bruce Posted November 13, 2014 Report Share Posted November 13, 2014 (edited) Got a 4K that's missing under load, like going up hills, or hard acceleration. Been trying to get rid of the problem. I think it's mainly electrical, with a weak spark. When I first put the engine in to replace a 3K it was quite bad so I put a new set of top gun ignition leads (standard replacement) in and it made a far bit of difference, but the problem was still present. Went ahead and replaced other ignition parts: spark plugs points rotor button distributor cap condenser That made a bit of an improvement, but problem still persisted. I did noticed a small manifold leak so I replace the gasket. That had different symptoms, and didn't really contribute to the missing under load. The two earth leads to the engine look good. Lately I replaced the battery and the ignition coil. The newer Bosch ignition coil made a good improvement. Though, each time I make an improvement I drive the car a bit harder to the point where the missing is still there. The other day I had a look at the carby and sprayed some carby cleaner down the throat and through the idle adjustment screw. Played around with the ignition timing and left it a 10 degrees, with the idle at 800 rpm. I decided to block and remove the vacuum advance line from the carby to the distributor and that gave a smoother idle and better throttle response. Probably a leak somewhere. Blocked off the other pollution lines resulting in more snappier throttle response. Can accelerate more harder now when driving. However fuel economy has dropped a bit (8 L/100Km to 9L/100Km). So I'm running out of ideas. Other things: its got a reconditioned cylinder head, and I've recently replaced the timing chain. There's a few small holes in the mid muffler. The missing under load is quite bad when I put the rear demister on, which drains a fair bit of power with the charge light coming on. The charge light came on with the demister with the 3K as well. With the 4K I tried a different alternator but the charge light still comes on. Checking the voltage across the battery terminals while the engine is running with nothing turned on gives 13.5 V, and with heater fan, lights and demister the voltage comes down to around 12.5 or 13.0 V. Not sure if the missing under load is caused by a weak alternator. Or old wiring somewhere in the ignition and the demister makes it worst. Edited November 13, 2014 by bruce Quote Link to comment Share on other sites More sharing options...
Super Jamie Posted November 13, 2014 Report Share Posted November 13, 2014 Not sure if the missing under load is caused by a weak alternator. Or old wiring somewhere in the ignition and the demister makes it worst. Try running a nice new 60A wire from the B pole of the alternator (if Bosch) or external regulator (if Denso) to the positive terminal of the battery. That'll at least rule out whether the charging wire in the harness is worn out. Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted November 13, 2014 Report Share Posted November 13, 2014 Yeah, if you've replaced the points/coil/condensor/plugs/leads/rotor/cap.... that's pretty well all the ignition system. A dropping voltage feeding that could be the problem, although the motor only draws a couple of amps. Certainly the rear demister shouldn't bring on the charge light and that extra missing with it on suggests a voltage problem. What does it start like?? Voltage supplied to the coil would be low with the starter cranking. Quote Link to comment Share on other sites More sharing options...
Banjo Posted November 14, 2014 Report Share Posted November 14, 2014 (edited) Hi Bruce, Wow, you've just about replaced everything. What about the "starting" or "ballast" resistor in line with the coil. Does it have one ? Was it replaced ? Have been known to cause issues you describe. If you have one, then short it out, & take it for a short hard drive & see if the problem persists. If not, that will eliminate another item & we'll go from there. Cheers Banjo Edited November 14, 2014 by Banjo Quote Link to comment Share on other sites More sharing options...
tojo2 Posted November 14, 2014 Report Share Posted November 14, 2014 A couple other easy things to check is for good ground cable and Connection from battery minus to chassi and chassi to engine block, and free movement of dizzy timing advance . Quote Link to comment Share on other sites More sharing options...
bruce Posted November 14, 2014 Author Report Share Posted November 14, 2014 (edited) Yeah, if you've replaced the points/coil/condensor/plugs/leads/rotor/cap.... that's pretty well all the ignition system. A dropping voltage feeding that could be the problem, although the motor only draws a couple of amps. Certainly the rear demister shouldn't bring on the charge light and that extra missing with it on suggests a voltage problem. What does it start like?? Voltage supplied to the coil would be low with the starter cranking. It starts alright when cold, just need a bit of choke until it warms up a bit. But the last couple of mornings I go to turn it over and nothing happens. Can hear the click under the dash with the relay and I think the solenoid on the starter motor. I just keep on turning the key till it turns over. Starts straight away throughout the day. Did happen a couple of months ago and I thought the battery was getting slugish, so that's why I replaced it. But looks like the problem is still there. Might need to checkout the starter motor. Edited November 14, 2014 by bruce Quote Link to comment Share on other sites More sharing options...
bruce Posted November 14, 2014 Author Report Share Posted November 14, 2014 Hi Bruce, Wow, you've just about replaced everything. What about the "starting" or "ballast" resistor in line with the coil. Does it have one ? Was it replaced ? Have been known to cause issues you describe. If you have one, then short it out, & take it for a short hard drive & see if the problem persists. If not, that will eliminate another item & we'll go from there. Cheers Banjo It has a white ballast resistor in line before the positive side of the ignition coil. Hasn't been replaced, looks original. I measured the resistance at ~5.5 ohms (varies a bit). I'll by pass it and see if it makes a difference. Quote Link to comment Share on other sites More sharing options...
bruce Posted November 27, 2014 Author Report Share Posted November 27, 2014 I changed to another ballast resistor that was a couple of years old and the missing actually got worse. So I put the original one back in and took it for a test run and the missing was gone. Both resistors measured to be 2 ohms. So I cleaned up the connections at the ignition coil with sand paper and WD40 and tighted them up. I could hold the accelerator flat to the floor from a standing start and the engine not miss, also up hills as well. Only a hint of a miss up a hill when the rear demister or head lights were on. However I just got the exhaust done: 2" piping, wildcat extractors, redback sports muffler as the mid, then megaflow muffler as the final, and the missing has come back. Its worse with the head lights and windscreen wipers on. There wasn't really any power increase, actually lost power or low end torque. Like there is a flat spot when first accelerating. When I had the exhuast done with a stock 5K I noticed a difference in power, but with a stock 4K its not really beneficial. Measured the voltage at the iginition coil when idling: 11V at positive and 8.5V at negative. Got 13.6V before the ballast resistor. Quote Link to comment Share on other sites More sharing options...
