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engine stutter, kinda?

Y'all,

I've got a vexing problem. My '73 2L is running great guns, mainly thanks to this board, and I've got the FI fairly well sorted.

However I've just developed a new and unexpected problem. Sometimes the car hesitates adn stumbles some. This is fairly independant of rpm and load. I do notice that it tends to be when the throttle is in the mid range. The solution is to simply wait the 10 or so seconds for it to go away.

Now the last three problems I've had ALL come from a FI wireing harness that is dead! The wires are snapping left adn right and insulations is dropping off all over. I've repared every fault I can find and it runs well. However I cannot deny that I think this may be a harness gremlin.

That said what are the symptoms of a faulty Throttle Positioning Sensor and how do they usually die?

Thanks
Ian
Old 01-18-2000, 05:25 AM
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They can fail in a number of different ways. One of the common ones is that the tracks on the circuit board inside the switch get worn away. This usually happens at the throttle position where the car spends most of its time--at cruise.

Typical symptoms are a "bucking" at a constant RPM and throttle setting. The easiest test is to unplug the TPS--the car should run reasonably well without it. If the stumbling goes away, the TPS is most likely the culprit.

--DD
Old 01-18-2000, 07:24 AM
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OK, So I can run the 914 WITHOUT the TPS plugged in?? How well will the car run without it?

Ian
Old 01-18-2000, 09:15 AM
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Ian,

Have you taken out a spark plug to check to see if you are running somewhat rich? If it is not the TPS, then you might want to check the spark plugs. But, it would seem that the problem would get progressively worse if this were the case.

Just a suggestion.
Paul
Old 01-18-2000, 11:04 AM
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How well? Pretty well, actually. It may idle a little rich or a little lean, and the acceleration will suck most fearsomely. Apart from that, just fine. Cruise, in particular, should work well.

--DD
Old 01-18-2000, 11:12 AM
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Y'all,

Well I pulled the TPS and still had problems. It just felt a little different. Actually the stuttering/bucking/missing? is almost continuous at >5K. Any more ideas??

Thanks
Old 01-19-2000, 10:17 AM
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couple of suggestions.
1) check to be sure the fuel filter is not clogged/partially clogged
2) does it do it in neutral? I heard of a case where a wiring harness would get pulled apart momentarilly due to engine movement in the bay.
hope it helps and I'm not sending you on a wild goose chase
Old 01-19-2000, 12:36 PM
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I've got a new filter adn am waitign for the weather to clear enough to put her in. It's been all cold rain for days. I'll also check the idle rev and report back.

Thanks guy for all the suggestions.

Ian
Old 01-20-2000, 06:48 AM
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I had a similar problem on a motorcycle of mine many years ago. It ran great but then in some situations, especially in mid range to higher rpms it would start to stumble. It drove me nuts. I broke down both carbs and cleaned everything out, reassembled... still the same problem. This mystery went on for about a month. Then one day while doing some cleaning, I noticed that the nut on an ignition coil connecting the juice to it was slightly loose. Tightened it up and no more problem.

Apparently when I hit the right RPM... the one that resonated with the bike structure, it caused just enough extra vibration to jiggle the connection on and off and screw up the firing.

Since that time I have seen a couple of other peoples cars experience the same problem. Could be some slightly loose electrical connection some where or an occasional shorting... in ignition system or fuel injection control?

Hope this helps.

- Dave

[This message has been edited by Dave Bell (edited 01-20-2000).]
Old 01-20-2000, 07:49 AM
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As I've said before the last three, 3, problems I've encountered have resulted of a VERY COOKED 30yo FI harness. I'm currently looking at alternatives to buying a new/aftermarket FI wiring harness.

Looks like I can use a 1.7 or 2L FI wiring harness only. The bus 2L used L-jet, no? So are there any other type IV's that use D-Jet?

Otherwise I'm down to fabricating the thing myself. This is what I'd love to do, except for the plastic terminals. Those I can't find cheap, any ideas??
thanks
Ian
Old 01-20-2000, 08:01 AM
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Beck-Arnley carries almost all of the terminals. They're a pretty large import auto parts distributor.

They carry: The metal 1/8" female spade connectors that actually are the conductors. The plastic housings the metal conductors snap into, in 2-, 3-, and 4-conductor variety. The metal 1/4" female spade connectors that are used in the plug for the relay board. The metal V-shaped connectors that connect the FI wiring harness to the relay board. A tool to help remove the 1/8" and 1/4" spade connectors from the plastic housings. (More or less a thin flat piece of metal of the right width.)

You can, with those parts, make most of a new harness yourself. I cannot find the TPS five-connector plug, nor the odd-shaped four-large-connector plug that goes to the relay board, nor the big plastic housing for the ECU connectors, nor any of the rubber boots. But using the pin removal tools, you can get those from your old wiring harness.


Part # Description Price Qty/pak
91H2 2-wire housing $5.98 5
91H3 3-wire housing $7.98 5
91H4 4-wire housing $8.49 5
91HC housing contact $16.98 25
91EC Control unit contact $19.98 25


"Price" was the price I was quoted by a discount import parts chain for a package. "Qty/pak" is how many things are in each package. I do not have the part number handy for the 1/4" female spade connector.

If you're more willing to spend money than time, you can buy a new-manufactured FI wiring harness for BIG bucks from http://www.res-systems.com .

--DD
Old 01-20-2000, 10:56 AM
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Well I replaced the fuel filter. It needed it but the problem remains. I'm going to check the mixture this weekend and see it I can get the stutter to happen while I've got the O2 sensor hooked up.

Dave do you have a phone number for those connectors?

Thanks Y'all
Ian
Old 01-21-2000, 10:17 AM
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Nope, sorry. Try your FLAPS. Ask if they carry "Beck-Arnley Worldparts". That's the distributor.

--DD
Old 01-21-2000, 04:52 PM
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Also try NAPA ask for the Echlan FI connector kit. It's in a big yellow tackle box. It contains the D-Jet, L-Jet and Japan FI connectors.
Old 01-22-2000, 03:31 PM
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I had, what seems to be, a similar sounding problem several years ago with my 73 1.7L. The performance wasn't all that smooth beginning at about 3000 RPM and continuing on up. Turns out the fuel injection points were a bit fried - I replaced them and the problem vanished.

1-and-a-half-cents String
Old 01-29-2000, 01:50 PM
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I have just recently developed this
oft-mentioned bucking/stumbling
problem although in my case it
only happens when I hit a sizeable
bump in the road. I assume this
would point more to a problem
in the harness rather than with
the throttle switch.

Any suggestions anyone?
Old 01-31-2000, 05:25 AM
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