Razathorn

I originally posted this in the prelude section, but since its probably not a prelude specific thing, im putting it in here in hopes of getting some views by people who frequent the tech forum. I hope this isn't violating some rule.

My brother in-law's 96 prelude was oil starved. We swapped in a jdm h23. We had to wire the obdI motor to work with the obdII ecu (block vs distributor sensors -- this is an auto btw). The motor runs awesome, pulls like a champ, but after it warms up and heat soaks a bit, we get random missfire codes. It can be under full load, or just crusing at 40kpa on the highway -- and it doesn't feel like it's missing most of the time, but I think we 'felt' it once. In other words, it's a frustratingly hard problem to troubleshoot.

The ecu is not throwing any codes other than the p1300 p0300 and various p030x codes. The thing is running new plugs, we've swapped wires, ignitors + coil, cap and rotor, checked and double checked the wiring, checked timing (cam teeth and base timing with a gun), ensured the im dual runner vac motor is indeed operating, datalogged (via obdII scan tool) and watched to ensure the o2 voltage was showing lean when it should, rich when it should (like under full load), that the rest of the sensors were reading values that were very sane (including ignition & map values at cruise, load, and idle). I've done a compression test, leak down, and valve adjustment.

About the only thing we haven't done is to swap actual distributors -- and that is our planned next step.

I really need ideas here -- it's like there's a ghost in the machine. Please gimme some ideas for the next time I get to work on this car -- it's driving me nuts!

Wayne

alexm

Random misfires can be from worn spark plug tube seals. If you pull off your valve cover you'll see them right in the middle of your head, if they don't pull out with the cover. You could try replacing those, could do the trick, but then again it might not help.

Razathorn

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by alexm &raquo;</TD></TR><TR><TD CLASS="quote">Random misfires can be from worn spark plug tube seals. If you pull off your valve cover you'll see them right in the middle of your head, if they don't pull out with the cover. You could try replacing those, could do the trick, but then again it might not help.</TD></TR></TABLE>

Nah, there's no oil or anything in the tubes.

Razathorn

Is it possible that the sensors in the distributor have been wired wrong but it would still work perfectly for the most part but randomly detect a missfire?

Razathorn

Hrmm... no suggestions? I can't imagine we've thought of *everything*. Surely there's some silly thing that can cause this that we haven't ruled out.

King V

You went from a 2.2 to a 2.3 and didnt compensate for the difference in displacement?

Razathorn

No, it started with a h23 and ended with a h23. But in other news, I found out what it was with enough research into the difference in OBDII and OBDI on the prelude -- turns out the TDC sensor in the JDM OBDI distributor isn't compatible with the USDM OBDII ecu. It isn't a real missfire -- it's just noticing TDC oddness, and it doesn't seem to affect anything other than to illuminate the CEL and make it flash every 10 or so minutes, but it works wonderfully otherwise.

From what I read, the only solution to this is either to move to a jdm auto ecu or put a usdm oil pump on and use the tdc sensor from the old motor. So, until I find a compelling reason to spend more money when we're already in there, it's just gonna have to stay as is.

1stcrew

u KNOW WAT iM HAVE ONE ISSUES like dat 2. obd 2 to obd1 h22 dizzy