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93 eclipse 4g37 turbo.

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Caution, boring story time.

Okay so i got my arp head studs and installed them. So now that i'm satisfied with my head getting proper clamping force it was time to retune it and start having fun with it. Well so i thought. Was quickly disappointed again. Came to find out it has a nasty miss at 3-4k. I haven't put my foot down on it since i swapped out the head due to the boost issue, and the head nut situation, so this seemed to pop up out of now where(turns out its probably been an issue for a very long time). So for the past 2 weeks i've been trying to figure out just what the hells going on. Tried leaning it out, enriching it, advancing timing, retarding timing. Nothing made a difference. 99% of the time it missed in that rpm range, the other 1% it pulled just fine. Eventually figured out it was rpm dependent. It didn't matter how much boost or what the throttle position was, it missed at that specific range. So im thinking its something electrical. So i decided i had to get my data logger working again. Got it working and started logging. First off noticed my engine temp sensor was bouncing all over the place. Narrowed that down to loose pins on the plug. Fixed that but didn't make a single difference surprisingly. After that the logs looked perfect, nothing seemed out of the ordinary when it started missing.

Completely lost i decided to go over everything. First thing i did was put in new spark plugs, did some pulls and then removed the plugs to see what they could tell me. Aha plug number 3 looks lean as shit. Ohm out injector 3 and it fine. Tested the others and they were good. Replaced injector 3 with a spare in case it was clogged. No change, miss is still there, but that cylinder doesn't look lean no more. So then i go through and ohm out the injector wires, all were fine. So i pulled the pins from the ecu for the injectors and tightened the pins, did the same with the injector plugs. Still misses. Looked up how to test the distributor, primary coil comes back right at the limit for replacement, secondary, can't get a good reading for some reason, same thing for power transistor. So i'm thinking it might be my distributor or maybe a bad injector driver in my ecu. Not 100% sure whats wrong so i keep testing stuff.

Wondering if my valves are sealing right i go through and readjust all my valve lash settings. Get those good. Time to see what a compression test and leak down test say. Compression test came back at 180 across the board, leak down was just as good with at the most 7% leak down. Those numbers made me very happy since that's as good as new practically.

So its either my ecu or distributor. At first i was leaning more toward the ecu, but after a lot of reading up on ignition systems (admittedly before i just figured either they work or they don't, not no in between iffy things) It all started to make sense. Lately my car has run like crap for the first minute of the first start up of the day, and then smooths out once it warms up. I just figured it was due to the fact that i'm running way bigger injectors than stock and the startup enrichment procedure the computer goes thought didn't play well. Also has a slight miss every so often when idling. Turns out that could be a symptom of a coil with too much resistance and/or a power transistor going bad. So then i go back and do what i need to do to be able to get a good reading from my secondary coil. Finally figured out a way to do it, and it comes back right at the limit as well.

So now i'm convinced of the issue, the distributor is going bad. The upull it yards here don't have any 1.8s and i don't want to drop over 200 on a new one. Definitely don't want to order a used one either, so i start seeing what else i can do. Stumbled across a thread on talk in the 1.8 section talking about how the mazda mx-3 guys distributor may be similar in the way it works compared to ours, and how they run external power transistors and coils. Thread didn't have any solid answers just a link to the mx-3 write up. So i checked it out, looks promising. Dig up a circuit schematic for our distributor and see how the internals are set up. Pulled apart a spare harness i had to see how everything was wired together, and also ripped apart a spare distributor to see how it looks and to understand the schematic better.

As far as i can tell it looks like it should work, so i head out to autozone and pick up part # dr100. Wired it in, flicked the key, and its good Internal power transistor succesfully bypassed. Take it for a spin, First 2 pulls perfect! next one misses some but pulls through it and clears up. Play around and have some fun. Still misses but no where as bad. Just need to replace my weak coil and it should be golden. Hopefully in the next 2 weeks i'll be able to add a msd/accel coil.

I neglected to mention some details about the head i swapped in since i wasn't able to push the car to see the fruits of my labor, if any. The work i put in it seems well worth the days i spent on it. Lapped all valves. Intake side was ported a lot, and i would say a good amount of work to the bowls removing the sharp edges and opening up the sides. Exhaust side got the same treatment, but it was also polished. Intake and exhaust(stockers) valve faces and combustion chambers were polished to help lower combustion chamber temps. The ass dyno says 15lbs of boost feels like 20lbs on the old head. And full boost 20lbs + is just wow. I actually get some wheel spin in 4th gear now. Need to come up with some more cheap traction upgrades now.


arp head nuts.
View attachment 245373

Valves before polishing.
View attachment 245374

Valves after polishing
View attachment 245375

Kidneys polished
View attachment 245376

Had ported this head along time ago. Went back and did more porting/reshaping on the exhaust, then polished it again.
View attachment 245377

Can't remember if i touched up the intake side some or left it how i originally ported it.
View attachment 245378

The power transistor wired in and mounted.
View attachment 245379

wiring diagram i made
View attachment 245380

ecu pinout diagram i made.
View attachment 245381

The 1.8
View attachment 245382
What does this help with exactly?
 
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