NewRXr

I've been trying to track down a WOT misfire for-ever now. I've made many improvents in the last year but never found the real culprit until now. I least I think so. I took a long day trip in the 7 last month and when I got off the freeway it wouldn't idle unless I maxed out the idle screw and then it constanly surged. All the way home anything more than half throttle stalled it. Basically it started doing what it does at WOT all the time, great, now I can find it.

All the basic and the advanced diagnostics have been done to death and there is no spec that is out of range or component that isn't functioning properly.

Here's what I believe, the injector screens or pintles are clogged, most likely with rubber from the engine compartment hoses. The hoses look a little ragged.

Here's why. It runs so lean at idle that it doesn't even pull my new O2 sensor reading off flatline lean without tremendous help. I had to run propane into the AFM, slightly prop the AFM open more than normal, adjust the variable resister to full rich, and pinch the fuel return line spikeing the PSI upto 70-80 just to get a varying A/F ratio, at idle. Using the oscillioscope on the EFI shows the injectors are running at 22-24% duty cycle just to stay running at idle and also during the test that finally got my A/F on the chart. I believe this to be maxed out for the EFI's adaptive learning at idle. Am I correct in that assumption? Also the physical evidence supports this, the engine runs much smoother and idle speed incresed a great deal when artificially enriching the A/F as much as possible. There is no ignition misfiring going on, I can smell nothing at the tailpipe and it had just passed an emissions test with flying colors a few weeks before the long trip. Exhaust runs really hot, like WTH hot, might be normal but also signifys lean A/F.

Injector electronics - check
Ignition - totally rebuilt, replaced, blueprinted, and tested to no end. - check
ECM- swapped with known good, no change.
AFM- swapped with known good, no change.
Fuel pressure - check
Everything you can name - checked and rechecked, I am a professional tech. This is what I specialize in and this car has tested my skills and patience beyond mention.

The electrically fine injectors that are incapable of delivering the needed fuel is what I've finally come down to.

THE BIG QUESTION:
What is the normal duty cycle for a stock SE at idle? Nothing runs 24% at idle does it? I only ask because I realize that I still don't know everything about this engine and want to make sure I'm not going to rebuild these injectors only to have this car kick me in the butt once more.

Thanks,
Vernon

NewRXr

Woo hoo, finally got the post up, stupid forum kicking things back for the title.

Update, I got two rebuilt injectors for $45 each from BAP GEON here in Houston. They're Python brand, whoever that is. Beat the hell out of the only alternative, NAPA at $285 list each.

Another thing, the injectors fire into a screened cup on the port. My rear injector screen had a three cent washer laying in it. FPO.

Should know this weekend how it turns out. I've got high hopes. I now realize that a Rotary engine can still run at a very lean A/F ratio. One that wouldn't even humor a piston engine into a fast crank.

Vernon

LongDuck

Well, it looks like you're focusing on the right components. In my experience, the injectors on SE's are 680cc nominal flow and will usually develop cracks and leaks at the injector body before they start throwing a bad enough pattern (or clog) to cause idle problems or acceleration problems. I have replaced the 2 original injectors in my SE with Mazda factory parts, and the difference is immense.

I also bought some 'Python' aftermarket, rebuilt injectors from BAP for $100 each and these weren't even built correctly, one was missing the filter screen and the other had a mis-aligned pintle. After finding some good factory injectors, sending them off to a local shop for cleaning, and reinstallation, the car new idles much more smoothly and throttle response is much better. I never had a problem with WOT misfire, but this could certainly be the fuel injectors hitting full duty cycle due to a clogged flow.

Based on your first thread, I would have suggested changing the fuel filter, but you say pressure is good. SimRX7 (another member) had a similar problem that we worked on where the car would hit a wall at 3500rpm - sitting still, would rev to WOT redline, no problem. As soon as you got that car on the road, it would die at 3500 - fuel pump was bad and needed to be replaced. Fixed that problem.

Only other suggestion is to run the engine at idle and grab the wiring harness that's tied to the water pump housing - this has the pigtails for the injectors and O2 sensor, and sometimes those injector pigtails can get chewed up under the manifold and cause an intermittent short - this is usually the symptom of 'running-on-one-rotor', and when you wiggle that harness, the injectors kicks back in and you get normal function. Have a look at those pigtails, Borg-Warner replacements are $7 each at Autozone, and may be worth looking at replacing if your rebuild injectors don't fix it.

Reply back with what you find. HTH,

NewRXr

Thanks for the long and informative post as usual LongDuck. Things like fuel tank, screen, pump, filter, and lines have all been attended too. I ran two cans of injector flush through these injectors long ago, usually that fixes them, we'll see. I followed SimRXr's post, I was the one who suggested a collapsing intake hose. I follow all the SE problem posts too look for a solution, of late there was a guy who's rear injector just quit and it sounded very similar. On my car injectors are the only thing that I and the previous owner and his wrench friend (Rotarygod) haven't tried. RG and I have started talking again and he's been insightful.

I going to take your advice on the injector harnesses. Mine are cracked up. I made sure the terminals would be tight but now that you mention Borg Warner has them at that price I'll get a set today. Thanks.

I'll let you know how it goes.

Vernon

Anex 570

Do you have a part number for the borg warner pig tail? I know for a fact that if I go there right now, they're be complete morons too me, until I look it up myself.

rotarygod

iTrader: (1)

Vern, If I'd have known that you were going to try injectors too I'd have let you use my GSL-SE injectors. I'm not using them anymore. Here's a stupid question. How are the grounds to the battery? Is the ground from the engine to the cassis still good?

