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720s hesitating/bogging during acceleration (WOT)

21669 Views 126 Replies 22 Participants Last post by  K-1
Hey guys, hope everyone's healthy and well. I have a fully stock 18 720s that I bought last september from Ohio with 1200 miles for 262k. Its VIN ends with 1805. If you'd like to go straight to the problems facing my 720s, kindly skip to the next paragraph gentlemen (and the one lady who thought this was her husbands dating site). I parted with my '14 SLS for it which was a big deal for me. Although I made a hefty sum on the SLS, I willingly got into a car that I knew was a money pit because I never intended to sell it. You see, I am kind of in love with the 720s. Its presence is strong yet sublime and its speed is second to none in the segment. I am not going to discribe the 720s any further in fear of being superfluous after so many other reviews. Anyway, I am one year and 9000 miles in. I changed the oil twice and the tires once so regular maintenance have been like 8-9k. I drove it from Ann Arbor to Boston and back with no problems.and after the first six months I began to.think it's the best car ever made (very subjective reasons). But around the time the two year service interval of the car came close it started to show some problems.

You see, I had other smaller issues which I don't mind and got taken care of (mostly) and they are the following:
1) Leather moulding surrounding b pillar getting its clip broken and replaced.
2) Driver side door sill leather panel sliding down and needing to be re-glued.
3) Passenger door seat housing discoloring
and having the part replaced
4) rear badge logo peeling off and having the badge replaced.
5) Rear passenger side area rattle > still to be diagnosed :(
6) passenger mirror squeaks likes an old door > still to be diagnosed
7) Door struts giving out and being replaced
8) Vehicle shaking roughly at 193mph due to dealership in Boston putting new rear tires with 37psi on the left and 33psi on the right. Minor error by the dealership honestly. I should've known better.
The real issues that have been bothering me/bothered me are:
1) Vehicle bogs at around 7000 rpm. This is the main problem omg. I need some knowledgeable advice please. Mclaren Boston replaced the fuel pump controller and it fixed the issue from like March to June but it came back. There is usually an engine system failure light at wide open throttle and it goes away after a few more WOTs but after a while the bogging at 7k rpm starts (INTERMITTENTLY). I am finally writing today as I got it on tape actually. Video link provided. I just came back from an oil change and warranty repairs a few weeks ago in Troy, Michigan and they said the power train was fine but the problem's consistent to this day.
2) Suspension Failure. I diagnosed the problem to the accumulators as when I set the dynanics of the car to track while the car's idling on neutral, the whining suspension noise starts going crazy lol like the noise the car's suspension(?) usually makes is long-ish but now it goes, swizuswizuswizuswizuswizu... it constantly goes on with the suspension failing to adjust. If i turn of the car off without putting the dynamics back to sport/comfort (in which after a while the suspension suddenly adjusts and the noise is normal again), upon turning the car on again I am 90% of the time greeted with a suspension failure light..love it.
3)Check engine light, p420 and the 30 or whatever catalyst codes. Both cats and downpipes replaced a few weeks ago at Mclaren Troy, Michigan. Problem solved (in so far). BUT WHY

The Mclaren dealers were great. Real gentlemen, the service advisors. Just wish they were quicker, but that is not a mark against them! Love mclaren and id be delighted to get the successor as well. They respected the warranties and never treated me any different from older multiple mclaren owners. Now the worst ordeal here is having my car's performance restricted since March and with the impeding cold season, I am very sad about my first world problem of not being able to thrash around in my beloved 720s.

Anyhoo here is the link to the video please watch it carefully. Engine revs up fine on second gear but bogs around 7k rpm on 3rd. Maybe bogs twice. I only put 93 and only from Shell. Notice there no fault lights this time. Its kind of random but the bottom line is, the car bogs bad!!! I really want my car back as it were in the first six months, idc if i have to pay for it really. I just hate to see it like this.

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Update..new fuel pump ordered. Testing pending. One week till next update
I noticed my car do the same thing a couple times today in 4th gear.. Please let me know if fuel pump solves it.. And thank you very much for documenting all of this and keeping us updated, Highly appreciated over here.

PS. I have pure turbo inlets sitting waiting to be installed.
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I noticed my car do the same thing a couple times today in 4th gear.. Please let me know if fuel pump solves it.. And thank you very much for documenting all of this and keeping us updated, Highly appreciated over here.

PS. I have pure turbo inlets sitting waiting to be installed.
I'd be delighted if any of the info im providing would help your case sir. I should be having an update regarding the fuel pump this week. I will make sure to convey everything ill have learnt about my problem including service notes. You can then ask your tech to follow my diagnosis process while you also have your air inlet pipes replaced

As a recap my fuel pump control module, catalytic converters+downpipes and air inlet pipes have all been found faulty and replaced under warranty while trying to diagnose the rpm cut off problem. Hopefully the new fuel pump finally fixes it.
Update! New fuel pump said to have finally fixed the issue. The car has been test driven in three separate occasions and will be test driven one more time before they send it over. Mclaren Troy handled the situation well at the end, going the human route instead of the corporate.

as a side note: Turbo air inlet pipe baffle dislodgement issues (now thats a mothful) and fuel pump issues may therefore be mistaken for one another. Air inlet issue symptoms are perhaps less discernible as my air inlets were bad and replaced but they were not really showing any explicit symptoms(or perhaps masked due to overlapping issues). Advice is to replace air inlets either way though. If someone notices hard fuel cut offs at rpms lower than redline (8500 rpm but as long as the needle is passing 8 it is fine) than suspect the fuel pump. Mclaren Boston WAY back initially did the same and they changed the fuel pump controller, perhaps they should've replaced the real thing...
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Glad to hear your issues are resolved! Enjoy the car in good health!
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Glad to hear your issues are resolved! Enjoy the car in good health!
Thank you sir! It has been some ride but the 720s is worth the trouble and much much more, i am sure you can relate ;) i wish you good health as well
Thanks OP for the thread and updates, very helpful to us owners that may have the same issues and know now what to look for!
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Thanks OP for the thread and updates, very helpful to us owners that may have the same issues and know now what to look for!
Thanks for that Richard :)
Thee thy thou thus, thy thee thus though

