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720s hesitating/bogging during acceleration (WOT)

27K views 126 replies 22 participants last post by  K-1 
#1 · (Edited)
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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#12 ·
Something you can try doing yourself, get a Bluetooth or Wi-Fi ODB2 adapter and download Torque Lite. In there you can monitor your boost pressures. See if you're getting a boost drop-off. I don't know what you should be getting on the 720, but it's common to hit 19 PSI on the 600.

Also ignore the useless trolls. You're going to have problems with this car, it's inevitable. The key is to get it to a dealer that is good and can fix it the first time. I can tell you from personal experience Troy is horrible. They wouldn't know a spark plug from their own poker. Take it to Chicago if you are in the Detroit area, it's a four or five hour hike but the tech there is way better. Troy kept telling me my engine was fine in my 570S, but I happened to have the car in Florida and had Tampa take one look at it and they found out that I had a bad head gasket. Troy performed the engine swap, and royally screwed that up. It dumped nearly all it's coolant a week later and nearly blew the second engine. I would only take it to Troy for small things, like oil changes and basic warranty stuff, but that's it. Even then I would think twice.

I hope this helps.
 
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#13 · (Edited)
Thank you so much for the reply. it's a lot of information, I really appreciate it. I will see if I can manage to do the OBD testing! Story time. The problem first happened whilst I was in Boston around March, Mclaren Boston performed tests and found that the actual fuel pressure values were less than specified so they changed the fuel pump control module slapped the car on the roof (probably) and gave it back to me only for the problem to keep happening again, but I guess I must understand that that is a part of the normal diagnosis process for problems regarding such cars. Anyway, they asked me to bring it back right away and were very cooperative but I had already driven back to Michigan. By then a check engine light was also on and once I got it in to Troy around early August they immediately greenlighted changing the downpipes and cats on my car (big repair, both cat codes) and also the accumulators (along with other minor inevitable problems as you say). Still waiting on the accumulators (first shipment got destroyed?), but the check engine light's gone. Mclaren Troy never found problems or stored codes relating to the engine system fault light that usually (but not always) preceded the bogging problem at WOT and figured all engine problems were solved. So the bogging is not due to the fuel pump control module (although that was also faulty, god knows the symptoms), and not the cats (or any lean/rich running associated with it) and I suspect the accumulators wont fix it either, the dislodging baffles theory sounds right but I digress, no point speculating so much. Overall, my experience with both dealerships was quite fair. I am however very disappointed and sorry to hear about your horrid experience with Troy sir. Id have torn half my hair out if i were you. I am a full time international student and i dont have a lot of friends so driving 4 hours to chicago especially right now is tough, but i swear id heed your advice and do it if i could make it feasible. For now, forgive me (and wish me luck) for giving Mclaren Troy a chance with diagnosing this problem once i tell them to check the air intake tube and also show them the video
 
#14 ·
I agree with having turbo inlet pipes checked. I was getting intermittent hesitation under WOT and the inlet baffle had come loose and was blocking airflow to turbo. Replaced under warranty. Happened to the other side too ane the baffle got sucked into turbo, destroying it and intercooler. $12000 repair denied by warranty.. Had to fight. See posts on here.
 
#15 ·
Thank you for sharing your experience sir. It sounds very similar to what im facing. The thought of causing the car more damage while it is susceptible like this occurred has occurred to me but the potential risks feel even heavier after hearing about your ordeal. I thought of waiting till my accumulators were in before taking my car down to the dealership but umm i guess itd be more prudent to make an appointment now.

On a side note, check engine light (fixed in august by replacing cats) came back on today as well. I feel like these cars have a ~10k mile "good" mechanical life cycle after which known issues realting to accumulators, inlet pipes, cats etc begin to surface. As long as it isnt as bad as rod bearinngs in the e60 m5 or ims in 996 porsches i feel alright about it but then again rod bearing and ims issues occur after 50k miles which would be great if that were the case with mclarens.
 
#17 ·
For clarity, the car was not driven hard prior to the video. Just went to get gas today and while coming back, the engine light came on and then it started to not rev over 4 to 5k. upon trying to rev it, the engine system failure light also came...on. I returned home and only blipped the throttle once for this video. I do not want to put pressure on the car, it is clearly suffering. I gotta wait the weekend out to call service. Hopefully they have appointments available soon. Any advice as to whether i should prepare transportation arrangements for it or if i could at least trot around central campus to pick up some girls for the time being (never actually happened).
 
#28 ·
Mclaren plug it into their computers. They diagnose with the check engine light. They fix whatever is needed to get the check engine light off.

Anything else (ie; checking turbo inlet for example) is a fishing expedition for them. They will make you pay ahead of time if they don't find anything wrong with it.

They have been very clear that a check engine light has to be on and they diagnose from there. If not then not much they can do. It doesn't matter what people on the forums are telling you to get the dealer to check (unless you are a DIY person). Dealers follow certain protocols and the check engine light is the main driver with what they check in your issue. They want to find a problem (they get paid when they find the problem and fix it).

fwiw; the turbo inlet issue for me did not have a check engine light. I noticed on track that the temps went red and the car hesitated. After a few seconds it reverted to green. WOT for 5 seconds then red. Let off then green. No check engine light. Dealer as a favor checked the turbo inlet for me free of charge. This is when they told me that the check engine light has to be on. Otherwise it is a fishing expedition for them and they don't want to waste their time trying to find a problem that probably isn't there.
 
