Shaky Idle....Whats going on?
 

Hi everyone,

I'm having a problem with my 92 Svx, it has 91,000 miles. Get ready this is a long one.........

The car runs decent, and I stress decent, not good, when its cold but as it warms up and the idle settles it starts to idle extremely rough (enough to shake the car violently) and it sounds like it is missing (the car has an exhaust leak and you can hear it missing) also at the muffler tips instead of the normal SVX deep growl i'm hearing a more popping/huffing sound, like its not running on all 6 cylinders.

When you switch on the A/C the idle goes way down (like to 300 rpm) and just fluctuates up and down really rapidly as if someone is inside the car gassing it and letting off and gassing it and letting off over and over again quite quickly. Sometimes it will even stall.

When you rev it up (A/C off) it kinda of stumbles up and even if your holding the throttle steady at say 3 thousand rpm it still idles badly as if someone is gassing it and letting off continuously even though you are holding the pedal steady.

When you rev it up and hold it at the 4-5rpm range its more smooth but when you listen to the leaky exhaust gasket it sounds like a snowmobile, like a 2 stroke engine, with the random popping/missing sound even though the engine sounds smooth the exhaust definetly indicates that the engine is missing.

I have pulled the plugs and checked for spark all there, everything is checking out ok. The CEL is not on, but does work. I have swapped TPS off my good working SVX, replaced the idle air control valve and selenoid, MAF is fine, knock sensor is ok, coolant temp sensor checked out alright. All vacuum lines are intact and in place, Air filter is fine......What could possibly be causing this? Am I overlooking something very simple? When at idle it is shaking hardcore, enough to rattle a can of pop right off of the roof.

Everything is pointing to a spark problem to me but i've checked it all out and the coil packs all have spark and the plugs seem ok.....

I'm at a loss, I really want to get this thing up and running but i'm completely stumped on this....any help would be GREATLY appreciated.

Thanks in advance
~Tim

I am having this exact problem at the moment, and the solution is relatively easy to fix: Bad Spark plug coils. The SVX uses a coil-on-wire system, so you will need to diagnose which coil is bad. with the engine idling, unplug each feul injector 1 at a time. If you unplug a good one, the engine will die down a bit, and when you plug it back it, it should return to its previous power. You will know the bad coil(s) because when you unplug it, nothing will change in terms of engine power. I have 2 bad coils, and my new ones should be here on Monday. Everyone reccomends replacing all 6 at once, but I am only replacing my bad ones..

spark
 

Hi, I guess I forgot to say that I pulled the coils one at a time and put a plug into them fired up the car and checked for spark and they all have it, could it be possibe that one or more of the coils is still bad?

This is driving me nuts...
~Tim

According to your signature, you have several other SVXi. IMHO, you should pull all of the coils from a known to be good SVX, and switch them to the one running badly. See if this helps.

coils
 

Sounds like a plan, i'll switch them out today and see what happens.

Thanks
~Tim

update....
 

Well I went and got new NGK plugs and headed out to swap the coils and change plugs.

I changed all the plugs and then swaped over good coils onto the car. Started it up with absolutely no difference :-(

Upon further investigation, all the drivers side cylinder bank plugs looked ok when I took them out, the passenger side's plugs were completely black and one of them was wet with what smelled to be gas when I pulled it out. I think the problems lies somewhere within the passenger sides fuel/spark delivery system. When I started the car after the plug change and after it warmed up...I started to unplug the fuel injectors, when I unplugged any of the 3 injectors on the drivers side the engine idle got even worse. When I unplugged any of the 3 fuel injectors on the passengers side there was no change at all, at one point I had all 3 of them unplugged on the pass side and it ran exactly the same, just sitting there shaking and missing as it has been and when I plugged them back in the same thing...nothing changed.

I think the injectors are working though, because I listend to them all and heard a ticking sound comming from each which I believe is normal right? I just dont understand why there was no difference when I unplugged the pass side ones, especisally if they seem to sound like they are working.....

Any ideas? I've never had a problem like this on any of my soobs.......its kinda frustrating

sounds like an internal engine oil leak is smothering the spark. that woul explain why the plugs are covered in black stuff

oil leak
 

Hi,

Could it be possible that the engine is out of cam timing? Maybe the timing belt jumped a tooth? I was thinking that if there was that bad of an engine internal oil leak I would see it smoking out the exhaust or something, and there is no smoke ever from the exhaust. I think it was carbon that made it black, as when I smelled the plug it smelled strongly of gasoline. Would these even run if they were off a tooth in cam timing?

~Tim

Anyone ever had anything like this happen to their 3.3? This thing has me stumped, I just cant figure it out....

I would doublecheck the timing belt alignment. It can be the culpret especially if the problem lies on only one half of the engine.

As you say,
 

This sounds like there is excess fuel getting to this side of the engine. More than likely the fuel pressure regulator may have ruptured the diaphragm, to allow fuel to be sucked up the vacuum pipe to the right hand side of the inlet manifold, to feed that side of the manifold only.

It will get better when it is reved over 4000 as the IRIS butterfly valve opens to join both sides of the manifold together, so the excess fuel is now spread over 6 cylinders, instead of just the 3.

Pull the vacuum pipe off the manifold, put your finger over the manifold pipe to block the vacuum, see if it corrects the problem.

Harvey.;)

4000 rpm
 

It actually does seem to stable out over 4000 rpm, not entirely but it runs MUCH better over 4g's... what is this vacuum pipe that you speak of and where is it located on the manifold?

~Tim

Hi Tim, its a small vacuum pipe that runs off the rear, of the right hand side of intake manifold, you can see it from the top. It runs down to the fuel pressure regulator, to apply manifold vacuum to the regulator. There is a metal diaphragm between the fuel and the vacuum. If the diaphragm cracks, it allows fuel to be drawn up the vacuum pipe to the intake manifold.

Harvey.;)

i had that same problem. problem was solved after i noticed 2 of my intake manifold bolts were loose. tighten em up and she purred.

Hi,
Is it the hose towards the back of the intake near the throttle body, about a 1/2 inch in thickness? If it is i'll pull er' off there and check it tomorrow and post back the results.

I already checked all the manifold bolts and they are tight :-( I wish my case was as simple as yours 92svx95.

I just want to hear it run smoothly like a 91k 3.3 should..................