jabob33

I'm having problems with the idle after the car warms up. It runs fine when I first start it but after it warms up the idle drops to less than 500 rpm and the vacuum goes below 10 and bounces.

It stalled the other day and threw code 25 (pressure control solenoid). I swapped out the solenoid but that didn't fix the problem. What else would cause that error code other than a problem with the solenoid? The car is completely stock btw.

Drifter288

iTrader: (3)

I would want to say you might have a vacuum leak somewhere but don't quote me on that.

Mahjik

iTrader: (1)

Check your wiring harness and verify continuity from the harness connector back to the ECU. The ECU just looks for resistance across the solenoid connection. If the resistance isn't there, it throws the code.

jabob33

I've checked for vaccum leaks and couldn't find any, unless something is opening up after warm up, like the PRC solenoid, which would lead me to the pressure regulator. Is there any way to test the fuel pressure regulator? I'll check the harness tonight.

jabob33

I've checked the continuity and all is fine. I hooked up a fuel pressure gauge and it is within spec. At idle it is 32 psi, after it warms up and the pressure goes to 38 psi. As soon as it raises the idle goes to crap, the engine shakes and eventually stalls. What else should I check?

jabob33

^^

revhardallday

iTrader: (1)

mine does that 2 94 fd.. after warm car idle drops especially if i step on the brake...

jabob33

I have been going through the sensors and checking voltages and the only one that I can find wrong is the air intake temp sensor. I don't know if that would cause the problem but I'm going to order a new one along with coolant temp and fuel temp.

I have also found a couple cracked vacuum lines. I checked the resistance on the injectors and 3 of them have 16 ohms but one of the primaries has 53 ohms. It seems to me that if that was causing the problem then it wouldn't even start or idle. I guess I'll just buy some new injectors.

What all changes after warm-up besides the fuel pressure? Are there any other solenoids linked to the temp sensors other than the pressure switch?

wstrohm

I just today replaced our '94's IAT sensor due to a CEL and a Code #11 being stored. The idle was rough and low but only after warmup. Test drive after replacement showed no problems. Part was $54.13 from Ray Crowe; Mazda part number is N3A1-18-845.

jabob33

Well, I spent all weekend replacing parts but the rough idle after warm up is still present. It started and idled great for about half an hour and then crapped out. A clanking sound was comng from the cat and I noticed that some flakes of metal from the cat had came out the exhaust. Things that I have replaced so far:

Air Intake Temp Sensor
Fuel Temp Sensor
Coolant Temp Sensor
Fuel Pressure Regulator and Solenoid
Primary Injectors
Spark Plugs and Wires
Oxygen Sensor

I think that I am just gonna have to give up and take it somewhere.

Mahjik

iTrader: (1)

Did you address the CEL codes, or do you still have codes being logged?

jabob33

Nope, I'm not getting any codes.

Mahjik

iTrader: (1)

You fixed the code 25 being thrown?

It's a little concerning that you mentioned you had metal flakes out of the exhaust. I would remove the catalytic converter and see if you have any metal residue before the cat. If you do, remove the turbos and inspect them as well as take a peek in your exhaust ports into the engine internals.

jabob33

Code 25 only showed up that one time. I don't know why it was there (can not find any faulty wiring). I just went ahead and replaced the solenoid in case it was failing at high temps.

Yeah, I was suprised to see metal come from the exhaust. It wasn't chunks or anything substanitial. It was thin, rusty, black flakes that blew out when the engine was sputtering. I let it cool down, started it back up and it idled great for another 30 minutes. I will check the exhaust and see if I can track it down.

jabob33

I gave up trying to diagnose this problem and ended up taking to a garage. They are pretty familiar with rotaries so i figured I'd let them give it a shot. They have been looking at it for quite a while and they just called to let me know what they think is going on.

They said that the inlet air was going in the 1st turbo, through the housing somehow, coming out of the 2nd turbo inlet, and dumping back into the airbox. They blocked off the 2nd turbo inlet and everything ran perfectly. The rough/stalling idle went away, vacuum was 18 and the 1st turbo was boosting 10 psi.

