Poor throttle response and fuel economy.
07-10-2018, 06:30 AM
#1
Pro
Thread Starter
Poor throttle response and fuel economy.
Hoping to get some help here, my 964 was runni g the best it's ever run a few weeks ago, I put the car away for a week and now it's rubbish! Idles fine, it's a bit fluffy when it starts up but doesn't stall and always starts first time but when driven it's down on power a little and the throttle response is awfull, as in impossible to heels and toe. A friend suggested disconnecting the afm so i disconnected what I thought was the correct plug and the car ran loads better. So last night I stripped the afm, expecting the barn door to be sticky but its not, it moves perfectly. While removing the afm it became clear that I hadn't disconnected it as I hadn't realised the plug was on the bac. However i can't find out what the plug is I've disconnected to help find the source of the problem. It's not the plug to the isv but the one next to it! Any ideas? Thanks in advance, Jim.
07-10-2018, 08:45 AM
#2
Burning Brakes
I dont see any need to change from Motronic unless you want to use throttle bodies. This means having an engine built to rev higher than the stock rev limit at which point the gearing is too long. Motronic can handle bigger injectors so long as the maps can be changed by someone competent.
07-10-2018, 09:21 AM
#4
Pro
Thread Starter
I'm guessing ras62's comment wasn't meant for me!
my fuel filter isn't very old so I'd be surprised if that's the case, also unplugging whatever it is I've unplugged wouldn't make it run better!
anyone any ideas what the plugs by the isv are for?
my fuel filter isn't very old so I'd be surprised if that's the case, also unplugging whatever it is I've unplugged wouldn't make it run better!
anyone any ideas what the plugs by the isv are for?
07-10-2018, 03:04 PM
#6
Pro
Thread Starter
One is for the vac controller for the resonance flap and the one closer to you is the cylinder 456 knock sensor-
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07-13-2018, 09:10 AM
#14
Pro
Thread Starter
Thanks peteinjp, I'll try that tonight.
I had a development last night and not a good one. I realised that since confirming that I have no power drains on the car I haven't used the kill switch, it also occurred to me that after cleaning the afm and all the electrical connections cutting the power and then letting everything reset might be a good idea. The car runs like **** now, barely able to drive it. It bucks and pops and bangs like crazy. If I now disconnect the plug that helped before the car is even worse and won't even tick over at all. The car wont rev past 4k and is hard work to get up to those revs as it bucks like mad under any load. I suppose this will make finding the fault easier as the fact it ticked over fine and ran well wasn't making it easy to diagnose. I'll test the idle switch, although the fact it won't tick over with it disconnected pretty much answers that but ill test them anyway.
if anyone has any other ideas based on the new issues I'd be gratefully, many thanks, Jim.
I had a development last night and not a good one. I realised that since confirming that I have no power drains on the car I haven't used the kill switch, it also occurred to me that after cleaning the afm and all the electrical connections cutting the power and then letting everything reset might be a good idea. The car runs like **** now, barely able to drive it. It bucks and pops and bangs like crazy. If I now disconnect the plug that helped before the car is even worse and won't even tick over at all. The car wont rev past 4k and is hard work to get up to those revs as it bucks like mad under any load. I suppose this will make finding the fault easier as the fact it ticked over fine and ran well wasn't making it easy to diagnose. I'll test the idle switch, although the fact it won't tick over with it disconnected pretty much answers that but ill test them anyway.
if anyone has any other ideas based on the new issues I'd be gratefully, many thanks, Jim.
07-13-2018, 09:44 AM
#15
Race Car
Have you tried changing the coils? Too bad you aren't in the states. I have a couple sets of 964 coils. I'd try to swap in a good set and see if that has an effect.
You can also unplug one ignition module and then the other to see if that has an effect.
It's plausible, also that since we get so much gunk in the intake, that some of that broke away and clogged your injectors...or the fuel system is clogged - but since it ran well and then started faultering again...it sounds more electrical. And likely culprits will be coils and dme relay. Most of the other stuff in the motor is fairly bullet proof. Though there are a few things that can still go wrong...hit the low hanging fruits first.
You can also unplug one ignition module and then the other to see if that has an effect.
It's plausible, also that since we get so much gunk in the intake, that some of that broke away and clogged your injectors...or the fuel system is clogged - but since it ran well and then started faultering again...it sounds more electrical. And likely culprits will be coils and dme relay. Most of the other stuff in the motor is fairly bullet proof. Though there are a few things that can still go wrong...hit the low hanging fruits first.
