Grizzly

Hi all.


To start of it had a Rebuild 18 months ago and i tested it today and its seeing well over 7 bar on each Bath. The car is basicly stock (Cat back and Induction kit).

I've been having a look at a mates FD, whats happening is its acting like its on Cold start all the time (Overfueling) when you drive it it pops and backfires etc (gets worse the warmer it gets) when it comes on boost (First Turbo) it's most ovious then when the second turbo is just about to spool up, then the Second turbo spools up and it clears (pulls ok), there is also slightly more Blue smoke than Usal coming out of it all the time (But not enough to worrie about).

I have Changed the Map sensor (for one i know is working of my car), Good plugs (swaped of my car), checked for Boost leaks (found one in the Turbo-IC pipe which was replaced), the air pump has been removed whilst the cat is still in place (but it goes better at high revs so i don't think its that), There was loads of cheap Silicone vac pipe all over the place which i've replaced with some Viton i had over from a job (still hate Silicone as its so soft, i could imagen it colapsing with vacuum going through it)

After i did all this i noticed it had an Aftermarket Water temp gauge in the car, so when i asked about what sort of temp it runs at i was told "The Temp gauges don't work" then it started to rain so i packed up for the day.

Now i'm thinking along the lines of the Water temp sender being dodgy, i know when they go the ECU goes into limp mode or could think its cold all the time? The thing is, isn't there Three Senders on the Pump housing? does the same one do the ECU and the gauge? If so that may be the Problem? I read that the lower (single wire) plug on the back of the water pump housing it the ECU and the single wire sensor on the Rear plate near the Oil presure sensor is the Dash gauge? Does this sound correct? if so it screws my theory up

I've spent the last hour searching and i keep coming up with Air temp or water temp Sencor? (which is next on the list to look at)

Has anyone had the same sort of symptoms? What did it end up being?

Thanks,
Chris

Cgotto6

iTrader: (8)

You have to have the air pump hooked up if you are running a stock cat. Otherwise it will clog very quickly and potentialy cause boost issues, which is what I suspect you are having. Do you have a boost gauge? IF so whats your boost pattern?

Oh, and your are correct, there are two different water temp senders on the car. One for the cluster gauge, and one for the ecu. The gauge's is on the drivers side of the motor, kinds near the oil pressure sender. The the ecu's is on the back of the water pump housing. This is also a potential cause for why your car was running rough. My old fd has this happen, and it drove similar to how your discription stated.

Grizzly

I did think about the cat, the thing is it Boosts fine when the second Turbo is spooled up, there was a boost leak which was'nt helping but thats fixed now and its better but its still doing it. i've had split hoses etc before and its not acting the same (the second turbo will spool)

It has had the Air pump removed but i have been told it does it with his cat or Decat pipe in place.

Boost wise, this may not be accurate because of where he's plumbed it in and its a C**P gauge but it reads 9-6-9 psi so its getting boost its just how it gets there, it runs REALY rich, even on idle it hunts (hunts 200prm, won't idle smoothly like a stock engine should).

Its realy odd, it Pulls ok when the second Turbo is going but runs realy lumpy and overfueled anything under 4500 at WOT.

Grizzly

the more i look into it the more i think its the Water temp sensor on the back of the Pump housing (lower one with one wire)

I do have another sensor thats not doing anything here but i don't know if that works or not? Is there any way of checking them without the use of a Power FC?

Mahjik

iTrader: (1)

There are two sensors on the back of the waterpump housing:

Top one: Water thermosensor
Bottom one: Water thermoswitch

The thermoswitch deals with turning on the fans.

Have you tried checking for codes? Considering its a Euro car, it might not have the Check Engine Light on the dash, so you can following this link:

https://www.rx7club.com/3rd-gen-archives-73/there-any-chance-read-ecu-codes-without-ecl-238994/

If the airpump is removed on the stock ECU, the idle will be rough. Generally, you need to raise the idle up to around 1000-1100 rpms to smooth it out.

