So, I've been chasing a problem with my daughter's '05 3 2.0AT (see other thread about O2 sensors). I've changed the upstream sensor (today), and it still isn't running right. I misunderstood my daughter- I thought the only problem she was having was CEL light and occasional die after first start of day, but apparently there's more.

I've changed the sensor, and driven the car. RPM hangs up at about 2k and you have to feather the accelerator to get it to rev past that, at which point it develops normal (seemingly) power and keeps going. When it shifts, and RPMs drop to that 2k again, it falls on its face again. I did NOT disconnect battery this morning when changing sensor, but I just did, hoping that had something to do with the problem. After letting is sit disconnected for 30 minutes, reconnecting, starting and letting it idle for 20 minutes, I tried to go drive it. It pops from under the hood (induction backfires?) and still won't rev up unless you work the throttle. CEL light was on after O2 replacement, but now that I had the battery disconnected, it has cleared- for now.

So, no CEL, but RPM hangs at around 2,000. Any ideas? I just read that there's no fuel filter in these things... Without CEL/codes, I'm at a loss. Looks like it's back to mechanic tomorrow for full-blown diagnostic. I'm getting sick of cars that just break halfway and that nobody seems to know how to fix. Ugh!

Thanks.

 

BTW- when you get the RPMs past the 2k hangup, it runs smoothly at higher RPM. Makes me doubt timing issue...

 

actual cel code(s) may have been helpful.
It could be running too lean (vaccuum leak) or too rich.
This condition could also cause an O2 cel.
Inspect for vaccuum leaks, leaks in intake hose before throttle body. While you are there clean your throttle body and MAF sensor.
These are all stuff that should be done by now.
Other things to look in to: spark plugs and ignition coils (especially if over 65,000 miles).
Change your PCV valve. Mazda doesn't change or inspect them but they do fail and could have a split in hose near pcv. I'm not saying this is your exact problem, but it's a real possibility and it needs to be changed irregardless.

 

I'll look for vacuum leaks tomorrow. I just cleaned the MAF sensor last week with the product you show. I also have the other can on hand- what's the preferred method for cleaning the throttle body? Remove filter and intake and soak it with engine turned off, or something else?

Thanks again, Noggin.

 

I'm tempted to order a $22 coil pack tonight and play musical coil packs- cheaper than a trip to the shop. The way it stumbles and pops under the hood (under attempted acceleration), an ignition problem doesn't seem out of the realm of possibilities. One of the Autozone code sheets from before did hint at a possible #4 ignition issue. I swapped 1 and 4 packs around. This was when I replaced all spark plugs and the problem (temporarily) went away.

 

Don't play musical chairs with the coil packs. From coil to plug you have a chain. So you are really playing "the weakest link". It is best to replace plugs, wires and coil packs together. And don't use the cheapest parts. Use quality parts.

 

^^^^^^^^what he said.
Make sure you disconnect battery when cleaning throttle body as it might otherwise throw it out of whack as it could be electronically controlled.
I like to try to remove it and have some room at back to catch all fluids with rags/paper towels. Get a new throttle boody gasket to intake.

 

The saga continues. Shop said ECM is fried and it has to go to stealership. Had it towed there and they said no to ECM, but wanted to do compression test. It passed that, now there's a fuel pump on order... Sooo much fun, this is!

 

WOW!

Hoping they checked fuel pressure.
Guess they are thinking not enough fuel pressure (lean).

I feel for you. I had lots of fun earlier as well: misfire, changed spark plugs, ign coil, fuel inector, fuel pump, gas tank---they thought it was warped (all under warranty), until finally it was exhaust/pre-cat manifold with poor exhaust design. pre-cat manifold was warranty but i changed everything from there back.
Oh, and I almost forgot about the automatic tranny replacement (warranty).
My car runs better than new now! :cool It better!

 

Oh, and its apparently a CA emission vehicle, so the pump would be under warranty even at 136k miles IF the car was registered in California. Ugh. The first and only time in the 21 years since I left that I actually wished I was back in CA!