Car trouble - running rough, flashing check engine light

Discussion in 'SN95 4.6L Mustang Tech' started by pinski, Dec 27, 2008.

  1. Hey guys,

    This morning, I took my car (1997 Mustang GT) to a local Precision Tune for a routine oil change and coolant flush. After they finished, I ran over to Best Buy to get an additional Wii-mote, and it was running just as well as it was before I took it in. After leaving Best Buy, I was headed to get some lunch, and the check engine light popped on. No biggie, I figure, this thing puts that light on all the time. I stop at my lunch destination, pick it up, and get back in my car to head home. As I'm sitting at a stop light, it starts to run a little rough, like it's missing a little bit - you know - burble, burble, burble *cough* (shudder) burble, burble, burble *cough* (shudder), etc.

    Anyway, I get it back to my garage at home, and popped the hood to check for anything looking out of the ordinary and for any leaks. Everything looks great, one weird thing I did notice was when I shone a flashlight under the intake manifold, there was a hold in the top of the block, like a plug was missing or something. I've never really looked too closely under there, so I don't know if that's what it's supposed to look like or not, though I doubt it.

    So, I let the car cool off for a few hours, and then head back out there. I notice the coolant level is low, so I mix up some and fill it back to full. Also checked the oil level and it seems fine, as did the gauges in the car when it was running. I crank the heater up and let the car idle for 5-10 minutes and it seems fine, burbling away happily, idling in my garage. I decide the time has come for another road test. I back out of my driveway and it seems normal, and then accelerate down my street, and feel the obvious lack of power. I turn right onto a bigger street and try to accelerate, and it's getting worse... to top it off, now the check engine light is flashing at me and the car is shaking a bit harder. Assuming this is bad news (a Google search when I got home confirmed this thought), I immediately turned down a side street and limped her back home. About halfway home, the flashing stopped, but the light remained on. It still drove roughly, and when I pulled it back in my driveway and hopped out, I thought I smelled a faint sulfur odor, which made me immediately think of the cats. I don't know what's wrong with it, but the behavior and slight odor are making me think it's emissions system related.

    Exhaust system is all stock, car is mostly stock now aside from a Densecharger, tune and few other minor things. Do you guys think anything the shop did today could've had an impact on what I'm experiencing now? Is it just a coincidence? Could that hole on top of the block have anything to do with it, maybe they forgot to put a plug back in after draining the coolant?

    Sorry for the long post.
  2. You need to make sure if you are missing a plug. That would give you the issues you describe. Do you have a digicam? Snap some pics and post them.
  3. Pic of teh hole:


    Hole circled, in case you couldn't see it. This is a threaded hole, like there's supposed to be some sort of plug in it:


    Other engine bay pics - aside from it being dirty, does anything else look disconnected or out of place?


    Another shot of the top of the block, underneath the intake, though it's a different view of teh hole:

  4. That's not a spark plug hole... that looks like its underneath your intake manifold. It's easy to see if your plugs are there... run your fingers along the wires and check!

    Sounds like a plug wire is not connected completely. Push down on all your plug wires to make sure they are seated completely.

    P.S. Clean your engine bay and become one with your car... And let me spank your ass some more... why are other people changing your oil and doing coolant flushes? If you want to own a Mustang and be all cool about it, be the guy that throws the wrench, don't pay people to do it.
  5. What GDawg said could very well be true about your spark plugs.

    I had a similar problem about a month or so ago - check engine light came on and the car was running rough. I took it to the parts store & had them read the code. Turns out plug wire #4 was bad & needed to be replaced. $50 for the wire and a bit of my sweet husband's time to put it in for me and my car was running like new again!

    Oh yeah! Oh OBDII code reader (like the auto parts stores have) run about $100. After my incident, my husband bought one so now we'll be able to read any future codes ourselves. Plus the reader will clear the codes.
  6. The flashing MIL indicates a randomly occuring misfire. The first thing I'd do is check the plugs and wires. Your damp-looking valve covers look to show a bit of gasket weeping; perhaps the plug wells have filled with oil over time?

