zli944

iTrader: (2)

So troubleshooting the rebuild continues. Not necessarily looking for a solution, just some pointers to what I should/should not be checking.

Symptoms

• No power under 4K RPM (and I mean no power, there's no boost, it barely revs. Going from 2K to 3.5-4K RPM takes ages and the car barely runs.
• What sounds like ignition breakup throughout the 2-4K RPM range, the car shakes an awful lot
• Over 4K RPM, car boosts into 10 PSI and seems to be running well. I have only taken it up to around 5.5/6K RPM just to test out AFRs.

Troubleshooting
AFR
PLX wideband O2 installed

Under 4K RPM, with air pump connected: Reading pure air (20 AFR)
Air pump disconnected: Reads around 19 AFR at idle (750-850 RPM)
I have not ran the car with the air pump disconnected except at idle.
Over 4K RPM, with boost: Reads from 14 AFR to mid 12s

Vacuum at Idle
Mechanical boost gauge installed

At idle: Reading 9 in Hg
Under 4K RPM: No boost
Over 4K RPM: seems to behave as it should, getting to 10 PSI if I put my foot down

Compression
Used a regular piston engine compression gauge

Got solid blips going up to slightly under 90 PSI. From aaron cake anything above 70 PSI should be healthy iirc.

Theories

• Ignition issue. At idle, the exhaust note sounds very cammed, and the lack of vacuum would indicate to me that one of the rotors is not firing as it should.
• Fuel issue: Secondary injectors come on at 4K RPM (iirc), I imagine the stock ECU map is pretty rich and safe. With the secondary injectors coming on, maybe I get enough fuel to run both rotors correctly. So one of my primaries isn't firing (not both since I am able to start the car and idle somewhat)

Next Steps

• I just swapped out the plugs before a test drive. I will check the plugs for soot and if they are wet. See if it's obvious that any of them aren't firing.
• Considering installing a PowerFC and Commander. I know there's a statistic for injector duty cycle. Could this possibly tell me the state of the primary injectors?
• If the PowerFC is not recommended or ineffective, disassemble the UIM, remove primaries and check with NOID lights.
• Remove the primary injectors completely and crank with water bottles to check flow.
• Pray fervently to the rotary gods

DaleClark

iTrader: (55)

OK, it sounds like the engine itself is OK. If the compression is fine, then you can proceed.

Usually most common thing is an ignition issue. Plug wires hooked up wrong, coil packs hooked up wrong, etc. Could also be the plugs for the crank angle sensors swapped - the white CAS plug goes to the left when looking from the front of the car.

Also, check for dumb stuff - MAP sensor hooked up to the proper port on the intake manifold with the stock FILTER in line. Had a friend hook up a MAP sensor to a 6mm stud on the firewall once .

Get the car to start, idle, and free rev first. Don't try to drive it or anything crazy, just get it running right in the driveway.

Also, you could in theory have a large vacuum leak, that will cause all sorts of weird issues. Any place between the throttle body and the engine that the engine can suck in air will cause a problem.

Dale

DaleClark

iTrader: (55)

Oh, swapping a PFC in won't do too much for you. The only thing useful would be looking at the sensor check screen to make sure all the sensors are putting out what they should be and are connected. The injector pulse width you would see would be what the PFC is telling the injectors to do, that doesn't necessarily mean it's doing it.

Dale

zli944

iTrader: (2)

Thank you very much for the input Dale.

I'll check the plugs and coils again.

Regarding the vacuum leak, I am running the Azeknightz solenoid rack which involved disconnecting a lot of the hardlines in the rats nest. I followed Eric's instructions and capped some of the unused hardlines but there are definitely some that I thought routed to solenoids or parts of the rats nest that are still being used..., for example, 3/4 of the four lines in the LIM are disconnected and left open.
I'm not being specific here because I don't want to post the installation instructions for the solenoid rack w/o Eric's consent but curious to see if anyone else with the rack did any additional capping than what was specified in the instructions.

K-Tune

iTrader: (26)

Maybe a stuck primary injector?

zli944

iTrader: (2)

Will also check if ignition checks out.
The injectors were cleaned by RC but could definitely have been some error during installation

Houstonderk

iTrader: (3)

Where they cleaned and stored for a bit though? Seen a fair amount of people that get them cleaned and then they don't run them until later down the road and the injector was the fault.

TomU

iTrader: (11)

The FSM details proecudures for testing the injectors. The primaries are a good place to look, but you may also want to go through your entire control system to make sure everything is hooked up properly. If you have the stock ECU, is it throwing any codes?

zli944

iTrader: (2)

Actually... yes. I had them cleaned near the end of 2016 I believe and only recently got around to installing them.

zli944

iTrader: (2)

I am running the stock ECU for now. It's currently clear of any CELs but I find it weird that there are CELs for the secondary injectors but not primaries...

during install I did check the FSM and at least inspected the injectors in terms of the resistance (13.8 Ohms).

But as Houstonderk, they might be stuck from being in storage for a while...

zli944

iTrader: (2)

Thanks everyone for the input. It's very much appreciated and I am feeling much more confident about what may be the issue.

I will update the thread with any findings as I get around to troubleshooting this weekend.

TomU

iTrader: (11)

There are procedures in the FSM for checking flow

FWIW, i had my injectors cleaned and they sat for several months before installing. I had no problem with them. That said, to rule them out, you may want to flow test them

OG BBF

Just to throw my 2c in, a very similar issue on a rebuild over here on a uk forum.....turned out to be an intermittent issue with the CAS wiring.....threw a different engine loom in there and was fine.....they believed it was an issue with the shielding being damaged :/

zli944

iTrader: (2)

Just a quick recap, car barely revs and has no power under 4K RPM. Getting it going from stop almost stalls the car because of the load.

