Anybody out there know how the charge relief works? I've done a bit of reading, but I have conflicting information.

Basically what I conclude is that if one of two conditions is not met the charge relief solenoid is de-energized, allowing vacuum to reach the charge relief valve. This "engages" the charge relief valve and vents the charge from turbo #2 back to the airbox. At this time the charge control valve is closed as well.

Then, when one of two conditions are encountered the ecu tells the charge relief solenoid to energize, which blocks the vaccuum to the charge relief valve, causing it to close. At the same time the charge control valve opens and the charge from turbo #2 is routed to the engine.

The two conditions mentioned above are...1) when the engine rpms reach a predetermined point for even an instant and 2) when the engine rpms continuously exceed another lower predetermined point. The exact points in the rpm range are where I've found differing information.

Am I interpretting my readings correctly or am I totally out in left field here?

The reason I'm asking about this is because my CEL comes on after say 10 minutes of driving. When I check the code it tells me the charge relie valve is the cause. I've done everything the FSM recommends, except replace the ecu, but I've been told by a VERY reliable source that the ecu will not normally fail in this manner. As a matter of fact he says in his considerable experience he has never seen an ecu fail in such a way as to produce just one fault code. Therefore I'm trying to determine if the charge relief valve is actually working. Is there any way to tell if the valve is actually opening/closing? How will low-end performance be effected if the charge relief is not opening? I'm pretty sure it is not stuck open because around 3000 rpm it's like someone lit a rocket under my ***. That could be from the charge control valve opening, but only if the charge relief valve is closed.

Another thing I don't understand is how the ecu knows if the charge relief valve actually opened or closed. There's no connection between the ecu and the charge relief valve, only the solenoid. If you put a meter on 4S of the ecu and drive the car the voltage should go low at some point. Theoretically that would indicate the charge relief valve is good. In actuality that will only tell if the ecu is sending a signal to the solenoid, not whether the valve is functioning.

Note - I do not have a boost gauge yet. Actually I've got one,but it's not installed yet. Can't decide what to use for my 3rd gauge. I've got a boost gauge and an air/fuel mixture gauge. Thinking about oil temp for the 3rd. Any recommendations?

Sure hope someone can help me out with this. I'm tired of looking at that damn light.

 

You have to keep in mind that the FD's ECU is relatively stupid, especially compared to the ECU's in most modern cars. If you get a check engine light, something is either unplugged or VERY bad to trip it.

The ECU has NO way of knowing of the charge relief valve itself is working. It does know about the charge relief solenoid which is in the rat's nest. If you're getting a code, the charge relief solenoid is either unplugged, the wiring to it is damaged, or the solenoid is REALLY broken. The vacuum lines going to the solenoid that make the CRV "go" can be totally unplugged and doing whatever and the ECU would have no idea.

In other words, you're looking for an electrical problem. Pull the upper intake manifold and see what you can see. And get that boost gauge in pronto, even if you have to drive around with 2 empty holes in a gauge pod.

If you're interested in learning more about the sequential system, get a copy of the 1993 Service Highlights manual from Mazda (preferably from Ray at Malloy Mazda). It's not too pricey, and it explains the philosophy and design of all the systems on the FD, with a lot of time spent on explaining the sequential system.

Dale

 

I've done a continuity check from the main power relay to 4S on the ecu - checks good and the solenoid is brand new. I've got +12 to the solenoid, and to the ecu with the car idling. Can't say what is at the ecu while driving cause I haven't figured out a way to check that yet. Can't unplug it to check it cause the car won't run. Not gonna strip the wire.

I hear about "Ray" alot. How do I get in touch with him? Malloy Mazda got a website?

 

Bump for myself. C'mon, More than one person out there has to know something about this.

 

Nope, Dale Clark is the only one.


If the code is telling you its the charge relief valve then check the FSM for the possible causes. The FSM is thorough in trouble shooting.

As far as Ray at Malloy Mazda look under M in the FAQ sticky and you'll find his info.

 

I've already been through the FSM. Checked all connections, as stated in the original post, and replaced both the solenoid and the valve. Over $200 and still I've got the CEL.

My next step is going to be measuring 4S on the ecu while I'm driving the car. So I guess it comes down to knowing when the voltage should go low. I do not find that info in the FSM.

 

Real dumb observation - you have cleared the codes on the ECU? Disconnect negative battery terminal, hold down the brake pedal for 10 seconds, reconnect battery.

Also, what is the code you're getting? I just thought about it - the charge control valve solenoid shouldn't flag a Check Engine light, the CE light only comes on for major engine components.

Dale

 

I did clear the code...same code came back after I drove the car. The code is 46, which the FSM says is the charge relief valve....not the charge control valve.

