Toymans generosity (a tale of a 2004 Mazda 3 manual)

Re-skimming the thread, have you checked the air filter and cleaned the MAF? OBDlink SX cable and ForScan might not be a bad Google rabbit hole to go down if you need more diagnostic power in the future. 

I'll look into that for sure.

I disconnected the upstream 02 sensor.  No difference.

I'm gonna go do the same test again with the o2 electrically connected, but not in the exhaust stream.

Tomorrow I do a compression test.

Still no codes even with a code reader that can read all of the modules and everything.

Did a compression check.  All cylinders right at 150 across the board.

All spark plugs / coils go zappy zappy.

No weird looking spark plugs.

I didn't start the car again because I ran the battery down doing the compression and spark checks.

Okay, I got some more data.  But I need some help understanding what it means.

I hooked up a pressure gauge to the fuel system.  I got about 54psi (at idle or revving to 4k - unloaded in neutral).  This seems sufficient to me.  Even sitting still,  it won't rev over 4k.  It does not appear to be a controlled limiter.  The engine starts running very rough at 4k.

If you hold your foot on the floor, the engine will rev quickly to about 3.5k and then struggle to get to 4k or a bit above.  If you keep your foot in it, the engine will start pinging and misfiring after a few seconds.

I have pulled a few codes from the ecu.  The first was for random misfires (makes sense because you can hear the misfires).  The second was for bank 1 sensor 1 lean.  I do believe it is running lean and thus won't rev.

I also looked at live data while running.  The short term fuel correction quickly goes to 25.  The engine runs pretty well when this is happening.  After some number of seconds (like 5 seconds), the correction resets and the engine goes back to running like crap.  The long term fuel correction is sitting at about .7.

So, where do I go from here?  How do I check the MAF? 

Should I pull injectors and check for dirty injectors? (I have an injector controller and graduated cylinders to check if they are meeting their expected flowrate.)

Also, all of these symptoms could be from timing being off.  It seems like a big pain in the butt to check timing on this engine (mechanically).  

Any way, I'm open to suggestions!

Summary:

-idles like crap - tries to die while idling at like 800rpm and shakes.

-Won't rev past 4k rpm.

-makes about 30 hp.

One of my next steps was checking timing. Physical and electronic.  

In reply to Toyman! :

I forgot, did you change the coils or was that the PO?  If it was you, can you tell me what was happening to the connectors that they were all replaced?

Last thing...  did you ever find the title?

Thanks!

In reply to wvumtnbkr :

I changed the coils. When I bought it the coil connectors were severely deteriorated and I replaced them. 

The wife mailed the title week before last. If you don't see it soon, I'll get a duplicate and send it to you. 

How old is the gas in it?

On my Mazda 3 the coils are 3 wire, I noticed yours are only two wire, But I have the 2liter.

echoechoecho said:

On my Mazda 3 the coils are 3 wire, I noticed yours are only two wire, But I have the 2liter.

My wife's 2.3 powered mazda 5 is also 3 wire.

I looked at rock auto and it seems that 2004 was just 2 wire.

I'm starting to be convinced that this is a fuel injector issue...  I have the tools to diagnose them.  I will get around to it in the next week or so.

Any chance there's a big vacuum leak somewhere? 

What about amount of fuel v. pressure? Although if that were the case I'd think the ECU would just keep trying to add more fuel even though it couldn't with a dying pump or clogged filter. 

Maybe snag another ECU from a junkyard and throw it in as long as you don't have to get it reflashed by Mazda?

Those suggestions aside, I know the code indicates a lean condition but those plugs don't look lean to me. Maybe the coloring of the pic is funky or maybe the ECU is getting bad/inconsistent information about what's going on in the engine and is just constantly chasing its tail trying to fix issues that aren't there.

What was the setup when you got it to rev to 7k?

A copy of the title was mailed today. Priority mail with tracking so maybe the idiots won't lose this one. 

You should have it by the end of the week. 

AxeHealey said:

Any chance there's a big vacuum leak somewhere? 

What about amount of fuel v. pressure? Although if that were the case I'd think the ECU would just keep trying to add more fuel even though it couldn't with a dying pump or clogged filter. 

Maybe snag another ECU from a junkyard and throw it in as long as you don't have to get it reflashed by Mazda?

 

Those suggestions aside, I know the code indicates a lean condition but those plugs don't look lean to me. Maybe the coloring of the pic is funky or maybe the ECU is getting bad/inconsistent information about what's going on in the engine and is just constantly chasing its tail trying to fix issues that aren't there.

 

What was the setup when you got it to rev to 7k?

The plug coloration does NOT indicate lean.  However, the inability to rev is pointing that direction.

There has been no load applied during these tests.  They are all stationary tests in my driveway.  I did drive it a bit just to make sure all of the other car parts worked.  

I am starting to think that rev to 7k was a fluke.  It for sure happened.  It coincided with removing the upstream 02 sensor. (Which indicated plugged exhaust to me).  However, I have not been able to replicate that.  

I do have a couple of tests planned.  

- check injector flow rate with my injector driver and graduated cylinders.

- disconnect exhaust and see how it runs.

- verify mechanical timing.

The engine runs smooth if you keep some slight pressure on the throttle pedal.  It gives me confidence there isn't something majorly wrong with the engine.

Edit to add: I did spray brake cleaner all over the place to check for vacuum leaks.  Nothing noticeable popped up.   I may need to remove the intake to check the pcv system.  They are known to have issues with these cars that can cause vacuum leaks.  I have visually inspected the corrugated intake hose and all connections.

We had a 99 S10 that the catalytic converter started to break apart on. It seemed like it would rattle around then get bounced sideways and plug the exhaust. Thought for sure it was a fuel issue as when that happened (maybe every 3rd time driving it), it would fall on it's face from a normal drive and just go back to max of 3 or 4 k in a gear. It'd do that for maybe 5-10 minutes, then go away and drive normal. A buddy who'd had something similar reached under the car and smacked the cat and you could hear it moving around. We had been driving it intermittently (just for truck stuff locally) for about 3 months trying to figure it out. Took the exhaust off and you could see just loose material. Drove if around with no exhaust and ran fine. Threw a cheap replacement on and has been driving well ever sense

In reply to johndej :

That was my initial diagnosis.  Got a new cat and manifold on it and it does the same thing.

Probably a dumb question, but does it have a secondary cat in/after the downpipe?

In reply to wvumtnbkr :

Ah, somehow I missed that you actually installed that! Will keep pondering on it.

One thought, the chunks from the old cat may have ended up in the muffler causing a restriction there. I have seen that one before.