Super Jamie Posted November 27, 2014 Report Share Posted November 27, 2014 redback sports muffler Hells yeah! I had one of these on my KE25. I tried every 2" muffler at the exhaust shop and this was the best sounding by far! Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted November 28, 2014 Report Share Posted November 28, 2014 The starting problem sounds like the solenoid, although it would pay to pull the wire off and measure 12V getting there every time you turn the key. At least then you know you have voltage, even if you might not be getting enough amps. Probably the contacts inside the solenoid are worn away. In the past I have either reversed the contact bar inside so it is woring on a new surface, or put washers under the contacts to move them closer to the bar, just depends on the solenoid manufacture.. The misfire being worse with headlights on suggests that not enough current is arriving at the coil. Try hotwiring the coil straight off the battery and see if the misfire vanishes. Did you check the earth leads from the motor to the chassis and the chassis to the battery negative carefully like Tor said? The 11volts is actually higher than I expected if you have a ballast resistor in there, so the voltage is fine. That's assuming the Bosch coil is the "R" version, made for working with a resistor... Certainly this suggests the alty is not up to its job and there is not enough power being produced- when I put the rear demister on, which drains a fair bit of power with the charge light coming on. Are the altys using external regulators? If you changed altys either both were poor of the voltage regulator is not working correctly. I figure a 2" exhaust is larger than a 4K needs, I'd expect it to kill some low-down performance. It might all change with a single DCOE Weber fitted... Quote Link to comment Share on other sites More sharing options...
lexsmaz Posted December 4, 2014 Report Share Posted December 4, 2014 (edited) You might have fixed it by now but I can't see you actually mention about replacing the ignition coil itself .. And as has been said make sure its one that requires a ballast resistor if you do change it .. Also those voltage readings your are getting at the coil are a bit high, at idle it should be around 9 volts at the positive terminal, I would try that other ballast resistor & also definately change the coil too as high primary current can cook a ballasted coil .. And refit your vacuum advance vacuum line as that is what gives you the economy gain & better throttle response at light throttle openings too .. Edited December 4, 2014 by lexsmaz Quote Link to comment Share on other sites More sharing options...
bruce Posted December 4, 2014 Author Report Share Posted December 4, 2014 Hells yeah! I had one of these on my KE25. I tried every 2" muffler at the exhaust shop and this was the best sounding by far! Yeah they sound alright. I had a chambered design muffler with hotdog on my other car and it sounded ballsy. I wanted a chambered design again but they put the megaflow muffler on (straight through design with a bend). The note is not as deep. Still sounds alright echoing in an undercover carpark. Quote Link to comment Share on other sites More sharing options...
bruce Posted December 4, 2014 Author Report Share Posted December 4, 2014 Are the altys using external regulators? If you changed altys either both were poor of the voltage regulator is not working correctly. They are the later Bosch alternators with the internal regulators. Yeah it could be possible both are faulty. Thinking of doing the commodore alternator upgrade. Quote Link to comment Share on other sites More sharing options...
bruce Posted December 4, 2014 Author Report Share Posted December 4, 2014 I decided to pull a spark plug out and check the spark, and it was yellow and weak. They seemed to be a bit dirty but not real bad, bit black around the rim. Spark plug 1: Spark plug 3: Spark plug 3 seemed the worst. I cleaned them up with sandpaper and hit them with a wire brush and carb cleaner. Also noticed the spark plug leads weren't fully pushed into the distributor cap. Since they are new the terminals need adjusting so they can be pushed all the way in. Spark was brighter but still yellow. Went for a test run around the block and down the road and it was pretty good. Could hold the accelerator flat to the floor and it wouldn't miss. But the next day the missing came back again, and was worst, even at light throttle or feathering the accelerator. Tried another condensor that was 25 micro F instead of 22 micro F, but no real change to the spark. Cleaned up the earth leads: Decided to get some new NGK BP5EY, since the fouling is like fused in, and it's hard to get into all the places to clean them up. Probably stuffed them up with the sanding. Tried a new spark plug for a spark test and it was bright blue. Put them in and no more missing. In the rain today had the head lights, wipers, and demister on, flat to the floor in 4th up a hill, no missing. Quote Link to comment Share on other sites More sharing options...
bruce Posted December 4, 2014 Author Report Share Posted December 4, 2014 You might have fixed it by now but I can't see you actually mention about replacing the ignition coil itself .. And as has been said make sure its one that requires a ballast resistor if you do change it .. Also those voltage readings your are getting at the coil are a bit high, at idle it should be around 9 volts at the positive terminal, I would try that other ballast resistor & also definately change the coil too as high primary current can cook a ballasted coil .. And refit your vacuum advance vacuum line as that is what gives you the economy gain & better throttle response at light throttle openings too .. I've replaced the coil with a Bosch SU12R from my other car, it's about a couple of years old. Yeah I might put back the vacuum advance, and try out the other ballast resistor to get lower voltage readings. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.