Strange question. Phase 2 standard throttle bodies dieing?

[Chip-mk1]

We've had 3 throttle bodies fail on our 172 in the last couple of thousand miles, one was the original one on the car and the other two were secondhand ones so could potentially have had faults. But to me it seems unlikely 3 would all die so close together.

Anyone ever seen one of these cars wanting to kill the standard throttle?
Mom struggling to think of any other fault the car could have which would case the body to get killed

Always seems to fail first at big rpm ( 7700-7800rpm normally)

 

[mitch1503]

We've had 3 throttle bodies fail on our 172 in the last couple of thousand miles, one was the original one on the car and the other two were secondhand ones so could potentially have had faults. But to me it seems unlikely 3 would all die so close together.

Anyone ever seen one of these cars wanting to kill the standard throttle?
Mom struggling to think of any other fault the car could have which would case the body to get killed

Always seems to fail first at big rpm ( 7700-7800rpm normally)

Im on my 3rd since owning the car.. The 1st packed in on a few mile stretch of top speed the 2nd kept sticking the throttle at 2k and now the 3rd seems ok... touchwood

 

[Fred@BTM]

i chucked about 10 dead ones in the bin last week, some are 10years+ old now

 

[Dan@SJM]

I did have a thought earlier when travelling home thy maybe because of the position of it with the RS2 its more susceptible to road spray and moisture coming in through the grill?

 

[MicKPM]

Chip, you say you've had three fail but what symptoms are you experiencing and what, if any, equipment are you using to diagnose the fault with?

Three separate failures, all with the same symptoms, seems unlikely to me and is more likely to be a vehicle fault but I'm making an assumption here.

Mick

 

[Chip-mk1]

Rev car hard, light comes on, it then ignores the pedal ( tried swapping pedal too ) and then sometimes it will work again after turning off and on and sometimes it won't.
Today when it happened we swapped it to dans Clio and when we opened the throttle it opened but then wouldn't shut again, tried manually closing it and then it wouldn't open.

 

[Chip-mk1]

I did have a thought earlier when travelling home thy maybe because of the position of it with the RS2 its more susceptible to road spray and moisture coming in through the grill?

Certainly no spray today though. It's closer to the radiator in terms of heat, but the first one was in that position for nearly a year and about 20 trackdays without a problem.

 

[MicKPM]

Chip, sorry to ask stupid questions but I'm just trying to build a history in my head... it's forced a reduction of engine response and caused it to stick at WOT with three TB's on three occasions?

Do you have access to anything like a scope with at least two channels? Also, is the 172 in question a Cup or a full fat?

Mick

 

[Fred@BTM]

i had similar symptons and it turned out to the be a duff fuel pump

 

[Chip-mk1]

i had similar symptons and it turned out to the be a duff fuel pump

Similar in terms of you fitted it on another car and it wouldnt work?

Or in terms of it putting the light on and going into limp home?

Would make sense if it was pump in terms of the fact it seems to happen at very high RPM when the engine is consuming the most air. But the air fuel ratio is staying in the high 12s, so it doesnt look like its losing fuel pressure.

 

[Chip-mk1]

Chip, sorry to ask stupid questions but I'm just trying to build a history in my head... it's forced a reduction of engine response and caused it to stick at WOT with three TB's on three occasions?

Do you have access to anything like a scope with at least two channels? Also, is the 172 in question a Cup or a full fat?

Mick

None of them stuck at full throttle.
First one went into some sort of limphome mode and did 3K rpm only and ignored the throttle pedal.
Swapped that one out, and next one drove fine then kept tripping the light on at high rpm and then going into a limp home mode.
3rd one does nothing at all, wont even open at idle, this is the one that when tested on another car it went to full throttle and stayed there (Engine not running during test) and then after we manually closed it, it then wouldnt open again.

So its not a consistant failure, they are all slightly different.


Not got scope near me at the moment, can probably lay my hands on one, although will need a running engine again first, lol

Its a normal 172, its got an RS2 inlet and a set of 197 cams, but otherwise pretty standard.

