Is there a difference between the JDM primary injectors and the US primary?

 

No.

 

Okay. I ask because I swapped my engine over the weekend. I spun a bearing. I swapped over all components from the original engine with the exception of the primary fuel rail and the eshaft sensor. Vehicle runs great, but stalls at idle. I've seen and read many threads on fixing the idle issue, but still I have not gotten it resolved yet. I reset the read-only memory for the eshaft offset. So I figured I would check if the injectors are dissimilar before moving forward. I've also noticed with the new engine installed that there is a slight hesitation around 6K when the aux ports open up. I think at this point I will investigate ignition-related failures despite everything working normally prior to engine replacement. Perhaps the increase in compression is just enough to manifest an ignition problem. Thoughts?

 

Chances are you already had problems or something is hooked up wrong. It could be many things considering you swapped engines and components. Also assuming that your "JDM" engine is a good compression engine to begin with.

 

I agree, could certainly be hooked up incorrectly. I never assume to be perfect. It's certainly possible that I made a mistake. Compression is good across the board. After I reset the eshaft sensor, it idles at about 700 for ten-fifteen seconds smoothly. Then it dips, revs, dips, revs, etc, then stalls.

 

How did you test compression? Why didn't you swap in the P1 (reds) and fuel rail from your old engine on to this one?

I would check your vacuum lines for the air pump, SSV, and VDI to the solenoids and make sure they are hooked up correctly also check that the check valve on the back of the UIM is installed correctly and flowing the correct direction.

 

I will triple check the vacuum lines this evening. The engine also came with a different ECU. I swapped everything to be sure there were no differences, and I didn't feel like having to get my keys reprogrammed to start it. It was a N6K2, and mine is a N6H3 ECU.
I really don't know why I dropped the ball on the primary injectors. I may just swap them out anyway to take that out of the mix. Compression was done at about 250 rpms with a compression tester. Pulses were even across the board.
During re-assembly, I simply removed the lower intake from the old engine, replaced the gasket plate, and slid it into the replacement engine after scraping off some coked oil. If I recall one side was closed and the other was open (looking at the manifold from the top-down). By 'closed' I mean there was an opening in the metal on the left side, and the opening in the metal on the right side was downwards.

 

Ohhhh, so you tested it cold and with a piston engine tester? Should be okay I guess but sort of a crap shoot. If the APV gear didn't move then you should be fine, just double check everything else. Process of elimination.

 

Status update. I removed and replaced the primary fuel rail and injectors with the one that was on my original engine. Also replaced the eshaft sensor. No change. Just for kicks I cleaned the MAF and throttle body. No change. I ordered new coils and wires from NGK. Will shoot you more info once I've received them. Any other ideas?

 

Interesting bit. I noticed at idle it was pulling about 18.8% fuel on the long term trim. Seems a little excessive given that the only mods to the engine are a magna flow cat converter. So I cleared the trims. It seems to idle about 850 rpms without issue on startup until it hits closed loop. I'm going to unplug the upstream O2 tomorrow morning and see if using a base map will allow the engine to idle. If so I'll be even more perplexed. As I was driving home today I was watching the O2 voltage in a graph on the modus and it was fluxuating pretty well... just at insane negative trims. The mystery continues.

 

Did you notice what your STFT trims are? And how did you clear the trims?

 

Stft was varying while driving, but generally around negative eight or ten while maintaining a negative 18.8 in the ltft. Cleared trim with a battery disconnect and capacitor discharge. I confirmed ltft was reset after that procedure when I fired the car back up.

 

So I took the RX-7 to work today. I'm going to unplug the O2 on the RX-8 and test 'er out when I get home this evening. Yesterday was not fun getting to/from work with the car stalling every time I let off the gas pedal.

 

High negative LTFT are weird. Could be the wideband 02 is lying or the MAF is lying, or injectors wired wrong. Do you have a way to log all the OBD2 parameters at the same time? STFT, LTFT, MAF voltage, airflow, calculated load, O2 reading, etc?

 

If you have a negative or positive STFT of more than 3% at WARM idle then typically it indicates a vacuum leak. It could be something else like and O2 issue but most often it is a vacuum leak. Also what are you AFR's at idle with the engine warmed up?

 

Hey guys,
Update. New ignition. Plugs, wires, coils. Slight change, but still stalls. So that rules out improper cumbustion causing negative fuel trim. Leads me to the O2 sensor. That simply has to be bad. STFT are above -10% at 'idle' (about 1100 rpm before the ecu attempts to reduce the speed). LTFT at that time varies but generally around -20%. The hesitation at 6k when the aux ports open is still present. I went ahead and unplugged the O2 and drove. No more hesitation. Idled fine when let down slow. Off acceleration the car died 4 or 5 times. Restart - idled fine. Given it was idling higher than normal (about 900 rpm). I believe (and surely hope) this is a valid test to prove the O2 is junk. Possibly the reason for blowing my other motor. I am of the opinion that the fuel trim at idle is trying to pull so much fuel that it causes a misfire, then kicks the idle up and tries to go back down, then finally stalls because the ECU is literally leaning it out so much it cannot combust. Updates to come with O2 replacment. Still trying to find the best deal this evening. As always I appreciate everyone's input here to put this incident to rest.

 

Wideband O2 should be at my place by tomorrow. I had it send overnight. Let you guys know tomorrow whether or not this repairs it.

 

What is the normal idle range of the MAF in grams per second? Mine is reading about 4.4 -4.5 at about 750 - 800 rpms.12.5 grams per second holding it at 3000 rpm. Cam someone confirm good readings?

 

Replaced the MAF. Still stalling. Still pulling tons of fuel. Would this indicate a potential bad engine? Even though it starts right back up when hot?

 

Did you replace the O2?

 

So i figured it out. One of those stupid moves. I honestly can't remember who hooked up the injectors, but the primary and secondary injector connectors were flip-flopped! I took the intake back off on a whim, and sure enough they were hooked up backwards. So great! I switched them back and fired it up. It started idling much better. Then began to stall again even after clearing the fuel trims and resetting the Eshaft sensor again. Well i got a little frustrated and took a few days off. Last night I fired her up, drove around a bit, and noticed a bit of surging while driving. I took off the brand-new MAF sensor and put the old one back in. Now it's fine. Crappy aftermarket parts! Anyway, I appreciate everyone's input on this. I'm looking at the parts I replaced as 'early maintenance' :-)

 

Nice, congrats on figuring it out.

 

Well that will do it. Labeling is key when doing this sort of thing.