Above 4K, the revs even out and it seems to run much better.


Spark Plugs (picture upload isn't working)

L1 and T1: T1 is very clean. It's still white mostly. L1 is less dirty than L2 and looks to have water spots (maybe of fuel/oil/premix?/condensation).

L2 and T2: Both consistently "dirty". Looks like the old spark plugs I pulled from the engine when it was working.

Fuel Injectors

Got a noid light on the front primary injector. It lite up during crank.

Next steps/Theories

• T1 being clean is weird. If it was just a front rotor primary injector issue, I would still expect it to have seen combustion and be dirty. During a test drive, I took it above 4K RPM, where secondary injectors should have kicked. The car also rev'd and behaved much better above 4K RPM. That should have provided the fuel into the front rotor to have full combustion and therefore, dirtied both plugs. So... I'll have to test the coil pack. T1 may not be firing at all. From other forum posts, it seems lacking trailing spark shouldn't have such a drastic effect on my lack of power under 4K RPM.
• Remove all the spark plugs and with the EGI fuse still in, crank the car. I should expect to see atomized fuel from the spark plug holes on both rotor housings.
• If there's a discrepancy from either rotor, I'll have to remove the rat's nest and coil pack to get to the injector, manually actuate them with 12V and possibly remove the injectors entirely for testing.

I had originally also considered an electrical issue but the noid light test seems to have eliminated that possibility.
The T1 spark plug being so clean and the difference in L1 and L2 "wear" suggests a combustion issue, either fuel or spark.

Maybe somebody can confirm, but a vacuum leak, electrical issue, turbo issue shouldn't cause a weird difference in combustion....

Oh and I tested compression again, still steady 3 pulses around 80-90 PSI on the piston engine tester.

DaleClark

iTrader: (55)

Sounds like the front rotor isn't firing. Leading does all the work running the engine, trailing plugs just clean up. There are methods for testing the coil packs in the shop manual, ohm them out with a meter. I've found that test to be pretty on the nose.

It's also possible the ignition coil harness is bad or flaky. If it's an original harness that has a ground wire on it that goes to one of the coil packs, it's an old harness. The updated harness doesn't have a ground wire. Around $80 or so from Mazda. Even if that isn't the problem it would be worth doing just to get that out of the way.

I'm still leaning towards the ignition system for a problem. Have you checked out the crank angle sensors?

Dale

zli944

iTrader: (2)

Front Rotor Primary Injector

• Checked CAS, all good
• Cranked with old plugs on the spark plug wires, all 4 had spark

I then cranked the car while holding clean paper towels over the spark plug holes (very scientific, I know). The front one was clean, and the back one was dirty (from fuel, oil, carbon).

I also got 12V onto the injector plugs and tried to hear a click, got nothing.

So at this point, I am fairly confident that it's a seized primary injector on the front rotor.
As mentioned, I had the injectors cleaned by RC months ago, but they may have seized while in storage.

I guess I'll have to remove the coil pack, remove the solenoid rack and remove the injectors. I am not sure how best to clean them other than sending them back to RC...

Anyways, thanks for all the contributors to this thread! Here's a quick summary of the issue, troubleshooting steps and conclusion for people in the future.

Symptoms
-Lean AFR even with air pump disconnected (19 ish at idle)
-Vacuum @ around 10 in-Hg (not the usual 19)
-Low Idle
-No Power under 4K RPM
-Generally running rough until 4K RPM

Troubleshooting steps
-Checked compression
-Checked state of spark plugs (noticed fronts were cleaner than rear)
-Checked spark (old plugs hooked up to wires)
-Checked injector harness (noid light)
-Checked injector firing (paper towel to empty spark plug holes method, probably not the best but... just wanted to make sure)
-Checked injector firing (manually using 12V supply)

Conclusion
-As Dale said, the trailing plug really is meant to clean up combustion and that was why it was so clean. At 3.8 (4K?) RPM, the secondary injectors come on and therefore, I was getting fuel to the front rotor and the car started running much much better.
This is a bit scary because it means I was running the front rotor LEAN comparatively to the rear (without fuel from the primary injector), but just goes to show how safe the stock mappings must be at the higher RPMs.

TomU

iTrader: (11)

Call RC and see what they think

Houstonderk

iTrader: (3)

Called that one.. ~__~

jza80

iTrader: (32)

Not sure what it is with FD fuel injectors and sticking after having them cleaned... I had the same problem with both of my secondary injectors stuck firmly shut after cleaning. They did sit for about 3 months while I finished putting my car back together, but I never imagined this would be a problem. They remained stuck even with 12v directly applied to the contacts.

No other car I have ever owned or worked on every had this issue. What is so "special" about FD injectors I wonder?

DaveW

That's a common problem with injectors in general. The guy who does mine for my racecar (Zetec engine) seals them in a vacuum bag so they won't dry out and seize while they're waiting to be used.

DaleClark

iTrader: (55)

Don't know if it helps, but any time I go through a motor or put in injectors that have been sitting I squirt a little PB Blaster on the tip of the injector then pulse the injector a few times with 12v to open and close the injector. I had one injector once that was stuck (hadn't been cleaned, but it had sat for quite some time) and it was happy after that.

Dale