[DML] Let's review: Loss of power (was fuel system values)

["cruznmd" <racuti1@xxxxxxxxxxxx>]

I've been getting lots of good advice regarding my problem and I
appreciate it so keep it coming.

Again, this morning for 3/4 of my drive to work the car ran very
well. Foot to the floor and all of that. It didn't start to buck
appreciably until the engine had been at operating temp for a while.

After the engine compartment is good and hot, the tach flickers
even when parked and idling. It's rock-steady after things cool
appreciably. (Like overnight)

Dave Stragand has rightly advocated the scientific method for sticky
problems so I am trying to take that route.

Problem: Loss of power under load, and skipping idle (both when
engine is hot) as noted at the tach, sometimes by ear. Occasional 
popping heard when pedal is floored after engine is hot.

Theories:

Fuel:
I haven't totally ruled out the fuel system but I think I can rule
out clogs because a clog is a clog, hot or cold. Primary pressure
doesn't change hot or cold so I don't think the fuel pump is slowing
down when it warms up. Control pressure is in spec. The low primary 
pressure wouldn't account for better performance when cold. I've 
replaced my fuel filter and tank pick-up screen 3 times in the last 5 
months just for paranoia's sake. Every time I change 'em out, the 
contents are cleaner. Another owner has seen my tank and agrees that 
it's clean.

Electrical:

Martin, your distributor spring story is very interesting. I will
definitely keep it in mind. We know that electrical circuits hate
heat. Here are some theories, and I need ways to test them:

#1: The ballast resistor, or resistor relay may be faulty. The
resistor regulates voltage to the coil. Too much and the coil
overheats and is ruined. The relay cuts out 1/2 of the resistor
during cranking. If the relay is stuck, (only .5 ohms vs. 1 ohm) then
the coil could overheat during driving. I can measure this with my
ohm meter. I can also get the engine good and hot, then swap in a 
cold coil.

#2: Distributor pick-up coil: Could it be breaking down when it gets
hot? My experience with them is that they work or fail, not in
between. Anyone have experience with them causing something like this?
How could I measure its output when the engine is hot, and running?

#3: Sparkplug wires: Although new, they are not the type that most
owners buy. They are 7mm but maybe they are just a poor quality that
doesn't like heat. Could I be experiencing cross-fire/misfire? How can
I test for this? I tested all wires with a timing light. The light
flashes but that's a long way from saying that they fire correctly.

#4: Timing advance: The distributor is clean and the timing advances
but is it advancing enough? How can I tell? It shoots off the scale
so how do I measure it?

#5: Vacuum leaks: My fuel injection manual recommended checking for
leaks first. I've installed some silicone vac lines on the fuel evap
canister, the cold start valve and from the dizzy advance to the
solenoid. I found an A/C actuator hose for the center console vent
dangling free. The actuator is physically broken. Grrr...I plugged 
the line with a golf-tee for now. I checked the brake booster lines. 
I can not find any other vacuum leaks. I've mostly ruled this out 
because a leak is a leak, hot or cold.

#6: Faulty relay: The RPM relay is not clicking on and off when hot.
I removed the relay cover when everything was good and hot and 
observed the relay. It seems fine. Lambda relay: I hear no clicking 
but that doesn't prove anything. The dwell meter indicates the freq 
vavle is behaving properly. If the lambda ECU were intermittent due 
to a fault or a bad relay, the valve would be too. I've mostly ruled 
this out.

#7: Faulty ignition module? How much heat does this build up/get 
exposed to? Anyone have a way to test, or experience with this 
happening?

I know this much for sure:

When the engine is cool, the tach is perfect. Idle is steady. If I 
drive on the freeway, many times the car runs ok for as long as 20 
minutes before things start going wrong. Especially if the ambient 
air temp is cool. Once components in the engine compartment are 
exposed to engine heat for a while, that's when things degrade. It's 
very gradual at first, then it accelerates to the point where 
profanity comes into use. I'll park and idle. The engine -sounds- 
reasonably steady but the tach flickers, or jumps.

I've already replaced 99% of my fuel and ignition components. I want 
to -test- and find the faulty component, not just replace parts willy-
nilly until I stumble on the cause.

I will be bringing a fact-sheet with fuel pressure values and parts 
replaced to the Spring Social to aid in troubleshooting.

What say you?

Rich A.
#5335





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