ALFAGTV6.COM

[mjr]

Hi all.

After a recent water pump change my 83 GTV6 is running rough on tick over and smells very very rich indeed. no problem I thaught, and I went through all the hoses, didn't find any air leaks. pulled the ecu, checked ecu connections, checked and cleaned all grounds, checked CSI for leakage, changed the air cleaner, dizzy cap and rotor arm, inspected plugs and leads. all a ok. checked TPS. convinced it is a fuel problem, I removed the AAV, cleaned it out, and opened it up another 20% or so whilst cold, and then reset it, to improve my cold starting a little, which has always been a little on the low side. when I next ran the car, as expected the engine ran at a higher than usual tick over for the first minuteed due to the increased aperture on the AVV. ran smoothly and perfectly at 1200 rpm cold. As soon as the AVV started to close up and reduce the air, the tick over got rougher and rougher, and smelled more rich. At this point IM thinking " ok this proves that shes getting too much fuel as the AAV closes down with warm up". Anyway after checking all again, I pulled the coolant temp sensor connector off and measured cold and hot. cold the CTS measures 3.2K at 20C. About right I think. However with engine warm and running bad, the CTS measures 528 ohms. The book specifies 200-400ohms max at 80c. 1) presume this means the CTS is toast or corroded or got damaged while removing the thermostat 2) would the extra 128 ohms provide enough resistance to fool the ECU into providing way too much fuel at idle?. The hotter, the worse it gets. off of idle with open throttle it runs fine, if a little too rich still. fuel economy is down too, unsurprisingly.

[fedezyl]

Well I have not the same alfa (a 33 16v) but had sort of the same problem, did you check the fuel pressure? you may have a faulty fuel pressure regulator (i had mine go bad and my fuel mileage cut in half also), I was having 3.5 bar instead of the usual 3.

Just a thought that might be worth checking

[Mats]

Sounds like the sensor is fine, usually they read infinite or zero when dead and don't change at all.

[mjr]

haven't checked the fuel pressure yet. I need to get my hands on a pressure gauge. Im ordering a new fuel filter today too. just seems odd that the problem has started after changing the water pump, where both CTS and TTS would have been disturbed. Re the CTS. thinking about it, as the coolant gets hotter and the resistance increases, shouldnt that cause the ECU to shorten the injector duration? in which case too much resistance is unlikley to cause a rich running condition at tick over? just thinking out loud here

[Mats]

Stock air filter and box?
I'd check the AFM and replace rotor/cap + plugs just as a service point (unless this was done recently...)

Also have a look at the cold start valve, I've heard about leaky ones.

[mjr]

, replaced cap, arm and plugs. have removed CSI and can't see any leak on it. yep stock intake set up. I would like to check the AFM, but dont know how, asides from taking the lid of and visually inspecting it. What is the adjustment procedure on it to get it within factory tolerance?. Any offical test procedures for the AFM?
Im hoping that it is a fuel pressure regulator problem. I will be picking up a pressure gauge today, to test it later.. bloody annoying. not a peep in 10 years, now shes missbehaving just spent a damn fotune on the ungrateful little bitch too. new water pump, wheels, tyres, RSR kit, interior, steering wheel, and valet, and this is how she repays me.

[fedezyl]

, replaced cap, arm and plugs. have removed CSI and can't see any leak on it. yep stock intake set up. I would like to check the AFM, but dont know how, asides from taking the lid of and visually inspecting it. What is the adjustment procedure on it to get it within factory tolerance?. Any offical test procedures for the AFM?
Im hoping that it is a fuel pressure regulator problem. I will be picking up a pressure gauge today, to test it later.. bloody annoying. not a peep in 10 years, now shes missbehaving just spent a damn fotune on the ungrateful little bitch too. new water pump, wheels, tyres, RSR kit, interior, steering wheel, and valet, and this is how she repays me.

Well my pressure regulator went dead after 14 years on the car....right after some 18 laps on the circuit....but I can tell you, I checked all the electronics, even cleaned up the injectors and the fuel pressure regulator ended up being the culprit...

[kevin]

Maybe rust in tank blocking filter. Pressure fluctuating. Running rich then lean. Just had it in my 159 (Alfetta).

