EXEIIU

Idk if I'm tripping or not but only S5 rx7s have the fuel cutoff with the pedal completely down on startup right? So why does my S4 only start up with the pedal completely down or it flood's without it?? I am so confused rn 🥲

WondrousBread

Most likely your fuel injectors are leaky and need rebuilding. They are leaking down after you shut off the car and fuel is pooling in the manifold and housings. The extra air from the pedal fully open helps clear the fuel and start the car.

And you're correct, only S5s have the flood-clear function, but in this case the extra air is probably doing the trick either way.

doug910

My S4 has always had the same issue since I bought it. Always struggles to hot start unless I floor the gas pedal or cut fuel using a fuel cutoff switch. Assumed it was leaky injectors, but I sent them to get cleaned when I rebuilt the engine, but the issue persists. I still don't know what's causing it but I also haven't put in the effort to truly diagnose it because I fuel cutoff switch and/or flooring gas pedal methods works flawlessly to hot start the car.

EXEIIU

I've heard that a bad ecu or coolant temp sensor can cause the car to dump more fuel in than necessary I for one have never tested to see if that's true as this is the first rotary I've owned
But it might be something to look into if you haven't already, I'm thinking that might be the issue with mine or it's low compression not sure yet but I'm still learning and diving deeper into the forums

doug910

I've heard that as well with regards to the coolant temp sensor. I'm actually getting ready to do a coolant flush, so thanks for reminding me about that. I just ordered a new temp sensor to see if it fixes anything, will report back if it helps. And FYI to anyone reading this - the ECU reads the coolant temp sensor that's right behind the thermostat. The gage cluster reads a sensor that's under the oil filter pedestal on the left side of the engine, so make sure you order the right one. I ordered NTK EF0090 from Rockauto, $15 w/ shipping.

WondrousBread

The ECU actually has a fail-safe mode for the coolant sensor, where if it is out of range or failed the ECU assumes a coolant temperature of 176 degrees F. Unless it's possible for the coolant sensor to get "stuck" at a certain resistance and read cold all the time, that is probably not the issue.

But last I checked the sensor is like $12 and only takes an hour or so to replace, so it's worth replacing either way

EXEIIU

Ighty so after installing a fuel pump Killswitch I have still needed to hold the pedal down, it's still choppy for a few seconds and lots of small pops on idle. I'm thinking it's most definitely a coolant seal failure (what I was thinking originally) and/or low compression. I'm gonna see if my automotive teacher is willing to let me rebuild it in the shop and do a hydrocarbon test 😕 but the engine has had a strong life so far (fully stock engine with 127,474 Miles so it was only a matter of time) so I'm not too bummed about it going as it's not blown a apex outta the cats... Yet...

I'll be back with results on what went wrong with it sooner or later

doug910

Those symptoms don't sound like coolant seal failure tbh. Coolant seal failures most often exhibit lots of white smoke in the exhaust, overflowing of the coolant reservoir, "champagne" bubbles in the coolant while you bleed the system, and overheating. While true that it's just a matter of time before a rebuild, might not be a bad idea to pull the injectors to get them sent off for cleaning. Poor/old injectors can definitely cause engine flooding, poor idle, and small pops.

EXEIIU

I probably shoulda mentioned that yes I do have some white smoke on startup, I do get bubbles after shutoff and I am loosing a bit of coolant but not too too much but it could be a bunch of things like the injectors and other problems as well

doug910

Ah okay, in that case it might be time for a rebuild. If your engine is otherwise, you should be able to reuse the keg which will save you a lot of cash. Sounds like you have access to a shop, so use it if you can. Rebuilding rotaries is not difficult at all and will be a great learning experience. I just rebuilt mine last year in my garage so feel free to PM me if you have any questions. Good luck!

EXEIIU

Gotcha man thanks for the help

EXEIIU

Ight so it is definitely a coolant seal failure (fml) temp spiked hard this morning while I was driving to school then dropped as fast and it had risin, I parked it for a while went to start it and a very very very hard start waited for me along with bubbling in the coolant reservoir, drove it home parked it, let it cool for Abt a hour popped the rad cap off and did a champagne test and behold bubbles upon bubbles 😐