Wavy surgy revpattern while keeping rpm steady

kaneelschep · Post by **kaneelschep** » 15 Apr 2016, 04:05

Hi.

Did you ever have that feeling when you just started driving. Still slowly leaving the street. you hold the gas equally at a steady rpm. But it feels like the engine revs a tiny bit faster, slower, faster slower in a wavy pattern.
Anyway, i allready read a lot of people felt it and were interested in why. So it wasnt just my imagination.

I also noticed it drving my t5.

Last week i changed all injector rubbers. 4 per injector. 2 on the injector. 1 in the rail. 1 in the manifold.
Now it revs up smoothly steadily and evenly without that wavy feeling. Even my girlfriend noticed it without me saying it.
Its more direct on the gas. dropping in rpm faster. Benzine usage display reacts faster.
It actually missed one of the small flat rubbers in the fuelrail. A few other rubbers clearly leaked because of drying out.

Maybe other people can use this info.

Post by **Clemens** » 15 Apr 2016, 05:09

Thanks, that´s intersting to know. Where did you get the pintle caps for the injectors (the plastic caps that hold the rubber o-ring on the injector). I´m having a hard time getting these in Europe. Or could you slide them over the caps?

kaneelschep · Post by **kaneelschep** » 15 Apr 2016, 06:20

I dont think you are supposed to take anything of the injector itself but the rubbers, so I just slid the rubbers over the caps.
To get the rubbers off I used a tiny tiny screwdriver. Wich I hooked under the rubber and so pulled the rubber over the cap. to put them back on is simple.
I put a tiny bit of ball joint grease on my fingers before I put all the rubbers in place. So the rubbers would go on nicely and the injectors would go into the rail and manifold easily without pulling out the rubbers or damaging them.

Sommerfeldt · Post by **Sommerfeldt** » 15 Apr 2016, 06:22

That's very interesting. Could possible play a part in fuel economy too, I imagine... Did you simply get a double kit of o-rings, or are they different sizes?

- S

chrillew · Post by **chrillew** » 15 Apr 2016, 07:11

Nice find! i have this problem in my car and never figured it out! gonna try it

bugs11 · Post by **bugs11** » 15 Apr 2016, 07:58

Interesting that the engine would rev faster, then slower but the rpm stay the same. One would think there is a direct correlation between rpm and engine revs. I haven't noticed this phenomenon, bit then I replaced the injector seals last fall, not the rubber injector o-rings though.

Post by **polskamafia mjl** » 15 Apr 2016, 08:10

bugs11 wrote:One would think there is a direct correlation between rpm and engine revs.

There is... RPM = Engine Revs.

bugs11 · Post by **bugs11** » 15 Apr 2016, 09:45

There is... RPM = Engine Revs.

My point exactly.

Post by **Clemens** » 15 Apr 2016, 10:15

I guess he means that the Motor sounds as if it was revving up and down slightly, but the rpms Keep steady. At least this is how I´d describe this problem which I´ve encountered occasionally myself.

kaneelschep · Post by **kaneelschep** » 15 Apr 2016, 10:38

Me and the parts guy just looked at the pictures in the parts programm at the local Volvo dealer. And came up with these rubbers. I think I have the bill with parts numbers.

Lets see if I can still find it.
The 2 rings on the injectors are the same. the other two are clearly different.

@ bugs11
I meant you try to keep your foot steady to keep the same rpm. But still it feels like the speed you drive goes up and down ever so slightly.
Maybe that is a better way to put it?
If you ever had this, then you would know what I am talking about. It was one of the first things I noticed when I bought the car. Never felt it in another car before.
If you search for it, you will find others who have the same thing in these cars. I/them never found a solution on the fora for it.
Now I cant guarantee this is the solution, but it helped me.

I go and see if I can find the bill with part numbers.