[mjr]

when i take the fuel filter off that should show any rust. well im working on it right now, with wireless in the garage . im getting some pretty weird readings. took off CSI fuel line and electrical connector. connected the CSI fuel line to a high quality aviation manifold pressure gauge, then started her up. fuel pressure is slightly uneven at between 30-32 psi @800 rpm. at 1200-1500rpm, the gauge drops down to 28-30psi. with the engine off, it recovers back to 35psi rock solid. just measured the CTS @ 75c, is 354ohms, when i measured yesterday the engine hadn't warmed past 60c, hence the high CTS reading. so fuel pressure is on the low side on tick over by 2-3 psi. is the 35.5 psi critical on Ljet? looks like maybe it could be the regulator. next job, fuel filter off and plenum off tommorow.

plenum off this morning, inspected all the couplers and they are good, put them all back on and tightenend them good, so no air leaks there it seems.

[kevin]

Unclip the ECU, open it up and see there is no water that has run down the harness into it. Check the board to see if there is no rust build up at the bottom and general inspection. Had this problem once , never thought of cleaning it out.

[Alessandro]

I have had a similar problem before - the wires connecting to the coolant temp sensor at the thermostat were oxidised. If you have ever had your thermostat gasket leaking antifreeze (like mine) this is probably a likely cause. Try and disconnect the wires leading to the temp sensor and start the car (should start and run very rich) Connect the wires and see if it makes a difference? If there is no difference there is probably a wiring problem. The black wire goes to earth, and the white wire goes to terminal 13 on your ECU. Try and also open up your ECU and check for any oxidation.

[mjr]

have checked the cts wires, and zero resistance. so all good there. Have also removed the ecu, and there is no corrosion at all, even the pins are bright and shiny. I will replace the fuel filter this week. if that doesnt work, then I'm going to the local garage to plug in the exhuast gas analyser, then go for altering the idle mixture on the AFM, see if this sorts it out. no CATS on european gtv6, so no O2 sensor, which would have been handy in this instance. plugs are fowled and blackened though, so and obvious rich running state at idle.

[fedezyl]

when i take the fuel filter off that should show any rust. well im working on it right now, with wireless in the garage . im getting some pretty weird readings. took off CSI fuel line and electrical connector. connected the CSI fuel line to a high quality aviation manifold pressure gauge, then started her up. fuel pressure is slightly uneven at between 30-32 psi @800 rpm. at 1200-1500rpm, the gauge drops down to 28-30psi. with the engine off, it recovers back to 35psi rock solid. just measured the CTS @ 75c, is 354ohms, when i measured yesterday the engine hadn't warmed past 60c, hence the high CTS reading. so fuel pressure is on the low side on tick over by 2-3 psi. is the 35.5 psi critical on Ljet? looks like maybe it could be the regulator. next job, fuel filter off and plenum off tommorow.

plenum off this morning, inspected all the couplers and they are good, put them all back on and tightenend them good, so no air leaks there it seems.

Did you check what the manual said about the fuel press? on the 33, with the vacuum connected it should read 2.5 bar or about 25 psi, when it was running rich it was running at 35psi with the vacuum off...

[kevin]

Dont laugh but try another battery. I have just had a misfire and overfueling problem on my Haltech GTV and the problem was bad battery. The car could swing over but battery was on its way out. I know this is totally different to the bosch but we are clutching at straws here .

[mjr]

no stupid suggestions here, I am open to all ideas, and trying them! the battey is good. I know, because It turned the engine over 15-20 turns with the CTS disconnected, without even struggling. I have got as far as removing the fuel filter, but the hoses won't come off, so I'll have to cut them off, and replace. the manual doesn't really say a great deal about fuel pressure, just that it should be around 32.7 to 38.4psi. mines at 32-33, but that doesnt account for rich running.Im just hopeing now that it is simply the AFM out of adjustment for idle, because everything else has checked out ok. the only test I havent done, is checking each injector. I want to try all else before disturbing them little critters! the key here, is that the rough irregular idle only happens as the engine warms up, ie coolant gets hotter and AVV throttles the air down. Its definately are rich running issue I think