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74TT's Avatar
 
Join Date: Aug 2013
Location: Dutchess County, NY
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Whay am I missing?

My '74 2.7 CIS car developed a miss when driving last July. It was running fine
when I drove it. Parked for about 10 minutes, went to start and it feels like it's
running on 5 cylinders.

A good friend came over and we did a compression test, all cylinders were fine
and within spec. The injectors are all spraying. I just put in new plug wires and
new plugs. It starts right up but doesn't kick on all cylinders. For a short while
it would start like that, but then the missing cylinder would fire and all would be
well. Just in July, it wouldn't run smoothly. There wasn't any noise or anything
else that was noticeable, it just won't run on all cylinders. I did find a couple of loose
head nuts, one tightened, the other didn't. I can live with that for now and don't
think that's the issue due to the compression test.

Scratching my head, but would really like to get it out for a few more drives
before the snow flies.

Any and all suggestions greatly apprciated!
Cheers!
Steve
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Old 10-27-2018, 11:34 AM
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Checked the dizzy ?
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Old 10-27-2018, 11:40 AM
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Check your points.
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Old 10-27-2018, 12:00 PM
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The Mighty Pieholio
 
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Quote:
Originally Posted by Paulporsche View Post
Check your points.
+1

Focus on secondary ignition also. Get out in garage tonight and let your eyes adjust to the dark for five minutes. Then peer into engine while running for stray sparks.
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Old 10-27-2018, 12:16 PM
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You put in new plug wires? Are they shielded factory wires or aftermarket? The after market wires often times are not as good as the shielded factory wires and could leak spark more easily.

Rahl
Old 10-27-2018, 12:44 PM
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As said above, the points should be properly gapped. 0.012 inch is spec for 2.7 engines. Since the points carry almost no current, serving only as a trigger signal for the CDI, they are often taken for granted. The wear pad becomes thinner and that causes the gap to diminish over time. Also, sometimes with new wires, they are extremely tight, making it difficult to seat them fully onto the distributor cap. Check that the wires have not migrated away from their contacts on the cap.
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Old 10-27-2018, 02:56 PM
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Thanks for the replies! I did put in new Beru shielded plug wires as I wasn't going
to take a chance on anything else at this point.

I haven't checked the points, and that was suggested by my good local friend
as well. My question on the points is would that make it not run on one cylinder?

My experience is with British cars and points will make the car run crappy, but it still fires on all cylinders.

Thanks again!
Steve
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Old 10-27-2018, 03:14 PM
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Quote:
Originally Posted by Targalid View Post
As said above, the points should be properly gapped. 0.012 inch is spec for 2.7 engines. Since the points carry almost no current, serving only as a trigger signal for the CDI, they are often taken for granted. The wear pad becomes thinner and that causes the gap to diminish over time. Also, sometimes with new wires, they are extremely tight, making it difficult to seat them fully onto the distributor cap. Check that the wires have not migrated away from their contacts on the cap.
You're right, the wires are very tight. It was a battle to get them on the cap!
I have it in mind to double check them before I do anything else.

Thanks for your input!
Steve
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Old 10-27-2018, 03:16 PM
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My experience with points gapped too tight is that the engine will miss and be almost impossible to start. Car would start with the engine cold but once warm the problem became more apparent. The miss on one cylinder sounds like a bad spark connection to me. Always ask yourself "what was the last thing I changed?" The good compression rules out a tight valve on one cyliinder.
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Old 10-27-2018, 05:41 PM
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OK. I think I need a clarification. I took it that when you said it feels like it is running on 5 cylinders that you meant it was running badly, eg missing, sluggish, popping etc, Apparently what you actually meant is that it is not running on one cylinder in particular. Always that one cylinder. Is that correct?

