bigbloodyturbo Posted March 27, 2012 Share Posted March 27, 2012 My car has developed a problem with running rich at idle (warm or hot doesn't matter). After reading on here about cranking enrichment I tried pulling the 7.5 amp fuse which seems to have improved it. When I pull that fuse the afr's and idle quality noticeably improve after giving it a rev and I can get it to sit nicely at 14.6. However when moving it about the drive the mixture would drop out again and the car would die. I also noticed the starter motor still worked with the 7.5amp fuse pulled? I'm hoping i pulled the right one. Has anyone got any idea as to what could be casuign the problem, if it is the cranking enrichment thing how do I rectify that? Or if its load related could it be my map sensor? Quote Link to comment Share on other sites More sharing options...
Nic Posted March 27, 2012 Share Posted March 27, 2012 What is the spec of the car? Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted March 27, 2012 Share Posted March 27, 2012 Firstly what 7.5 amp fuse are you pulling, and why? no fuse will effect the idle control (cold cranking)of the ECU independently, normally if the idle is really rich when hot it will be one of two problems, either the ECU temp sensor is faulty, or the lambda sensor is faulty, both of these condition will make the ECU default to running the AFRs rich, however i have never know it to run the fueling that rich. Quote Link to comment Share on other sites More sharing options...
bigbloodyturbo Posted March 28, 2012 Author Share Posted March 28, 2012 Sorry for the lack of response chaps, i left the supra yesterday and decided to install an iphone adaptor in the audi, wish i'd stayed on the supra:-( The spec of the car is singled on a cast manifold and stock ecu and injectors. Everything stock except singled and fmic. I have the rest of the package to go on but I'm trying to get a sneaky mot done and the car was running perfectly. @ricky- I pulled the middle fuse, was labelled alt-s. Only options where dome, trac or alt-s which i assumed was alternator/starter. This did make a bit of difference when sitting idling but tbh it could of been wishful thinking. I can get the car to sit at 14.4-14.7 perfectly if i give it a rev and let it come down to idle nice and easy, however if i rev it and let it drop the idle almost stalls out and the afr instantly goes to 9.5-10. It's not missing as i can rev it up to 2-2500rpm and it holds nice like that, but the afr's are still 9.5-10 at this point. It did this once before and i replaced the plugs, pulled and dropped the o2 sensor in some lime juice and it seemed to fix it. Would an o2 sensor cause the misture to almost instantly drop to 9.5-10 afr, feels like a switch sometimes. When it happed first it was idling fine and wheni put it in gear and pulled away it instantly went rich and could barely move the car. Quote Link to comment Share on other sites More sharing options...
bigbloodyturbo Posted March 28, 2012 Author Share Posted March 28, 2012 also just stuck a meter on OX1 and its sitting at 1.8-1.9 when my wideband is reading 13-14:1, when the coolant had heated up a bit the afr went to 14 and the stock o2 went to a bit mental and was oscillating between 0.8 and 1.9v and the idle got shitty with some missing and popping. Should I just get another O2 sensor from Toyota? -edit, this was after i had revved it a bit and managed to get it to stop sitting at 9.5 Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted March 28, 2012 Share Posted March 28, 2012 Sounds like the O2 sensor to me, i would replace it and go from there, try Just Lambda or somewhere like that, it will be cheaper than Toyota. Quote Link to comment Share on other sites More sharing options...
bigbloodyturbo Posted March 28, 2012 Author Share Posted March 28, 2012 Sounds like the O2 sensor to me, i would replace it and go from there, try Just Lambda or somewhere like that, it will be cheaper than Toyota. Cheers, I'll get a replacement and update this thread with the results in a few days. Quote Link to comment Share on other sites More sharing options...
bigbloodyturbo Posted March 30, 2012 Author Share Posted March 30, 2012 Ok bought a new o2 sensor and installed it, it hasn't changed a thing. AFR still sitting at 9.5-10, best i can get is 11 (it was warm at this point). I have got it idling (nasty sounding) and pulled each of the coil clips and each made a difference so I don't think it's coils or ignition. I'm running out of ideas so any more thoughts would be appreciated. Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 30, 2012 Share Posted March 30, 2012 Could be your air intake temp sensor to a degree, but more likely is the water temp sensor. If the ECU thinks the engine is stone cold, it'll fuel around those levels. Check the two-wired plug on the upper rad feed elbow coming out the front of the engine. Quote Link to comment Share on other sites More sharing options...
