Hey folks,

Ok, here is the deal. I have a 93 touring 5spd, with the following mods:
t70 turbo
HKS style manifold
Custom 3.5" dp
3" full exhaust
Custom intercooler setup
KG Parts, fuel system w/1680cc secondaries 550cc primaries
walbro 255 fuel pump
Apexi Power FC w/commander
Wideband 02
Other stuff I can't think of.

Ok, here is the deal. Sometimes, the car starts beautifully, idles nicely around -.55 kpa at 8-900 rpms, and seems to make perfect power when driving. But, after I seem to rev it up or get on the throttle hard, idle, drops to 5-600 rpms, and vaccum goes to -.25-.30 kpa. Also motor sounds like it is running on 1 rotor.
Also, my lambda meter reads .9's instead of .6's and .7's
AFR increases from around 13:1 to mid11:s to 12's.
Also when I rev the car, huge amounts of smoke come out the back, and it sounds like it is going to explode. The car shakes violently. The smoke smells rich with fuel.

When this used to happen, I could cut let my car cool down, and when I started it up again, it would usually be fine again until I got on it hard.

However, for the last few days my car has been stuck in the shitty mode, until yesterday. I was sitting inside my car while it was idling shitty, and all of the sudden on its own, it started idling very nicely and steady. I looked at my boost guage and there was -.55kpa vaccum.
So I took it for a test drive, and it felt nicer than it has for months. I went easy on it, no boost or high revs.
Then, when I pulled in at my house I actually heard the change from nice running, to shitty running. There was a small pop in the exhaust, a few stutters and then no more nice idle. I then thought I would take it for a test drive while it was running poorly, but it didn't have the power to back out of my driveway without stalling or turning my clutch into molten sludge.

Anyway, I decided to check a few things out. I cut my car off and removed the plug wires from my rear rotor.
I then started the car. It ran off the 1st rotor, it seemed to run identical to what it was before (what I considered shitty) with the same .25-.3 kpa Same lamda readings. So I connected the rear rotor sparkys back, and removed the front rotor plug wires. It wouldn't start.

Does this mean my rear rotor is blown? Or has a stuck apex seal? Could it be some part of the ignition?
Or bad grounding?

I checked the plug wires to see if they had spark and they all seemed to have a good arc coming off of them.

I wanted to drive it to the mazda dealership and get a compression check. But I don't think it will make it.

I have heard of people using automatic transmission fluid to clean there motor and unstick seals, but I have heard this is bad for the o-rings.

Anyone have any ideas?

 

Why have you not compression tested it? I would have done that months ago.

 

This has not been a problem for months. A couple of Weeks maybe. I don't trust the car to go to the dealership, it is 30 miles away. And I haven't decided to tow it yet.

 

Oh yeah, my motor is ported.

 

Well whatever, you should have ccompression tested it the first time you noticed it. You dont need a dealership to compression test the engine. Do you not know how to do a compression test?

 

my car did the same thing and eventually started to flood out.Only I had this problem in the front rotor.engine was fine.The fuel smell youre describing is unburned fuel that is probably burning off in the exhaust.Im betting on an ignition problem.check for spark while cranking.Do this several times as The first time me and my father in law checked for this everything checked out.After extensive troubleshooting I decided to check for spark once again and sure as **** the front rotors trailing coil wasnt firing all the time.I replaced both trailing coils with new ones and guess what ,still had intermittent spark on the front trailing coil.
It turned out to be the small piece of the wiring harness that goes to each of the three coils.I cleaned up the wires and wouldnt you know it.It fixed the problem.Well 95 percent of it anyways.I still get some hesitation from time to time.But I dont have the means to replace the entire harness right now.It took about 10 months for us to figure this crap out after changing a shitload of parts..Hope this helps.
From what I understand once a apex seal goes it runs like **** but doesnt fix itself and then breaks again.Hence I think the engine is still good.

 

Hello. It's obviously not the motor. It's an ancillary control or sensor issue.

Read ppb13's thread in advanced tech on his water temp sensor troubles for example.

 

I am going to check my coils and wiring today. Thanks for the great info!!!

