RV-7 AOG West Memphis

[VIN2020]

Need suggestions!

RV-7 configuration
- 0-360 Titan
- Constant speed prop.
- 900 hours
- Left standard mag
- Right electroair electronic ignition
- upper spark plugs Bosch Automotive
- lower spark plugs Regular champion aircraft

Symptoms:
- Engine stumbling on cruise power settings, max power seems better.
- Stumbles - power loss for 1to 2 seconds and then runs smooth for 45 seconds (all times are not exact and varies unpredictably).
- Fuel pressure reads good and even during the event.
- Manifold pressure rises during the event.
- Doesn't seem Mag dependant. Run-up mags check fine.
- Run-up no problems.
- #1 cylinder few hundred degerees higher EGT than other three on takeoff and climb out

Things checked and flew again with same symptoms.
- Gascolator checked filter -good
- Carb checked filter -good
Both little debris was found but nothing concerning.
- Lower Spark plugs cleaned removed and cleaned - normal for hours
- Very careful checked manifold pressure lines aft of firewall and all good.

Currently talking with a mechanic on field but will not be able to help for several days.

Hospitality has been great and someone is loaning us a hangar while trying to figure this out.
.

[rocketbob]

Pull auto plug wires and check the ends are screwed on tight on the plugs.

[TX7A]

Intake tubes/hose clamps tight?
Just another thing to check

[Jpm757]

Ditto on possible intake leak.

[Bob Martin]

Originally Posted by Jpm757

Ditto on possible intake leak.

The reason we think Intake leaks, is your comment about it getting better at higher speed. An intake leak at idle is a large percentage of the total intake and makes the engine run rough. The same leak at high power is a small % of the total intake......therefore if the issue improves with power it may be a intake leak leaning the mixture in one or more cylinders.

Given your higher EGT on #1 cylinder I would look there first.

[Jpm757]

Look for cracks around the intake tube flange.

[Boyd Birchler]

I had a similar experience with my Electroair ignition. Half of one of the coils failed. There is a post somewhere on VAF about how I proved it and the part number I used to replace it. Some GM coils of the correct part number will not go on the thick tangs of the Electroair...

[Tim Lewis]

Originally Posted by VIN2020

Symptoms:
- Engine stumbling on cruise power settings, max power seems better.
- Stumbles - power loss for 1to 2 seconds and then runs smooth for 45 seconds (all times are not exact and varies unpredictably).
<snip>
- Manifold pressure drops during the event.

Engine diagnosis typically looks at the "big three" of spark, fuel, and air.
I noticed that you observed manifold pressure *drop* during the event, which points to "air".

*Dropping* manifold pressure would be consistent with something restricting air flow into the engine, which could be causing the stumble. Some suspects would be air filter blockage (I understand that's been checked), carb ice (is the problem happening only on high humidity days?), throttle plate issue (throttle control linkage issue, problem inside the carb such as throttle plate loose), or perhaps blockage inside the intake (a rag left in the intake, perhaps).

[VIN2020]

All good inputs.

I made a mistake in my original symptoms description.
The manifold pressure actually rises when the event happens.
(I edited the original post to correct mistake).

Wife and I decided to take a break for a couple of days and rented a car to try and recoup some family time. Timing seemed to make sense because the mechanic will not be available for a few days.

The input really helped in clarifying what I think could be happening.

It is all part of this grand adventure of this thing called life.

Thank you, and merry Christmas.

[VIN2020]

Originally Posted by Boyd Birchler

I had a similar experience with my Electroair ignition. Half of one of the coils failed. There is a post somewhere on VAF about how I proved it and the part number I used to replace it. Some GM coils of the correct part number will not go on the thick tangs of the Electroair...

Boyd,
I read your thread on the Electroair:
http://www.vansairforce.com/communit...d.php?t=122690

I'm not sure your symptoms align with mine being an intermittent stumble of the engine as I described for mine.

The following is a picture of my coil install. My coils do not look like the Oreily part number you referenced.





I PMed you with my phone number if you wouldn't mind calling me to discuss more.

Thank you