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Intermittent pulsing idle more pronounced with accessories on by mckaymotoworks
Started on: 02-04-2014 10:20 AM
Replies: 18 (251 views)
Last post by: 2.5 on 02-07-2014 02:18 PM
mckaymotoworks
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Report this Post02-04-2014 10:20 AM Click Here to See the Profile for mckaymotoworksClick Here to visit mckaymotoworks's HomePageSend a Private Message to mckaymotoworksEdit/Delete MessageReply w/QuoteDirect Link to This Post
I did a Search and did not find anything specific to what I am experiencing. I noticed this morning after I left my driveway the idle was pulsing below 1000RPM's, more pronounced with the heater on/running lights on. I switched the heater off, not as noticeable, but still there, needle was still pulsing slightly. Under load unable to detect, made my first leg of commute about 30 miles, on the off ramp I notice it again. again, not noticeable under load. Drive 15 miles to the final off ramp, I again notice the pulsing, I turn the heater off, go a few feet, this time it seems to have disappeared in stop/go traffic until my arrival at work. SMH

I did not notice this previously, seems to have appeared over night. PO did tell me he put in a new battery, voltmeter is reading 14v under load.
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Gall757
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Report this Post02-04-2014 12:50 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
The heater fan takes a lot of Amps...... There must be a ground connection that is loose or dirty. A bad ground could be anywhere, not necessarily right at the heater motor.
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mckaymotoworks
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Report this Post02-04-2014 12:53 PM Click Here to See the Profile for mckaymotoworksClick Here to visit mckaymotoworks's HomePageSend a Private Message to mckaymotoworksEdit/Delete MessageReply w/QuoteDirect Link to This Post
Is there a wiring diagram on the net that shows all ground contacts or is it only in the service manual?
I am ordering the disc from FS in a few weeks. Already nickeled and dimed......
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phonedawgz
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Report this Post02-04-2014 02:43 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
The wiring diagram really doesn't indicate the grounds too well.

If you have the V6 there are two grounds between the engine harness and the bellhousing stud bolts on the front lower side of the engine. Quite easy to see them if you look. There is also at least one strap between the engine and the body. It is recommended that you add at least one second one. Then also there is the negative battery cable that bolts to an exhaust manifold stud.

The ECM is programmed to deliver a different amount of fuel if the voltage drops. This was intended to compensate for assumed low fuel pressure if the alternator failed. It has been found to be the root of some of the troubles of surging idle in some Fieros. Stock programming isn't supposed to kick in the battery voltage correction factors till 9.6v however.

What year/engine are you dealing with?

[This message has been edited by phonedawgz (edited 02-04-2014).]

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mckaymotoworks
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Report this Post02-04-2014 02:45 PM Click Here to See the Profile for mckaymotoworksClick Here to visit mckaymotoworks's HomePageSend a Private Message to mckaymotoworksEdit/Delete MessageReply w/QuoteDirect Link to This Post
84' SE 2.5L
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phonedawgz
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Report this Post02-04-2014 02:52 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
Ok

I don't know exactly where the engine grounds are on the 84 2.5 but if you just follow the harness you should be able to follow them. I believe there are two from the harness to the engine. Again two between frame and engine are recommended.

GM also gave you a present to work with. They used the positive starter terminal as a power distribution post. Because of the location of that post on the engine it is not unusual for the nut to come loose and cause problems. Check to make sure that nut is tight. It's the one with all the wires on it.

WARNING - With the battery connected that post has live voltage on it at all the time. So if you put your wrench on it and allow the wrench to touch anything metal it will short out the battery, perhaps causing the battery to explode with acid flying all over, perhaps causing the wires to start on fire or perhaps causing the links of your metal watch band to melt while on your arm and fuse into a single piece while burning a new scar/tattoo into your arm. Disconnect the battery first.
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mckaymotoworks
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Report this Post02-04-2014 02:56 PM Click Here to See the Profile for mckaymotoworksClick Here to visit mckaymotoworks's HomePageSend a Private Message to mckaymotoworksEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks, I'll look for this over the weekend. The suspension is beat, would not be surprised if all connection of any sort are loose.
It's been nice to have it running and commute so I can learn what issues it does have. Much like a doctor spending the entire day with a patient.
Like that would ever happen......
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mckaymotoworks
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Report this Post02-04-2014 08:33 PM Click Here to See the Profile for mckaymotoworksClick Here to visit mckaymotoworks's HomePageSend a Private Message to mckaymotoworksEdit/Delete MessageReply w/QuoteDirect Link to This Post
No pulsing on the ride home, but noticed the dash lights/wipers dim when idling and the transmission is engaged, under load they brighten/pick up speed as normal . In Park, at idle, lights are bright and normal, they only dim/slow when the transmission is engaged. What's the correlation?
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Csjag
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Report this Post02-05-2014 08:49 PM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
Could be a weak battery or weak alternator
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mckaymotoworks
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Report this Post02-05-2014 09:02 PM Click Here to See the Profile for mckaymotoworksClick Here to visit mckaymotoworks's HomePageSend a Private Message to mckaymotoworksEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks for the reply, I'll test both.

[This message has been edited by mckaymotoworks (edited 02-05-2014).]