 

Thanks, I am definitly having those same problems that ppb13 was having. Come to think of it, my water temperatures seem to be off lately also. Like really cool readings even when car has been idling for a long time.

 

I havent heard anything about the water temp sensor problem.anyone got a link on these issues.id surelly appreciate it.

 

the water temp gauge sensor and water temp ecu sensor are two different sensors, so just cause your gauge works or dosent work, dosent mean theres nothing wrong with the ecu temp sensor

 

heres a link to vids of my compression test i did on my engine.

both front and rear are dead... see the uneven bounce on the rear... front had no compression at all

(just a reference)

https://www.rx7club.com/showthread.p...mpression+vids

 

The exhaust pop, probably was a backfire of some sort. Possible that one of the rotors got carbon locked? First thing I would do is get new spark plugs. And then compression test it. Is there anything you have done most recently that could be related.

 

One thing I can think of is that when I put my kgparts secondary rail on, there was no spot for the fuel temp sensor. I heard somepeople just snip it off, which is what I did, others tape it to the rail, and then a select few have even tapped there secondary rail for it.
When I look at my sensors in the PFC, the Fuel Temp is highlighted, and reads nearly 5 volts all of the time.
Could this be causing my problem?
I checked my ignition harness today, and switched out the water thermo sensor. It seemed to run a little better, but not worth writing home about. There is still a violent shaking problem, and of course the low vaccum. I checked and the PFC was fluctuating between 290 to 330 mmhg vaccum at 5-700 rpms.
Usually it is up over 400 at around 800 rpms

I am really tired of this, and I am almost at the point of selling the car to someone who has the time and knowhow to tune this car.

I have already changed spark plugs twice, I guess I should do a compression check.
Anyone know what I need to do a decent compression test on my own? Much like the video xstransam posted.

 

He's obviously checking with his Power FC.

 

Install a resistor on the fuel temp sensor leads. I don't know what resistor is proper, but it has to be in the archives somewhere.

 

Any progress? You should be able to at least test if the rear rotor is spinning by using your fingers to test for pressure, and listen to any un-even sounds. Although its not going to be as accurate as buying a compression gauge, it should give you some useful information.

 

Actually, this weekend, I took my car apart. And decided to give it the white glove treatment. I want to flush all systems, clean clean clean, and then clean some more.

I removed the Upper and Lower intake manifolds to bead blast. As well, I am having my compressor cover, fuel rails, Intercooler piping, intercooler and any other aluminum parts, bead blasted.

I went ahead and changed out my primaries to the 850's. The ones I have seem very clean, they weren't tested, but they were working when they were taken off to switch to 1680's.

When I took out the injectors, I noticed one had a chunk of debris in one of my new 1680's. I KNOW, Not good. Could This chunk be the culprit for all of my problems? It was tough enough to keep the pin in the open position, to totally flood out my rear rotor. This would explain the sudden crappy running, rich afr's and high lambda readings. Also would explain the ultra rich smoke in the exhaust. I assume this would also flood the cumbustion chamber to the point of drowning my plugs. I noticed a rich fuel smell when I removed the UIM, it was eminating mostly from the rear rotor, secondary port on the LIM. This would support my claim of a stuck open injector.

Luckily, it didn't stick the injector pin closed. Or at least I hope it never did. I hope my motor isn't gone. It wouldn't come out of its shitty running condition for over a week before I took it apart. In other words it just ran crappy the whole time, instead of getting better sometimes. But again, the afr's were always rich, never lean.

Whilst everything is apart, I am going to redo part of my wiring harness myself. Mostly the stuff under the engine bay that is pretty much fried. Also, I am going to test my ignition system and do some serious cleaning. I want my **** to look right. And one day, with Gods good graces, perhaps it will be rinning right too.

 

It looks like you found the problem. As you said, the symptoms all support a open injector. Take your time reinstalling all the parts. Sound like good news to me.

 

I sure hope so.

My real worry is where the chunk came from. Maybe it is time to relocate and change my fuel filter.
It almost looked like a hard piece of carbon or plastic, which seems strange to find inside the fuel stream.