Is my accelerator an "on / off " switch
Discussion
Bit of advice required please. My car's just come back from a service. I think there was some trouble setting up the engine & it's had two new lambda sensors, since it's come back it's popping & banging permanently, which I don't mind.
Thing is, when it's warmed up the throttle is like an "on / off " switch. No matter how slowly I put my foot down, it goes flying off.
Great on a race track, I've no doubt, but the passengers head is taking a bit of a battering.
Apart from dumping the passenger (Hello Julie), is there any advice please.
Thing is, when it's warmed up the throttle is like an "on / off " switch. No matter how slowly I put my foot down, it goes flying off.
Great on a race track, I've no doubt, but the passengers head is taking a bit of a battering.
Apart from dumping the passenger (Hello Julie), is there any advice please.
With that much power on tap, being able to throtle it accurately is important. Do you mean the engine just pulls better than it used to 
, or is it more like the engine doesn't respond to small increases in throttle and then suddenly comes in with a bang? This would probably be a sign that it isn't running right.
, or is it more like the engine doesn't respond to small increases in throttle and then suddenly comes in with a bang? This would probably be a sign that it isn't running right.It wasn't any fun all weekend, compounded by the fact that today the accelerator pedal went all the way to the floor.
The cable's knackered hence the original post, by the looks of it.
Also the tick over's started playing up, it dropped to below 500 revs & kept stalling. Is that the throttle cable aswell or something else ?
The constant popping & banging, I'd like to keep though.
>> Edited by RUSSELLM on Monday 15th November 14:46
The cable's knackered hence the original post, by the looks of it.
Also the tick over's started playing up, it dropped to below 500 revs & kept stalling. Is that the throttle cable aswell or something else ?
The constant popping & banging, I'd like to keep though.
>> Edited by RUSSELLM on Monday 15th November 14:46
Throttle like a switch sounds like the cable is bu99ered to me....
As for the low idle, thats normally the throttle pots being out, but that should be adjusted as part of the service.
Change the throttle cable (the part is £40 from memory, but isn't the easiest of jobs in the world), and take it from there.
Constant pops & bangs may well be over fuelling caused by the pots being out. Either way, change the cable & take it from there.....
As for the low idle, thats normally the throttle pots being out, but that should be adjusted as part of the service.
Change the throttle cable (the part is £40 from memory, but isn't the easiest of jobs in the world), and take it from there.
Constant pops & bangs may well be over fuelling caused by the pots being out. Either way, change the cable & take it from there.....
Only your garage would know if you needed new lambdas, but as they're still your property (i assume you didn't say to the garage *keep 'em I'll not be needing them again*) you cna ask for them to be put back in. Lambda sensor response time increases with age though so on balance having new ones in there isn't a bad thing, but as dealers put near enough 100% markup on them ask if they'll refund you say 100 pounds off the price you paid for them as a gesture of goddwill against them maybe not needing replacing at all?
ASfter that you've still got the running and cable issues. Sounds to me like the cable issue is separate .. it may have benn a routing problem, but it's difficult to route it incorrectly, it's an easy thing right across the back of the engine bay onto the throttle quadrant. It's breakage might be coincidental, but suspicious.
The running fault could be anything, had it been a 4.5 I'd have said throttle pots too .. they don't respond well if they start running near the start of their tracks .. on cold start if a odd bank 4,5 pot drops below a value of 15% it'll cause the symptoms you describe, but on the 4.2 you have it doesn't affect it in the same way. Also the popping and banging sounds suspiciously like it's there all the time not just on overrun? if so that suggests a massive bank-to-bank airflow inbalance such that one bank is doing a lot of work and the other at part throttle at least is always running in *overrun* type conditions ... ie massive airflow and low throttle pot position.
it needs sorting (you probably guessed that already though) ..
mail me offline if you chat to your dealer and suspect they're telling you a load of crap .. I'll try to cut through the bullshit for you
edited to add, it's possible when changing the lambdas that they got them the wrong way around .. so the weaker running bank gets the rich signal but tries to trim weaker still and vice-versa. that's a classic basic mistake to make, the sort you hopefully only make once!