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phonedawgz
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Report this Post02-05-2014 09:38 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
Take off your battery cables and clean them.
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mckaymotoworks
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Report this Post02-06-2014 01:24 PM Click Here to See the Profile for mckaymotoworksClick Here to visit mckaymotoworks's HomePageSend a Private Message to mckaymotoworksEdit/Delete MessageReply w/QuoteDirect Link to This Post
This get's a bit more strange. It does it with the blinkers on with the car in any gear other than Park. I can watch the lights, tach, battery meter go in sync with the flasher relay. The idle also goes along with this fluctuation. Unable to recreate this if the car is in Park. SMH
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Patrick
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Report this Post02-06-2014 02:03 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by mckaymotoworks:

It does it with the blinkers on with the car in any gear other than Park.


How about Neutral ?
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mckaymotoworks
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Report this Post02-06-2014 02:23 PM Click Here to See the Profile for mckaymotoworksClick Here to visit mckaymotoworks's HomePageSend a Private Message to mckaymotoworksEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Patrick:

How about Neutral ?


Pretty sure no effect there, but I will check on the commute home to be certain and post my findings. I just tried in the parking lot, let it warm for 5 minutes, was unable to reproduce. About 30* today so it wasn't fully warmed up, though I did drop it in to Drive a few times.

I'll find the other pieces to the puzzle.
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mckaymotoworks
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Report this Post02-06-2014 07:48 PM Click Here to See the Profile for mckaymotoworksClick Here to visit mckaymotoworks's HomePageSend a Private Message to mckaymotoworksEdit/Delete MessageReply w/QuoteDirect Link to This Post
Does not happen in Neutral. Pretty sure it's something with the charging system, if in gear at idle, say coming to a dead stop, it drops to 600-700 RPM. The blinkers etc are augmented by whatever issue is behind this. Volt meter drops from 15 to 12ish, lights, blower all go dim, only when in gear. Put it in Park, idles fine, nice bright lights etc. Something is taxing the system when in gear.

Noticed on the way home, had to stop at the grocery store. Put in park, high 2K idle after running 50 miles.
Did not do it when I returned to the car. Whether related or not, worth mentioning.
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mckaymotoworks
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Report this Post02-07-2014 10:10 AM Click Here to See the Profile for mckaymotoworksClick Here to visit mckaymotoworks's HomePageSend a Private Message to mckaymotoworksEdit/Delete MessageReply w/QuoteDirect Link to This Post
So I've confirmed for certain that something is causing the idle to kick down too low when in gear at a dead stop, I cannot detect the issue even if the car is rolling at 2-5 MPH, it seems to only happen at a dead stop when in gear only. So I assume it's a sensor for idle or the transmission? I'll research the various related sensors for the two systems. I also hope to check the ALDL this weekend to see if any codes are being thrown.
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Report this Post02-07-2014 10:39 AM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
So have you checked or added grounds?

It gets worse when the tranny is in gear because the idle gets lower. For sure seems like voltage dropping low, or not being regulated.

Voltage regulator in the alternator failing?
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mckaymotoworks
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Report this Post02-07-2014 10:49 AM Click Here to See the Profile for mckaymotoworksClick Here to visit mckaymotoworks's HomePageSend a Private Message to mckaymotoworksEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 2.5:

So have you checked or added grounds?

It gets worse when the tranny is in gear because the idle gets lower. For sure seems like voltage dropping low, or not being regulated.

Voltage regulator in the alternator failing?


Haven't had a chance to check the grounds, it's been 11* a night. Hope to this weekend, but I think you're right about it being in the charging system. The car did sit for 17 years, no telling how old the current alternator is, I did order a new belt so I'll already be part of the way there if needed.

I can stop by O'Reilly's to have the charging system tested tonight or tomorrow. Maybe that will give me a better idea.

ACDelco offers a 66, 78 and 94 amp alternator for my car. Though Amazon says the 94 AMP isn't for my model, I confirmed via the ACDelco catalog it list 321-1015 as a fit. Which AMP model should I run, I see in the P22 78 & 94 listed? I only plan to add maybe a 4 channel amp, 8" sub and 5.25 components in the future once all my mechanical work is sorted.

[This message has been edited by mckaymotoworks (edited 02-07-2014).]

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2.5
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Report this Post02-07-2014 02:18 PM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by mckaymotoworks:


Haven't had a chance to check the grounds, it's been 11* a night. Hope to this weekend, but I think you're right about it being in the charging system. The car did sit for 17 years, no telling how old the current alternator is, I did order a new belt so I'll already be part of the way there if needed.

I can stop by O'Reilly's to have the charging system tested tonight or tomorrow. Maybe that will give me a better idea.

ACDelco offers a 66, 78 and 94 amp alternator for my car. Though Amazon says the 94 AMP isn't for my model, I confirmed via the ACDelco catalog it list 321-1015 as a fit. Which AMP model should I run, I see in the P22 78 & 94 listed? I only plan to add maybe a 4 channel amp, 8" sub and 5.25 components in the future once all my mechanical work is sorted.



I would just get the largest amp one. As far as I know it cant hurt anything (IMO).
I went from 45 to 100amp alt in my 72 Buick and all is well, stereo on or not.
When replacing a battery in something I usually get higher CCA than stock as well.
If anyone sees a problem with any of that please chime in.
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