Hi Everyone,
I could use some advice concerning my Alfa 159 1750 TBI.
Stationary the engine appears to run fine at plusminus 800 rpm.
I can feel hiccups or subtle shakes, but no loss of power when I drive with the rpm's steady, for example at 2500rpm in third gear with cruise control at 50 km/hr or on the highway with the cruise set at 100 km/hr with rpm's about 2000.
When I accelerate in whatever gear, the car is a beast with no hessitation.
There are no fault codes and I do not have a clue about what parameters/live data could tell me. I use a registered version of MultiECUscan.
Last week, I replaced the last two of my four injectors after injector nr.4 was leaking. All injectors have been tested and the manifold gaskets are new. New spark plugs, new bobines(ignition coils). Air filter is also new...and ofcourse new oil and filter...again.
Tomorrow I will receive a new gasket for the vacuum pump, It's leaking very little oil, no droplets but enough.
I have had on two occasions failed injectors and both times it started with a hiccup and then fumes and then loss of power. On both occasions the error codes came and I replaced them.
The hiccups raise my bloodpressure. Now lately,I've been driving with a lot of acceleration to trigger a fault code. Thus far no dice.
I'm under the impression that a vacuum leak would cause more evident symptoms.
Can any of you help me trouble shoot?
Thanks for your time and Good weekend! Boyd, Netherlands
-
Ouwealfist
- Newbie
- Berichten: 32
- Lid geworden op: do feb 20, 2020 22:31
Re: Subtle hiccups or shakes
Hello,
I can only inform you of my experience with a '99 166 2.5v6
It would run perfectly, with plenty of power, but rough idle, emissions fail, and no MIL light.
After many hours of troubleshooting it (still) turned out to be a vacuum leak.
I'm not familiar with your engine, so I would take it to a garage with a fog machine.
My hunch is you have a vacuum leak somewhere, the symptoms certainly point that way.
I can only inform you of my experience with a '99 166 2.5v6
It would run perfectly, with plenty of power, but rough idle, emissions fail, and no MIL light.
After many hours of troubleshooting it (still) turned out to be a vacuum leak.
I'm not familiar with your engine, so I would take it to a garage with a fog machine.
My hunch is you have a vacuum leak somewhere, the symptoms certainly point that way.
Re: Subtle hiccups or shakes
is it for certain an engine issue? Or bad motormounts? Only use OEM motormounts, all aftermarket ones are junk and tend to cause vibrations.
As for values to check for the engine:
Lambda values should be OK but also check long term and short term fuel trim. These should be OK. If long term is high, then its maybe a vacuum leak indeed.
Also these engines are direct injection right?
Then its worth it to check the inlet valves for carbon buildup and get them walnut blasted if needed. That can actually cause all kinds of weird issues. With very hot, tiny carbon debris in the intake causing pre-ignition or not closing in the intake valve perfectly sometimes.
And also log fuel pressure if that is steady and not fluctuating.
As for values to check for the engine:
Lambda values should be OK but also check long term and short term fuel trim. These should be OK. If long term is high, then its maybe a vacuum leak indeed.
Also these engines are direct injection right?
Then its worth it to check the inlet valves for carbon buildup and get them walnut blasted if needed. That can actually cause all kinds of weird issues. With very hot, tiny carbon debris in the intake causing pre-ignition or not closing in the intake valve perfectly sometimes.
And also log fuel pressure if that is steady and not fluctuating.