Car question

[tw]

Originally Posted by glatt

There are so many vacuum hoses! I was looking for possible disconnected hoses and kept finding new ones to inspect.

Better designed cars have a number on each hose. A vacuum hose diagram confirms each connection. I once found two hoses reversed. Car still started.

EGR valve will not open fully with 'mouth vacuum'. But just enough to confirm its works. More important is no leak (ie stray piece of carbon) from exhaust to intake manifold.

[glatt]

I listened at the exhaust, but didn't hear anything other than a steady hum. After a while some water started consistently sputtering out, and I noticed some pinhole leaks in the muffler where water was dripping out.

I turned my attention to the solenoid that opens and closes the EGR. I checked for the proper resistance between the prongs, and then check that there was no continuity with the outer frame.


I blew in the lower nozzle, and saw that the air came out the filter vent, and then I applied battery current to the prongs, heard the solenoid activate, and when I blew in the lower nozzle, the air came out the upper nozzle. According to the manual, this confirms the solenoid is OK

Then I went to the EGR transducer and checked to make sure the filter was clean. It was very clean. I blew in one nozzle, and covered the two opposite nozzles, and confirmed the air came out the sides.
According to the manual, this confirms the transducer is OK.

Finally I took off the EGR valve. This was a little trickier because it was underneath and there wasn't much room. But I got it off and saw that it wasn't terribly dirty.


A little dirty, but not bad. I tried sucking on the hose that leads to the diaphragm, and could easily open and close the valve by sucking on it.

The air intake was a little dirty too, but I couldn't get at it to clean it. It was hard enough to take this picture.

[glatt]

As long as I had the valve off, I might as well clean it. So I did. Sprayed lots of carb cleaner in the different holes and sucked on the hose that leads to the diaphragm so the cleaner would get in valve area as I sucked the valve open and closed.



Then I put everything back together and started the car. It still vibrates a little, but it's not as bad as it was before. I can't get it to make the really annoying vibrating and sound. I'm optimistic!

There were a couple other tests I could have done if I had a vacuum pump, a vacuum gauge, and a scanner tool that showed RPMs in real time.

Maybe this fixed it. I'll pay attention for a while and see if it's fixed. Hardly drive this car at all though, so I don't know when that will be.

[tw]

Originally Posted by glatt

There were a couple other tests I could have done if I had a vacuum pump, a vacuum gauge, and a scanner tool that showed RPMs in real time.

Did not realize you had a vacuum gauge. Smooth sound in an exhaust suggests the vacuum gauge should show a constant vacuum in the manifold at idle. However confirm this. Intake manifold vacuum at a constant above 17 inches should be observed. If the vacuum gauge needle vibrates, then the problematic cylinder is indicated when the gauge point dips to a slightly lower vacuum.

Assuming the vacuum gauge is contant at idle. Then this is puzzling. Vibration at idle implies a missing cylinder. And yet the exhaust pipe sound suggests no missing. Vacuum gauge will probably report the same 'no problem'. If so, move on to some other suspect. This engine appears to be operating smoothly on all cylinders during idle mode. And gas mileage suggests it is also working properly during normal operation.

Every part of a drive train and engine must be isolated from the car's body. Even a radiator does not make a direct connection; connects to the body via rubber isolators. Is it possible that something (ie exhaust pipe) is touching the body as it gets warm? For example, an exhaust pipe was hung slightly twisted? Or a heat shield place moves slightly with heat?

[glatt]

Well, I don't have a vacuum gauge. Maybe I should get one. Seems like a waste of money for a tool I'll only use once. But I wish I had one.

I listened at the exhaust, but don't trust my skill at identifying the sounds I hear. It sounded like an exhaust. Didn't seem abnormal at all.

I'm confident that I eliminated the EGR system as the cause of the problem, and even cleaned the EGR valve, but last night I drove the car to a party in DC (because it's small and easy to park) and it's as bad as it ever was. The problem is still there.

When I watch the engine, one of the radiator hoses is vibrating like crazy. The engine doesn't seem to vibrate much. At times the battery is vibrating a lot too, so you can't read the writing on it, but yesterday it wasn't so bad.

I guess it's back to the drawing board.

Under the section for vibration diagnosis, the shop manual talks a lot about road vibrations, but those don't apply because the problem is only noticed when it's stopped. The only part of the vibration diagnosis that applies is the engine speed sensitive section. They list a bunch of scary sounding possibilities:
-Belt or engine driven accessories like generator, A/C compressor, power steering
-drive belts and their tension
-bad bearings
-bent shafts
-faulty or loose flywheel

For rough idle, which seems to me like it might cause cabin vibrations and loudness, they list the following:
Sensor checks
Check O2 sensors
Check Throttle position Sensor
Check Engine Coolant Sensor
Check MAP sensor (but they don't say how)
Fuel System Checks
Check if condition occurs under Rich or Lean conditions
Check EVAP control system
Check fuel injectors for leakage
Check fuel pressure
Ignition System Checks
Check ignition voltage with spark tester
Check spark plugs for wet, cracks, wear, gap, burned, blistered, dirty
Check spark plug cables for resistence
Check ignition timing
Additional checks
Check for vacuum leaks (I did this)
Check ECM/PCM grounds for clean, tight, routing
Check ECM/PCM with scan tool to look for A/C signal
Check EGR (I did this in the post above)
Check battery cables and ground straps (battery cables look fine)
Check Crankcase Ventilation Valve
Engine Mechanical Check (It's like they are just listing engine parts now)
Motor mounts
valve timing
low compression
bent push rods
worn rocker arms
valve springs
camshaft lobes

[glatt]

I thought I would check the PCV valve since that was suggested. I pulled off the vacuum hose to the PCV valve, and the engine almost stalled and then started revving and then cycling between to two. When I put my finger over the end of the vacuum hose the engine settled down into its normal rough idle. It had been sucking air in like crazy.

