So I was on my way home from work doing 80ish and all of the sudden all engine power vanished. I was coming up to the stop and go leg on my way home and when I let off the gas and started on the brakes the engine started running very rough. After ward I couldn't get the car past 40 is was like a brick wall at around 4k rpm. The engine would still idle just very rough and loud at a much lower rpm. When I got it home and let it cool off, I did a visual check. Everything seems to be in order all hoses intact. I felt around everywhere I could and nothing seemed broken. I checked the CEL nothing there. It will start up a little hesitantly, but it does fire up. Just, like I said, rough, loud and shaky. I don't think its limp mode. I have had the OMP fail before and when that happened the car would still start and idle normally. I don't think its a fuel issue. I'm not getting any backfires or anything, but I'm not going to rule out fuel just yet. Obviously not a spark issue, it is running, if you can call it that. 2 monthes ago I had the transmission out replacing the clutch and I did the tranny mounts and diff mounts while under the car. Car ran perfectly afterward. Could I have messed something up while doing that I wonder. I kinda at a loss. searching the forum doesn't give me alot to go on. Honestly it's becoming hard to search the forums for what you want now a days. Does anyone have any ideas of what to look for? The car is a S5 NA.

 

This sounds semi-similar to what happened to me, so, odd as it may seem, check your cat.
You must actually remove it and shake it to see if the matrix has collapsed/fragmented and is blocking the exhaust.

 

I would check the grounds. Usually for the FC's that is a source of many gripes that are intermittent. Especially now the car is getting long in the tooth.

 

This happened to me along time ago too on a previous car. However this car does not have a cat. It has a RB Road Race setup.


I can see a ground issue, but the problem is not intermittent. Maybe if a grounding bolt broke clean off letting the wires free dangle.


Oh and I forgot to mention in case its relevant. While I was replacing the clutch and mounts a few months back. I also did the full tune up thing. All fluids, fuel filter, plugs.

 

The transmission housing has a ground wire. Make sure it's good. Check fuel pressure w/an in line gauge. Check for spark on both coils. Check engine compression. And make sure the grounds are good, especially the main engine ground, as the secondary injectors come on at close to 4k and a ground issue precludes that from happening. You could also take readings from the ECU and compare them to the FSM's numbers. And lastly, check the voltage output of the alternator while idling (should read 14 volts).

 

The ground on the transmission, I assume you are talking about the one on the starter bolt. That one is good and solid.

I don't have an in-line fuel pressure gauge available to me right now. so I can't check that properly. What are the common symptoms of low fuel pressure?

I checked for spark. All 4 are firing.

Compression testing is problematic. I don't have a helper right now and I only have a piston engine tester. But I did try it out. I hooked it up and turned over the engine then checked the gauge and it would always say 90+ psi, unfortunately it only reads the highest of the 3 pulses each time. So thats still up in the air.

All my grounds I can get to without tearing down the intake are good. The engine ground on the rear iron remains unchecked. I'm confident its good, but who knows what has happened over the last 5 years when the last time I bolted that one down. You mentioned the secondarys having problems with that ground being bad. However that shouldn't have an effect on the idle and lack of any power down low right.

ECU readings... Do you have any suggestions on what ones to check that would cause my problems?

Alternator checks out. 14.4v

Edit: I did notice something weird. I'm hearing an odd snorkel sound coming our of the ACV port. the one that normally has a silencer on it. It would make the sound when I rev the engine and it would go away if I block the opening. Is it normal to make that kind of sound? Previous owner once upon a time ago had done a bad rats nest removal and ditched the hose. I undid the removal when I swapped engines 5-6 years ago.

 

Perhaps you'll have to get input from someone else but there should be a ground wire from the bell housing and it runs to the firewall near the wiper motor.

A bad engine ground could also cause the car to act wonky.

There aren't that many pins at the ECU so while you're in the hood just take a reading and write them down perhaps on a copy you printed from the FSM pinout list.

Faulty fuel pressure could cause a host of different problems as opposed to just one.

An auto store ought to allow you to rent a gauge to measure pressure.

 

Thats interesting. I don't think I have ever seen a ground wire there before. Not on this car anyway.

 

the wire is by the wiper motor on the firewall.
It goes from a bolt on the trans to a spade connector. This connector slips onto a 10mm bolt on the firewall.(so it's an eyelet affair with a spade connector)

 

Sorry, not buying into the ground theory, the symptoms are too drastic and sudden.
I'm still inclined to the engine breathing approach and if it's not an obstructed exhaust, then maybe a gaping intake.
Perhaps a torn intake snorkel or one of the metered air hoses came loose.

 

OK I'm back with an update. I believe I found the problem and I'd like to fill everyone in following and maybe get a little checking of my work. Long story short I think its the fuel pump. So here is what I did. Since last update I took satch's advice and start in on checking ecu pins. I checked the voltage on everything I could that was related to intake, ignition, and fuel. Everything checked out according to the FSM. I didn't I'd find anything but what the hell. I was rather inclined to agree with clokker in his assessment of and intake or exhaust problem. So I started to take apart my intake but I didn't get far. I wanted to check fuel pressure so I only went as far as I could before I had to start disconnecting fuel lines and I still wasn't seeing anything out of place. Next up fuel pressure. I was finally able to get my hands on a pressure tester late last night. I did 4 tests the fsm called for. First the Hold Pressure test with the gauge connected inline. The spec should be more than 18 psi. My reading was about 16 psi. Then the Fuel Line Pressure Inspection, Spec says 34.1 - 39.8 psi. I got 32 psi. I then did the feul pump hold pressure test and max pressure test. This is with the gauge just hooked up to the line after the filter and the other end plugged. The FSM spec is 57 psi and 71.1 - 92.4 psi respectively. I got a reading of only 32 psi on both tests. And finally I should note while the pump is running during the tests I should be able to hear the pump going at the back of the car. I don't hear a peep. So this tells me the pump is on it's last legs and can no longer support the fuel system. So my question to the floor would be. Is there anything on the car that would cause the pump to not put out full pressure however small? I realy realy don't what to be in a situation where I order in a pump and install it only to have the new pump do the same thing.

