Car running like crap, 4 days before Hershey |
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Car running like crap, 4 days before Hershey |
saigon71 |
Apr 16 2019, 07:29 PM
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#1
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Senior Member Group: Members Posts: 1,997 Joined: 1-June 09 From: Dillsburg, PA Member No.: 10,428 Region Association: MidAtlantic Region |
Could use some "check this" help:
Running a 2056 D-jet. Over the winter I adjusted the valves and changed the oil. It didn't need much else. This Spring, I installed a new distributor cap and new set of points. Adjusted dwell to 50 degrees before setting timing dead on at 27 degrees BTDC. The car was running awesome. (IMG:style_emoticons/default/driving.gif) All of the sudden, the car has developed a pretty serious intermittent miss. There have been times it runs flawless on a test drive, only to start sputtering the next drive. When the sputtering and bucking occurs, there is sometimes an audible "pop" or "knock" sound coming from the engine bay. I've got a new FI wiring harness from Jeff Bowlsby installed. So far I have done the following: -Check fuel lines for kinks -Added "Star-Tron" enzyme fuel treatment to fuel stored in tank for winter, have since added two tanks of fresh gas -Fuel steady pressure at 31PSI (but I couldn't get the car to act up when I had the gauge attached) -Verified point gap hadn't changed after setting dwell -Verify that CHT is tight (CHT is almost new) -Cleaned & adjusted trigger points -Unplugged TPS - it did not make a difference -Checked FI harness grounds at the back of the engine -Pulled all 4 spark plugs to check for fouling - they all looked good -Swapped the coil with a known good one Any advice on other things to check would be appreciated. |
Minerva's 914 |
Apr 16 2019, 07:36 PM
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#2
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Member Group: Members Posts: 378 Joined: 24-December 15 From: Chapel Hill, NC Member No.: 19,489 Region Association: South East States |
I would check the points, it's a cheap and easy check and apparently the likelihood of a defective set of points is greater than one might imagine according to a long time friend that has been a 914 starwort for 40 years.
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Big Len |
Apr 16 2019, 08:01 PM
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#3
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Senior Member Group: Members Posts: 1,747 Joined: 16-July 13 From: Edgewood, New Mexico Member No.: 16,126 Region Association: Southwest Region |
I would check the points, it's a cheap and easy check and apparently the likelihood of a defective set of points is greater than one might imagine according to a long time friend that has been a 914 starwort for 40 years. (IMG:style_emoticons/default/agree.gif) |
wndsrfr |
Apr 17 2019, 06:07 AM
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#4
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Senior Member Group: Members Posts: 1,428 Joined: 30-April 09 From: Rescue, Virginia Member No.: 10,318 Region Association: MidAtlantic Region |
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VaccaRabite |
Apr 17 2019, 06:30 AM
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#5
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En Garde! Group: Admin Posts: 13,423 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region |
When the car is acting up, put a timing light on the different plug wires and see which one is acting funny.
I agree with the others that your issue sounds electrical. Could be a faulty plug wire. Zach |
rgalla9146 |
Apr 17 2019, 07:29 AM
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#6
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Advanced Member Group: Members Posts: 4,545 Joined: 23-November 05 From: Paramus NJ Member No.: 5,176 Region Association: None |
Not mentioned: plenum and intake manifolds for vacuum leaks or cracked hoses.
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dr914@autoatlanta.com |
Apr 17 2019, 07:44 AM
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#7
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914 Guru Group: Members Posts: 7,814 Joined: 3-January 07 From: atlanta georgia Member No.: 7,418 Region Association: None |
can you get it to do it when the car is stationary, or do you have to drive it and put a load on the engine?
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saigon71 |
Apr 17 2019, 10:39 AM
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#8
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Senior Member Group: Members Posts: 1,997 Joined: 1-June 09 From: Dillsburg, PA Member No.: 10,428 Region Association: MidAtlantic Region |
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Spoke |
Apr 17 2019, 10:56 AM
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#9
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Jerry Group: Members Posts: 6,972 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None |
Does the tach bounce or jump when this happens? Sometimes that could signal ineffective burn or ignition issues.