bigbloodyturbo Posted March 30, 2012 Author Share Posted March 30, 2012 Would that sensor cause this problem even from cold? On wednesday the car decided to go back to 14.6 afr for 5 mins untill I revved it and it went loopy again. Is it worth checking any type of wiring and if so which of the wiring would cause drastic changes to afr. I'm starting to think the stock fpr is faulty and the ecu can't compensate enough or something. Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 30, 2012 Share Posted March 30, 2012 ALT-S fuse is for the charging systems of your alternator, by the way You were after the ST fuse in the drivers' footwell, but without that in, the car won't crank or start. If the water temp sensor fails in some fashion it could be sending something like a -20degC signal to the ECU, so it'd be adding in loads of fuel. A dodgy connection or wire could make this intermittent, and the act of revving the engine could provoke it - especially as the sensor is right by the massive radiator fan. Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 30, 2012 Share Posted March 30, 2012 I just checked, the water temp sensor works off resistance. The higher the resistance, the colder the water temps. So a break in the wire would make it report the lowest value, -20degC Quote Link to comment Share on other sites More sharing options...
bigbloodyturbo Posted March 31, 2012 Author Share Posted March 31, 2012 I just checked, the water temp sensor works off resistance. The higher the resistance, the colder the water temps. So a break in the wire would make it report the lowest value, -20degC Cheers mate, I'll have a look at this. I'm sure I saw a thread with that's sensors' response plotted out. I'll also retry with the correct fuse pulled haha. I hope I don't have to go as far as probing wires on the back of the ecu or I'm going to cry.... Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted March 31, 2012 Share Posted March 31, 2012 Make sure you test the right one, IE two wire sensor, the other is the gauge sensor, although i still wouldn't expect the ECU default to running things that rich, which is why i suspected the lambda, but i agree with Ian that if there is an intermittent short/broken connection, it could cause an odd cold response from the ECU Quote Link to comment Share on other sites More sharing options...
bigbloodyturbo Posted March 31, 2012 Author Share Posted March 31, 2012 Make sure you test the right one, IE two wire sensor, the other is the gauge sensor, although i still wouldn't expect the ECU default to running things that rich, which is why i suspected the lambda, but i agree with Ian that if there is an intermittent short/broken connection, it could cause an odd cold response from the ECU I think its the green coloured one? I remember two when I took the water elbow off. As far as I know the ecu can only trim out 20% or something in accordance to this sensors response? the idle is shocking at the moment though, it sits at 700rpm and splutters its way along, if i hold the revs at 1500 its reasonable but still rich as hell (10:1). It isn't missing though, when i hold the revs up at 2000rpm it actually thrums away smoothly by comparison, just with mega rich:-( Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted March 31, 2012 Share Posted March 31, 2012 The fact that it isn't missing, kind of rules out a stuck injector, so in theory its got to be down to the ECUs response to a sensor, is the ECU std? or are you running a piggyback or stand alone? Yes AFAIK the limits to fuel trim are not that large, IAT is pretty minimal and wouldn't affect things like that, and you have ruled out the lambda, and even so it still wouldn't result in that rich as default, same goes for the ECU water temp, unless Ian's theory is making it play tricks on the ECU. The only other thing that i can think of would be the MAP sensor, might be worth checking the output voltages against spec. Quote Link to comment Share on other sites More sharing options...