 

[MicKPM]

It sounds to me like an interference issue. The TB that is stuck is done and fit for the bin but the others are consistent with a wiring fault between the pedal and the ECM

A scope will help greatly

 

[Chip-mk1]

Interesting comment about the pedal, as when we changed the first one we never touched the wiring near the pedal at all, we just swapped the TB and it started to work fine, so that doesnt point at the pedal in that respect, but I will certainly try and investigate there if you think it is likely.
The wiring plug itself certainly looks fine, and I couldnt see any damage to the wires at all, but obvioulsy its not always something you can easily see with these sort of things.

Is the loom to the pedal relatively self contained (doesnt seem likely) or am I going to need to swap out a big chunk of loom?

Only "scope" I have to hand really is a basic meter, I suspect that wont be much use, could test resistance but doubt it will be that simple to spot?

 

[MicKPM]

It's bundled into the main dash loom Chip and a complete C u Next Tuesday to isolate out.

A DMM won't have the range or frequency to see the problem I'm afraid and even a continuity test across the 5 wires won't be scientific proof that the wiring is good and Ideally you will need to go point to point with your own loom from the pedal to the ECU to ensure there's no fault lurking in any of the Infrastructure.

Another thing worth checking are the three blade fuses in the engine bay fuse box. I think it's the 15a but look for corrosion on them all as one of these can cause unplausable signal and in-cohesion faults on the electronic TB setups.

Petes Cup came in for a check with a similar issue for a few days but it just refused to misbehave for me so I couldn't find a problem. I don't know if Dan cured it with a TB replacement but I ran his TB on a customers Cup for an hour and again couldn't replicate the fault.

 

[Chip-mk1]

Thanks for all your input Mick, much appreciated, will check those fuses out as a starting point, then go from there.

 

[MicKPM]

No bother, give me a nudge if you need anything else. The Cups seem to suffer with this fault more than the FF's for some reason and Renault even have a pedal only short loom available for them to fix the issue (of course you need to prove the fault first of all though).

It could even be the dreaded gearbox area loom at fault but until you start properly looking and getting balls deep in her you're not going to know.

Enjoy

Mick

 

[Chip-mk1]

Yeah when I mentioned it briefly to mike at MWM earlier he mentioned the gearbox loom is a common cause of these sort of issues too.

Must confess I hate this sort of thing, such a pain to trace, would much sooner have a more severe problem thats easier to see! My time is in quite short supply.

 

[MicKPM]

Welcome to my world! Customers just expect me to plug in a computer and give them a miracle answer and bill them 20mins... Afterall, thats "what the dealers do" and when they see 5hrs at £45 an hour for what was really two days work they suddenly become experts in the field and demand justification #jebends

There are a few areas that attract corrosion though and allow the elements in but rather than just throw them all at you we'll start simple and walk thru it.

 

[Chip-mk1]

Cars would be fine to work on if it wasnt for customers eh mate? lol

Trouble is people think cause its a cheap car it should be small bills from a garage, but in fact a lot of jobs on these particular cars are VERY time consuming, and time=money of course when it comes to the bill!

 

[Dan519]

crank sensor error. new sensor and loom fixed it.

 

[Cr33do]

Chip. We had a problematic throttle when we installed our new engineer. No throttle at all and 2.7k idle. Swapped tb and pedal for known working items and still no joy, so swapped back. As per Mick's post, our engine fuse box contained lots of oxidised contacts. I cleaned all of of them, including the white loom connector block, and bingo it worked straight away! I'm not saying there isn't an underlying short somewhere but it's been working fine for nearly 300 miles now

Certainly easier than tracing wires around that area. Think I put some related info in our project thread.

 

[Dan@SJM]

Certainly no spray today though. It's closer to the radiator in terms of heat, but the first one was in that position for nearly a year and about 20 trackdays without a problem.

No spray today, but was it driven last week with all the rain? I did think heat aswell, but the standard one is practically over the exhaust manifold.

