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Need some help diagnosing intermittent power loss on a Clio 2 ph1 2.0 16v

  Clio 2 ph1 2.0 16v
@Sgt Nuts

Is this holding back at 3.5K rpm every time now?

Have you got any way you can check the ignition timing advance?
The rpms at which the car holds back are not fixed. One minute its from 3500 rpm, the other it's from 5000 rpm. I have the feeling (but cannot prove yet) that it happens the second the fuel system goes into open loop.
I can say for sure that it's not the moment that I start accelerating. Always whem rpms have been climbing rapidly for a few seconds.

I think my scanner is able to record the sources that I tell it to. Should be able to record open/closed loop and ignition advance. Will try to get a reading.

I did what you suggested earlier btw, drove the car a bit without the fuel cap. No change.
Did find out that there's some kind of EVAP system in the car that seems to regulate fuel tank vapours and feeds them into the engine. Some carbon cannister in the right front wing with a small electric valve. Seemed to be clicking rapidly once I put the car on ignition.
Not sure how this system works or is supposed to work though.
The line coming from the evap canister goes into a thule on the rocker cover. When I take this line off the engine revvs up quite a bit, so it must have some connection to the intake manifold.
Seems to me it could be a source of air going into the engine without being detected by the MAP sensor?

If extra air was getting into the engine through this pipe I can imagine that the O2 sensor would correct the extra air it detects by injecting quite a bit more fuel. Once the fuel system reaches open loop, the O2 sensor is disregarded and the ECU uses a predetermined map which might not compensate fuel to the level the O2 sensor has been doing up to that point..
Might block the line off for a testrun, see what happens


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  PH2 172
@Sgt Nuts

I don`t think the canister solenoid should tick just with the ignition on with the engine not running, but a full description is in section 13 of the F4R manual.

Cap the vacuum take off to remove it from the equation, though it only vents the fuel filler tube, I cannot believe it will make any difference,

Any air entering the system this way will be monitored by the MAP as it passes through the upper inlet through the egg shaped O ring.

If you have a strobe you can clip to a HT lead and tippex the flywheel & crankcase, you could observe any irregularities when the ECU goes open loop.$&vid=1247&cid=2043672269&uid=3089&q=

Manifold upper inlet 182.jpg


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  Clio 2 ph1 2.0 16v
Thanks! The manual is quite short on the subject but with your explanation on where the vacuum from the carbon canister goes through the egg shaped hole it makes sense that any air passing through will be measured by the MAP sensor.

Looking back at my vacuum readings from today I am still not a 100% on the whole back-pressure/restricted exhaust thing either though.
The vacuum dropped from 400mbar@idle to 330mbar@ 3729 rpm and I did find the following information ona couple of car diagnostic sites: What I found on a car diagnostics site:

"Manifold vacuum should increase slightly as the engine is held at 2,500 rpm at steady throttle. If the vacuum is the same or decreases, the exhaust might be restricted."

I did manage to take the mid section of the exhaust apart today, but did not dare to try and take the complete cat off as the bolts with the springs that keep the cat to the exhaust manifold are rusted to the point I cannot distinguish nut from thread. Did not see any viable way to get to cut them off either since they are located above the chassis.

Would be quite interesting to have it off to check for blockage from the engine side, and it would be a great opportunity to use my endoscope to have a look at the exhaust valves inside the engine without having to dismantle it.
  PH2 172
@Sgt Nuts
Cat fitting kit 6000073668 is £19 from RPD.

We had to spark erode my old bolts.

The inside of your cat look very good, so that is unlikely to be the problem.

Throttle position switch?

Is the power loss accompanied with a misfire with pops & bangs, or just a case of hitting a brick wall and will not pull anymore?

You can get a cheap borrscope with a mirror if you want to look at the valves from inside the cylinder.

@Louis can provide details.
  Clio 2 ph1 2.0 16v
The backside of the cat looks really good indeed, but it's the other end that gets most of the sooth and crap from the engine I imagine. At this point I'm willing to check everything just to rule things out.

Throttle position switch is shown by my scanner at 10% at idle going up tot 88% WOT. value increases nicely, no problem there.

The power loss is just hitting an invisible wall. No pops and bangs ever. Car is accelerating nicely and then just stops accelerating. it doesn't fall down in rpms, it doesn't stutter or jerk. it just stops going any faster. sometimes it clears up by itself and I'm able to accelerate again.