Do any of you turbo guru's have any comments on this diagnosis? They have not removed the turbo yet to inspect it, but I guess I probably need to start shopping for some turbos.

MSilk

iTrader: (1)

So the Problem your having is under boost? I can not see how the primary turbo could "push" air back into the air box under vacuum doesn't make any sense as there would be boost or positive pressure when the turbo is spooled, yet there would be vacuum when at idle.
So I guess I should ask is this problem showing up during warm idle? or under boost?

I had a similar problem under warm idle where the rpm would bounce and the car would want to stall. I ended up having to adjust the TPS to get the bouncing to correct then turned up the idle. It is quite easy to check you TPS voltage. i will look for the thread on it. Edited this in : http://www.fd3s.net/tps_adjustment.html


If it is under boost then I can see where air would be pushed into the air box if the secondary was not producing any boost, the primary boost would go back through the Y pipe bypass the compressor and come up the intake pipe. If that is the case then I would say before getting too involved take the intake pipes off at the turbo housing and see if you can turn the turbos by hand, they should turn freely and there should be very little play (I do not know if you could even feel play by hand I am sure someone with some more experience will pipe up) To do this with the secondary turbo you will have to get under the car and take the pipe off the turbo housing and I think there is a bolt holding the pipe up top as well.

Try this and let us know I will look into some other things as well.

Mike

jabob33

The problem isn't under boost per say, but I think its causing the problem after warm-up. I'm thinking that I have a problem with the charge control actuator since everything runs fine when the inlet is capped off. Maybe something is causing the butterfly to stay open, allowing the primary boost to go back to the air box and causing a major vacuum leak. I'm going to pick the car back up from the shop and check the charge control actuator and solenoid to see if anything is wrong with it. The problems might not even be related, but I guess I gotta start somewhere.

BStallion

iTrader: (3)

after my '94 warms up it shakes, oil pressure drops to zero and exhaust rattles.. before that it sounds normal..

MSilk

iTrader: (1)

The only thing I can see wrong with where your going with this is that there is no boost while the car is at idle, the engine is "sucking" hence the vacuum at idle there is no boost under a certain rpm where the exhaust is moving enough to cause the turbos to spin fast enough to produce boost. Honestly if I was you I would check the TPS. the reason I am saying this is that while the fast idle cam is engaged ( when the car is cold ) everything will seem to work well then when the fast cam disengaged the TPS sees the throttle in a different position then it is and all hell breaks loose.
As for blocking the secondary inlet and everything seeming to work does not make any sense to me unless the car was under boost and the secondary turbo was not spinning then I could see a lagging problem where it would feel like the car hit a performance wall.

Let me know
Mike

ttmott

iTrader: (1)

The engine should idle just fine without the turbos, intake piping or intercooler (you can take this stuff off, plug the hoses and it'll idle just fine).
Things that will affect idle and vacuum readings are:

EGR valve could be ruptured not controlling gas mixing in the intake charge. This will contribute to a very lean mixture causing the problems you may be seeing at the exhaust.

Injectors are leaking. When the engine comes off of rich warmup yet the injectors are leaking causing a very rich idle the engine will stumble and eventually expire. Rich mixtures will also make strange noises (fuel burnoff) in the cat.

Power brake diaphram has ruptured allowing continuous air flow to the intake manifold and will realize in a very low idle vacuum.

AWS sticking open. The ECM will not detect a stuck open AWS and this will cause low intake readings.

Failed PCV valve.

Secondary butterflys not closing. When the internal butterflies open and if the secondaries are open it will not idle worth a crap and will not throw a code.

Apex seal failure.

MAP sensor hose plugged or leaking.

BStallion

iTrader: (3)

I went to the nearnest garage that works on rotaries, they have 5 fds there, and they said it was an intake leak.. I just changed the nasty filters that was on.. plugs wires and tune up kit came in today from pettit racing.. gonna try that..

jabob33

The weird thing is that it does idle fine, great actually for about 30 min, then it goes to crap.
EGR valve has been blocked off for about 5 years.
It is running rich. I replaced the primary injectors and ran the pump with no leaks detected.
The shop checked the compression and said that it was good.
I will check the other stuff this weekend.