74 1.8 L-Jet Issue Options

[SteveL]

I have a 74 1.8 with L-Jet. Driving down the road, once in a while it sto firing for a moment, then cough and be fine for a second, then do it again - usually around 3000-34000 RPM. If I don't move the throttle, it will stay "dead", if I back off the throttle or floor it, that is when it seems to come back to life. No idiot lights come on.

Here's what I've already done:
All new vacuum hoses
New aux air regulator
Cold start injector tested plugged in and unplugged
New cap, rotor, plugs, wires
New gaskets for oil filler
New head temp sensor

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Any ideas? I'm thinking maybe:
1. Fuel pump
2. Throttle position sensor
3. Air flow meter

Thanks!

Steve

[scotty]

usually around 3000-34000 RPM

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Seriously, check the electrical connectors at the throttle switch and air flow box. Can you tell if it's flooding out?

[SteveL]

I have unplugged and reconnected both of those connectors, not that it can't still be one of them. The connection at the air flow meter might be suspect, but then playing with the throttle wouldn't make a difference, right?
It does feel like it is flooding out.

[SirAndy]

head temp sensor is loose or wire brittle or contacts corroded ...

check your ground too while you're in there, especially the block that sits on top of the case near the intake/throttle body.

Andy

[ClayPerrine]

The throttle switch on an L-Jet system would not have any effect on part throttle problems. It only has 2 contacts, one that is closed at idle, and one that is closed at wide open throttle.

The first thing that I would check is the grounds under the intake plenum. Then make sure that you have NO vacuum leaks, Including the oil cap seals. Unlike a D-jet, which will idle fast when there a vacuum lean, the L-jet will run lean at all ranges. This inculdes the large black tube betweent the throttle body and the air flow meter. Check in all the folds for splits. The air flow meter is mounted to the body and the tube constantly flexes as the engine torques up. They suffer really badly with broken motor mounts. Also make sure that the head temp sensor is working and solidly grounded, and check the dropping resistors for breaks in the wires on them.

The last thing I would fool with would be the air flow meter. It should not need recalibrating. But if your car ever backfired, it can cause the flap inside the air flow meter to warp and stick at times.

Hope that helps.

Clay Perrine

74 914 1.8L (Parade P3 AX class winner! )
73 914 2.4L MFI Six (In process of reassembly)

"It is better to wear out than to rust out."

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