mad00544

hey guys

just finished putting my 99 s8 back together after getting the engine rebuilt and mild porting.

now when i started the car was rough as hell... which i expected for the first start, wouldnt idle for ages then would idle but very rough and violent. the rev meter and temp gauge wasnt working.

a few days later i gave it another crack, the car started, revs popped up for 30 sec and then went down to a normal idle smooth as! great i thought. then it died, started again died after 5 sec. out of petrol i thought as i only put in a bit.

went and got some petrol, started up again but rough as guts again and the add coolant alarm came on. check the fuel pressure and its sitting over 50psi right before it dies again. wouldnt start, flooded i thought

so pulled out the plugs cleaned em up check the gapping was at 0.7mm popped them back in, found the water temp sensor plug wasnt on so plugged that in.

backed the fpr right off and give her another try. starts! but still somewhat rough and the add coolant alarm is going off again. tacho is working and its idling so i start bleeding the coolant system properly after reading a better way to do it on here than what the service manual says.

but i realise the temp gauge still isnt working after the car is running for long enough that it shouldve moved a bit. water temp was def 50deg plus.

i read that sometimes the water temp sensor unplugged can cause the car to over fuel and idle rough. could it be running in limp mode or something from when it was unplugged?

also i checked again that the plug on the water temp was on properly and checked the other one on the front of the water pump the coolant level one. there connected.

any help or ideas would be much appreciated.

thanks
Mark.

oo7arkman

iTrader: (2)

Ok, so what I think I am understanding at the end of that is: The car will now start and idle, but it is very rough and the temp gauge is not working. Is that correct?

If the temp gauge is not working it is the temp sensor towards the left rear side of the engine (if looking at the engine its the right). If all those are plugged in correctly (and you verified the wire colors are going to the right sensor) then you have have a wiring short. Yes, if the ecu does not see the temp sensor, it will not run correctly.

Also check and make sure the map sensor is plugged in correctly.

Make sure the TPS is set correctly.

The air bleed screw under the elbow will need adjusting.

These are just a few things I am thinking of off hand. Hopefully someone else will chime in here in a minute and add to what I have said.

arghx

iTrader: (3)

does the car have any modifications?

Funkspectrum

iTrader: (5)

Make sure the Thermoswitch connector and the fuel temp connector are connected properly.
I had mine connected the wrong way and it caused a nasty rich condition...

mad00544

Ok car has mild port, alloy radiator, dp and rear section but stock mp, intake.

Today I made sure the ground near the water temp sensor was good and that it was connected properly. When putting the uim back on didn't connect the map sensor back up, engine flooded soon after starting. Pulled out plugs they were pretty fouled but in some others I had.
Reset ecru
Started! Held at 2k nice and smooth the dropped to 900rpm not too rough.

Add coolant alarm still going off and temp gauge not working still. Also noticed the stock boost gauge stopped working.

Now what I find weird is that before I found the water temp sensor wasn't connected my tacho wasn't working and the add coolant alarm wasn't going off as well as the the water temp gauge not working. But the boost gauge would go up to over 10psi when it was at the key would be on "on" before starting. Connected water temp sensor and tacho worked, so obviously it's connected properly.

So as it stands idle isn't too bad drove car around shed seems smooth, I'm sure adtjusting the tps and air bleed valve will fix that. Could my coolant level sensor be gone? What voltage should I see going to it? I measured the voltage and it was very low can't remember exactly but under 1 volt. If this sensor is gone could it cause an open circuit and temp gauge not to work?

Sorry about the lengthy explanation don't wanna leave anything out. You guys on here are very helpful much appreciated

mad00544

Oh I also deleted the air pump and egv using a block off plate but leaving it connected.

oo7arkman

iTrader: (2)

You must forgive some of us, we never had the luxury of a stock boost sensor. Is that sensor electronic (receives signal electrically) or manually (vac line)? If it is electronic it sounds like you have a couple wires switched under the hood. The coolant buzzer constantly going off sounds like another harness ground that connects over near the power steering (single black wire, round black clip) that will cause the buzzer to go off even though there is plenty of coolant.