If so, then I would second a previous suggestion to check the distributor, incl the cap. I might try another cap, or flip it around 180 degrees and see if the opposite cylinder misses, or if the symptom stays the same.
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Yellow 77 Sunroof Coupe/cork interior; 3.2L '80 SC engine/10.5:1/No O2; Carrera Tensioners; 11 Blade Fan; Turbo tie rod ends; Bilstein HDs; 28 tube Cooler; SSI, Dansk; MSD/Blaster; 16x7" Fuchs/205/50 Goodrich G Force Sport Comp 2; PCA/UCR, MID9
Never leave well enough alone

Last edited by Paulporsche; 10-27-2018 at 06:05 PM..
Old 10-27-2018, 05:59 PM
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You mentioned the injectors were all spraying but how well? Not contradicting a possible ignition problem but my 77 with CIS injection did THE EXACT SAME THING. Did a power balance test to locate the dead cylinder and checked the spark plug. It was somewhat fuel fouled but not drenched. Spark delivery looked good and steady. Checked the injector spray pattern on that cylinder and it was OK. Put it back in and the engine ran perfect. I don't know what happened except maybe there was some carbon stuck on the tip of the injector that dislodged when I removed it to inspect. Anyway, just a story not intended to confuse you or take you down the wrong path, just a possibility. BTW, if you don't know which cylinder is firing, find out and address that. PLEASE post your outcome.
Old 10-27-2018, 07:55 PM
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Thanks for the replies! This forum is the best for getting some clarity.
I have to add that when starting the car last summer it would start like it was
missing on one cylinder and then clear up and run fine, sort of like something blocking the fuel. I pulled all the injectors and they seemed to be fine. One was a little dribbly
( if that's a word) so I changed that one with a known good one.

Sometimes it would start right up and run perfectly, other times it started like it was missing but it always cleared, except for the last time I drove it. I'll go through all
the injectors again and see what I find.

Again, thanks for all the advice. You guys are the best!
Cheers!
Steve
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Old 10-27-2018, 08:04 PM
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Quote:
Originally Posted by Avanti View Post
YDid a power balance test to locate the dead cylinder and checked the spark plug. .
That sounds interesting. How did you do a power balance test?

Thanks!
Steve
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Old 10-27-2018, 08:06 PM
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An inductive timing light will tell you which cylinder is missing if it is an electrical issue which it sounds like to me. Once you know which cylinder it is it should be relatively easy to find the culprit. A defective plug wire? A cracked distributor cap can cause issues like that also.
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Last edited by 74-911; 10-28-2018 at 05:23 AM..
Old 10-28-2018, 04:29 AM
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to check for missing cylinder...start the engine and start removing spark plug connector(remove from spark plug) one after another when you see that particular cylinder drop that means it is firing. You have take out one at a time.
Once you see no difference that is your culprit...
Ivan
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Last edited by proporsche; 10-28-2018 at 11:04 AM..
Old 10-28-2018, 05:10 AM
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I have an inductive tester that measures voltage at the end of each plug wire. See if you can borrow one of these and test.

Information here: https://gtc.ca/Products/TA100.html

Last edited by dicklague; 10-28-2018 at 03:37 PM..
Old 10-28-2018, 09:57 AM
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Thanks again for all the replies! No time to work on the car today,
hopefully will get to it tomorrow.

I have a timing light and will try & find out where there's no spark.
I'll report back with my findings.

Cheers!
Steve
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Old 10-28-2018, 04:14 PM
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OK, stole some time to work on the car a bit today. Timing is spot on. The points were a
little tight, so I adjusted them, to 0.012. All cylinders are firing, except #6. New Beru shielded wires, new Bosch plugs.Dizzy cap is like new. I took the injector out of #6 and it sprays perfectly.
So it looks like spark is getting there, but fuel is not. I pulled the plug and couldn't smell gas, nor was the plug blackened from ignition.

I'm thinking that #6 intake rocker is either loose or the rocker shaft has walked out
and the rocker is just sitting there not moving. It's puzzling though as the compression test showed good compression.

Is it possible to have a non moving intake valve and have the compression test come out with good numbers?
Still scratching my head!

I'm going to take the valve cover off tomorrow and see if my hunch is right.

Cheers!
Steve
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Old 10-29-2018, 02:16 PM
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Quote:
Originally Posted by 74TT View Post
So it looks like spark is getting there
How do you know this?

Your description does not say you verified spark.
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Last edited by Bob Kontak; 10-29-2018 at 03:41 PM..
Old 10-29-2018, 03:39 PM
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The beru plug connector ends have an internal resistor as part of the EMI suppression system. The wire connections to these often break.

Use a Multi-meter to verify that the wire has conductivity from the distributor cap to the plug electrode. Use a spare plug to verify this test.
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Old 10-29-2018, 03:48 PM
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