The manual says that if you put your finger over the PCV valve inlet, it should snap back into place. I tried it and the valve did nothing. So I pulled the valve. It was perfectly clean, and I could shake it and hear the plug inside rattling back and forth. I guess the PCV valve is fine.

So then I started disconnecting the spark plugs one at a time and listening to the engine. Now I know what missing sounds like. It's very distinctive. The engine wasn't missing before. As I disconnected each spark plug in turn, the engine would sound worse each time. So I think it's not missing.

But now my check engine light was on! Disconnection a spark plug will do that. Fortunately, the CarChip Pro did exactly what it's supposed to do and I was able to turn that light back off.

So I haven't solved anything, but it's been fun playing with the pencils on the bench.

Maybe cars just sound like shit as they get older.

[tw]

Originally Posted by glatt

I pulled off the vacuum hose to the PCV valve, and the engine almost stalled and then started revving and then cycling between to two. When I put my finger over the end of the vacuum hose the engine settled down into its normal rough idle.

Understand what you did. Fuel injection monitors intake manifold vacuum. If the vacuum decreases, then the injector system assumes you have opened the throttle plate (pressed on the accelerator). So it pumps more fuel into the engine to accelerate. But then it sees the throttle not open (throttle sensor) and faster engine RPMs. So it cuts back on fuel (there is an RPM number above which injectors cut off all fuel when the throttle is fully closed). Confused because the amount of fuel to maintain intake vacuum is not desireable if you have taken your foot off the accelerator. So it stops injecting fuel. But then intake vacuum falls too much. So it again thinks you have pressed the accelerator.

Exhuast - is the sound constant? Then no "poofff" exists. Its simple. Either the sound is constant - good engine. Or is has a change (or short loss of sound) - cylinder miss. If in doubt, go around listening to other cars. Then notice, for example, how much smoother Acura, Lexus, Audis, etc are because they have higher performance engines.

Mouth the word "poofff" using lungs and not using any vocal cords. That is exactly what you are listening for. A not properly working car should make that sound.

Sensors will be seen by, for example, Car Chip as the O2 Sensor was also reviewed. MAP changes with throttle changes. The shop manual may provide some graphs that relate voltage to air pressure. Which could probably be confirmed by viewing those voltages via CarChip.

Don't know how you checked vacuum lines for leakage since that usually requires a vacuum gauge. Some lines can be tested by simple squeezing the line to learn what happens. Then comparing that line to its function defined in the shop manual.

A small vacuum leak could be apparent by temporarily plugging the offending line and its manifold connection. You saw what happened with a major leak. What would a minor leak do? The engine would constantly be searching to inject enough fuel to maintain vacuum but then lower the resulting high idle.

I do not know what they recommend for a throttle sensor. In at least one case, that throttle sensor was only factory adjustable. Any inadvertant change meant buying a new throttle sensor assembly. Don't know if that applies to your design. A precaution about doing any throttle sensor adjustments without consulting the shop manual.

EVAP system would create problems similar to a vacuum system leak. And located by similar procedures.

Low fuel pressure would result in poor acceleration. You would need a pressure gauge to measure a maybe 45 or 60 pounds pressure on gasoline. I built one once by using a water pressure gauge from Lowes and some fitting from a company selling pneumatic hose fittings. Then discovered low fuel pressure on a pump the mechanic said was good.

He could not bother to read spec numbers. He saw pressure. Then assumed everything was OK. And yes, I was pissed I had to do his job. Low pressure did not affect idle. But did restrict acceleration and eventually (but rarely) triggered the check engine light if I did full petal accleration with multiple, consecutive engine restarts. I had to create the same problem with every restart by doing a full pedal acceleration - that I never do.

Why did I find it? I would be damned if a check engine light was reported by a mechanic as an 'unknown problem'. He failed to do what all solutions require - numbers.

Low fuel pressure would be apparent when accelerating in normal mode. Pressure would be higher (and sufficient) in idle due to less fuel consumption.

Any ignition system failures would be indicated by a missing cylinder (as reported by the vacuum gauge or "poofff"). Eventually by poorer mileage. And by poor operation (ie inconsistent acceleration) during normal operation mode.

Valve timing, bent valves, low compression, worn cam lobes, valve springs, etc would result in poor normal mode operation or in noisy 'ticking' in the overhead cam. I am surprised they also did not list valve lash which is adjustable on overhead cams for better engines. I cannot think of any condition here that would cause rough idle, not create the 'missing cylinder' symptoms, but permit good normal mode operation.

Those visible vibrating parts may simply be frequency reasonant to the vibration. May stop vibrating as engine speed (and therefore vibration frequency) increases slightly.

However, is some other part (ie heat shield on the exhaust pipe) vibrating against the body only when it also resonants at that frequency? Might be heard inside but not outside the car.