Engine mis-fire/ shutter / skip
 

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

"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.

Coil shorting out.
 

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.;)

Not a coil - darnit!
 

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!

:o

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.

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

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

check the rubber boots around the end of the coil that goes onto the spark plug.

It's not the boots. I inspected each very closely for any sings of spark leak. I also replaced each sequentially to no avail. Intake bolts are tight.

Seems a lot of people have this problem but nobody on here in the past 14 years has ever fixed it. It's the big SVX mystery. I've got this problem too so let me know if you get it fixed.

discouraged
 

Update
Replaced both cam sensors and fuel filter. No change :(

To do
Swap ignitor and crank sensor (although I don't crank sensor will make a difference)

I found out why the car dies under hard acceleration...Rev limiter is kicking in around 5500-6000 rpms. :o I also found that the car idles high for the first 15 minutes of running after cleaning the throttle body, plates, and intake chamber. It goes back to normal idle after warmed up good. Well, at least it's nice and clean now and the top of the engine is spotless...no more grease evywhere :)

Still I can't figure out why I get this shudder under light acceleration 1500-2000 rpms under load (uphill usually). This can't be normal, right.

im assuming there is no chedk engine light? This soundsl similar to my bypass air control solenoid code that i've been throwin a code for quite some time now...

no codes
 

Yeah I'm leaning back toward air flow. I read some more posts and I'm going to try another MAF. When I measured my original (according to the SVX manual) the top value was out of spec but the lower value was in. I cleaned both with carb cleaner and the top value came into spec but the bottom value fell under and remained unchanged when the car was running. I did'nt think much of it at the time but maybe I'm being an idiot and screwed up the MAF cleaning it too much. I know these resistors are very sensitive. :o

I'll see how a new (all values in spec) MAF works and report back. Thanks for the help.

Please solve the great svx mystery and let us know.

Here's a couple of cents worth of info...

I fought an intermittent stalling problem for months. I changed everything I could think of except the MAF sensor. Those dudes are so expensive new. I cleaned the old one a couple of times and still stalling. Finally found a used one and installed in. The car hasn't stalled since. Never a check engine light by the way.

Thanks for the info Bill. My problem is a little different. I get jerks or stumbles as the car accelerates, usually under load and under 2000rpm. I also get a serious stumble/jerk when accelerating hard sometimes between 3000-4000 rpms. I did have a stalling issue until I changed the MAF. I'm totally stumped.

I've swapped the following parts to no avail.
-MAF
-Ignitor
-both Cam sensors
-New TPS a couple months ago
-Cleaned intake and TB
-New PCV valve
-New plugs (OEM)
-replaced all coils with used working
-new fuel filter
-?????

I'm going to look at my crank pulley, crank sensor, and timing setup. I have'nt changed the timing belt since I bought the car. It is due. Maybe there are some clues under the timing covers. Also even though I never saw evidence of spark leak I may try and seal up the boot or find new boots and eventually new coils :eek:

Question
Anyone no where to get new boots for our coils and what the part number was (Assuming you bought a new wire set and used the boots)?