Went to replace the spark plugs on my 2006 Mazda5 2.3L when I discovered engine oil in the #1 spark plug well. I'd been losing about 2 qts of oil per month and after not seeing any signs of a leak below (well, not since fixing the engine oil cooler gasket issue but that's another thread) assumed it was burning it. Apparently it is burning it, just on the exhaust rather than in the cylinders.

Anyway, disconnected the coils and other lines and sensors and removed the valve cover to find the gasket around the number 1 plug to be not quite all there. Replaced the gasket, installed new plugs, reconnected everything, and now the car cranks but won't start. Attached the MODIS and first it tells me P0230. Check the voltages on the fuel pump circuitry and everything seems okay. Then I clear and retest and it tells me the crank position sensor is bad. Replace it and still no start (tested the old sensor and it was fine). Next it tells me the cam position sensor is bad. Replace that one (of course the old one tests fine) and still no start.

It seems like the engine can't make up its mind about what is wrong with it. I feel like I'm missing something obvious but I can't think of what. Meanwhile I'm taking up a bay in my mechanic's shop and I feel I'm starting to wear out my welcome. Ideas on what to try next?

 

Bring up the RPM data on the MODIS and see if your getting any RPM reading while cranking. If yes, crank sensor good and PCM knows its cranking. Before you start your RPM test, turn key to on position and listen for the fuel pump. Should run for about 2 seconds. If you have a crank signal (RPM) and can hear the fuel pump run, pull a spark plug and see if it's wet. That would be a yes or no to fuel injectors triggering. Double check, as I'm sure you have, all the connectors you took apart to replace valve cover gasket, especially the grounds. If wet, your last piece to the puzzle is spark.

If the plug is soaked, and in the rare case the engine got flooded, do a clear flood start attempt. Key off, put the throttle to the floor, then crank the engine. This turns off the fuel injectors to clear any excess fuel from motor. Keep your crank time to 10-15 seconds.

I threw a bunch of common errors at you and hope one of them helps find the problem. If it was working before your got it there, then chances are your missing something and bets are it's something simple.

 

Thanks for the ideas. I'm sure it's something simple I'm missing - the car was running fine when I brought it in. It was one of those "dead simple" jobs of "I'll replace the lower control arms and oh, I suppose while I've got it in here it's due for new plugs" that just escalated out of control and I wasn't in the mental state to be diagnosing engine control issues. I'll take a look at the grounds and make sure I haven't missed anything and also do the RPM test on the MODIS. Barring something obvious, my suspicion is that I broke a wire internally somewhere removing the leads from cover.

 

Just realized I never followed up on this.

It turns out it was a broken wire to the cam position sensor. Testing continuity with the harness disconnected everything checked out. As soon as the harness was reconnected the wire opened. I wish I had figured it out, instead I had it towed to the dealer who diagnosed the intermittent open. Installed a jumper and the thing started up fine.