On here there is a wiring diagram for the 94 FD (link in my signature). I am not sure if some of the wire colors will be the same for the same sensors, or I would try tracking down a wire diagram for the 99. I know that is not the most fun thing to do, BUT it tells you FOR SURE that the wires are connected properly.

mad00544

And I don't get the luxury of a check engine light which I would much prefer! Haha. I've been using the 93 workshop manual as a guide but I'll have a look at the 94 one.
I've tried looking for a 99 wiring diagram or manual, near impossible to find, well I haven't found one, and apparently If I do it will be in japenese as the s8 was only realeased there. I'll check the ground near the power steering. As for the wires switched under the hood I'm pretty confident there all right as with the 99 loom how it runs with the solenoid vac box and all, each plug only really reaches one
Spot/sensor. And where there was 2 or more we marked them

mad00544

ok so did some looking around this morning and no luck. everything seems connected fine. the color of the wires on the sensor on the back of the water pump is the same as the 94 and its connected fine. the only thing i noticed is that the series 8 only has one sensor on the back of the water pump/therostat housing. series 6 has 2 it looked like in the service manual. useless info i guess.

cant find this black wire that grounds near the power steering either. where exactly is it?

oo7arkman

iTrader: (2)

Ok, that black ground wire splits off the loom just to the left of the alternator, goes behind it and has a small square (not round, I was wrong before) black clip. The other side comes off of the harness near the battery.

mad00544

ok i had that ground wire connected up wrong, all right now and coolant low buzzer isnt going off

i replaced the water temp sender as the connection was half broken so thought that may have been causing problems. still no luck with the water temp gauge though its not working. and the factory boost gauge still isnt working.

any other ideas boys?

theo481

iTrader: (10)

maybe just go aftermarket for both, to at least see if everything is ok...

mad00544

Yeah I was thinking that as I'm scared to run the car long enough up to temp to are if the thermo fans are coming on cause I can't see any temp.

oo7arkman

iTrader: (2)

Glad to know that fixed the buzzer, that is a very annoying problem to deal with..

Still sounds like there are some wires mixed up. Is the rear coolant temp sensor plugged in a working correctly? There are two, the one up front and another in the rear iron back near the oil pressure sender. It has a single brown wire going to it. I even think this is the one that works the needle on the temp gauge but I could be mistaken. The buzzer and needle are fed signals from different sources.

The boost gauge I am at a loss b/c we are not fortunate enough to have the oem boost gauge. BUT it does again sound like a wiring issue. I feel your pain, wiring gremlins are a bitch...

arghx

iTrader: (3)

removing the airpump isn't doing your idle any favors. Stock computers don't seem to like it.

mad00544

the idle isnt too bad now. havent adjusted the tps or anything yet and its already better sits on about 1000rpm and smoother than before. im guessing the roughness might have just been from being a rebuilt engine. will adjust the tps and that still though.

i have set the fuel pressure and took the car for a spin around the block. goes good nice and smooth. but i noticed that the speedo isnt working either. boost gauge water temp and speedo all be not working maybe cause of a blown fuse for the dash?

the read temp sender is def connected as i just replaced it and it was a brown wire. another person on here had the same problem as me with the temp gauge not working, said it ended up being the water temp sensor on the water pump housing was corroded and broken. but i checked that its connected and it is the right color wire according to the 94 diagram.

mad00544

anyone got any ideas on what my half working dash could be? i checked all the fuses and they look fine. studid fuse box cover on the interior is all in japenese so had to check every one haha.

im guessing the stock boost gauge is electronic as i doubt they run a vac pipe to the back on the dash. can anyone guess where it would be read by though? or does the map sensor read the boost for the ecu? this is killing me the car runs good enough to drive now but i cant without thethe gauges working..

oo7arkman

iTrader: (2)

MAP sensor reads the boost for the ecu. Possibly the same signal feeds the gauge. I really thought it was possibly a fuse too. Everything was fine and worked prior to the rebuild? All I can say if that is true it HAS to be related to anything that was touched during the rebuild process. I hate to say it, but go back and recheck all connections to ecu, grounds (this could be it, common ground for all those gauges/sensors not grounded well), etc. OR if you have a buddy that can help and read wire diagrams, have them read it. Sometimes problems like this just need a fresh set of eyes. If you grounded anything to a bracket instead of the chassis or block redo it. This caused me issues that took me a week to find.

The bit of roughness is more than likely just do to it being a fresh rebuild.

mad00544

Yeah everything was fine before the rebuild. I have one grounding wire in mind, I wasn't sure where it went so I grounded it to a bracket. Not sure where it grounded on the block or the firewall. It was a thickish grounding wire that came off the tail of the loom thy goes to the ecu which runs behind the engine. Different to you guys cause I'm rhd. I'll start going thru the loom i guess. Going to be fun!

oo7arkman

iTrader: (2)

I will really be interested to hear what it was. I despise electrical issues. They are the most tedious, pain in the *** issues to work out. Good Luck!

mad00544

hey ppl

fixed my problem! thought i would post it up.

so after heaps of searching for similar probs i thought i should check the white plug in the loom near the ecu plugs. was disconnected! so plugged it started boost gauge worked! and the water temp started going up after a min.

thanks everyone for your help much appriecated.