carzntune

I'm going to need some help on this one. My car is misfiring in the midrange and I'm having tach issues.

Here's the brief setup:

b18c (AEBS 9:1 Manley/CP combo)
S2 valves/springs/retainers/stg. 1 tuner cams
Full-Race kit...GT30R .82 housing
AEM alky injection (50/50 meth/water)
S300 boost controlled via MAC solenoid
RC 1000cc injectors


Here's the problem:

On the dyno and street the car breaks up in the 5-7k range if boost is above approx. 15psi. Seems ok below that level and it's ok before and after that rpm range. Plugs had to be gapped super tight (somewhere in the .017 range). I wish I could post boost/dyno plots but I do not have them.

Another item related to this is my tach. It has a mind of its own. Typically works on initial startup but will sometime quit completely. When it is working, this is what I see. It'll bounce to zero if I reach somewhere in the 5k range (ironically enough roughly where the misfires occur). If I let back off the throttle it usually starts working again. Another small thing I noticed about the tach is it's extremely sensitive to voltage drops(turning the headlights on, switching hi/lo beams, turn signals). It'll bounce slightly with those events but the engine won't stumble.


Here's what has been tried:

1. Another coil in original distributor
2. Another distributor
3. I replaced a poor condition ground wire on the valve cover.
4. The different nozzles in the alky injection kit
5. I believe the spark plug wires were swapped as well

I think that is all. I don't want to give up on this setup quite yet but it's far below the potential. It made 505whp/350tq at one point (20psi dropping to 17psi at 9k). The Perrin solenoid was swapped to a MAC cause it wasn't holding boost in the upper range. Since then it hasn't been right. Plan is to go with the AEM EMS/C.O.P. setup but I'd rather do that later than earlier.

Any ideas are welcome. Let the troubleshooting begin!


Modified by carzntune at 6:15 PM 4/1/2008

JordanCivic

Whats the battery voltage reading on S300 display? If its below 13.5v check the alternator/ charging circuit. Low battery voltage can cause all the symptoms you are having.

carzntune

I can't tell you what Hondata is reporting till Saturday...friend borrowed my laptop. The battery is new and my multimeter is showing good voltage at idle.

NJIN BUILDR

Try disconnecting the tach.I have see a couple tachs cause misfires (not Hondas ).My latest first move is changing the igniter.

carzntune

I'll try disconnecting the cluster. The ignitor is something I've been wondering about based on the tach issues. We did try a second distributor so it makes me skeptical of that.

I got my hands on yet another distributor this afternoon. I'm told it's good so we'll see if that helps tomorrow. If 3 different distributors and coil doesn't clear it up then it'll probably become much harder to find.

I have a bunch of 4 gauge audio power wire so I'm going to make a grounding system. Unfortunately I don't have any connector ends so I have to wait to get to the stereo shop.

carzntune

Did some work on the car this afternoon. I went through all the connections on the "new" distributor and installed it. Good news is the tach works beautifully. Sadly it still misfires. At this point I'd say distributors can be ruled out as the problem.

The engine ground connections were all cleaned up as well.

To answer the question about battery voltage....Smanager is reading ~14.2V.

RedneckRicer

tach issue is most likely tied in with the ICM in the dizzy. My bet is on the coil. have you tried stepping up to a HVC coil external or something similar?
Also what kind of plug wires are you using and brand of plugs?

carzntune

Tach works good now with the new distributor. I guess it could have been the igniter. 3 different factory coils have been tried at this point. I'm running stock wires and NGK BKR7 plugs.

I haven't tried an external coil yet.

extralargenog

iTrader: (1)

If you are running non resistor plugs Thats the problem. I had the same **** happen and went crazy trying to figure it out.. NEver mind saw youre running the resistor plugs....


Check all your grounds.

carzntune

That's next on the agenda. I cleaned up the connections already but I'm going to replace all of them with 4ga. audio wire now that I finally got ahold of some ring terminals.

These are the stock grounds I know:

tranny bracket to chassis
shock tower to neg. battery terminal
valve cover to front support
the harness grounds to thermostat housing

Am I missing any?