Problems and Misfires

[ksmustng]

I sold my aunt my 98 SHO and the other day she was driving over a speed bump and the car died on her. She started it up and it was missing very bad. I went and picked it up today from her work and took it and scanned it. It's showing misfires on all cylinders but 2. It will start but it's apparent that it's not running on anywhere near all cylinders. I listened for any ticks as I thought maybe the cam had failed but I don't hear anything.

If the cam did fail would I be able to hear something?

I feel somewhat obligated to make something happen with this beings I sold it to her.

 

[NebraskaSHO]

Does it sound like a diesel? If it's missing on all but two I can only imagine it's a cam, or some wiring might have got jarred loose.

Question is, how many miles are on it?

 

[ksmustng]

It's over 100k. Not exactly sure where at though. Hopefully tomorrow it won't be snowing so I can dig into it a little more. I do know I replaced one of the coils before I sold it to her. Just seems weird that multiple coils would fail all at once. What's weird is 5 and 6 are the two that aren't misfiring. Those are on the backside right?

 

[Mr Anonymous]

5 and 6 are on the front bank. Here is the cylinder layout:

Firewall
1 2 3 4
5 6 7 8
Radiator

I highly doubt it's a cam issue. IIWM, I'd check the following items:

1. Crank sensor
2. Fuel pressure
3. Electrical system (including power ckt to coils)

Also, any chance she could have injested any water into the motor when going over the speed bump?

Remember that the misfire detection monitors detect misfires generically and it doesn't always mean a coil. Bad coils and injectors have their own codes and while a misfire is usually a coil in this case a 6-cylinder misfire suggests a problem not related to one or more individual coils.

 

[stephen newberg]

However, even if Chris is right, at that milage the cam issue is only a matter of time, possibly very little of it, and you might want to discuss that with your aunt, if you have not already done so, as selling to family can have reprecussions without full disclosure.

pax, smn

 

[ksmustng]

Well it definitely smells of unburnt fuel when it's running. Which would indicate something in the ignition. Other then that it may take a day or two for the weather to start cooperating again.

 

[66goat]

Just a thought, bad bump ,surge tank bounces, shorts/pinches worn rear wiring harness=misfire

 

[ksmustng]

I know this post is a few months old. But I started working on this car again. I bought a new coil and that don't seem to improve anything. I tried a spark plug tester (attachment thing that goes between the coil and plug). The light lit up on all of them like it should be firing. Seemed semi erratic so I've been thinking about replacing the CPS. I also stuck my inductive timing light on one of the leads to a coil. It seemed to fire off as the light flashed. Just not sure if it was in sink or not. Would it be possible for the coils to partially fire? Or is it a if it's bad it's completely bad type of thing?

 

[ksmustng]

Well I've checked two out of the three listed above. Replaced the crank sensor and the coils are getting power and signal. I'll pull out my fuel pressure stuff tomorrow and see where that gets me.

Could it be the cam sensor? Maybe the injectors are firing at the wrong time? I pulled one of the plugs and it seemed to be wet so it is getting some fuel.

 

[SHOZ123]

Cam sensor is only really used at start up.

Have you pulled the valve covers off yet?

Have you checked the rear wire loom for the coils for shorting out against the valve cover?