Rebuilt Engine Install - Ran for a bit, now won't
 

Just installed rebuilt engine from IRP, had the car running for about a week. Put approx 50 miles on it. Ran fine besides small lumpyness @ idle that went away with electrical load. Pulled 14" vacuum at idle, up to 19" under light throttle. Never revved above 4k rpm or boosted past 0 psi.

Relevant Car Specs:
Rebuilt 13B-REW w/ Stock Ports
PFC w/ Commander
Stock Fuel Pump
Stock Fuel Injectors (Cleaned/Tested prior to install)
New Fuel Filter
New Spark Plugs 9's all around
New Spark Plug Wires from SBGarage
Stock ign coils
New Engine Harness from LMS-EFi
RA Adapter w/ external OMP resevoir + Pre-Mix
Deleted emissions, ACV, airpump, PCV, double throttle.

Now the Problem: One day I start the car and let it idle for about 15min. Start to test drive it and it runs like crap.

-Lumpy Idle around 650~900 RPM.
-Vacuum 10~12"
-Revs VERY sluggish -- dies once let off
-Almost impossible to move under own power.
-Wideband reads 16.0~
-Sprayed Carb Cleaner around manifold and could find any leaks.

Took off the UIM to check for leaks:

-Fuel pressure holds at 35psi for more than 20 min
-All 4 injectors click on/off
-Lots of soot/oil/crud in rear secondary intake runner
-Spark plugs had small black crud on tips - wiped clean and re-installed.
-PFC reads all sensors in spec
-O2 feedback disabled - no airpump

Figured maybe it was just a weird bug hoping the issue would go away. Re-assembled UIM, reset PFC settings and started it. No change, still ran like crap. except the AFRs were down to 10. Idle'd terrible, tried to rev and it died. Tried to start it again and it won't catch. Sounds flooded.

Checked MAP sensor both times.

Any idea on what to check next? Not sure why it would randomly die one day...

Compression test before anything further.

Sounds like you flooded the motor. New motors are easier to flood before the seals break in. What happens is you wash the lube off the seals and they can stick.

Also, check for spark on all 4 coils. You may have one not firing.

A flooded motor will not give accurate compression numbers and can ruin the sensor.

I compression test blown engines every week, all of them have a massive degree of flooding due to being blown. Never have I ruined a sensor, it is the products job to capture readings on weak engines.

Flooded engines will yield different numbers, that does not mean he should not do it to verify that he is not chasing his tail.

Pull the EGI fuse, pull the plugs, deflood the engine, check compression ...if you are worried about the sensor.

Is it ported? I had similar symptoms on an aggressive street port. A tune fixed all of that.

Also, it never hurts to perform a compression check. If it hasn't been broken in, it may be a little low but not by much

It mentions stock ports so probably mostly stock build then. I ended up driving the beltway here about 3-5 times on the first startup just to make sure the seals matched the housings and get out of that flood timeframe. Haven't had an issue yet and heard alot a people not wanting to turn the engine off after getting that first start for that very reason. Kind of weird you mentioned it ran good for a week though which would mean something else.

I'm on my third Mazda tester in 12 years. Each time it failed it seemed to be when a motor was full of gas or coolant. Maybe I just have bad luck.

He is on stock ignition . . . there aren't 4 coils ...

While technically there are 3 coils there are 4 terminals. Check for spark on each one and test each wire. It is very possible for only one of the leadings plugs not to be sparking.

Yup, on two occasions I've seen a functional leading coil with only a single post actually firing properly, the others were intermittent.

Hi All,

So I actually never solved this. Between a deployment a bunch of random exercises I’m only getting around to it now.

I did revisit a bunch of your inputs:

1. Deflooded Engine then tested for compression with Piston tester:

Engine Compression

1. Front Rotor, schrader valve out - 92, 92, 92 [psi]
2. Front Rotor, schrader valve in - 92 [psi]
3. Rear Rotor, schrader valve out - 110,110,110 [psi]
4. Rear Rotor, schrader valve in - 115 [psi]

Turns out when first inspecting the fuel rails I pinched the front injector grommet, which explains less than stellar compression. I haven't compression tested since replacing the grommet, but I doubt this is the issue. Engine cranks evenly, and if not flooded, cranks within first 2 seconds.

1. Tested all 4 coils, they tested In-Spec, but close to out of range, so swapped them with some new low mileage ones that test way within spec. That didn’t fix anything.
2. Replaced coil harness with brand new OEM (the one w/o the ground ring)
3. Tested Fuel pressure -- holds at 36 psi when jumping at diagnostic box
   1. After shutting of fuel pump, pressure falls at 1 psi per sec til about 12 psi
   2. Voltage from PFC to pump is 4V
4. Fuel injectors aren't stuck (tested by direct jump with 9V battery)
5. Thought maybe it was something with my Rotary Aviation OMP adaptor, so pulled the reservoir off

Video of how it currently runs:



One new weird thing is the odometer stopped working and the speedometer is bouncing in correlation to the revs… Feel like it has something to do with a ground but not sure where since all the grounds I see are properly connected.