CanisLupus Posted March 31, 2012 Share Posted March 31, 2012 Check the FPR and Vacuum Line that connects to it Quote Link to comment Share on other sites More sharing options...
bigbloodyturbo Posted March 31, 2012 Author Share Posted March 31, 2012 (edited) took the line of the fpr and checked for splits but its ok. I'm unsure as to how to check the fpr, what would happen if the vaccum line was taken of the fpr, would it go mega rich or mega lean? @Ricky- Its a stock ecu, I have a syvecs to go in but thats been put back now obviously lol. I enquired at toyota for a price for a map sensor when i bought the o2 sensor and was quite surprised to get quoted £260 INCLUDING discount! How does one go about checking the map sensor? Do I check resistances with it unplugged straight to the pins or do I break into it with some needle probes? -edit- should add I checked the injectors with a screwdriver to my ear and each one is ticking away. Edited March 31, 2012 by bigbloodyturbo (see edit history) Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted March 31, 2012 Share Posted March 31, 2012 You can check the supply voltage of the MAP sensor by disconnecting and putting a volt meter between the two outer pins, you should see 4.5 to 5.5v But the only way you can check the output voltage is by accessing the ECU pins, and then checking with and without a vacuum applied. You would normally set the static (no vacuum) fuel pressure at 33-40PSI, once idle vacuum is applied it will drop slightly, but i am pretty sure that it would not result in the kind of AFRs you're seeing. There is also a VSV for fuel pressure control, but i am not sure if thats limited to the UK spec? Quote Link to comment Share on other sites More sharing options...
bigbloodyturbo Posted March 31, 2012 Author Share Posted March 31, 2012 You can check the supply voltage of the MAP sensor by disconnecting and putting a volt meter between the two outer pins, you should see 4.5 to 5.5v But the only way you can check the output voltage is by accessing the ECU pins, and then checking with and without a vacuum applied. QUOTE] I thought I could monitor the output by just taking the plug off and jumping each terminal to each terminal (simulating the plug beign installed) and then just use a pin on the end of the meter probe to pierce the sleeving and take a measurement? Would this not work? Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 31, 2012 Share Posted March 31, 2012 The fact that it isn't missing, kind of rules out a stuck injector, so in theory its got to be down to the ECUs response to a sensor, is the ECU std? or are you running a piggyback or stand alone? Yes AFAIK the limits to fuel trim are not that large, IAT is pretty minimal and wouldn't affect things like that, and you have ruled out the lambda, and even so it still wouldn't result in that rich as default, same goes for the ECU water temp, unless Ian's theory is making it play tricks on the ECU. The only other thing that i can think of would be the MAP sensor, might be worth checking the output voltages against spec. The water temp is one of the biggest adjustments the ECU gets at idle, I've poked around some old cold start logs and it can increase injector duty cycle by 20 to 50%, and that's without it reporting anything like -20degC, so I think this one is quite possible. I also recently fixed my Mondeo's shocking fuel economy due to the oil thermostat sticking and the car never warming up. This dropped the mpg down from 36-38 to about 28, so that's about 30% more fuel going in just because of the water temps. If there is a dodgy wire causing high resistance, the ECU won't throw a fault, it'll just record a low coolant temp. The MAP sensor is a good idea too. One quick easy test would be to pull the vac hose off the bottom of the MAP sensor while the engine is struggling to idle at low afrs. It'll either stall instantly because the ECU adds even more fuel, in which case it's not the MAP sensor, or it won't change at all, in which case it makes the MAP sensor more likely Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 31, 2012 Share Posted March 31, 2012 Actually, you could take the plug off the water temp sensor and bridge the two pins with some wire, make it think the coolant is up to temps - 100ohms resistance = about 100degC. It might suddenly cheer up the AFRs, be an easy test. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted March 31, 2012 Share Posted March 31, 2012 Actually, you could take the plug off the water temp sensor and bridge the two pins with some wire, make it think the coolant is up to temps - 100ohms resistance = about 100degC. It might suddenly cheer up the AFRs, be an easy test. Good idea! i always miss the simple and obvious:) same goes for the MAP sensor test, it should stall. I know water temp sensor can make a fair impact on fueling, just didn't think that it could change it by that much. Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 31, 2012 Share Posted March 31, 2012 I know water temp sensor can make a fair impact on fueling, just didn't think that it could change it by that much. Yeah, it's a crazy amount. As proven by my diesel weasel Quote Link to comment Share on other sites More sharing options...
bigbloodyturbo Posted March 31, 2012 Author Share Posted March 31, 2012 Ok I'll get stuck in with your suggestions tomorrow and see how i get on. Thanks a lot for all the help btw, it is really appreciated, I had started to run very short of ideas lol. Quote Link to comment Share on other sites More sharing options...
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