Engine mis-fire/ shutter / skip

svxcuseme · #1 01-16-2006, 01:30 PM

All,

I occasionally get, what I call, a mis-fire. It is RPM independent. It does'nt happen often but when it does it's very noticeable. I'm statring my troubleshooting.

I have cleaned MAF sensor. - This brought voltage back into spec.
I am replacing plugs and coils this week. (coils will be used but are all funtional). I'm also going to pull the intake, replace PCV, and give the baffles and IAC a good cleaning in Carb cleaner.

However, I think it may be coil related. When pulling the coils, a couple have cracked wire insulation just as they go into the coil housing. I think these wires could easily short out causing the skip. What do you think? Has anyone ever repaired/insulated these succesfully?

I can wrap them in electical tape, bought thought 100% silicone around the wires, as they enter the coil housing, might insulate them from each other better. Any thoughts / experience here?

Thanks

mbtoloczko · #2 01-16-2006, 02:49 PM

"Liquid" electrical tape is available now. I've seen it at Home Depot or Lowe's. Can't remember which. If its related to the IAC or the PCV valve, that would imply that one of these is causing a momentary very rich or very lean condition which doesn't seem likely.

oab_au · #3 01-16-2006, 03:09 PM

Coils can break down in the internal windings, especially if they are run open circuit, not fitted to the plug. Most of the shorting takes place at the rubber boot that covers the plug. They age over time to conduct down the side, shorting the spark from the plug. If you check the plug covers carefully, you may see a black line running up the side of it. This can be scratched out, and sprayed with a light oil to seal it, but they can be replaced with some off a set of 'after market' plug leads.
The leads that run to the coils, should not cause a misfire, but I would seal them anyway.

Harvey.

svxcuseme · #4 01-25-2006, 12:30 PM

I replaced the coils with known working used ones (from spare SVX). Unfortunately it was'nt the coils. At the back of the SVX manual, Fuel Injection Section, there is a troubleshooting table. That tables describes a condition called "Shocks while driving".

"Shocks" definately describes my condition. It's felt as a shock to the drive train, so I guess shock is appropriate. I'll start using their hierarchy which starts with CrankSensor 1, CrankSensor 2, Cam sensor, ... and ends on coils, plugs, and MAF. So, I'm off to parts swap and a little volt meter detective work. Wish me luck!

P.S. I ended up using High temp RTV Silicone to seal the exposed lead wires into the coils. Everything I read says it is an excellent electrical insulator.

Earthworm · #5 01-25-2006, 03:08 PM

Have you checked that all the bolts are tight on the intake?

svxcuseme · #6 01-25-2006, 04:31 PM

Nope. Thanks for the tip. I'll give em' the once over.

19svx94 · #7 03-11-2006, 12:38 AM

hi, i have a 1994 svx, and i just started having a problem in the upper rpm's, around 5000-5500rpm the car cuts out for a split second and then comes back in, the check engine light pops up everytime it cuts out, i know this problem exists in park, nuetral, d,3,2, and 1. i have not tried anything to fix it saying how the problem just started arising today, i believe it may be my MAF due to my idiot friend who sprayed about a half can of carb cleaner straight on it while keeping it floored to try and clean out the carbon out of my intake. i will keep my solutions posted.

19svx94 · #8 03-12-2006, 11:01 PM

i have solved my problem and i do feel stupid, my air filter had become soaked due to the massive puddles that i was driving through the other day and my intake sucked the filter up causing the mas air to read wrong, i also took my intake manifold off and cleaned my bypass air control solenoid valve, this fixed the idle problem, the only bad thing that happened was while i was in the process of redoing all of my vacuum lines because they were all brittle i broke the infamous black solenoind that is on the passenger side, i had one on my parts car and while i was trying to take the "plastic" vaccum hose off of that i broke that one to, so until i have time to go to subaru and get another one i have just bypassed the solenoid.

Dessertrunner · #9 04-15-2006, 02:01 AM

Do the US cars have EGR value and does anyone have experiance with them causing problem with the running of the engine.
Tony

svxcuseme · #10 04-15-2006, 01:21 PM

Yes, we have an EGR valve. No problems with mine. sorry

svxcuseme · #11 05-20-2006, 10:55 AM

Well I replaced the coil boots with new ones from another set of spark plug wires... they are a little longer, much tighter, and seal much better. No luck.

My problem is getting worse. Now it's missing like crazy once the car gets warmed up. When the car is cold no noticeable miss. At this point I'm leaning back towards a bad coil.

My wife had this issue on her car. Car ran fine until warmed up and then started shuttering like crazy. Turned out to be the primary coil. Anyone want to weigh in on this. I think I'll pull all the coils from the spare car and replace the 3 on the PS, drive it to see if it was one of those, then replace the 3 on the DS if necessary.

Would you guys agree that the symptoms are pointing to a bad coil?