 

Bypass all the wiring- go straight from the battery to the pump and see what she does.

 

You'll want to check the voltage on the wire supplying power to the pump. It should read about 10 volts or so at least w/the car running. The wire is Blue and comes from the rear harness as it plugs into the pump harness. If it checks out you might want to redo the ground for the pump. If it's low then the resistor relay for the pump might be at play here.

 

Cant seem to find any wire around that can do the job... kinda embarrassing. So I checked out the fuel pump control system. Current runs from the battery to the open circuit relay to the fuel pump resister relay to the pump. Both relays seem to work just fine. So the old wire running back to the pump would be the only impedance. Somehow I don't see a strip of wire going from good enough to not good enough, but still good enough to do something in a split second with out there being any variance to it. Pumps on order, will be here on Friday!!

 

To bad I can't run the car right now with part of the intake apart. Oh well. That resister relay is a funny piece of work. I was looking at the wire diagram for it. Looks to me like it will still provide a resisted current to the pump if the relay portion fails. Which screams out here is the problem to me. However the resistance test the FSM calls out for check out just fine. Also if the relays fails the ecu should be kicking out CEL 51, which it is not doing.

 

That relay could be bypassed by jumpering the 2 Blue/Red wires. The error codes are usually connection warnings as opposed to the item being problematic, but not always.

 

Its been about a week and a half without any word so here it is. I did the fuel pump replacement. Unfortunately it did not fix the problem. So the short of that is a fuel pump that maxes out at 32 psi on an NA will still run a 13b...

So here is the bad news, Engine is blown. Words of wisdom to everyone out there using cheap rental tools. The "OEM Tools" compression testers Auto Zone rents out DOES NOT work for rotaries. It would not give me proper readings and it does not have a removable Shraeder valve. Pressing the button doesn't work, don't let the counter guy/gal tell you otherwise like they did to me. A coworker of mine happened to have a good Snap-on tester w/removable valve, it worked perfectly. Using that the front rotor is reading even rapid pulses of 100+ psi while the rear rotor was reading single pulses with "long" gaps in between of about 60 psi. Also with the engine running I can feel the exhaust pulses out the rear with the true duel RB setup. Its very clear the front rotor is running fine while the rear rotor is putting out far weaker and colder pulses.

So I blow an Apex seal... sad, sad, really sad day for me.

 

Never good news. Sorry to hear.

 

So after some thinking I am going to go ahead and rebuild the engine myself. I limped the car to its new home for the next month and in doing so I heard a fairly loud metallic clunk and a bit of chatter for a half second. Didn't effect the engine but I going to call that an apex seal going out the exhaust.

I have not cracked open the keg yet, but I'm going to assume that I will need at least a new housing and maybe a rotor. I got a spare set of S5 NA rotors. However I can only get a line on a good set of used S4 T2 housings locally. Now I will only need to plug the coolant feeds on the housings going into the intake correct? Everything else is plug and play into a S5 NA keg right?

 

Open up the engine before you worry about parts. If the silly OEM 3 piece seals just rolled out of the rotor, then there could be no damage.

 

No dice Aaron. One of the apex seals broke at the pointed end where it meets with the corner piece of the seal. That small chunk took a bit of the lip on the rotor with it and proceeded with gouging the hell out of the housing.

I will be using spare rotors I happen to have and will need to replace the rear housing. Possible getting the end plates flattened out too. Still need to check the tolerances on those.

 

Dang, that sucks.

at 160k on my OEM, never rebuilt engine, it still ran after ingesting a spark plug anode insulator.

At 165k, I had the engine rebuilt with all new parts (reused the rotors) and really, the worst worn portion of the housings was where apex seal corner piece was digging into the chrome. If it wherent for that, I could have reused them. Other than the corner seal gouge they are mint. It's amazing what a worn out 3 piece apex seal can do. The car still drove and ran perfectly fine, but the front iron cracked in 3 places and was letting exhaust gas into the coolant....have no idea why because it never ever overheated.

During a rebuild, I suggest this...

1) FD corner seals and springs
2) OEM 2 piece seals (Mazda can't and won't sell you 3 piece seals, they don't exist anymore)
3) NEW rotor housings, yes...they are extremely expensive, but worth the investment.
4) multi window FD bearings.

I think Aaron would agree with me on those.

 

I plan on going with the Atkins kits with their 2 piece apex seals and the solid corners.
A NEW set of housing is out of my unexpected budget, unfortunately.
Multi window bearings sounds good, but oddly enough my bearing are in great shape. They have no visible wear marks or anything. I was very surprised to say the least. The engine didn't have very many miles on it and no it wasn't the original engine in the car. Which is what really sucks about this situation. I don't know off hand for sure but it has around 70k ish miles. Dispite that fact, here is a quick pick of the rotor!

 

that rotor doesn't look that bad