172 Cup mystery misfire...

[Sparko]

Hi there, my debut post as this is the first thing I haven't actually been able to diagnose and fix by searching the forum!

I have an intermittent misfire which I am 99% certain is caused by a fuel pressure problem. In search of the problem I have changed plugs, leads, coilpack, cleaned the TDC sensor and cleaned the contacts on all relays, run ZX1 through the engine and fuel, cleaned out the throttle body and yet still the problem persists. I have bought a fuel pump which I intend to fit this week, although recently I noticed that the pump NEVER primes with the first turn of the ignition cycle, but primes every time thereafter. The problem rears its ugly head when starting from cold or warm, and lasts for around 5 mins with a juddering misfire between 1 and 2k rpm. So my real question is this: would a faulty relay be the cause of the pump not priming first time, or the pump itself? Would taking off the plug at the pump end and testing the voltage answer this?

Thanks in advance for any guidance!

 

[Nick r26r]

i think the kid who had my car before me had a similar problem and it turned out to be the head , here is the thread , http://www.cliosport.net/forum/showthread.php?t=323089

 

[ForceIndia]

Hook up an rstuner and see of there are any stored fault codes.

 

[Sparko]

Diagnostic scanner cant find anything, so pretty sure its not electrical. This leaves fuel pump or relay surely? If it was the head ( :s ) what might be the problem with it and how would I go about ruling it out?

 

[ForceIndia]

Mine was hooked up to a snap on code reader, nothing showed up. But the rstuner showed older faults, and that's how we found the lambda issue. Worth a try before throwing more cash at it.

 

[Sparko]

Hmm worth a look then, what exactly is an rstuner? I already have the pump and a relay is pennies, so not worried about replacing those, just hope it isnt something more sinister!

 

[Cron]

Are there any other symptoms apart from the misfire? Any cases of it stalling at all?

 

[Nick r26r]

Hmm worth a look then, what exactly is an rstuner? I already have the pump and a relay is pennies, so not worried about replacing those, just hope it isnt something more sinister!

rs tuner is a remap box for the car , available from rs tuning or on here 2nd hand

 

[Sparko]

Hi Cron, no other problems associated with the misfire, just kicks badly when idling and kangarooes for a while when driving, though the harder you push it the more it seems to clear its lungs. The fact that it will NEVER misfire when I can hear the fuel pump priming tells me that it is connected to that at either end - either pump or relay. Will be changing the fuel pump in a couple of days so will update this with any news!

 

[Russ_16v]

rs tuner is a remap box for the car , available from rs tuning or on here 2nd hand

Wrong mate, RS tuner is a bit of kit made by Fastchip,plus into your laptop and can read fault clodes and also you can pull uprated maps off Fastchip's website and load them on your ECU, and has nothing to do with RS Tuning which is a tuning company

 

[Sparko]

Just a quick update, I fitted a used pump (done 5k so nearly new) to my sender unit yesterday and it seems to have cured the problem There was a rough vibration coming from the sender unit through the fuel line when running which has now disappeared, seems proof to me that the pump was not well. As for not priming first time, it makes the same noises as before but starts nice and smoothly and also revs a little smoother than before.

I have seen quite a few threads on here where people have had similar sounding symptoms but never resolved the cause of the misfire - this should be added to the list of possible causes/solutions for sure as it has made a definite difference to my car.

Thanks to those who posted suggestions, enjoy the sun and look after those sticky steering wheels!

 

[SBV116]

Mark?

 

[Sparko]

Steve!

 

[SBV116]

Ha ha! You think you have nailed it then?! Had some very weird symptoms!!!

 

[tonksy26]

Sounds like the same symptoms im having mate,

Did you find the problems started once the engine was warm or when you had started driving it ?

 

[Sparko]

Haha, yeh hope so.. on reflection it just wasnt delivering fuel right, you could feel the sender pulsing when the back seat was off, then with small amount of throttle it just couldnt keep up and chugged/misfired. We shall see but fingers crossed that was it. just the small matter of the mystery bearing rumble now!

On a separate note, I managed to get your keyrings sorted while nobody was looking on friday - Liam at Camble sorted me out with the graphics and they look gooood

 

[Sparko]

Sounds like the same symptoms im having mate,

Did you find the problems started once the engine was warm or when you had started driving it ?

Hi mate, problems began right from start up, but not everytime hence the confusion.. It did it pretty regularly from starting the car after it had been cooling down for perhaps 30 mins or so, so not a cold start but somewhere in the middle! Whip the back seat off, take the black plastic cap off to reveal the fuel sender and put your fingers on the fuel line that comes off the front of the sender unit. You should feel nothing but if you feel it vibrating/pulsing quickly then I suspect you have the same problem!

 

[ash_s3]

Sounds like the same problem im having at the moment,

Did you have an engine light on the dashboard?

 

[Sparko]

Sounds like the same problem im having at the moment,

Did you have an engine light on the dashboard?

Hi Ash, no light on the dashboard just a judder when you press the throttle even lightly, like the pump isnt keeping up.

 

[Sparko]

Wtf. Two days of perfect starts and now were back to square one. Started fine this morning then halfway down my street, chug chug chug returned to many a swear word.

Luckily I have a very automotively minded mate at work who is always keen to investigate a problem. We put a voltmeter on the contacts under the fuel pump relay in the engine bay which showed a full 12.45 volts. We did the same on the fuel pump plug under the back seat and switched the ignition through its cycles, trying the trick of turning it on, off and quickly on again which always seems to make the pump prime, only to find it does not get a constant 12v. So somewhere the power is escaping.. How very french! With the voltmeter on the plug at the pump end, the readings were all over the place with brief flickers of 12, 8, 6, 5 and 10 when the ignition was turned on. One of the pins gets a constant 5v even without ignition - is this right?? The obvious thing to do next is swap my relay with someone else's to rule that out. Any more ideas people?

Getting a little tired of this now..

 

[Mark51]

Can you trace the loom back at all to see where it may be broken or fouling something?

 

[Sparko]

Possibly - I was going to check the voltage at the fusebox but have no idea which fuse is responsible for the fuel pump.. Any ideas? As I said the pins under the relay receive a healthy 12v so you are probably right unless it is the relay itself. The loom goes under the trim and carpet along the side of the car so its worth a poke about - next job!

 

[Sparko]

Quick update - changing the relay has made no difference to the car, still does not prime on the first key turn and chugs as before. So somewhere between the relay and the fuel pump lies the problem... I hope!