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dr914@autoatlanta.com |
Apr 17 2019, 10:56 AM
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#10
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914 Guru Group: Members Posts: 7,814 Joined: 3-January 07 From: atlanta georgia Member No.: 7,418 Region Association: None |
so rev the engine and pull one spark plug wire at a time from the cap and try to localize it to a cylinder or two. If two diagonal cylinders, trigger points, if two on the same Side injector grounds if only one then switch the injector leads and see if it moves and switch the plug wire with another one
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saigon71 |
Apr 17 2019, 06:36 PM
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#11
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Senior Member Group: Members Posts: 1,997 Joined: 1-June 09 From: Dillsburg, PA Member No.: 10,428 Region Association: MidAtlantic Region |
Update:
The trigger to the poor running is turning the headlights on. Almost immediately, the car starts jerking and I hear the knock sound. Battery is new. Resting voltage is 13.06, it is 13.6 running without lights and drops to 12.5 running with the lights on. Alternator belt seems fine. |
Spoke |
Apr 17 2019, 07:17 PM
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#12
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Jerry Group: Members Posts: 6,972 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None |
Where are you measuring the 13.6V and 12.5V when running? At what RPM are you at? If 12.5V is at the battery, you have an issue. Also what is the voltage at the coil?
With the engine running at high idle like 2k, measure all 3 pins of the VR with respect to chassis ground. Not the engine but the chassis. D+ should be 13.5V, DF should be 6-10V and D- should be less than 0.5V. All voltages DC. Don't disconnect anything; just jam the DMM probe into the connector to the VR. |
saigon71 |
Apr 17 2019, 07:36 PM
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#13
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Senior Member Group: Members Posts: 1,997 Joined: 1-June 09 From: Dillsburg, PA Member No.: 10,428 Region Association: MidAtlantic Region |
Where are you measuring the 13.6V and 12.5V when running? At what RPM are you at? If 12.5V is at the battery, you have an issue. Also what is the voltage at the coil? With the engine running at high idle like 2k, measure all 3 pins of the VR with respect to chassis ground. Not the engine but the chassis. D+ should be 13.5V, DF should be 6-10V and D- should be less than 0.5V. All voltages DC. Don't disconnect anything; just jam the DMM probe into the connector to the VR. 13.6 running without lights on, 12.5 running with the lights on. Both measurements taken at the battery, car idling at 1100 rpm or so. I'll run your other tests tomorrow after work. |
Spoke |
Apr 17 2019, 07:37 PM
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#14
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Jerry Group: Members Posts: 6,972 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None |
Where are you measuring the 13.6V and 12.5V when running? At what RPM are you at? If 12.5V is at the battery, you have an issue. Also what is the voltage at the coil? With the engine running at high idle like 2k, measure all 3 pins of the VR with respect to chassis ground. Not the engine but the chassis. D+ should be 13.5V, DF should be 6-10V and D- should be less than 0.5V. All voltages DC. Don't disconnect anything; just jam the DMM probe into the connector to the VR. 13.6 running without lights on, 12.5 running with the lights on. Both measurements taken at the battery, car idling at 1100 rpm or so. I'll run your other tests tomorrow after work. Does the battery voltage come up w/lights on as RPMs rise? |
Olympic 914 |
Apr 18 2019, 07:46 AM
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#15
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Group: Members Posts: 1,661 Joined: 7-July 11 From: Pittsburgh PA Member No.: 13,287 Region Association: North East States |
13.6 seems low.