    You might want to check your battery terminals; in the one pic, I can see what looks like a fair amount of corrosion setting in on the positive terminal (the white, powdery stuff...) I'd clean your terminals and verify the condition of that wiring too.

    As well, your accessory belt looks to be in need of replacement. Lots of small cracks...
  7. don't feel too bad, I'm at 72k miles and just changed my oil for the first time a few weeks ago. I wasn't allowed to change oil at my apartment complex though.
  8. Sounds like a plugs and wire problem. If that's not the case, ck all hoses for leaks(air, fuel)...good luck...Damn oil change companies!!! Sorry, if you can not work on your car yourself....find someone(very mechanic shop) and establish a relationship.
  9. Thanks for the reprimanding - the only reason I've had it done elsewhere is just because I've yet to pick up the right tools to have the job done right. Bought this house in April and haven't gotten around to it. The year before that I still lived with my folks, so I could borrow all my Dad's stuff and do it myself.

    As far as cleaning it up... it's a daily driver, not a show car. It would be laughable to keep a $3000 car in concours condition.

    I appreciate the thoughtful response - it was pretty much spot on. Limped it over to Auto Zone and had them read the codes.... one was a bad EGR valve, and the other was the misfire in cylinder #3.

    From those codes, the recommended solutions were to clean out the EGR with some carb cleaner and to replace the plugs to help with the misfire.

    My Dad came up to help me, and we started with the EGR valve, cleaned it out - it did have quite a bit of carbon, and then we created a vacuum on it to ensure that we could hear it open and close. We also tested that the vacuum line was sound once we had the car back together again.

    We replaced the plug on cylinder 3 first, and it came out covered in some fluid - didn't smell like gas or oil, but was definitely one or a combination of both (possibly the seepage you mentioned). Our estimation is that the plug went bad, and then the fuel started getting up in there, but your observation might also be the culprit... it also didn't seem like it was seated down in there properly. So we cleaned up that hole, the connection in the boot, and replaced the plug. Since we were into it, we ended up replacing all the other plugs, and it's amazing the amount of sludge that was built up on some of them. I had thought that they had never been replaced, but it was running Bosch Platinums, which we replaced with Motorcraft Platinum.

    All new plugs, new serpentine belt (I've wanted to replace it for awhile), and the cleaned up EGR valve - cranked right up, CEL still on (but I think it has a certain number of cycles it must go through before going out) and took it for a test drive. Drove like a dream, just like it used to - took it for highway, stop and go, stopped and started the engine twice and it seems to be back to its old self.

    That fluid on the plug in cylinder 3 still concerns me, and I'm a little worried that it might just be a matter of time before I have to replace it again. Do you think it might be prudent to pull the valve covers off and replace the gaskets?

    Yeah, it's mainly because I haven't taken the time to get my supplies yet. I really need to get the proper tools necessary to do the job myself. It appears as though it wasn't anything that shop did, just a bad coincidence, but I understand the thought that it's nice to know exactly what was done to the car by your own hands.
  10. Excellent. The MIL will probably go out after a few driving cycles. Might want to double check all of your connections just to be sure.

    It's a pretty harsh, non-sterile environment so I wouldn't worry too much unless stuff is gushing out. A little bit of weep is generally more of a cosmetic nuisance than anything. If it's bad enough to get into the plug wells you might want to diagnose a bit further.

    There's generally two sources of fluid in that area: coolant or oil. You might have residue in there if you've ever degreased or power-washed the engine too. Even if it's oil from weeping VCGs, it mightn't look like oil after a year or two due to dust and grime mixing with it. Cylinder #3, BTW, is close to the PCV valve (at least it is on my 02GT): You might check that area on the passenger side VC for signs of leakage there. The PCV valve is probably due for replacement anyway...

    What you can do is clean up the area with a rag and solvent and go back in a week or two and (a) double check the plug torque and (b) check to see if there's any fresh fluid.
  11. That hole in the block would be for a knock sensor if I am not mistaken. Our cars don't come with them, but I believe thats what would go there, just for future reference.

    Glad to hear it's fixed.
  12. "...your sweet husband..." You know you're still in love with me. You only married him cause I wasn't available... And now you won't talk to me anymore. I wonder if you ever come around anymore...

    (back from the dead)