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Wow my friend!! Its been a journey for you and I appreciate you so much for documenting it.. My 720s is literally doing the same thing.. Cuts out 3rd and 4th gear like that. Reading over the document you posted it appears that the metal shavings they found clogging the pickup may be the culprit. I wonder where those came from? Maybe cleaning those out and replacing the fuel filter but keeping the same pump would be okay?
Wow my friend!! Its been a journey for you and I appreciate you so much for documenting it.. My 720s is literally doing the same thing.. Cuts out 3rd and 4th gear like that. Reading over the document you posted it appears that the metal shavings they found clogging the pickup may be the culprit. I wonder where those came from? Maybe cleaning those out and replacing the fuel filter but keeping the same pump would be okay?
Thank you sir!

What you pointed out is indeed noteworthy. I really wasn’t given an answer as to where the shavings came from. I wonder if they would have done further testings if this was not the 3rd time the service center was trying to diagnose the problem. If the fuel pump‘s the origin for the metal shavings, I would expect more damage, so we can assume the origin of the savings preceded the fuel pump (and did not pass the filter). Perhaps a factory defect or a one in a thousand chance that a top tier, 93 grade fuel promising gas station did not service their pumps at all

Edit: I am sorry boss, I can’t assure you nor can I deny that using the same fuel pump again will work (as was designed by mclaren). Also first verify it is not your air inlet pipes
Wow my friend!! Its been a journey for you and I appreciate you so much for documenting it.. My 720s is literally doing the same thing.. Cuts out 3rd and 4th gear like that. Reading over the document you posted it appears that the metal shavings they found clogging the pickup may be the culprit. I wonder where those came from? Maybe cleaning those out and replacing the fuel filter but keeping the same pump would be okay?
Yes, as long as the filter has no ruptures or the pickup screen, thin poliester fabric bit usually, pump will probably be fine, and can be tested so you are 100% sure. Dealers will replace them given their cost is not that high and having them fault after such a long hour job will give them a bad look, they will have to repeat to repeat the whole tedious disassembling job again and leave a sour taste on the client mouth..
But maybe try fishing the tank with a magnet for metal bits...
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Friends, I am still chasing this problem. My car is doing the same thing as taw6189.. cutting out in 3rd and 4th above 6k rpm.. I have a fault code P253900 fuel rail pressure rationality range check range low.. I have replaced the turbo inlets, the fuel pump and fuel filter.. but the problem is still the same. I am considering replacing the controller or the rail pressure sensor next.. I noticed on Mclaren tech site that the fuel pump controller part # was superseded. Any help will be greatly appreciated.
Friends, I am still chasing this problem. My car is doing the same thing as taw6189.. cutting out in 3rd and 4th above 6k rpm.. I have a fault code P253900 fuel rail pressure rationality range check range low.. I have replaced the turbo inlets, the fuel pump and fuel filter.. but the problem is still the same. I am considering replacing the controller or the rail pressure sensor next.. I noticed on Mclaren tech site that the fuel pump controller part # was superseded. Any help will be greatly appreciated.
The fuel pump control module was also changed for my car. Maybe changing that would prove to be the last piece of the puzzle? If you are having your car worked at a Mclaren service center it really is not fair that they are taking so long to diagnose the problem. But for what its worth it took months of trial and error to diagnose the problem with my car. I well and truly hope you get your car fixed sir, and wish you good luck. Your car will be better than it ever was!
I just ordered the updated part # 14ka063cp fuel pump controller for it.. Will update you guys after I install that.
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Is this happening only to 2018 cars, or is it a known problem on the newer cars also? Waiting on a 2020 720 Spider and coming out of a rock solid 570. Hoping it was sorted in later years. I know that doesn't help the OP, but at least I know where to go if the problem happens with mine.
Is this happening only to 2018 cars, or is it a known problem on the newer cars also? Waiting on a 2020 720 Spider and coming out of a rock solid 570. Hoping it was sorted in later years. I know that doesn't help the OP, but at least I know where to go if the problem happens with mine.
Congratulations on the 720s spyder! The 2020 model is most likely to come with the updated fuel pump controller and turbo air inlet tubes (with welded components). It should be safe to assume you will be getting a rock solid car mr cmargosi but it doesn't hurt to put on the miles during warranty as most issues surface around the first 8 to 12k miles (in my opinion)
My 2020 is having the same issue. Replaced the fuel pump to no avail. Going to check the inlets, injectors, and coils next week. Wish me luck.

It is having trouble climbing past 5k rmp. At wide open throttle it will climb slowly, stutter, and it sounds like mini misfires.

It has a tune and exhaust. 7k miles with no hiccups until now.
Apologies for jumping into the fold late, but I had to read the entire thread a few times. I have a 2018 that is doing the exact same thing! Still not fixed and this is what we've thrown at the problem so far;
  • Inlets changed (Pure Turbo silicone)
  • Updated fuel module
  • Checked fuel mapping (car is tuned)
  • Checked for exhaust leaks (new exhaust installed)
The problem seems to be intermittent. From a start, or from launch, the car will give me all the power. But sometimes, after driving for a bit and I try to launch or take off hard, it will bog down. I'm tired of throwing theories and money at this anomaly that seems to too elusive for most shops.
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