#31 ·
Yes sir, the service advisors always made me feel like what you are saying is indeed the case and I completely understand it. I am sure everyone else would too upon deeper reflection, in this world everything more than required is a favor and i dont mean that to detract anything from mclaren. About lights showing up, youll find that i posted a second video today when the symptoms of the car's problems had exacerbated. Check engine light now on along with engine system fault. Trying to get it to service asap now.

Thank you for taking the time to share your experience and helping me understand this fishing expedition analogy, it helps understand how things work in the industry a bit better for me. Also just as a note, my car never had any problems with temps until now.

You shouldn't have posted about the 193 mph run's that you are doing... That can be considered abusing the car and can cause warranty problems.

Next time you go out (like the video you did while revving the car in neutral); cycle through the menu screens and show any errors that the car has. It should show up on that screen and post it. I can't remember but the rev's might be limited in neutral (your car was warmed up but generally if it isn't warmed up then the rev's are limited.

the catalytic converter issue that you had is a sign of sustained high speed driving... that sort of gets you on the radar of possibly abusing the car (I only know two people with the catalytic converter issue and they both had thousands and thousands of track miles on their car's).
 
#32 ·
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Yes sir, the service advisors always made me feel like what you are saying is indeed the case and I completely understand it. I am sure everyone else would too upon deeper reflection, in this world everything more than required is a favor and i dont mean that to detract anything from mclaren. About lights showing up, youll find that i posted a second video today when the symptoms of the car's problems had exacerbated. Check engine light now on along with engine system fault. Trying to get it to service asap now.

Thank you for taking the time to share your experience and helping me understand this fishing expedition analogy, you helped me understand how things work in the industry a bit better. Also just as a note, my car never had any problems with temps until now.
 
#36 ·
don't drive it anymore and have it trucked to dealer. and forget about the top speed run thing. if mclaren claims abuse from that than they need to get out of the supercar business.
last video has a buzzing or low pitch whining sound but hard to say with certainty on my subrate computer.baffles being chewed up by compressor wheels perhaps? just some armchair diagnosis.
 
#40 · (Edited)
Thanks for the reply big boss, ill get the transportation for it sorted as well. Hopefully, ill get an appointment soon. I dont want to think about potential escalation of the situation. Only thing i can say for sure is there is no way it will rev high and give boost as youll see in the previous second video of mine (wheee the buzzing is present) it does rev higher on idle when everything on track but doing so enable engine system fault warning to come on probably the mclaren saying PLEASE STOP.
 
#39 ·
Oh and cats changed have literally 0 to do with high speed runs 😂 The things people come up with... cats were changed because they were likely wrecked by having too much oil in them, caused usually by a leaking turbo, that in these cars usually comes from inlets getting into the impellers.

By the looks of the video, you will need a second set of cats by now, clean the intake system, IC included, hope and pray there is no plastic that ran inside of the engine and didn't got lodged in there (camera inside of pistons and compression test), change turbos, change inlets and it will be fine. Have them check the fuel pressure again tho while they are at it.

After fixes are made, you can be quite stress free. Inlets have apparently been fixed, you will get new turbos, new cats and hopefuly a long trouble free ownership
 
#43 ·
Thats a good assessment sir, but i just had the cats replaced like 3 weeks ago. Your comments have both piques my interest and confused me :( heres an invoive from the cats being replaced too
206560

On a sidenote big brother, let us not call others out (i really reaaally appreciate you and restosud assuring me its fine to drive my car fast) because their opinions do have truth to them and stem from personal experiences that might be different from ours (some times unrelatably so), im sure youll see the positivity in unmac's advice if you try. Anyway, leave I REALLY HOPE MY CAR IS FIIIIIINEEEE. I will relay all the info i get from mclaren troy asap
 
#48 ·
Went out to get gas as a courtesy to the dealership before i call roadside assistance (i just put lie 5 gals at a time). Came back and idk why i thought id see if it revs one more time. Engine revs normally. Video attached. Since it purrs again I guess I should hold off taking it to service until more lights come on again.
Sidenote baby: youll hear the suspension going awol on track. Accumulators still need to be changed (repair greenlighted). I imagine this is how the car will always sound like once retired..ah the nostalgia.
Side to sideside: check engine on probably because of bad cats

 
#49 ·
Went out to get gas as a courtesy to the dealership before i call roadside assistance (i just put lie 5 gals at a time). Came back and idk why i thought id see if it revs one more time. Engine revs normally. Video attached. Since it purrs again I guess I should hold off taking it to service until more lights come on again.
Sidenote baby: youll hear the suspension going awol on track. Accumulators still need to be changed (repair greenlighted). I imagine this is how the car will always sound like once retired..ah the nostalgia.
Side to sideside: check engine on probably because of bad cats

Im joking about not taking it to service. Its on a truck rn
 
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