Jdmrx700

Hi, new here, first post and need help diagnosing an issue with my rx7.
I have a 2000 rx7. (Auto)
Starts and idles perfectly, sits at about 1200rpm then drops back to just below 1000 after a minute or 2.
I can rev the engine at idle and climb to redline but in gear / under load it cuts off at around 2000rpm and will backfire, if I let off the throttle and accelerate gently (10-15%)I can climb through the revs up to highway speed.
This issue was initially intermittent and would happen every 2 or 3 times i drove it but now it's constant.
I initially thought it was injectors, I have replaced the injector and air blade sockets with new oem. Changed the fuel filter, it was pretty clogged, checked the fuel pump, new plugs and leads.
I pulled codes from the diag box with an led and got 12 - throttle sensor full range 18 - throttle sensor narrow, 32 - solenoid valve, 44 - solenoid valve turbo control and 46 - solenoid valve charge relief. ( I'm pretty sure 32,44,46 are due to me cracking the solenoid vacuum nipple when I replaced the injectors - the two green ones under the uim. (I have a new one on the way),
I checked continuity from the ecu to the tps narrow and full range, both ok, bottom screw on the tps was a bit lose, tightened that, reset the ecu, went for a drive around the block, still cant apply any throttle without cutting out and backfiring. Checked fault codes again and now only giving code 44 and 46.
is this limp mode? Will just the faulty solenoids cause this. Any ideas on what to do next? Please help

RotaryRKT

You check the vacuum line from the UIM to the MAP sensor? I left mine off one day after installing the UIM and had the exact same issues.

Jdmrx700

I double checked all the vacuum to the uim and replaced with new hoses. I'll check the sensor to be sure though. Thanks.

Akagis_white_comet

iTrader: (4)

Welcome to the club. I'm our resident Japanese FD expert. Code 32 is Port Air Control Solenoid, 44 can be either Turbo control solenoid (there are two), 46 is Charge Relief Solenoid. In short, when the ECU sees the wrong amount of resistance on these items, it goes "WTF?" and spits out the appropriate code. It's comparing this against the ECU grounds for reference. Just for consistency, have you ever serviced your grounds? Series 7/8 (1996+) FDs have 6 ECU ground pins that end up as two ring terminals on the engine shortblock, underneath the Upper Intake Manifold. If these see corrosion, it skews everything the eCU can see, making it panic and do weird stuff like you're experiencing now.

Jdmrx700

I checked the ground that goes from the back of the uim that clips onto the firewall, no corrosion or anything obvious and checked the whole uim is grounded with multimeter. I haven't paid alot of attention to the other ones, I will clean them up this weekend and report back! Thanks.

Jdmrx700

So all the grounds look good. Pulled codes again and still 32, 44, 46.
I'll put new turbo control solenoids in when they arrive and see how that goes.

Akagis_white_comet

iTrader: (4)

Before you do anything, STOP. The last thing you want to do is introduce more variables into the equation. Also, grounds can LOOK fine, but still be failing since everything goes through the Negative Battery Cable which has the same Middle Terminal bolted to the Body like a FC, which is where all the corrosion and weirdness begins.

ECU is looking for a certain amount of resistance between the terminals on each solenoid. I believe it is around 40ish Ohms, but it's been a minute since I looked. The proper thing to do is get the multimeter out and start testing the solenoids in question. And if you could, get a picture of the solenoid box with everything connected for me too. I need to confirm a couple things.

Jdmrx700

I checked the resistance on what I believe are solenoids that may be the cause of the fault codes, wastgate and pre control solenoids, the green pair. 30ohms each. I thought it might be because I cracked the vacuum hose nipple. I've fixed it as best I could but will replace it anyway to prevent any leak.

Should I start by removing all the grounds and cleaning/replacing the connections? I'll have to go back in and check the restance of all the solenoids in the box.

Akagis_white_comet

iTrader: (4)

Just for the sake of ruling it out, I would be doing this to every ground throughout the entire car to rule it out:
https://www.aaroncake.net/RX-7/grounding.htm

FDs follow similar "logic" to the FC, so the Negative Battery Cable's middle body terminal is usually where corrosion begins running amok. Between there and the Battery, every single circuit in the car runs through it. Generally speaking, the "lightest" devices such as solenoids will be affected the least, while the "heaviest" ones like the ignition coils fall on their face.

Many thanks for the picture. It'll make things a lot easier for what I'm working on.

Jdmrx700

So finally got some time to get back under the hood.
Tested all the solenoids in the box. All 30-38ohms except 2 of them. I think they are the turbo control solenoid 1/2 and the charge relief solenoid. No continuity / resistance across either one. Also found the same issue with with the turbo control solenoid 2/2 mounted next to the box.
Tested them with a 9v battery and confirmed they do not actuate.
Is there anything that is likely to cause both turbo control solenoids to fail?
Hopefully starting to find the cause.

turbodog

Have you checked your fuel pressure? Symptoms also resemble fuel pressure regulator.

Jdmrx700

I haven't tested the fuel pressure yet, with the faulty solenoids matching the fault codes the ecu is throwing I'm hopeful this is the issue. Got a new turbo control solenoid and new vacuum unit on the way to replace them all. Fuel pressure test might be next on the list for troubleshooting. Thanks.

Jdmrx700

Back up and running properly.
Confirmed 3 faulty solenoids. Both turbo control solenoid and the charge relief solenoid. Replaced the whole vacuum unit and the turbo control solenoid.
no more fault codes. No more limp mode!