Monday, March 14, 2011 - 11:42 pm, by: John Stafford(Johng12)
Today I developed a miss in my V8 from between 55 and 70 klm/hr under load going up hill mainly. It stops when I change back to second and accelerate. It seems to be getting worse too. I did a 200 klm run and it started at about the 80 klm mark. I have new plugs and leads tested perfect as per the specs for Toyota leads just last week. I have had my caps replaced just recently too and had no troubles till today. Any ideas? Thanks in advance John
Tuesday, March 15, 2011 - 07:43 am, by: Tom Richards(Tomr)
check the coils. primary resistance should be 0 ohms secondary should be ~12k ohms this test is not 100% as they could mesure ok, but break down under high voltage.
Tuesday, March 15, 2011 - 09:24 am, by: Michael Toet(Myke31)
Sounds like what my car was doing. I had the ECU checked out and it was okay, but since I had already bought one, I waited for it, and installed that one. So far it seems to be running well (at least 4 weeks or more so far).
The issue I had is some of the cylinders were running rich. At 80kph going up hill (under load) around 2000 to 2500rpm the car would shudder/miss slightly. If I got over 3000rpm it was good, and if the car kicked down a gear and reved harder it was all smooth again. It wasn't my coils because the ones running rich shared coil packs with the cylinders that were all good. Like yourself, I have put in all new leads, coils, dizzy buttons & caps. Also I ruled out oxy sensors as I had 4 cylinders running rich, 2 on each bank, so I assume they don't share oxy sensors, also, my fuel economy hasn't changed. Typically the economy goes bad when the oxy sensors play up. The other thing I was going to check out were the injectors. I don't know if they are putting in the wrong amount of fuel under load at low revs.
The ones running rich on my car are the centre 4 cylinders (2 on each bank). I was also considering heat soak or something, but I haven't chased it down further since everything now seems okay since the new ECU. I need to pull out the plugs at some stage and check again.
Pull the plugs out and have a look, see if they share a common element, ie, dizzy/coil pack. Maybe check the injectors, but I don't know how to check them/rule them out, except to change them over between good and bad cylinders and see if the problem occurs again, but in the other cylinder where the suspect injector is.
If you solve the problem, post back, as I would like to know, just in case I see the issue again.
Tuesday, March 15, 2011 - 11:57 am, by: John Stafford(Johng12)
Ok Tom, I guessed to do just what you said before you posted and I got 00.9 ohms between the 2 wires in the primary and I got 14.45 ohms for the primary the main lead to the distributor cap. How does this sound? I have only done the left bank so far, cleaned the terminals in the distributor cap and the rotor button contact too. Thanks for the help. I still have the miss. The post above by Micheal sounds interesting, like it may be the ECU that I had fixed? I will do the other bank and check again and then contact the guy who did the ECU. I will let you know how it works out. Don't forget to comment on the figures that I got when testing the coil Tom. Thanks. Cheers John
Thursday, March 17, 2011 - 04:40 pm, by: John Stafford(Johng12)
Yes Tom, it was K ohms and the other one tested out at .9 between the 2 connections on the primary plug and then from there to the high tension lead that runs to the dissi cap. It was 12.95, a bit lower than on the left bank. Well I reset the computer for about 10 mins and nothing improved so disconnected the battery overnight but no improvement so decided to test the plug leads again and found all the same as before (right on spec) but one of them was hard to get a reading on but when I could get one it was 10.8 for Number 7,which should have fine, then I remembered that it was hard to get a reading on one the last time I tested and think it was the same lead so thought that this might be the culprit. I cleaned the right hand rotor and the terminals in the cap and put it all back together as I had to go out. Guess what? I think the miss has gone, probably the way that I put number 7 lead back. Looks like a crack in that lead. Christian who did my caps for me said that my ecu board was in good shape and that he doubted that, that was the problem. So looks like all is good. Thanks guys Cheers John
Thursday, March 17, 2011 - 07:28 pm, by: Brett Harrison(Bretto)
John if you ever need to change the coils, you can just buy generic, Champion brand Coils from Repco etc, only about 30-40 bucks each. Not that they are faulty, however heat is a killer for coils, and the one on the left bank near the exhaust manifold gets a bit hot on long runs.
Thursday, March 17, 2011 - 10:38 pm, by: John Stafford(Johng12)
Thanks for the info on the coils Brett. I may get a special lead made for plug #7. I have heard of "Qld. Ignition leads" who make good quality performance leads from your fittings. Not sure how much they are but the genuine article is about $80+ Cheers John
Previous
