hard start when hot

[Jeff4764]

Can someone please help?? my car starts fine when its cold, once it warms up it just cranks and cranks and sometimes eventually starts. I changed the coils and still no luck. i have no idea what it could be

[RotaryXperiment]

its prob flooding. check comprssion.
might be a bad coolant temp sensor as well.

[Jeff4764]

I did change the coolant temp sensor but i can start it cold and drive it for 10 maybe 20 minutes, and then it does what i explained above. But it does sound exactly the same as when it floods, but can you point me in the right direction of why it might flood even after warmed up. its been like this for about two weeks now and im out of ideas.

[djmtsu]

Put in a 'fuel cut' switch in.

Or, if it is an S5 push the gas pedal to the floor when cranking then let off.

[Jeff4764]

sorry to ask this question but how would I go about doing that??

[RotaryXperiment]

hook up a "on-off" switch inline on the power wire to the fuel pump. turn it off when ur gonna start the car,crank it and then turn it on.

what yr is ur car btw? also try revving the car to 3k, hold it and shut it off.

[Phoenix7]

DO the simple deflooding procedure:

get in car

Push gas all the way to the floor

crank car for 10 seconds (IT SHOULD NOT START WHEN YOUR FOOT IS ALL THE WAY DOWN)

remove foot from gas pedal and see if it turns on.

Try it for a total of 3 times (30 sec. cranking). See if that helps.

[RotaryXperiment]

dats for s5, s4 u gotta remove EGI fuse. crank it a few times to clear and put fuse back in

[TehMonkay]

Test your compression, if it's good, and you changed the correct temp sensor, get your injectors cleaned. Dont half ass fix it.

[Phoenix7]

apparently (mind you I haven't tried it on an S4) it works for both but that's just hearsay. :dunno: I used to think it was S5 ONLY also but others said otherwise and I've never verified it.

[TehMonkay]

S4 doesnt have a full range TPS, it's impossible

[WE3RX7]

S5 only on the pedal fix.

Its compression - lol. Sorry to be a downer, lol but I'd check compression before wasting time on anything else.

The fuel pump switch is only a temporary fix until you can affrord a rebuild.

[RotaryXperiment]

S5 only on the pedal fix.

Its compression - lol. Sorry to be a downer, lol but I'd check compression before wasting time on anything else.

The fuel pump switch is only a temporary fix until you can affrord a rebuild.

like i said in post #2 lol

its prob flooding. check comprssion.
might be a bad coolant temp sensor as well.

[yeti]

The pedal to the floor never has worked for me but, I've never had to use it.

[vex]

apparently (mind you I haven't tried it on an S4) it works for both but that's just hearsay. :dunno: I used to think it was S5 ONLY also but others said otherwise and I've never verified it.

It does work... but it's on a different principle:

When you crank in an S5 with your foot to the floor the ECU actually stops the Injectors from firing, allowing you to burn up the excess fuel that's in the chamber so you can start it just by lifting off your foot when you hear it start to crank.

With an S4 the ECU does not shut off the injectors. Instead it's looking at the cranking map and realizes that you are flooring it, so it's going to look at the flooring portion of the cranking map (unfortunately I do not know the P/W of the injectors at this portion, perhaps a more experienced person can chime in with it). I suspect that the P/W is much, much lower than during normal operation as what we're attempting to do with this is to take in enough air to offset the increased amount of fuel while still kicking the excess fuel out the exhaust. About 9 times out of 10 it will work. The other times you'll have to pull the fuse.

I recently switched over to the RTek7 2.1, but I have awesome compression last I checked (about 110-115 both front and rear on 50,000 miles) I still get flooding, but it's not as much of a headache to deal with as when I was stock.

Here's a simple run down of what you should check before you start doing any work by hacking up your fuel system:

1) Check your compression. Get real numbers. If unable do a poor-mans compression check. It will at least tell us the condition of some of the more important seals.

2) Figure out if your injectors are leaking or are clogged. The FSM covers how to do that and running the test shouldn't cost you more than some mechanics wire.

3) Check to see if you are throwing any CELS such as having your O2 sensor out or another sensor within the AFM is out. If you have a sensor that's out you are looking at the wrong part of the cranking map and hence trying to start it with much too much fuel.

4) Lastly do not, I repeat do not put a switch in between the Fuel pump and the battery source. It's a stop gap measure and will cause more headaches than not.

Now you should be able to find out what's instigating the problem before you even spend money on a replacement part. There's other instances where you may need or want to wire in a resistor to the ECU harness as that will alter the reading from some sensors but I would recommend replacing a faulty sensor or fixing the root cause of the problem.

1) If you're NA and you're throwing anything less than 90PSI I would recommend an immediate rebuild. I've heard of some Turbos being able to turn over fine at 90PSI so I do not think that's a linear cut off for every car, but a rule of thumb or guide line.

2) If your injectors are clogged or the spray pattern is crap, send them out to be cleaned. Running injector "cleaner" or fuel system "cleaner" will not fix your injectors. You will need to ship them out. I recommend KGParts as they have cleaned my injectors (and have made the list of the top 50 worst injectors ever cleaned--which by the way are still running strong, but I'm about to upgrade 'em). They also have extremely competitive prices.

3) If your throwing CELs you are running in a fail safe mode which usually tells the car to dump in extra fuel just in case. If your O2 sensor is bad replace it. You're running extra rich with it busted and so when you shut down you're having excess fuel in the combustion chamber causing flooding. If your TPS is out then your car thinks that you're going wide open throttle all day long and will dump in more fuel than normal. You see the trend?

So find out what's wrong with your car and fix it. Don't just fix the symptom.

[Herblenny]

How many miles are on the engine?? Check your compression.

[Jeff4764]

150000 but if the compression was bad would it still run right... once the car is started it runs beautiful. there were a couple times were i would hit the brakes or turn the lights on and it would bog down and i would have to keep giving it gas to idle. but it doesnt do that anymore now it just wont start when its hot. I dont know much about these cars, i really need to get it fixed though, and noone will work on it because its a rotary. But if someone has a clear idea of what it is i can most likely fix it myself depending on what it is.

[djmtsu]

Where do you live? Rotorheads are everywhere!!!!

[Jeff4764]

i live in a small town in Northeast PA. the only place i know of withing 50 miles is a mazda dealer and they would be extremely expensive