stuttering at 4000 rpm

roverti

New member
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Car
620ti
help ive got a 620ti which stutters at 4000 rpm but only at full throttle change plugs and leads but to no avail driving me mad:(
 
Re: 620ti Forum?

Can I ask for a few more details on the car mate? When was it last serviced? Has it had any head work done recently? Has the cam belt been changed recently? And have you got a boost gauge?
 
It sounds a bit like fuel starvation to me. Either the injectors, fuel pump or an engine fault is causing it to run rich and the lambda is backing off the fuel prematurely. It may also be the MAF sensor giving a erronious air reading.

Were the old plugs sooty - if so what colour?
 
are you running standard boost ?

also check all the air lines i had a vitesse that started doing this and it turned out to be a hgf but that was running slightly lumpy on tickover
 
plugs were clean air filter has been done and it was service bout 8000 ago idle is a little bit lumpy running standard boost only mod is dump valve and i took the muffler pipe off the air box for some noise very frustrating i use super unleaded always and nitrox injector cleaner once a month might change fuel filter see if it helps
 
no just tells you that their is compression loss

when i did it on my vietesse

cylinder 1 was down on compression turned out to be a hgf

if you want more detail try a leak down test

similar to compression test but using compressed air instead
 
i'll give it a try mots up in feb if i cant find the problem by then i'll probably just get rid shame cos it was an awsome car to rack the miles up in had a fantastic drive from surrey to lincoln in it bit of everything in that journey must have averaged 90-100 on that journey be sad to say goodbye but at 140000 miles cant realy warrant spending loads:(
 
Does it go past 4000rpms? If not it almost sounds like your in (limp-home-mode) which is a safety feature on most ECU's. Have you had any Engine Management lights flashing or staying on for a few seconds then going? If so, do a paperclip test and read off the fault code, that will give you the exact problem.

It also could be your boost. On alot of turbo's, there is an automatic cut off point for the fuel if the boost goes too high. Check your waste gate to make sure it's not sticking, and also check for boost leaks on all of your pipe work. This is where a boost gauge comes in handy as you would be able to tell staright away if its the boost ;)

You could also check your dump valve. If it's anything like a HKS dump valve then there should be a little adjustment bolt to raise or lower the piston inside which also can mess up the running of the engine if not set correctly. Oh and which make of dump valve are using. If it's a Bailey's, get rid of it and put the standard bits back on, or find a different dump valve as Bailey's will doo the engine no good. I have been advised by many different sources from tuning companies to normal garages that they are crap and to stay away ;)

Couple of bits for you to check anyway :)
 
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well it seems like the balistic barge has head gasget failure along with various other probs i'll be running it till april when the mot runs out im undesided whether to buy another or just buy a scooby or alfa 156 tough decision the cars worth a oner at the scrapys but if anyone wants to make me an offer for it as spares feel free i'd rather it was used for parts than crushed must be getting sentimental in my old age
 
well it seems like the balistic barge has head gasget failure along with various other probs i'll be running it till april when the mot runs out im undesided whether to buy another or just buy a scooby or alfa 156 tough decision the cars worth a oner at the scrapys but if anyone wants to make me an offer for it as spares feel free i'd rather it was used for parts than crushed must be getting sentimental in my old age

Where are you located buddy?
 

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