 

Change the charge relief solenoid. It sounds like it's going open circuit only when it's hot. As has already been stated, the ecu can only know about the resistance of the solenoid coil. Nothing about the valve itself.

The alternative, which is no fun, is bad wiring that goes open when the car is hot. That harness is running nearly $800 now.

As for CRV operating conditions, i've spent a little time trying to figure it out and it's not documented or simple to observe. I think it comes down to a range of RPM (3k-4.4k) and load, where it's only open when the load is high and in that rpm range.

Dave

 

Major break-thru today. I figured out a way to measure the voltage at 4S while driving the car, so I connected it up and went for a drive.

According to F-176 in the FSM, the charge relief solenoid should energize, which means 4S should go low, when the engine rpm is 4000 – 5500 for 8 seconds OR if the engine rpm goes over 5500 rpm. In order to get the rpm up to that point I’m driving around 1 gear lower than I normally use and I can see the voltage at 4S go low and then back high. Guess what…no CEL. I figure it must have been a bad connection and head for the house. On the way home I go back to my normal mode of driving and the CEL comes on after about 10 minutes. So I stop, shut the car off, restart it and drive around 1 gear lower than normal for like 40 minutes. The CEL didn’t come on 1 time. That’s not the end of the story though.

Where the FSM says 4000 – 5500 rpm for 8 sec or over 5500 rpm, this is not what I saw. As long as I kept the rpm over about 3000 – 3500 I got no CEL, but the voltage at 4S stayed high. If I accelerated harder than usual at any engine speed, 4S went low and again, no CEL. SO, I’m thinking the ECU has to be monitoring something in addition to engine speed to control the charge relief valve. Anybody know the story with that?

 

And I already changed the solenoid AND the valve...over $200 and still had the same problem. At least now I know why. Question is, is it suppose to work that way?

 

It's hard to say if it's working normally until you get a boost gauge installed. If you get good pull then it's probably ok. The ECU is tripping because the resistance of the solenoid goes too high.

It would seem that for all the effort you're putting into this you should install your two gauges now.

Dave

 

Same thing again today. As long as I keep the rpm's over 3000 I don't get the CEL. If I go into 5th at normal highway speed the engine rpms are only 2500 (slightly less) and the CEL ocmes on. My only question now is, is this the way the ecu is suppose to operate? Sure makes driving around town a bit more challenging. Anybody else encountering this "problem"?

BTW, code 46 is not a "memorized" code, so just shutting off the engine clears it.

 

Ever hear of cranial-rectal inversion? It means I had my head in my ***. Today I found out that I actually have 2 fault codes, neither of which is 46. I was mis-reading the code. I have a code 16 (EGR) fault and a code 40 (Purge Control) fault. Thanks to Cam at Pettit Racing for helping me figure this out.

What I was saying about the symptoms is correct though, as long as I keep the rpm's above 3000 I get no CEL. Doesn't make sense to me, but I am not sure how either of these codes are detected. Back to the drawing board.

 

Ahh, that sucks. $200 in new parts. While replacing the charge relief solenoid is a good thing, the valve itself almost never goes bad.

By chance, is that not your original ECU? Or did the car originally have EGR and then it was removed?

You'll definitely want to look into the purge control fault. It's all in the FSM.

Dave

 

Far as I know it's the original ECU, but I'm not the original owner so who knows for sure.

Aren't all the solenoids the same? If so maybe I can us the solenoid I replaced for either the purge control or the EGR, if that's what it turns out to be.

 

The Purge Control solenoid is different from the others on the rack. Send a PM to Fritz Flynn, he'll most likely have a bunch of good ones laying around that he'll sell.

 

every time my CEL came on, it was the EGR or O2 sensor. you can clean the EGR and i bought an extra O2, so... hope that helps

 

Your car must be a 94 model. I didn't notice any where in the post what year you have. If your looking at modding the car at all just get a PettiT ECU for a 93 or 95 model and you won't have to worry about the EGR code ever again. You still need to resolve the purge code. Just placing a resistor in the connector for the EGR won't work. The final option to correct the EGR issue would be a new EGR valve for a 94 (only model that monitors this in a non-Cali. ECU)

 

Title says it's a 93. Might have been imported from Cali, who knows. I'd love to have the Pettit ECU, cause eventually I'm gonna need it, but $650 is a little rich for my blood right now.

 

Heh, ain't that the truth...Fritz Flynn, your friendly neighborhood FD parts pavilion ...


$650? I've usually seen them in the FD parts forum for $450, tops.

 

Yeah, but Cam from Pettit has been helping me out with some phone troubleshooting and he said their price is $650.

Anybody know if the charge relief solenoid is the same as the solenoid for either the EGR or the purge control? Been in Cali for a couple days, so I haven't had time to check it out.