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914World.com _ 914World Garage _ 914 with the hiccups

Posted by: James Adams Sep 29 2003, 11:13 AM

'74 2.0 stock FI. Ignition parts are all recent. Nothing was touched for a couple weeks before the problem started.

It is an intermitent misfire, can buck the car pretty good depending on the gear and speed. Not related to outside temp, not related to engine temp. It may do it once every 30 seconds at the highest frequency, sometimes it seems to be gone for entire trips.

Does not seem to be RPM related.

The tach does not move (flich or drop) when it occurs. It does it steady-state cruise, mild acceleration, light decel, I have not noticed it at idle or hard accel, but I may just not have hit it at that time (can't rule it out).

I cleaned the fuses, cleaned and swapped the relays on the relay board, and threw another coil on it just for the heck of it.

What do you suggest next?

I was planning on swapping the relay board (have a few) and cleaning the throttle switch, next.

Posted by: Nemo914 Sep 29 2003, 12:04 PM

My car was doing this a year ago, and it turned out the the head temperature sensor wasn't making a good connection. It "looked" connected in its plastic sleeve, but was loose. Check that and the throttle switch. A bad throttle switch can do the same thing (so I hear).

Posted by: James Adams Sep 29 2003, 12:09 PM

Ah yes, Jeff (PO) told me that the head temp sensor was loose when he got the car and he fixed that. Maybe it has worked itself out again.

Thanks!

Posted by: SirAndy Sep 29 2003, 12:35 PM

QUOTE(James Adams @ Sep 29 2003, 10:13 AM)

I cleaned the fuses, cleaned and swapped the relays on the relay board, and threw another coil on it just for the heck of it.

are all the spark-plug wires connected tight on both ends?
and i mean tight

Andy

Posted by: need4speed Sep 29 2003, 12:38 PM

Now here's a perfect example of why this list ROCKS!

Posted by: James Adams Sep 29 2003, 12:47 PM

QUOTE(SirAndy @ Sep 29 2003, 10:35 AM)

are all the spark-plug wires connected tight on both ends?
and i mean tight

Andy

They've been off and back on but it wouldn't hurt to check again...

Posted by: garyh Sep 29 2003, 03:52 PM

Another popular culprit is the throttle position sensor.

They can (and do) wear out from being held at the same point for long periods of time.

A leaky MPS will aggravate the problem at crusing and light acceleration.

G.

Posted by: vsg914 Sep 29 2003, 06:39 PM

The tps sounds like the culprit, but the accelerator cable sould also be at fault. It doesen't like to be too tight. Give it a little slack.