I'll provide all information regarding the car as no maybe "spark" someones memory incase they've come across this before. Having just lost my job due to COVID i don't have the money for lengthy garage fault finding. So as i am fairly useful with a spanner i am doing this myself and hopefully with your help we can narrow this down. Car - F1 r26 Engine - 2.0 ltr Turbo (RS275) Stock internals. Mapped Running 630cc Injectors Front Mount Intercooler RS275 fuel system That is i think all anyone should really need to know about the engine. I have recently serviced the car given that i've done approx 6000 miles since purchase in June and as part of that fit new plugs and new Bosch Coilpacks. I did some research before buying and given they weren't cheap ECP specials i figured couldn't be too bad although obviously cheaper than Renault OEM BERU packs. Reason for original change - nothing much to report really, there was a slight misfire around 4000rpm sometimes. So as no paperwork for coil change i decided as part of service to refresh them. Keeping them though as backups. I swapped out the spark plugs too for colder new NGK plugs that were recommended here and gapped them accordingly to 6mm. Issue - Yesterday i was driving home from the shops. Stop start traffic for about 45 minutes to an hour. I parked the car, went to a shop and was about 20 mins in doing so. On restart car drove ok, but a minute later coming round an island after giving it a bit of acceleration, the car stuttered heavily and there was quite a misfire, the engine rev'd but intermittently - rev,stutter, rev more stutter and so on. Till it cleared itself about 5 seconds later. The car drove home fine. I inspected everything and no visual issues. So left the car to cool and went about my day. This morning the car started fine. Drove fine. However, i felt the car have a very slight lumpy idle, not so much you can hear it and the rev needle wasn't moving but could feel the vibration through the car at traffic lights etc. The tone and engine vibration was such that it was just different enough for me to notice. So this afternoon, i've visually inspected everything again. No signs. Having read that these cars are subject to being a bit picky about coil packs. I decided to swap out the packs again, back to the originals. In doing so , i checked and refit each spark plug. Cylinders 1 to 4. None smelt of fuel. No real visible issues to report though spotting a bad plug is not exactly easy. Anything i should look for specifically? I restarted the car. The lumpy idle had disappeared and it sounded healthier but drove it 15 minutes and had exactly the same stutter and misfire as i did the other day. Maybe even a little worse. Felt like a complete cylinder had gone or a lack of fuel to one. Car jerked up the hill, stuttering, for about 20 seconds and then cleared itself up and drove home fine. If i'm on boost btw this does NOT Happen. It only seems to effect normal driving not under heavy load. So home i went. Left it on the drive. Idles fine. NO misfire present. No vibration. Each cylinder doing its thing. Head scratching time. It has the same misfire as it did with different coils and new plugs. I Decided to unplug each coil. Plot thickens. I've numbered them in my head Left to Right as 1 to 4. If i unplug coil one the car runs like crap. Lumpy, vibrations, audible misfire from exhaust. Exactly what you'd expect and as a test of a coil i'd say it is good. Plug it back in, the car runs fine again in a matter of a second. The car does this for each of Coils 1, 3 and 4. Coil pack 2 is a different kettle of fish - this pack has a broken wiring clip - assume due to heat and poor quality. But the plug itself is secure enough. If i pull this plug, the car runs as the other coils does - bag of spanners. Vibrates and audible misfire. Plug it back in and the car clears up BUT if i do it again, and plug it back in, maybe wait 1 to 2 seconds longer to do so (I timed it ) the car does not recover, it remains running like a bag of crap. It does NOT do this on the other coils/cylinders 1, 3 and 4. Just cylinder 2. This would ordinarily tell me that coilpack 2 is knackered correct? BUT It runs exactly the same with the new coil as the old one? The other test i have to do - which will be tomorrow is to refit the original NGK plugs As i'm using colder plugs i am not sure if the engine is liking this (it is mapped so i wonder if going colder has caused an issue with the map?). The other issue i thought could be the MAP sensor - i unplug this and the car instantly stalls indicated that the sensor is good in my opinion. There is another sensor on a pipe going to the intake manifold. The pipe is ribbed/bellowed and i don't know what sensor it is but looks ordinarily like a different kind of MAP or MAF - if i unplug this, nothing happens but i do get a "check injection" warning on the dash but the car runs as normal. I would expect a warning light for an unplugged sensor but i would not expect the engine to continue to run as normal with it unplugged - could this be at fault ? If anyone has any ideas i'd really appreciate it. This car is my pride and joy and i love it, i really want to get to the bottom of it as i cannot afford lengthy garage diagnosis. I am hoping i've been descriptive enough so that people have a fair understanding of what i'm experiencing. As its intermittent i can't really capture it on video and it may mean its useless taking it to a garage as they may never see it happen.
Having read through the rest of that, you’ve done everything I would of apart from changing the plugs and as it’s still the same with either coil pack I’d be checking that, I had one years ago with a hairline crack in the insulator part of the plug and mine ran like crap until I swapped it. Other possible is the dodgy plug connector, for what they cost for new ones it’d be worth changing that too.
Those are the two things on my list for trying tomorrow. I'll see what happens. Thanks for the reply.
also would be worth taking out the crank sensor and giving that a clean, maybe even change it. If its mapped colder plugs and 0.6mm gap is what it needs
yep done that, but its had the issues since they were fitted along with the new coilpacks I'm going to run the older plugs and coils and see if it goes away. I am hoping that is the knackered clip. But it was techincally broken on the car, me undoing just meant it fell apart. Don't suppose you can point me to the crank sensor location on this engine - quite new to the car / model.