NewRXr

LOL, so true. Don't be to rough on them, it's a hard business. I work along side them everyday in my auto shop, there are more parts than there are grains of sand on the beach. AutoZone-NO, Napa-hmm, I know what you're talking about but I can't find a listing, O'Rielly-I don't see anything, when I get some time to reasearch it I'll see if I can find them and call you back, Mazda- no longer availiable. Hmm, how much for new Mazda injectors? $370 > Napa $385.

What happened is I stopped into O'Rielly later and dug into the Borg Warner catalog. I found a "Fuel Injection Repair Parts" page in the back. It had them there, I'll be getting them tommorrow and be able to post the part# from the reciept.

Vernon

NewRXr

Fred I didn't know until I knew if you know what I mean. I tried calling you early Sunday on your cell, yea that was me, sorry if you were asleep. Then I tried making this post about two days. Then after I found rebuilt injectors for that price I thought it was worth a shot. Hopefully they will work out. They look really good, nothing like LongDucks set. It all depends on the guy who did the work so hopefully these are decent. If not maybe I'll get with you on those injectors, I need to return your other stuff and get you one of these superchargers anyways.

The grounds are all done. I relocated the battery to the passenger side storage bin a while back and while I was at it I installed another ground from the body to the battery along side the main ground cable from the engine. Checked with an Ohm meter and grounding is in order.

I'm planning on hitting the 7 Saturday afternoon and we'll see how it works.

Vernon

Anex 570

WooT! well pm me with your results please, I'm this close () to putting my wiring harness back in.

rotarygod

iTrader: (1)

I'll be out of town Friday through Sunday so call me Monday if you need anything.

NewRXr

Well ca-rap, I just got it all back together and have found no difference.

Now here's where my knowledge of GSL-SE fuel injection and imagination are taking me. Could it be a trailing pick-up or ignitior? The trailing ignitor signal also triggers the RPM in the ECM. So if the signal is intermitant and or flaky while my leading spark is strong and steady then conceivably The ECM doesn't send enough fuel. Like I said before there's no unburned fuel just seriously lean with lean misfiring at any time. It runs like it can't make up it's mind to stall or haul. Only under WOT and high RPM do I hear any exhaust popping.

In any case I've got only two parts I can replace, the pick-up coils and ignitors. I'm going to replace the ignitors with MSD anyways so I'll be getting a set of pick-up coils next week.

Vernon

gsl-se addict

iTrader: (3)

You can move the blue spade connector from the trailing (-) over to the leading (-) if you think it may be an ignition problem. I had to do that when my trailing igniter was flaking out (sometime wouldn't fire when cranking=no fuel and no start). I moved it over to the leading side and it worked great.

Kent

NewRXr

Good idea, thanks Kent I'll go try that now.

Vernon

NewRXr

It wouldn't start but I think it helped verify that there is a problem in the trailing circut. There is a continuous current draw, evertime the wire goes on or off with the key on it makes a strong spark. It's never done that before.

Vernon

NewRXr

WOOT!! Finally found this problem!

The trailing ignition circut was grounding inside the wire harness. There is a bare wire that spirals around the trailing coil (-) wire from the distributor to the coil to absorb EMI (electromagnetic interference) thereby preventing false triggering in the circut. Well the insulation on my trailing (-) lead got hot enough and was in the right position for the bare EMI spiral wire wrapped around it to rub, cut, or melt through and ground the circut. It was just touching, so that the short circut was intermitant and would have happened frequently with engine vibration and movement.

Once I had figured out that the circut was grounding I started disconnecting all the components in the circut to isolate the short. There was the ignitor, ECU, and the tachometer. After all were unplugged and I still had continuity to ground I figured it was a shorted harness. I started at the trailing coil (-) clip with plans of splitting the two major halfs of the circut (ignitor to coil) and (coil to ECM/TACH) right there were they are spliced together in order to narrow down the location of the short to one side or another. But I noticed that as I moved the (-) clip around that the short would come and go. I had it connected to a DVOM with a continuity alarm. So I started peeling back the electrical tape and the short was only about an inch under the tape. As soon as I found the problem I left it pulled apart and tried to start the engine. After several cranks I realized that in my excitement I neglected to reconnect my ECM and distributor. So I paused briefly to curse my own stupidity then quickly hooked them back up. It fired right up and ran smooth. WOOT WOOT!

Now I can start putting it all back together and finishing up the important stuff, like getting some serious HP and hooking up the Pioneer stereo sitting in the back.

The big clue to future peeps who find themselfs in this position is that with the key on engine off anytime you connected or disconnected the coil (-) lead it would spark. That and the coil got very warm from continus current flow with the engine not running.

I'm glad this chapter of my life with Mazda's wonderful sports cars is closed. Sheesh.

Vernon

NewRXr

By the way here's the part# for the Borg Warner fuel injector connectors with wire pigtails. I recommend getting the ones without pigtails as they replace the factory cups perfectly with the factory wires snapping right in. The replacements with pig tails are of a smaller guage wire and that wouldn't be good on a low impendence injector that draws more current than what those smaller wires could handle. I don't have the part# for the ones without wires because I didn't buy those but they are on the same page. I just removed the Borg Warner wire ends and snapped in the Mazda harness ends. Perfect fit and a much better connection.

It's Borg Warner Part# 27427

That's a new cup with wires. Spring locks are availiable separatly as are cups without wiring.

They call it a ASM housing or something similar

Vernon

gsl-se addict

iTrader: (3)

Glad to hear that you got it fixed. Electrical shorts like that can be tricky to find and cause all sorts of weird behavior. I am glad that you posted the solution to the problem. So many people post the problem but they don't ever respond to tell what the solution was.