>> Edited by joospeed on Tuesday 16th November 08:27
ASfter that you've still got the running and cable issues. Sounds to me like the cable issue is separate .. it may have benn a routing problem, but it's difficult to route it incorrectly, it's an easy thing right across the back of the engine bay onto the throttle quadrant. It's breakage might be coincidental, but suspicious.
The running fault could be anything, had it been a 4.5 I'd have said throttle pots too .. they don't respond well if they start running near the start of their tracks .. on cold start if a odd bank 4,5 pot drops below a value of 15% it'll cause the symptoms you describe, but on the 4.2 you have it doesn't affect it in the same way. Also the popping and banging sounds suspiciously like it's there all the time not just on overrun? if so that suggests a massive bank-to-bank airflow inbalance such that one bank is doing a lot of work and the other at part throttle at least is always running in *overrun* type conditions ... ie massive airflow and low throttle pot position.
it needs sorting (you probably guessed that already though) ..
mail me offline if you chat to your dealer and suspect they're telling you a load of crap .. I'll try to cut through the bullshit for you
edited to add, it's possible when changing the lambdas that they got them the wrong way around .. so the weaker running bank gets the rich signal but tries to trim weaker still and vice-versa. that's a classic basic mistake to make, the sort you hopefully only make once!
>> Edited by joospeed on Tuesday 16th November 08:27
Thanks Joolz, I think that cable's been on it's way out for a while, as I've always found it a bit, "on / off ish". Hopefully when the cable's replaced it will cure it.
I'm sorry, I didn't make it clear, that the popping & banging is only on overrun, but all the way through the rev range, where it only used to do it when you had high revs in the past. As I say, I'm happy with that, as long as the car is
I'll mention the lambda sensors going in the right way round though.
Many thanks
Russell
I'm sorry, I didn't make it clear, that the popping & banging is only on overrun, but all the way through the rev range, where it only used to do it when you had high revs in the past. As I say, I'm happy with that, as long as the car is
I'll mention the lambda sensors going in the right way round though.
Many thanks
Russell
gazzab said:
Constant popping an dbanging is a bad thing. Deceleration pops n bangs at around 3K (from memory) is good. anything else sounds bad to me.
2600rpm and again at 1900rpm, those are where the best pops and bangs can be heard from my 4.5!!
And even louder with Joos sports exhaust!
joospeed said:I've had this does to mine.
edited to add, it's possible when changing the lambdas that they got them the wrong way around .. so the weaker running bank gets the rich signal but tries to trim weaker still and vice-versa. that's a classic basic mistake to make, the sort you hopefully only make once!
It made the pops and bangs most of the time!
It's not the lambdas being in the wrong way but the near side and off side lambda being swapped over
Hope you get it sorted Russell.
PS For best pops and bangs on my 4.5 the revs need to be 3,200 and again at 2,300 (ish)
olly said:Arrgh!!!! After me, *underfuelling*, *underfuelling*, *underfuelling*! Weak mixture doesn't ignite on combustion cycle, but does when it comes out and hits the hot manifold.
Constant pops & bangs may well be over fuelling caused by the pots being out. Either way, change the cable & take it from there.....
Well worth getting a new throttle cable, and a proprietary "Joolz" rerouting - made mine loads nicer - not that it's causing the issue in this case.
The car's had the throttle cable replaced & it's driving excellent. Ever since I've had the car, it's jolted forward when you apply the slightest pressure on the pedal.
This is the best it's ever been, not sure whether that's the cable or the fact that it needed the lambda sensors, but I'm not moaning.
The slow idle was due to a loose bolt, where the throttle comes to rest.
Now, after 8 months, let's see if I can last a week without something costing me money
This is the best it's ever been, not sure whether that's the cable or the fact that it needed the lambda sensors, but I'm not moaning.
The slow idle was due to a loose bolt, where the throttle comes to rest.
Now, after 8 months, let's see if I can last a week without something costing me money
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