Been working on this all day. Car was driving fine yesterday, then lost all power completely. Parked it and it wouldn't start. Had it towed home. It cranked and started later that night, and cranks and starts today, but sounds like a subaru.

Codes I have seen
po102 (MAF sensor voltage out of range low) x2
po103 (MAF sensor voltage out of range high) x1
po300 (random cylinder misfires) x1
po480 (cooling fan #1 complaint) x2

My boost gauge is showing me about 11in HG vacuum at idle. It should be and used to be 22in HG at idle. So that's a mechanical issue somewhere. Whether or not I have an electrical issue in the MAF harness remains to be seen.

What I have done so far on the electrical side:
* replaced MAF - no change
* inspected MAF harness back to where it joins the main harness - looks ok
* dielectric grease on MAF connector -no change
* verified coils/igniters are firing

What I have done so far on the mechanical side
* visual inspection showed nothing.
* applied vacuum to intake manifold & intake plumbing up to MAF with shop vac. Listened for leaks with stethoscope. Could not find one. I could hear air moving in the valve cover
* applied pressure to intake manifold. Sprayed soapy water. Didn't get any bubbles around the IM gasket, TB gasket, or any hoses that I could see.
* did a compression check on the engine. 180 on all cylinders.

At idle my A/F gauge is bouncing around a lot more than normal, which makes sense if there's unmetered air coming in.

At the moment I'm at a loss. Could a stuck EGR valve cause this? Any help is appreciated.

 

Peak idle vacuum happens when timing and mixture are spot on. So, the loss of vacuum is not necessarily a mechanical problem. Your compression check kind of indicates that it's not.

A stuck EGR could certainly cause this.

Another thing you might try is swapping the ECU for a known good ECU.

 

See my coil comment on CR, that's what I think it is.

Things that fail: coolant sensor, coils, WB sensors

Things that don't fail: MAF

 

how is he not pulling enough vacuum with a bad coil?

 

You loose vacuum with dead coils.

4 cylinders



3 cylinders



I thought I remembered seeing this when I was struggling with my COPs harness and constantly running on/off 2-3 cylinders, but I'm guessing without the ignition of the gas, it's not generating as much vacuum.

I would show you 2 cylinders, but my car is cold and idling at 300rpm right now.

 

hmm well that's a 1st for me. interesting

 

If mazdaspeed coils are the same, I know someone I'm pretty sure would let me borrow them. Email sent.

 

Sorry Curly, no soup for you. Swapped coils with no change.

One thing I haven't mentioned in this thread yet - I filled up 10 miles before this happened. Bad gas? Talk to me about bad gas. Tomorrow I'm going to drain the tank and replace the filter, even though the filter's only a month old.

 

Lots of ways for the ignition system to affect idle vac.

If the spark is too retarded overall, or if one or more cylinders are either not firing or firing very weakly, then power for a given MAP will be decreased. In order to maintain the proper idle RPM, the ECU will increase IdleDC in order to produce enough power to maintain idle. This will be observed as a higher-then-normal MAP.

Unless oil vapor is blowing out of every orifice on the engine, or fire and smoke is billowing out of the tailpipe, the symptom of greatly increased MAP at idle points to anything but a mechanical problem.

(eg: it could just as easily be fuel related as ignition related. Excessively lean or rich running or no fuel at all on one or more cylinders will have the same effect.)

 

Yep. Optimum idle vacuum is achieved with a combination of mechanical goodness, ignition goodness (timing and strength) and fuel mixture goodness. A problem with any of the three is readily seen with a vacuum gauge.

If you've got water in that fuel, it could create all kinds of havoc. Noticed you're in a wet part of the country. Did you fill up at a noname? When you swap the fuel filter, drain it into a glass container to look for water. If water is present, it will look like a bubble at the bottom (heavier than gasoline).

Did you check your EGR valve yet? Also, a quick ECU swap (if you have one available -- noticed you're on a Xede) would be a worthwhile test. Check grounds. The thing that throws me off a bit and points to some sort of ECU problem is the MAF codes. Like Curly said, those are simple, robust devices (unlike the earlier AFMs). Unusual to have a problem there.

 

No spare ecu unfortunately. I have not yet drained the tank. It's no-name 92 ethanol-free.

Evap solenoid and the similar solenoid for the EGR valve have been cleaned. EGR valve itself has not been removed yet.

I have a timing light and will go verify things look right timing wise at idle. I did not have one until this morning.

 

I drained the tank, no change with new gas.

 

Fuel pressure good? Noticed on your build thread that you recently installed a new fuel pump.

 

Am I coming over briefly tomorrow morning? I can spare a half hour if you think it'd help. 7:45-8ish.

 

Sure timing belt hasn't jumped a tooth? Didn't see where you checked timing.

 

Curly, don't, I'll be at the autocross. Maybe Tuesday if you have time.

I haven't torn into it yet, so no I have not checked the timing belt. Cams in the wrong phase might explain things ... there was no event when this started happening, though. No noises, over-revs, WOT pull, no nothin. I was at a stoplight, turned right, and it was literally "hey, there's no power."

Fuel pump - every time I've checked the plugs they've all been black. When I give it half throttle from idle it bogs to the point of dying and is super rich. Like 8-9.x. If I give it WOT from idle RPM slowly climbs, like there's a banana in the tailpipe or it has an 800lb flywheel.

I haven't done anything requiring removal of the valve cover because I have an autox tomorrow (sunday) and a track day Monday. Those are now blown, obviously. Tuesday I'll tear into it and check obvious mechanical things since there's now no pressure to keep it driveable.

regarding the fuel pump - it sounds fine. I do wonder now if maybe it has overwhelmed the FPR. I have found a couple instances online of it happening to NB1's, but not NB2's.

 

Hmmmm . . . . If you're running that rich, maybe you do have a banana in the tailpipe. Do you have a cat?

Sudden onset tends to point to something electrical/mechanical though.

 

Stock exhaust, cat, O2 sensors, etc. ECU has not thrown any O2 codes so I assume the cat is functioning.

Maybe my fancy Gates timing belt just decided to say **** it, let's let the cams slip.

We will know Tuesday.

 

Pulled the valve cover and the plastic bits over the timing belt. The timing is correct, so it's not a gross overall timing problem. Neither cam has skipped a tooth on the belt. 19 teeth between the marks like it's supposed to have.

Hornetball suggested in my track-prep thread maybe this was my chance to go MS. I've been waiting for Reverant to release his super-uber-duper version for a while now. When he does, I'll pick it up. But - I have to keep my stock ecu around for emissions every two years. Whatever this problem is, I need to find it and fix it and make it work with the stock ecu in place.

Next thing I'm going to try is to connect the maf and filter directly to the throttle body, bypassing the intercooler, all tubing, and the supercharger.

Edit: also, while I've got it this far apart, might change the crank and cam sensors.

 

Have you checked and cleaned the grounds?

Did you also check the keyway on the crank when you checked timing?