Yummybud924

I've felt this for a long time and my mechanic noted this also when I got my clutch replaced. Here is a little background on what I have replaced :

1) new, cap, wire, rotor (15,000kms ago), new spark plugs just recently.
2.)replaced fuel filter 10,000 kms ago.
3.) new fuel pressure regulator.
4) new motor mounts
5.) replaced vacuum lines.
6.) new intake manifold gaskets / fuel injector seals.
7.) new engine coolant temp sensor (on cyldinder head)


what I have noticed about the conditon

- It runs roughest in the winter when temp is coldest.
- idle is roughtest on idle and slowly gets a little better.
- Until I drive it hard for about 10 minutes the idle is very poor. Idles aroune 800 rpm and vibrates and feels like it doesn't have power.
-once driven hard for a while idle improves goes to 950 rpm and engine feels more powerful but still it isn't smooth like it should be.


so once the engine is nice and hot the idle improves but still vibrations on idle which go away full when I rev it up and start moving.


I"m thinking because it has to to with the engine heating up and getting hot it has to do with some temp sensor ?

could it be a bad oxygen sensor?

also my fuel pump seems noisy and makes a whinning noise especially on cold startup. I think it's the fuel pump, I can hear a whinne from the rear on idle at cold start up which goes away later.

I want to fix this as it's pretty annoying. In the mornings I usually let the car idle for 10 minutes so the idle is acceptable. Also on cold start up it feels like the engine has no power.

Yummybud924

one more think. when i turn my car off it shuts off and then split second later it shakes like it has turned it self on again on one cylinder. what could this be?

Yummybud924

oh yeah I forgot to mention I also replaced my idle stabilizer valve and it works as I can hear it vibrating when the ign switch is on.

aprotogerellis

I have similar issues (if not identical)... check out my post "vibrations at idle" - some interesting ideas have come up

PeteL

Fuel Pressure Regulator is a good guess.

Jfrahm

I would guess an intake or vacuum leak.

PeteL

Ooops. Noticed you already did the FPR.

Zero10

Identical problem here too. Dangerous to drive when cold because it can't even get out of its own way.
*subscribed*

Makis

Since you seem to done most things I would go back to basics and do a compression test. This could show possible burned valve or rings.

Jfrahm

Even a simple vacuum test will show such things as a burned valve or broken valve spring, or poor idle vacuum due to a leak.

-Joel.

gtroth

Loud fuel pump sure hints at FPR (was for me).
O2 did make a bit of difference for me on my idle.

Also over the years, I did a lot of little things that helped . Everything you did seemed to make real (albeit incremental) differences for me.

Cleaning and balancing the injectors was pretty good. I seem to remember cleaning the grounds at the rear of the engine helped a touch. Last year I replaced the AFM (chasing a hesitation when very cold), and that smoothed out the idle the last tiny amount - perfect now (better be, nothing left).

Good luck.

Yummybud924

Burnned valves or rings?? you guys are making me worried lol.

once it heats up nicely after 10 or so minutes of hard driving it makes much better power snd idle gets much better yet still rough.

My engine burns no oil. I rarely have to top up the oil and the exhaust does nto smoke.

my FPR is brand new so it can't be that causing the loud fuel pump on startup.

the fact that the engine has more power once it gets nice and hot and the idle smooths out seems like a fuel problem caused by a sensor to me.

would be bad ring / valve get better when hot?

Yummybud924

yes..... you described it perfectly lol. when it's cold it revs really slowly and makes no power but once I get it hot it is much smoother and more powerful.

when it's really cold in the morning on start up it feels like a vw beetle.

Equilibria

Check out the Fuel Pressure section on Clark's garage to diagnose fuel problems. Should give you a hint if its pump/filter/fpr.

I also unplugged all injectors, yanked the fuel rail off and then unplugged the dme relay, jumpered the necessary terminals and powered one injector at a time, filling a measuring bucket. Gave me a good idea how close each injector was to the others (crude, but it worked). NOTE: Make sure you clean up any small spills after!

Yummybud924

thanks. I'm pretty sure it's a fuel mixture problem

I've replaced all vacuum lines / intake seals though.

how can I check for vacuum leaks. I heard you can spray starting fluid around but I don't want to spray starting fluid and start a fire on my engine.



I also noticed that my engine doesnt' start easily right after I shut it off when it is hot. I'll have to crank it a couple times to start it. but when it sits overnight or for a coupler hours it starts up on first try.

I've also tried running some redlines fuel injector cleaner, / techron in the car several times but noticed no difference in anything.