At this point I want to try new plugs with 7's & 9's instead of 9's all around. Also might try the old NGK plug wires instead of the fancy SBGarage ones. Other than that, running out of ideas? Maybe new injectors (had them cleaned/flow tested twice and they were within spec).



Wanted to gather input before pulling the trigger on new plugs for no reasons. Last time I pulled the current ones out, they looked fine and I just wiped them down.

It sounds like the engine is running on one rotor. Maybe one of the primary injectors isn't firing correctly. I know you have already manually checked the injectors and they were clicking but I would remove the primary fuel rail and see if both primary injectors are firing when the engine is cranked.

I would throw some new leading plugs in. You don't really have to do all of them, just leading.

Even if you clean them with brake cleaner/rag/whatever and they LOOK clean they may not be good. I've seen clean looking plugs with a weak, yellow spark before. That's an easy thing to try, do that before pulling your hair out on other things.

The speedometer/odometer sounds like problems with the stock instrument cluster, shouldn't be related to the engine not running properly.

Dale

Compression looks fine. The difference is most likely because one rotor isn't firing and fuel and other buildup is in there. I know you said you tested the coils but did you verify that each one is actually sparking? With the stock injectors you can lift the rail out of the motor and apply voltage to see if they spray. Be very careful where it sprays. Did you check the wiring from the injector back to the ecu? Did you try a different pfc? I've seen a ton with burnt out injector drivers acting this way. If you are on stock primaries you can put in a stock ecu temporarily for testing.

I've seen something similar (one rotor firing intermittently) when the grounds at the ECU were somewhat loose after an auto PFC conversion. The wiring on these cars sucks.

- I did throw some premix in after deflooding the first time, but the 2nd time I just figured the OMP would do its thing (plus the tank is premixed).
- I didn't verify actual spark, I'll see if I get to this this weeknd
- I didn't verify actual injector flow, guess I could get crafty with a plastic bin

I'll grab some new leading's and try those. I have a previously working stock ECU to try out but I've ditched a buuuunch of stuff that will throw a code on the stock ECU, will it still idle alright?
- FYI - Car has no air pump, no stock rats nest (AzEKnightz aftermarket solenoids), no cat, no AWS, no ACV, no EGR, still have ISC

I also want to point out that before I recorded that idling video, it was backfiring LOUD at idle, about once ever 4 seconds, not consistently, but often.

Finally got a chance to watch the video and your TPS voltages on the sensor check screen are high. I doubt that's the whole problem but it's worth starting on.

Also, do you have the OMP hooked up? It was odd that the OMP voltage flashed to black a few times on sensor check, that usually means it's going out of range.

Dale

If you have stock primary injectors the car should still start and idle on a stock computer. It may throw codes and go into limp mode but at least you should be able to rule out a bad pfc.

I do have the OMP hooked up -- but it was partially disassembled to re-clock for the RA adapter to fit the twin turbos. Something tells me I might have messed it up since it didn't go back together smoothly and yes now it goes out of voltage range when the throttle is blipped.

Have you been able to resolve this? I am having similar issues with mine. Engine was also rebuilt by IRP and only has about 1,100 miles on it.

Unfortunately no matter how good an engine is built, all bets are off when it leaves a shop to be installed elsewhere. There are a ton of factors from improper installation, pre-existing conditions with the car, etc that play a factor. If you are having trouble contact me directly. I would be more than happy to help.

So good news update..

Fixed most of the issue, here’s what I tried:
-Tried running it without OMP reservoir (because I have an RA adapter) and it still didn’t go.
-Tried stock ECU and it just died after 3 seconds if trying to idle
-SOLUTION -- I went ahead and replaced all 4 plugs with brand new NGK 9’s. De-flooded one more time for good measure, popped the new plugs in and started up fine. Did the idle learn with the PFC. Idle is meh – but actually drives fine.Not sure why the plugs fouled randomly, and so early….

As typical for the FD I’m on to my next gremlins:
-My idle is erratic and hunts without electrical loadoHunts between 600 RPM to 900 RPMoI set the PFC to hold at 850 w/o Electric Load or AC but it didn’t helpo
Things I plan on checking are:
Grounds (maybe adding more grounds similar to the hyperground system)§TPS adjustment
Things I already checked:
Vacuum leaks, TB adjustment screw Motor has been running fine for 1.5 weeks (approx. 140 miles).

Idle hunting is related to the tune and throttle body settings 99% of the time. Get a professional tune and it should be resolved. If you want to mess with it yourself adjust the tps until the VTA1 is close to .4 and VTA2 close to 1.0. Close the air bleed all the way and crack open until you get a stable idle. If you need you adjust the throttle stop screw up front you will most likely have to readjust the tps. DO NOT mess with any of the other throttle body settings unless you know what you are doing. Glad to hear you got it running.