engine jerks, cuts off when idle - throttle body replaced, but a new symptom appeared

[appleman]

Hi,

Few weeks ago I got throttle body replaced in Nissan Micra K11 (1997) due to MAF diagnostics error and the engine jerking while accelerating and cutting off when idle.
(The throttle body used as replacement was new, though not the Nissan UKP 700 catalogue item.)

However all these problems persist after the replacement (the MAF error was reset by the service, but appeared again later), and in addition a new symtpom appeared: unstable revolutions (e.g. when idle, the revolutions go up and down slightly on their own, the same sometimes also happens when accelerating), and sometimes some kind of engine "shivering" can be observed (different to that jerking mentioned above - it's like if the engine would jump out of the car, althought not that intensive shivering).

Any ideas what could be the problem, and why after replacing the throttle body there is a new issue?
Can MAF error appear even when there is actually maybe no issue with MAF sensor?
Can it be a fuel pump or fuel pipes?
What does that engine shivering indicate? Could the new throttle body be to blame, or the mechanic not fitting it properly (or it would not work then at all)?

Many thanks for any hints!

Tomas

 

[getawaycar]

Air leaks can cause the MAF code/your symptoms to appear.

Perhaps the mechanic left a vac hose off? Tore the gasket? Covered the gasket in loads of sealer? Didnt tighten it? Didnt plug the connections in right? Bent some of the connectors while jamming the plugs in?

Good way to check for air leaks is start the car with the airbox off and gently cover the throttle body intake. If it violently sucks your hand down and cuts out its fine. If it still runs or whistles loudly its probably an air leak.

Could be the throttle position sensor or base idle isnt correctly set. Its unlikely an brand new throttle body off the shelf will be set correctly for your car.

When you say the throttle body is new but not from Nissan, is it from BBA Reman? Looks new but isnt. It is possible (and has happened to us before, more than once!) they have sent you a faulty unit.

 

[appleman]

Hi, the throttle body I got is made by "JECZ" company. Is it suspicious/bad, unknown, fine? Thank you.

Thank you very much for the ideas! I will try to share these with a mechanic (a different one that the one who did the original fitting, seems I found somebody reliable - but only after TB replacement).

 

[Kris C]

Isn't a JECZ original as in Unisia-Jecz?

 

[appleman]

As far as I was able to research, it is some Taiwan company.
You mean, this Jecz would actually be the typical original part that Nissan themselves had used for Micra K11 manufacturing?

By the way (getawaycar) - are there any particular steps in regards to possible faulty installation of the new throttle body (causing these idle misfires now that were not happening before) that are recommended to be done first?

I mean, the two old problems (cutting off and occasional jerking) were happening all the time, but misifre at idle only after TB replacement. So my "amateur theory" is that cutting off and jerking may be related to this airbox, injection, fuel pump etc., while misfire to TB installation or unsuitable configuration etc. (there was some engine shivering before TB replacement, but it was very decent compared to the current performance).

Either way it should be noted that the cutting off and misfire seems to be getting more intensive over days.
Earlier (June, when I bought the car - needed something to commute and get into the country) the engine was dying about every second or third time when the engine got warm and was idle. I got the TB replaced three weeks ago. When I took it for a longer ride to see, the engine wanted to die only once when idle for the whole ride - but I added fuel and it was fine. But later on, these "dying tendencies" got more intensive again, perhaps even more than at the very beginning (in June) - and in addition this misfire or unstable revolutions all the time...

I'm going to have this car only until October (max), I'm moving then, still would like to make some journeys around - but not for any price then, if not fixable easily then this one will probably have to go to dismantlers in the end - with me losing some UKP 1300 for the car, parts and repairs within three months.