I have a flexible endoscope with accesories like mirrors so will have a peak at the valves whenever there's a possibility.
  Clio 2 ph1 2.0 16v
By the way, I managed to get a hold of the chap that provided the current ECU. He's told me that he tried 2 different software versions on the car. First he had a 2003 program for the F4R730 with which the car seemed to be running ok, but he was not able to get my scanner to communicate with the ECU. So he installed a 2000 program on it with which the scanner was able to communicate.

Someone here allready mentioned that there's some difference between earlier model Ph1's and later model Ph1's that looked more like the Ph2 (Double O2 sensor for example.)
I found him willing to put the 2003 program on another ECU so I can testdrive with the other program to see if it makes a difference. should be somewhere next week/weekend.
At least then I can exclude the ECU/program as a possible source of the problem
  Clio 2 ph1 2.0 16v
you got the old crank sensor on still?
Yes I have. The resistance measured is spot on with the specs in the manual. When I backprobed the connector with my dvom and measured voltage between signal and earth it gave a solid pulse while cranking so I have no reason to suspect the DTC. If it where faulty I would expect difficulty starting the engine altogether.
I will be ordering some (non engine related) parts in Germany next week so I might order one with it for peace of mind. They're only a few quid.
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  Clio 2 ph1 2.0 16v
Ok, Managed to record 2 datasets around the moment power loss occurs. I plotted some of the info into a graph:
graph clio 2.png

Below I will include the two datasets which have some other PID's as well. I do notice inlet manifold pressure going up and down on the first dataset but it seems to correlate to the throttle position.. don't really know what to make of that. if anyone can make sens of the data i'd be glad to hear it! If you would like to see any particular data compared in one graph let e know.

I also managed to get a pressure reading from just before the Cat today which revealed there is no significant backpressure at idle or when revving up the engine. So I can dismiss the exhaust system as possible cause.

dataset 1.png

Dataset 2.png
  PH2 172
@Sgt Nuts

400 mb vacuum at tickover???

650-700 mb or 20 inches Hg is normal.

Have you got a real vacuum gauge you could attach to that carbon canister spout?
  Clio 2 ph1 2.0 16v
@Sgt Nuts

400 mb vacuum at tickover???

650-700 mb or 20 inches Hg is normal.

Have you got a real vacuum gauge you could attach to that carbon canister spout?
At idle the 2.0 16v should be between 320-500mbars so 400 should be right within spec?

I have a ton of gauges but I only have a vacuum gauge on my brake bleeder pump. I reckon it would be able to jury rig it to the manifold but I doubt it is actually calibrated. I deem the MAP sensor more reliable..
A dedicated vacuum gauge..still on the wishlist.


ClioSport Club Member
this may be stupid compared to everyone else's detailed analysis but have you had your battery load tested? can you try another battery?
  Clio 2 ph1 2.0 16v
this may be stupid compared to everyone else's detailed analysis but have you had your battery load tested? can you try another battery?

You are absolutely right in that a poor battery can cause rough idling. As the battery may not be able to supply enough power to the ignition system, while the alternator is not supplying enough power at low rpm. (Max. power from 1500rpm and up)

At higher rpm's though and provided the alternator is ok, the ignition would run from the alternator directly.

I must admit my battery is a bit on the weak side at rest, but the car starts without hesitation and alternator output is just fine.
  Clio 2 ph1 2.0 16v
Allright! Breakthrough time! (Although somewhat of an anticlimax)

Managed to visit the chap that supplied the replacement ECU for the car tonight. He had a second ECU on which he put a 2003 F4R730 engine software version. Instead of the 2000 software that was currently running the engine.

We swapped the ECU's and presto..the car ran better instant. Rough idling gone, 1500 rpm stutter gone. Only havent been able to do a WOT run yet since everything is iced over here at the moment.

I will test drive it properly tomorrow before I definitely call this one solved, but things are looking very promising! ?

Our guess is that there have been slight improvements and alterations to the F4R engine used in later production Ph1's. With it came updated engine management software. In this case the elder software was able to run the engine, but it was supplying too little fuel all the time. This lean running condition was being corrected by the short term fuel trim giving it's maximum correction. (Anything over 25% should trigger check engine and is not being copied by the long term fuel trim.)

As soon as the car then hit open loop fuel the program reverted back to it's default fuel map causing for again too little fuel getting to the cylinders stopping the car from accelerating.

Thank you guys for all your input! Will report if the problem is definitely solved.


ClioSport Club Member
  dan's cast offs.
i think some diagnostics can't read trims or if they aren't there they just read them as 99/100% ?