Engine missing under load

[krayn]

Hi all,
Im having a few problems with my conversion. I placed a 96 crown majesta 1uz into early Holden. When it was first put in it ran well, didnt miss and reved out nicely. It has recently developed a miss. At first I thought it may have been the fuel pump as there were air bubbles in the return fuel line. this turned out to be a faulty fuel pick up in the fuel tank. I made a surge tank and set up a second fuel pump. I am now not getting any air bubbles in the return fuel line. I am confident that the fuel is not a problem but I do not have a fuel pressure guage hooked up so cant 100% rule out fuel pressure.
The engine seems not to miss badly when you free rev the engine but if you put it into gear and foot on the brake and stall it up there is a very noticable miss. At idle there is a slight miss. It feels as though the harder I rev it the more it missis or that more than one cylinder then missis. The miss sometimes is not always there. Also the point at where it missis can vary, sometimes a bad miss at idle and then other times it may not start to miss untill aprox 2000 RPM. Every now and then you start it up and it will run ok and not miss. At idle with the slight miss, I disconnected each injector plug to locate the offending clyinder but I could not seem to locate which cylinder it was, although I could not get to the injector under the throttle body so cant rule out this cylinder. My suspicions now are the plugs leads, spark plugs, distributor cap or coil. Can any one shed some light on what the problem may be? Any help appreciated. Cheers Kris

 

[krayn]

Found the Drama

Guys,
Im a happy Pappy. I decided to test my spark plug leads. When I removed the plugs on 5,6,7 and 8 I found there was water down inside the plug tube which meant the plugs and lead end were in water. Pulled all the plugs and leads out and they all tested under 20k ohms. Cleaned the leads up with crc and blew the water out with compresed air. The plugs look a little well used so some new spark plus are in order. While I had all the plugs out I did a compression test and the minimum was 220 psi and the greatest was 240 psi. Preaty happy with all the results. Cleaned up the spark plugs and put it all back together. Runs like a brought one. Real happy now. Just need to put my 3.7 ratio diff gears in and put it down the quarter.

 

[Peewee]

Spend $110 and get new Bosch dizzy caps and rotors too.
New Topgun leads are about $150, and new iridium plugs are about $15 each.

 

[Zuffen]

Peewee,

Where did you get your parts from?

The leads sound like very good value if they fit properly.

 

[Peewee]

My local autoparts store gets everything in for me.
I can get the part numbers for most things when I get home, but I'm pretty sure they are in the latest Bosch/Topgun catalogues.
Just look under Lexus, I think its there for SC400 or LS400

Leads are 5mm replacements (or 5.5?) but fit fine.
Some leads are 1 to 2" longer than factory ones, but they still fit under the covers easily.
They don't come assembled like the factory ones (ie, with the clips, and spirally covers on them, you have to transfer all that over yourself).

But for a saving for $250, it was worth it.
Under an hours work, a few beers, and a bit of swearing is all thats needed.

Some don't recommend it, but I do.