chances are very slim that you would hear a vacuum leak. Look up and down all the plastic lines for maybe a bad end... How are your spark plugs and wires? Cleaned the injectors lateley? I know for a fact that this motor we have can produce stupid little problems that seem to have no solution... I've had my share of stupid problems on my car.

Yo've replaced pretty much every sensor on that motor! My ALDL program shows the MAP sensor as an error aswell, I think its just a "feature" of the program. Does your program flash "Rich Flag" on and off while idling like mine does too?

When I was having a lot of rough idling and missing while driving, I eventually found out that spark was jumping from a damaged plug wire end to the next wire, and creating cross-fire on occasion, and just generally crappy running alltogether. Took me forever to find it. If you have an old set of wires, swap them out just to see if your symptoms change.

Try buying different gas, if you are loyal to one store. Sometimes they get bad batches I've found. I dont know if anyone would agree with me. If it burns, they sell it.

Change your fuel filter if you havent, just while we're on the topic of fuel.

I've read that there isn't supposed to be vacuum at idle, which opens the EGR Valve. So I am replacing the EGR Solenoid as the EGR Valve is brand new and it did hold vacuum with the MityVac. I just changed the spark plugs and spark plug wires yesterday...no change. The old spark plugs were blistering white though...so that means it's hot...and this can be cause by a vauum leak, and an open EGR Valve at idle = huge vacuum leak. This should be it....I tried to apply voltage to the terminals to open and close the solenoid, but it appears to be stuck.

TOC Admin
Brando

I think it's the other way around.... lowest vacuum is at WOT, highest is at idle.

MANIFOLD VACUUM


Definition: Low pressure in an engine intake manifold formed just below the throttle plates. Manifold vacuum is highest at idle and drops under acceleration.

Ok, so highest pressure at idle, that would mean that there isn't supposed to be vacuum going to to the EGR, because the EGR Valve opens with vacuum present.

TOC Admin
Brando

http://www.misterfixit.com/egrvalve.htm

If it is open when it is not supposed to be open, at idle for instance, It will act like one monster vacuum leak and the engine will not idle or will idle really roughly.

TOC Admin
Brando

Well...I guess I'm going to replace my fuel filter....see if that changes anything.
It's weird though, it idles great when cold, starts to idle rough when warm. I replaced the thermostat and coolant sensor today, the thermostat seemed to help a little (installed a Napa Superstat). I'm thinking of replacing the fuel filter and then if that don't fix it...replace all the vacuum lines with new ones.

I will get this thing running tip top shape sooner or later!

TOC Admin
Brando

Yea....the fuel filter is starting to make some sense, the junk in the filter settles down in the morning, then I run it for a while and the junk builds up against the filter....causing low fuel pressure. Too bad I don't have a fuel pressure gauge.... :? Have to get one of them someday...

Although, I do have a hissing sound coming from the rear of the car...not sure if it's just an exhaust leak or if it's the fuel vapor line leaking....hmm...have to check that out.


TOC Admin
Brando

Brando, you might be on the right track there.

About vacuum leak at any item it may be used to operate (your third post back). Unless the diaphram of that item is damaged, there would be no vacuum leak, the vacuum (lower pressure) on the manifold side of the diaphram allows the higher pressure on the opposite side to move it in the direction of the lower pressure side, there is usually some shaft which is attached to the diaphram and that shaft operates the unit (egr valve, plenum door, base plate on a distributor, throttle position linkage etc....)

What condition is your catalytic converter in? How old is it? That might be the culprit. Engine cold, ok, engine hot (exhaust hot, cat hot) trouble. Aren't cats supposed to run efficiently when hot except if they get old and clogged up? Also, 88delta88 had an idea, how are your plug wires? If one is damaged or the insulation is broken down it might allow the spark to that respective cylinder to jump to ground or another cylinder.

Keep at it and you will find the solution.

The catalytic converter was replaced a couple years ago...if that. The spark plug wires and plugs were just changed recently. So I'm thinking the fuel filter.

TOC Admin
Brando

Well, no dice on the fuel filter...but now I need to change the fuel line, I now have a slight drip....

So, replacing the fuel line is on the agenda tomorrow....oh yea...and the hissing sound is coming from the fuel line, is that normal? :?

TOC Admin
Brando

Hi Brando, hello All If you can hear it, the engine will not run at all.
While the engine is up to operating temp and idling, use a can of aerosol carb cleaner to spray everywhere there is a possibility of a leak.
When the idle smooths out, you've found it.
A small vacuum leak will affect the signals from your sensors to your Computer.
A clogged fuel filter will act like you turned off the key when you are accelerating at higher RPMs.
If the filter is changed at the proper intervals, it will never clog.
Not unless it's related to the FI or computer system. If so I can't answer.
Regards, Norm

My fuel pump makes a high pitch noise when it is working. It may sound like a hiss to you?

So... No go on the filter, cat, wires and plugs.

Take a close look at your harmonic balancer. Mine went a few months ago, and the symptoms were very rough, sporadic idling. The rubber on the balancer was worn through, and would rattle back and forth, making the motor and car basically jump up and down. This would explain your excessive tensioner pulley travel. Examine all around the outside of the rubber and look for cracks.

Is your throttle body clean? if u pop off the whole iac body thats bolted to the TB theres alotta black soot build up in there, lubericate the throttle valve/spring and tps. Make sure the threads on the head where the spark plugs screw in are really clean.

Throttle body is pretty clean, sprayed some cleaner in there and wiped it out....took out the IAC (first thing I did) and sprayed the tip of that too. Spark Plug threads in the hard were pretty clean, I'll try lubricating the throttle valve once I get outta school though.

TOC Admin
Brando

how was the balancer?

as a last resort, you can try changing the air in the tires. This will ensure the tires absorb more vibration, making for a much smoother ride. I've seen too many people driving on stale air...