Changed OVP with no improvement. Could it be something else?

[sfloriII]

Hey Guys,

Last week I posted the problems with my E-320. Here's what I wrote:

Here are the symptoms:

random ticking from underneath passenger side of dash
slight engine surges that coincide with the ticking noises
abrupt hesitation upon hard acceleration
cruise control fails to work

These symptoms are much more noticable until the engine has been running for several minutes-- even after it's warmed up. Once past a certain stage, the clicking noise goes away along with all the other symptoms and everything runs fine.

Also, but not necessarily related: sometimes when I arrive at my destination and place the gear shifter in any postion other than D, the dash lights and center consol lights flash rapidly. Maybe that's related?

Also:

When cold, the engine regularly takes three turns of the key to start. There's no cranking involved, it just takes three times before it "connects". This began happening before replacing the OVP and is still happening.


Question:

My mechanic suggests changing some little thingy that tells the engine how much gas to mix when cold. It has something to do with the radiator or coolant, I believe. Could that be the culprit?

Can I rule out the throttle actuator and wiring harness since the symptoms are not present all the time?

Thanks again for any help!

[Jer]

Hi Stefano,

The "little thingy that tells the engine how much gas to mix when cold" is the cold start valve, which enriches the mixture when starting at low coolant temps.

The ticking sound could be high voltage ignition currents conducting to ground. I suspect this because of the sound and the coinciding "miss" of combustion/power. Check ignition wires for wear and replace if necessary.

You cannot rule out the throttle actuator or wiring harness because problems with either can manifest regardless of temperature, especially with an electrical fault. Inspect the wiring harness for brittle or cracked insulation.

Good luck!
Jer

[Q]

If it is an ignition arc, you can sometimes see that at night in a dark location. Just depends on where it is and how bad it is. Plug wires are always a good start to rule out if yours are pretty old.

[BenzRepair]

Like Jer said, you can never rule out the wiring harness or the M16 throttle actuator, unless you cut the harnesses open and verify that the wire insulation is not cracked/brittle/powder; if they are, start budgeting, because any good mechanic is going to require you to replace at least the wiring harness before he starts diagnosing the problem. In fact, remove the airflow intake tube off the top of the engine and remove the spark plug cover in the middle of the valve cover. slice the ignition coil control wires open (NOT the actual spark plug wires mind you) and verify that the control wires have not one single crack in the wire insulation; if they do, save yourself some diagnosis headaches and replace the harness. Had one come in 2 weeks ago with the exact problem, and you should have seen the control wires!!!

[sfloriII]

Originally Posted by Jer

You cannot rule out the throttle actuator or wiring harness because problems with either can manifest regardless of temperature, especially with an electrical fault. Inspect the wiring harness for brittle or cracked insulation.

Thanks for the advice!

Can I rule out the throttle actuator and wiring harness since the problems almost always go away after the engine is thoroughly warmed up?

I just figure it wouldn't be one of those problems since the symptoms aren't always present. Wouldn't a faulty throttle actuator or wiring harness manifest symptoms 100% of the time?

Thanks again!