Mileage drop of 21 MPG - need mechanical advice

[Frank Lee]

Right now, when it won't even fire, is the perfect time to do a quick diagnostic. Pull a sparkplug, connect it, ground it, have a helper crank it over, and check for spark- and the quality- nice blue snappy arc- of that spark. If that's bad focus on ignition problems. If it's good, focus on the fuel system. Perhaps do a compression test to rule out any long-block issues.

[Cd]

Thanks Frank.

Supposedly when I took the car in to the shop, they did a compression check and it checked out " just fine ".

I also am pretty sure the fuel filter is working O.K. since I hear the whirring noise when the ignition key is turned to the on position, but this is from inside the car.( I think the whirring noise that I hear is the fuel filter being pressurized. It goes on then shuts off after a couple of seconds.

I tried doing the spark test earlier, but I don't have a helper handy.

It's been so long since I had done a spark test that I may be doing it wrong. I just pulled the #4 plug out and cranked it over while having the plug dangling out of the wire. I couldn't see anything, so Ill have to wait till I can find a helper.

I didn't ground the plug when I did the spark test though. I'll research how to do that now.

Thanks everyone for the help.

[Cd]

If the ignition was bad though, I would think that the car would run rough at idle. The car ran very smooth at both idle and even when flooring it. No stuttering at all.

[vskid3]

Originally Posted by Cd

I tried doing the spark test earlier, but I don't have a helper handy.

It's been so long since I had done a spark test that I may be doing it wrong. I just pulled the #4 plug out and cranked it over while having the plug dangling out of the wire. I couldn't see anything, so Ill have to wait till I can find a helper.

I didn't ground the plug when I did the spark test though. I'll research how to do that now.

Just make sure that the threads or hex portion of the plug is touching something metal like the valve cover. You can probably find a way to set the plug down so it'll touch and you can still see it while cranking.

[Cd]

I just tried the spark test, and as I turned over the car, the thing tried to start.
I put the plug back in and it fired right up.

Great - now I have a ghost in the machine. It starts when it wants to and then quits when it wants to.

Im afraid to even drive the car now for fear that it won't start again.

The car idled perfect with no hiccups at all.

[Frank Lee]

On/off failures are often electrical in nature; sputtering is oftentimes fuel related *but not always*. Maybe the new coil has issues too????? Inspect connection tightness, wire integrity, cleanliness (oily grime can short stuff out)...

[Old Mechanic]

Clean your engine to chassis ground connections. Also battery terminals and both of the other ends of the battery cables. Make sure the battery is working properly. It should have enough reserve to turn the headlights on for 20 minutes (with the engine off) and still start the engine and run properly.

regards
Mech

[werner]

I would also check the TDC (top dead center) sensor. Especially if the starting/ not starting of the engine is temperature related.

I've had 2 cars in the past that had a problem with this sensor; one car wouldn't start after a cold night, but started just fine after it had warmed up during the day.

The other car started just fine, but during warm up, after ± 5 minutes of driving it sometimes just died and wouldn't start anymore. After waiting 5-10 minutes it started again without any problems.

In both cars changing the TDC sensor solved the problem.

[cfguy2000]

I had car start problems this week too. Turned out to be a corroded battery cable. At least it was a cheap and easy fix for a problem with severe symptoms.

[Backtobasics]

I'm with Old Mech.

I have seen a 1/2 a dozen problems recently, all are traced to poor grounds in the engine compartment. There should be a clean ground from the negative terminal to the body, and one or several grounds from the engine to the body.