 

[TheEvilGiraffe]

How easy is it to put a cable throttle in..? i.e.: a ph 1 setup ?

I'm guessing a lot of hassle...

 

[Chip-mk1]

No spray today, but was it driven last week with all the rain? I did think heat aswell, but the standard one is practically over the exhaust manifold.

Nope, its not seen any rain since fitting it. Les used the silver one for work last week as this one was loaded up with tyres etc from silverstone on sunday so we left it like that ready for combe.


Slight update to this.

Looks like we have 2 problems not one.

First problem, is some sort of wiring issue somewhere (Danny's crank sensor mention is seeming likely as it only normally seems to happen at very high rpm) which is making us think we have duff throttle bodies when we dont.

Second problem is that throttle body number 3, which failed at combe yesterday, really did fail dramatically.

Ive tried both the other ones, and they both work ok again after an ecu reset.


Have also bought 2 new ones in the mean time, so thats 4 working ones I will have in total now, so I should never run out of throttle bodies now even if we keep the car another 10 years, LOL


Will take a look at the fuses and will fit a new crank sensor just in case, and then if neither of those sort it, then I guess its going to be loom changing time!

 

[Fred@BTM]

fuel pump

 

[Chip-mk1]

How easy is it to put a cable throttle in..? i.e.: a ph 1 setup ?

I'm guessing a lot of hassle...

Monumental ball ache I would think, different ecu, different loom etc.

Plus we'd then have to start modifying the RS2 to fit an ICV as well.

Would much sooner just fix it.

 

[Chip-mk1]

fuel pump

Right, only a fool would ignore your experience with these engines so I will get another pump to try then.

At least if it doesnt fix it I will have a spare one for our ring trip anyway, which is no bad thing as we trying to make sure we are fairly well stocked with spares as its 3 TF days, then a trackday there, then a trackday at spa, so its going to be a total wreck of a holiday if the car goes wrong and we dont have the parts with us to fix.

On that subject actually, other than "a space car, preferably something german" what else would you be taking in the way of spares for a phase 2 172?

Ive already got a spare pair of hubs in case the bearings fail even though they are brand new, balljoints and track rod ends and track rods are all new too but was going to take spares of those just in case.
Got a spare throttle pedal too, and obviously will take stuff like plugs anyway.

Anything else you can think of that would be useful?

 

[Fred@BTM]

Or as some people say only fools listen to me

I've had the exact same issue on a few cars, you hammer it then it drops into limp mode, fuel pump never comes up on diagnostics it always just shows throttle fault

HT leads probably as spares, there's a good little renault dealer not far from the ring, he has a twingo with a megane RS engine

 

[Chip-mk1]

Or as some people say only fools listen to me

I've had the exact same issue on a few cars, you hammer it then it drops into limp mode, fuel pump never comes up on diagnostics it always just shows throttle fault

Well the description fits, and given that its on the RS2 and cams, its obviously working the pump a little harder than standard.

HT leads probably as spares, there's a good little renault dealer not far from the ring, he has a twingo with a megane RS engine

Yeah I'll chuck the old HT leads in with us that worked perfectly anyway, we only replaced them cause the mrs wanted the bay to look pretty and liked the red magnecores, they serve no useful purpose, lol

Whats the name of the garage, so that we know where to go if we really end up stuck.

 

[Chip-mk1]

Just taken it out to test it.
Drove mint, no probs in normal driving. Then revved it to 7800rpm in second and still no issue, shifted into third and pinned it again and at about 7700 rpm it flicked the management light on and lost power, flicked ignition off and on and it drove mint again for normal driving.
That does make it sound fuel pump if it's happening after fairly sustained high rpm like that.

 

[MicKPM]

Something is deffo struggling to supply at high load/WOT.

Mick

 

[Fred@BTM]

yup that'll be duff fuel pump, i'll put £1 on it

 

[mr.pink87]

Check the connector on the tb. Mine did similar stuff and the loom wasn't properly located and pulled on the plug.