Crank sensor is at the front of the engine, on the gearbox about 2 inches in from the engine gearbox joint. Its held in by 1x8mm headed bolt and a two wire plug, you will have to get to it from underneath and remove the under tray. I had knackered plugs on my 225, pushed the two wires onto the coil and it was fine for a long time.
So. Development. I have dug out the old plugs The ones i bought after they were recommended to me for this particular engine and tune state were BKr8eix Having just dug out and reviewd the plugs i had in the car before changing them - those are ifr7x-8g Quite different. THe IRF7X are what i actually used to run in my mapped 440hp Impreza and was always recommended to me. So i know they are good plugs. But as some of you have stated the BKR8's is what the megane prefers. So if the car was mapped on IRF7X am i best to stick with those - should it make any difference as it should mean is the that the plugs run colder? But obviously spark is part of fuel delivery, if that is off, fueling is off and so i would have issues. I just think its peculiar this all started after i changed them out It may be late but i'm going to go fit the old plugs with the new coils and run it that way, then swap out to the old coils tomorrow and see what differences it makes. I mean its only 9.30pm and got bugger all else to be doing at this time .
Its the 8's that you needed, i have BKR8EIX in mine, that's what i was told to fit by the guy who mapped it. The higher the number the cooler they run
I believe someone else on here has just changed there’s and found them to be the same as the 2jz supra engine ones.
This matches the other information i was given in another post here so stood to reason. Given that i am learning the Renault engine as i go. But for the most part, plugs are plugs. However, I'm not sure now. Reason? Well , i decided to check it by reinstalling my original plugs. So i've just gone out. I swapped the packs back to the new bosche ones and i've run the car with the original Ifr7x-8g plugs. 1. The original misfire / hesitation at 4000 rpm (reason for the start of this saga) is gone. So assume that original issue was the coil packs. 2. The car comes on boost stronger. Since swapping the plugs and packs its not felt this strong (possible placebo). 3. I drove it under heavy load (hard acceleration) on a National Speed Limit road - no misfires, backfires, boosted strong and no hesitation or anything. Since changing the plugs and packs i've had a number of backfires (not pops/crackles - there is a difference) 4. I drove it under normal load around town and back three times, changing gear, rev matching, no faster than 40mph, all same conditions as caused the misfire before and the car does not misfire at all now. 5. Idle is stronger - colder 8's ran about 600-700 rpm. 7's it runs 800-900 . 6. No smell of fuel on start up or after run - which i was getting after swapping out the plugs - this i thought was down to the donwnpipe - (Placedbo). Overall though i would have conclude that the fault lies with the plugs and the fact they are different to what the car was built/mapped with (EFI did the mapping so i know they are reputable). I did read this on quite a reputable UK tuning site "By selecting a plug in a cold enough heat range to cope with sustained high boost use you will be risking the plug 'over cooling' when off boost (e.g. driving in town traffic), the result will often be fouled plugs and misfiring" Which is exactly the product/pro i was having. So oddly, and i've never questioned this before. Can a car mapped to a specific set of fuelling tables using a specific set of plugs be thrown off by adding a plug in that is designed to run too cool for what the map is expecting? I am not even sure that makes sense. My answer i think will include a call to EFI tomorrow and see what they say. After all, they tuned the car, maybe i can datalog the car for them and send them a table and see what they can see their end. Regardless, for a test tonight, the results look positive. The original plugs and new pack combination has removed all of the issues i've been having over the last couple of weeks. Car is back to running what i would say is a better than pre-service state. If you guys are interested i'll let you know what EFI say? And i'll continue to test the car tomorrow and see if anything occurs, after all i did say it was intermittent so i'm not 100% on success as yet - but certainly feels better as i say.
I run the 8 plugs in mine as i have said, i have not had anything like the issues you have said, mine is not a daily though. I moved mine out of the workshop tonight only ran it for 10 minutes and drove it less than 100mtrs it always sounds sweet not hissing farting or spluttering Most of the things that go wrong with these cars its just a process of elimination to find the reason Great that you seem to have it sorted
No you are right. It's a good point. It's never happened to me before in the decades i've been driving but i have heard of it happening so its a possibility too. Regardless i emailed EFI and see what they say about the plugs etc. As they built the car i am pretty confident on their advice regards to it. So that is something i'll wait on. In terms of proving that theory though, i guess the only way to know that is to buy another set of the 8's - but if that is the case i'll wait till next month lol As it stands if the car continues to run as well as it does now i don't need to swap them out till i can afford to do so. Which isn't this month now. I appreciate all the help guys, as weird as it sounds, i love getting to the bottom of this kind of stuff.
My issue eventually came down to a faulty 02 sensor. Never threw a CEL but a pending code came up when i was testing coil and plug combinations. Changed it out to a new sensor and running well and strong so far. Question is, do i now change back the plugs to the newer 8's I've got sitting there or keep my og 7's?? Car seemed to run better with the 8's till it really started misfiring BUT if that was down to the 02 sensor. It theoretically should run better still with the 8's AND a new sensor - guess no harm trying right?
Swap them back for the 8’s, worst case scenario you’ll be changing them twice if you go back to the 7’s.