Had a recent issue where it was charging at that and after a 30mi. drive the battery was too low to start the car. first I suspected the new radio amp I had installed was drawing too much. but then found that the alternator belt was loose. it was probably slipping more at higher rpms, replaced the belt ($10 insurance) tightened it up and its now charging at 14.1, no other changes. I did read where you stated the belt on yours seemed okay. will still be bringing my jump start box to Hershey. and AAA card. Hope you get it sorted. |
dr914@autoatlanta.com |
Apr 18 2019, 09:43 AM
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#16
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914 Guru Group: Members Posts: 7,814 Joined: 3-January 07 From: atlanta georgia Member No.: 7,418 Region Association: None |
13.6 is great, sounds like a grounding problem, check the battery neg to right firewall connection, the ground leads at the back of the engine case on top and the rear trans mission to bottom of the trunk floor
13.6 seems low. Had a recent issue where it was charging at that and after a 30mi. drive the battery was too low to start the car. first I suspected the new radio amp I had installed was drawing too much. but then found that the alternator belt was loose. it was probably slipping more at higher rpms, replaced the belt ($10 insurance) tightened it up and its now charging at 14.1, no other changes. I did read where you stated the belt on yours seemed okay. will still be bringing my jump start box to Hershey. and AAA card. Hope you get it sorted. |
ctc911ctc |
Apr 18 2019, 01:22 PM
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#17
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Senior Member Group: Members Posts: 890 Joined: 9-June 18 From: boston Member No.: 22,206 Region Association: North East States |
[quote name='dr914@autoatlanta.com' date='Apr 18 2019, 09:43 AM' post='2706434']
13.6 is great, sounds like a grounding problem, check the battery neg to right firewall connection, the ground leads at the back of the engine case on top and the rear trans mission to bottom of the trunk floor [quote name='Olympic 914' post='2706413' date='Apr 18 2019, 06:46 AM'] (IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif) Or, number 329 in the 700 TT book should be considered! 13.6 is the right potential for optimally charging Lead/Acid Batteries to maximize the life of the cells. https://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery |
saigon71 |
May 5 2019, 11:27 AM
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#18
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Senior Member Group: Members Posts: 1,997 Joined: 1-June 09 From: Dillsburg, PA Member No.: 10,428 Region Association: MidAtlantic Region |
Where are you measuring the 13.6V and 12.5V when running? At what RPM are you at? If 12.5V is at the battery, you have an issue. Also what is the voltage at the coil? With the engine running at high idle like 2k, measure all 3 pins of the VR with respect to chassis ground. Not the engine but the chassis. D+ should be 13.5V, DF should be 6-10V and D- should be less than 0.5V. All voltages DC. Don't disconnect anything; just jam the DMM probe into the connector to the VR. Damn this is frustrating. (IMG:style_emoticons/default/headbang.gif) I discovered I had an adjustable voltage regulator and bumped up the voltage slightly. Still battling this problem. I installed a reman "Carquest" alternator from NAPA. Things got better, but the car still bucks when I drive it with the lights on. Spoke: I measured the voltages as you suggested with the new alternator at 2000 RPM. These are my readings: D+: 14.5V DF: 3.2V D-: negative 62 millivolts Does the low reading at DF indicate I got a bad rebuilt alternator? |
saigon71 |
May 5 2019, 11:30 AM
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#19
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Senior Member Group: Members Posts: 1,997 Joined: 1-June 09 From: Dillsburg, PA Member No.: 10,428 Region Association: MidAtlantic Region |
Where are you measuring the 13.6V and 12.5V when running? At what RPM are you at? If 12.5V is at the battery, you have an issue. Also what is the voltage at the coil? With the engine running at high idle like 2k, measure all 3 pins of the VR with respect to chassis ground. Not the engine but the chassis. D+ should be 13.5V, DF should be 6-10V and D- should be less than 0.5V. All voltages DC. Don't disconnect anything; just jam the DMM probe into the connector to the VR. 13.6 running without lights on, 12.5 running with the lights on. Both measurements taken at the battery, car idling at 1100 rpm or so. I'll run your other tests tomorrow after work. Does the battery voltage come up w/lights on as RPMs rise? Battery voltage increases slightly with lights on as RPM's rise from 13.6V to 13.77V |
ejm |
May 5 2019, 12:05 PM
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#20
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I can see the light at the end of the tunnel Group: Members Posts: 2,689 Joined: 3-February 03 From: Massachusetts Member No.: 224 Region Association: None |
You need to check the voltage at coil terminal #15 and maybe at pin 1 of the white 4 pin FI harness plug on the relay board. High resistance somewhere will reduce voltage to the consumers. I would plug another ignition switch into the harness and see if the problem goes away.
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