Would fuel pump problems trigger E-throttle fault codes!?

 

[MicKPM]

Would fuel pump problems trigger E-throttle fault codes!?

On a clio II just taking the key out of your pocket can trigger throttle related codes. The thing with that system is its very sensitive to voltage drop and interference - even tugging on the wiring loom in the right place can cause it to see an issue and reduce the engine output.

All of this, throttle, fuel pump and even CPS possibles are provable though with the right equipment (not code reading). Sometimes you have to go all Neo and look beyond the codes to see what the actual problem is:

If the CPS is loosing resolution at high speed the ECU doesn't know what position the pistons are in and so cannot correctly calculate ignition/fuelling requirements. The result is you get poor running or total running failure.

If the fuel pump is unable to supply adequate fuel pressure/is not getting the vac at fpr to tell it to 'ramp' the fp for WOT then you will also see a similar symptom (vehicle age dependent here)

As neither fuel pressure, cps signal is "monitored" by Borneo2/EODB vehicles like the Clio II it puts it down to a "possible" throttle issue. This is where experience normally comes in and again, knowing to read between the codes rather than put your faith in what the code reader says.

I would still personally break out the scope and go for a drive because the updated cps and loom section is still around £70.

Mick

 

[Chip-mk1]

Check the connector on the tb. Mine did similar stuff and the loom wasn't properly located and pulled on the plug.

Check and tripled checked mate, and its done it on more than one TB now.

Would fuel pump problems trigger E-throttle fault codes!?

Im struggling to see how it would know, even if the fuel pump was failing to meet demand, with only a narrow band sensor I dont see how the ECU would determine that was happening, and besides which, its quite rich at those RPM anyway.
But Im still going to try a new one at the weekend, even though it has no logical reason I can think of as to why it would trigger a TB/Pedal code.
But like Mick says, its probably just a case of the ECU literally guessing!

 

[Chip-mk1]

Fitted a new fuel pump, no different.

The problems I had with the body dieing totally appear to just be that I fitted a bad secondhand one.



I now have a fairly consistant symptom on either of two pedals and either of two other bodies that I have tried. Which is back what it did originally.

Very high RPM (anywhere between about 7500 and the limiter at 7850) it flicks on the light on the dash (middle one looks like a coil symbol) and the throttle shuts and the pedal does nothing.

Switch it off and on again, drives perfectly fine for as long as you want providing you dont absolutely rev the hell out of it again.

Ocassionally it makes it as far as the limiter before it cuts out, so its not an exact amount of rpm it does it at, but it does it everytime as the times it has made it as far as the limiter ive held it on the limiter for a second and then its done it, but it often does it just before the limiter as well.

I guess crank sensor and that bit of the loom is the next one to change, its on the older style black crank sensor so I will get a blue one and new plug onto it.

 

[sprintcup]

Genuine question, do you need to rev that high, would it be possible to lower the rev limiter to say 7600 and see if you get the same symptoms, I noticed my car used to run a bit rough after hitting the limiter on the OE throttle which is a 172 Cup, just wondering if it's a symptom of the cut, do these cut fuel or ignition or both.

Regards Russ............

 

[ben lee]

whats the fault code your getting chip?

 

[Chip-mk1]

Don't "need" to rev that high with it pulling so well midrange but as we've got arp rod bolts and super tech valves it's nice to have the option to on the way out of a bend rsther than have to change gear as it still pulls fairly well up there (it's on an rs2 inlet and 197 cams)
I could lower the rev limit to stop it going into limp home mode for now but if there is a problem there now it's no doubt only going to get worse over time and happen at lower rpm too so I want to fix it rather than start limiting what rpm I use to avoid it.

Fault code always shows as throttle body/pedal but have replaced both multiple times and tbh it's just blatantly not either of them wrong if it's rpm related as full throttle operation is the same action whatever the revs.

 

[MicKPM]

Chip, try the CPS an loom but I'd still be tempted to run five wires directly from the pedal to the ECU to see if that cures the issue.

Mick