Grizzly

TBH its not the idle thats the biggest problem, it does idle about 7-800 so raising it to 1000 would help it alot, the Issue is with the amounts of fuel its dumping in (so much it pops and bangs and the unburnt fuel coming out the back makes your eyes sore if you stand anywhere near the Exhaust)

If i could discribe it i'd say its still on cold start, i say this because it gets worse the more it warms up. From cold the idle is lumpy but not OTT when its been running for 10 minutes or so it starts to idle more like a Big overlap engine, if you rev it it goes smoother for a few minutes then it builds up and goes lumpy again. Driving it off Boost feels like its Holding back quite badly, on boost it pops and bangs (when hot) but clears and runs fairly well on the second Turbo.

I did have a go at checking the Error codes but this car does not have a Dash light and for some reason i could'nt get it to give off a code??

I've spent a bit more time reading today and have come up with this theory, if its the Thermosensor thats faulty they usaly give off a Low reading, if its unpluged the ECU thinks there is a Missing/Faulty Sensor and sets the temp to 160deg (or something like that) which makes it a Pain in the rear to start from cold but once going should cure the problem if its that?? then if i fit the Sensor i have here and it still does it i know its the Sensor or the Wiring thats faulty and i won't spend the next week chasing faults that are not there? Does this sound like it could work?

Mahjik

iTrader: (1)

I think you are confusing a few things:

Without the airpump, the exhaust will not be as clean. You will have a lot more fumes as you aren't burning them off as effectively as with the airpump.

Next, the coolant thermosensor problem will cause the car to run poorly all through the car's range, not just the lower range.

While it's possible that you have a leaky injector which is dumping too much fuel, its not something you can diagnose without pulling them out and having them cleaned & flow balanced. IMO, that's the last thing to do.

If the car pulls ok at top, then its not in limp mode.

I would start with the following:

Check the ignition harness. Make sure it's not damaged or has wires exposed. Same thing for the spark plug wires. You said you changed plugs, but not plug wires so check that.

Check/change the fuel filter and O2 sensor. Basically, get all the of the normal maintenance items out of the way so you can rule those out.

Next, check the TPS and make sure its adjusted within range. Also check the double throttle mechanism and make sure its working properly.

Grizzly

If it helps, the Engine was rebuilt 12 months ago and they fitted new Plug leads, Lamda sensor and did a full service at the same time.

You know some times its realy not good searching too much, i have read every thing from faulty ecu to Air temp sensor (basicly every thing that could go wrong??)

I'll have another look at it in the week but i'm going to get hold of a Good air and Water temp sensor and swap them and check the wiring while i'm there. When i was looking at it on saturday i had a look at the TPS just to check it was tight etc and it looked fine (lots of muck round the bolts and they looked like they had never been out)

As i say it realy does feel like the Primary injectors are overfueling, as soon as the second turbo spools it feels alot better.

I know the Coolant level wire is Damaged (some muppet has tryed to wire a Temp gauge into it but i don't think that would be causing the problem?)

I just wish the ecu would give me a fault code then i would have something to go off.

FD3S2005

iTrader: (11)

not 100% true... i havent had my air pump on for almost a year and when i took it out to put a midpipe on it.. it acually didnt look that bad. its just diffrent for every car

Mahjik

iTrader: (1)

That doesn't necessarily mean its within spec. That's something else to check. Here's some info on testing and adjusting the TPS:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/fixed-my-idle-problems-backfiring-bucking-more-170731/

IMO, you can't really tell whether its a fuel problem just by how the car does in the boost test. That's like sitting inside your house and judging the outside temperature by feeling the inside of a window. Just not the same thing as using a thermometer.

If you really suspect an overfueling issue, you need to hook up a wideband O2 to see whats going on. However, I doubt that's the problem.

Obviously, you should fix whatever is broken/damaged regardless of whether it will fix the immediate problem. Its possible that there is a combination of problems with the car. I would fix them one at a time as you come upon them. As you fix something see if the issues of the car change or go away.

Grizzly

There is no harm in testing anything that could cause the problem. I was chatting to some one today who says the best way to make sure its not a wiring/Sensor fault is hook it up to a PFC (Which would mean pulling mine out )

There is alot to be said for fitting a new Wiring harness when the motor was rebuilt, its allways nice to know its not something daft like a Broken wire that could have me searching for the next Month