs fine. I checked my throttle cable and springs to see if they're sticking but it seems like the problem is coming from within the carbuerator or the engine. I imagine this could be due to the engine overheating?(my engine temp meter doesnt work either). I know my radiator has a small leak but i dont know if that's what's causing it? Also, there's a small knocking coming from my engine. I'm a total noob with datsuns and car knowledge in general so please bare with me. any help would be appreciated. I'm thinking it could be off valve timing, a blown head gasket, or a vacuum leak? I have an L16 from a datsun truck i'm told, and some sort of webber carbuerator.

[I'm BLUE]

Hi Guy ,,,

 

Ok not gonna try to sound like an ass ,,, but help you save your car ,,, :)

 

(1) Stop driving the car :unsure:

 

(2) your engine needs a proper temperature gauge ,,, to be able to monitor ,,, while driving ,,, even an aftermarket one is better than none ,,,

 

(3) how small is the small radiator leak ? :blink: :mellow:

 

(4) Tighten all bolts ,,, properly ,,, no over torque to eliminate any loose items ,,, to verify knocking ,,, is it an acceleration knock ? or lower tone knock that gradually gets worse with engine rpm ( if main bearings suspected ,,,, to test main bearings ,,, put in higher gear and floor it at lower speed (20-30mph !? idk gearing on your car) ,,, if knocking still present ,,, main bearings bad ,,, unless a double-knock then proceed to suspect connecting rods) ,,, rod bearings have a double knock with acceleration ,,, piston slap usually occurs at idle ,,, and does not increase with any acceleration if it's not major at least ,,,

 

Exhaust leaks at manifold flange sealing surface especially headers ,,, can SOUND JUST LIKE a valve ticking ,,, but make sure engine is getting oil !!! ( oil pressure gauge/hookup , and pulling off valve cover to know at least it is getting to the head to drain back down and feed other parts of engine ! ,,, if valve cover pulled and very little oil ,,, you have a blockage ,,, and possibly a major problem/wear ,,, possibly = vary's !? ,,, could be ok ! who knows ! )

 

(5) Do not use Fram walmart Filters !!! Wix , K&N , Bosch , Napa/Napa-Gold , Factory Filters ! :D

 

(6) ticking ,,, check valve clearances ,,, and verify oil is getting to top of the engine ( take off valve cover ,,, should be plenty of oil up top ,,, perform valve clearance check/adjustment ,,, about 30minute to 1hour for me ,,, :) ( I am slow ) haha :lol:

 

(7) I had a Fram oil filter that blocked the oil flow to rest of engine ,,, BAD EXPERIENCE ,,, I will never use Fram AGAIN !!! <_< ,,, that goes for fuel filters as well , and possibly air filters !

 

(8) 2-3k idle is damn high :blink: ,,, are you sure ? ,,, hookup a tachometer to engine ,,, even in engine bay ! easy to do ,,, Tach Feed wire to (-) of coil , Red to 12v source , Black to Ground , and Bulb Feed/Tach Light wire ,,, well to light dimmer switch or light circuit ,,, :)

 

(9) if it IS the carb internally that is keeping that high of idle ,,, it will need to be opened up and cleaned ,,, BEFORE doing so ,,, check ALL mechanical pieces/linkages,,,, anything like a bent arm or screw turned into far on mechanical idle can do so ! ,,, Check for vacuum leaks ! for sure ! check ignition timing

 

(10) verify and check all little things before taking ANYTHING apart ;)

 

(11) compression check for blown headgasket ,,, check for water in oil ,,, check for oil in coolant ,,, make sure ALL coolant hoses in good operation condition ,,, and raditior is not blocked as well as thermostat is opening up ! ( at operation temperature ,,, both hoses are hot/warm at least ,,, check for cold spots on radiator to indicate blockage ,,,

 

(12) Check fuel pressure ,,, electric or mechanical fuel pump ? Does the engine eat oil ? eat coolant ? how much ?

 

(13) faster rev's at idle when pressing gas pedal ,,, usually means to me at least ,,, a leaner condition ,,, Does your oil smell very saturated with Raw Gas ? ( check dipstick ) ,,, if so ,,, carb/fuel delivery is def a huge problem ,,,

 

(14) what kind of mileage are you getting ? ( honest ) ,,, how long have you been driving like this friend ? :)

 

(15) one can run "B12 Chemtool" Or "SeaFoam" through their gastanks ,,, to clean the shit outta the valves ,,, and help clean the carb passages ,,, good stuff ! unfortunatley ,,, this is more of maintenance item to me ,,, as the only TRUE way to clean a carb ,,, and check parts ,,, is to open up the carb ,,, and dip it in carb clean ,,, being sensitive to soft metals , and plastics when doing so ! ,,, passages are sooooooo small ,,, to clean ,,, it's not even funny ! :blink:

[Stupid_fast]

it revvs to about 2k's, Stays at RPM instead of dropping? When I drove to LA mine started doing this in traffic (with weber 32/36... after driving about 6 hours, not very fun especially in LA), I pulled over and found a fix. Try spraying some WD-40(or other preferred lubricant) on the throttle linkages, this fixed it for me.

 

Also try loosening the nut that holds it down. It should not be tight, not even stug, just holding the throttle with the lock washer thing holding the nut so it does not get too loose.

 

I'm guessing the carb/linkages get hot after running a long time, and expand a little causing it to bind.

[I'm BLUE]

it revvs to about 2k's, Stays at RPM instead of dropping? When I drove to LA mine started doing this in traffic (with weber 32/36... after driving about 6 hours, not very fun especially in LA), I pulled over and found a fix. Try spraying some WD-40(or other preferred lubricant) on the throttle linkages, this fixed it for me.

 

Also try loosening the nut that holds it down. It should not be tight, not even stug, just holding the throttle with the lock washer thing holding the nut so it does not get too loose.

 

I'm guessing the carb/linkages get hot after running a long time, and expand a little causing it to bind.

 

very good answer ^^^ ,,, also in addition ,,, verify that your lock-nuts/bolt's ,,, are aprox 5ft-10ftlbs ,,, that's very very little ! ,,,(idk specifics but carbs in general) ,,, no more ! anymore can cause binding issues ,,, especially when an engine warms up ,,, :(

[banzai510(hainz)]

save and watch this 1000 times naked

 

 

1)Does the carb have a return spring.????????? Most carbs have one then on the 510 its self there is a return spring set up on the firewall.

 

2) find the wire for the thermostat yellow grn I think. olddatsuns.com might have the schematic or page 1818 on your haynes manual thay you have,right?

 

fix the temp gauge ASAP

 

 

How you know your overheating? Unless the cap is just going to explode of the rad I think your fine.But itf you ran it out of water you better let us know.

 

Anyways you can ground the temp sender wire and I think it will go fully to hot side.(Datzenmike) or ck for 12volts if in dought.

 

To pull a sender can go bad as most have been in there 30 years and can break a housing as you cant get them out. I have spares myself.

 

The radiator can be fixed by a local shop if its small and in a repairable spot. someitme a rad can be found cheap near you due to large amount of KA swaps

 

 

 

the tickeing could be a just valve adjustment. Mklotz has a post on here somewhere on how to do this.

[racerx]

Ticking can be a valve adjustment or cheap gas or timing off, maybe too advance.