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Its not often i get stumped by a car but this has me tearing my remaining hair out!
It's an 03 Civic type R, standard (ish) and original and the problem is massive overfuelling, particularly at low revs/idle. The situation is so bad that if I fit a new set of plugs, run it for ten mins and switch off (idle missfire will gradually increase during this time) the engine will not restart cos all the cylinders are flooded with fuel.
The management light is out and my diagnostic says "no codes". I've fitted a new fuel pressure regulator to no avail whatsoever.
If anyone can shed any light on this I will be deeply grateful!
Steve
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I would get in on a diagnostic tool and look at the live data, gotta be something like a lambda or coolant temperature sender throwing the values right out but not enough for the ecu to twig and throw up the light.
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rodney
Posted a lot
https://www.facebook.com/RD-vehicle-transport-and-recovery-services-525622614268010/
Posts: 1,677
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had this on my petrol ldv , was the temp switch , sends signal to clocks and ecu , that in turn uses that signal to control fueling and fan , wouldn't restart after being run for a few mins and smoked heavily , chocked up etc etc,.
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facebook: rodney dean / rd transport  |
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As said try changing the cts sensor
(Coolant temp sensor )
This relays the info back to the ecu about how hot/cold engine is and in turn helps decide how much fuel the motor needs
Usually a blue or green 2 pin sensor although could be different on Hondas
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I think the problem with this temperature switch / sensor theory is that whilst this certainly could result in over-fuelling if it were happening to that extent the lambda sensor would detect a rich mixture and throw up a warning light or at least generate a warning code.
I'm sure it's possible the Honda management system isn't that sophisticated as I don't have any knowledge of their set up but I would have thought it ought to be. Just to be able to sell the cars they'd probably have to comply with a standard for emissions regulation which would be able to detect this level of incorrect running.
SO...
Do you know the car? Is it possible some plonker has soldered resistors into the signal lines from the air-mass-meter (or whatever load sensor they use) and lambda sensor to fool the ECU into running more fuel so it does not even know it is over-fuelling? Check the wires connected to the sensors for signs of insulation tape or modification. Could also check for damage to the ECU. I've seen people running cars where the ECU was actually sitting in a pool of water before, I've seen other cars with corroded terminals on ECUs which have ended up doing funny things. Check the ECU case for evidence of tampering, like damaged screw heads, broken tamper seals or screwdriver pry marks on the casing.
If you can't find anything obvious the suggestion of getting it plugged into a machine which shows the live data from the ECU is a good suggestion although it is difficult if that same machine can't tell you what the readings should be. Sometimes you're looking at percentages, pressure ratings, voltage signals and you've got no way of knowing whether they are right or not.
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I do know the car, both with its current and previous owners and neither of them are sophisticated enough mechanically or electrically to have tampered with it. Moreover the car has been behaving itself for the last 2+ years until one morning recently when it refused to start. I went round with the diagnostic, found nothing so went back to basics checking for spark and fuel pressure at the rail. Finding both present and correct, I pulled the plugs which were all saturated with petrol. I put in a spare set of ALMOST correct plugs that I had lying about and it fired up straight away but after a couple of minutes it started to miss and needed to be revved to keep it smooth. At this point I switched it off and trying to restart a couple of minutes later got only a couple of coughs then nothing at all. I pulled the plugs again and found them once more soaked in petrol. I've since fitted a new set of correct plugs with the same result and also changed the pressure reg (which is in the tank of all places) cos it seemed like a good idea and would account for all 4 cylinders flooding. Ah logic - an organised way of going wrong with confidence! Temperature may be having an effect though since its fine when its bone cold and gets worse as it warms up - though the guage on the dash reads normally.
Its a good idea going for the live data though. My machine is not posh enough to tell me what it SHOULD be but I know a man who can!
Cheers for all the help so far, I'll post any results I get, any other suggestions also welcomed (i've already made the one about a gallon of unleaded and a match!)
I'm now getting a bit concerned about the amount of petrol going down causing bore-wash, its starting to smoke quite a lot when running!
Steve
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Last Edit: Aug 5, 2014 19:38:41 GMT by carledo
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ferny
Club Retro Rides Member
Posts: 983
Club RR Member Number: 13
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Civic Type R overfuelling!ferny
@ferny
Club Retro Rides Member 13
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It does sound like it's constantly on choke from that last description. Or, it's telling the injectors to fire for longer than they should - but all four?
What colour smoke? It'll probably be unburnt fuel and carbon being washed out of the exhaust.
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Smoke is white with a hint of blue. The cat is probably full of unburnt fuel too which won't do it much good!
Gonna go back for the live data tomorrow pm or Friday morning depending on workload.
Steve
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koma
Part of things
Posts: 238
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I'm just going to throw this one out there, PCV valve stuck open.... saying that, i guess it shouldnt over fuel as much as youve described at low revs/idle.
but in terms of ease to check why not
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Last Edit: Aug 6, 2014 20:28:58 GMT by koma
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Not sure if the civics have an air temp sensor ? But that can also cause issues too
Usually found in the inlet mani
Also sometimes known as the IAT sensor (intake air temp )
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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Coolant temp sensor seems likely to me. If it is the issue it's unlikely to light up the management light, as most set-ups (certainly narrowband) don't monitor air-fuel ratio for most of the warm-up period, so won't know that it's out.
Air temp or any other sensor that's used for small corrections during normal running is likely to be noticed by the ECU via the Lambda sensor and cause it to either correct for the error or flag it up on the dash.
The gauge can often read correctly while the ECU's got the wrong signal as a lot of cars either run 2 separate sensors or a single sensor with two circuits in it, so one can fail while the other's still reading fine.
It's definitely where I'd start. It'll be worth changing the oil as soon as the problem's found too, as like you've hinted at, it's going to have had a fair bit of bore wash thinning it down.
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If you burn the tip of a wet spark plug with a lighter... what colour is the flame.
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