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1988 Mustang GT 5 Speed Misfiring and Popping with Headlights

Tiffany

New Member
Hello! I introduced myself briefly months ago. I bought this vehicle in August, drove it for a few months then garaged it throughout the winter. I'm just beginning to find out it has some "quirks". I had it on the road for the first time today since October. I have been starting it and idling it regularly throughout the winter and drove it up and down our street. I didn't have full coverage on it as I have the back seats out to address a convertible top leakage issue and we are getting ready to replace the quarter window motors. Yes, I drove around today without back seats and the rain channel removed. LOL! When I drove it previously one night in September I noticed a slight misfire when I had the headlights and the heat/blower on. It did it one night and I didn't notice it again. Fast forward to tonight.

The car drove like a dream all day today. I drove it around town, drove it on the freeway, etc. As I left to drive it home I put the headlights and the fog lights on (I do have moisture in one of my headlights). I had moisture in one of my previous Mustang's headlights and the headlights would randomly turn on and off. Tonight, as soon as I really stepped on the gas and went to shift into second it misfired and popped like crazy. I remembered that I thought the heater/blower had something to do with it months ago, however I didn't have it on tonight. It was light enough to safely drive without headlights so I turned them off. The misfiring and popping stopped even when I beat the shit out of it and shifted aggressively. I then stopped the car, turned both the headlights and fog lights on again and it misfired and popped like crazy. I then left the headlights on and turned off the fog lights. It still misfired, but not as badly with the fog lights off and only the headlights on. I know, less draw. It's had some quirks most of which seem to be electrical. I lose my stock radio presets upon the first start of the day. I also had it misfire a bit on the freeway doing about 65 when I put my windows up and down. The misfiring tonight was definitely worse with the headlights on than it had been previously. At that time, it seemed to be the heater/blower and drove fine with just the headlights on. I took it easy driving home with just the headlights on and it drove okay, but I could still feel it slightly misfiring when revving up to shift into second.

HELP! PLEASE!

Thank you!

Tiffany
 

Tiffany

New Member
Coincidentally, I woke up this morning to find a puddle of water and battery acid under my car. The battery was bulging on one side. I was hoping there may be a connection between the battery/headlights and the misfiring/popping since right now it is only happening when I have the headlights on.

Nope. Just installed a new battery and took a test drive. Still misfiring and popping with the headlights on. Seems to drive fine without the headlights.

One things down, about a million more to go (insert sad, frustrated face emoticon).

Ideas?
Thanks!
Tiffany
 

i.playhard

New Member
It's a ground wire issue I have had same issue with my 88 gt I ran new from battery to frame and also added additional ground cable from under a compressor to frame and issue stopped hope this helps you can Google adding additional ground wire to my 5.0 fox mustang and see a lot how to do videos

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i.playhard

New Member
I should also mention it's also unfortunately also signs the ecc computer is done and tripping out and it's a back fire issue at least when I had that issue that's what mine did but most likely a ground wire ford didn't do a great job when grounding this year mustang you can also Google 1988 5.0 Mustangs wiring ground schematic and that search would give you pronounce of all the grounds so you can check everyone but adding an additional like I did from under AC compressor and then down to the frame made a huge difference after changing every Factory ground on my car Good Luck!

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Tiffany

New Member
Update from yesterday..... I don't know if this changes anything....

Thank you for the reply. The plot thickens. I'm starting to become disheartened by the purchase of this vehicle.

I drove the car on a short errand after replacing the battery. I parked the car at the curb outside my house then realized I hadn't turned the wheels. I turned the key to start the car and OMG! She turned into Christine! I had no idea what was happening! She started making a loud noise from what sounded like the front right end. I turned the key in an attempt to shut her down and she wouldn't turn off. Kept shaking and and acting like she was trying to start when the car was already running (or was it). I had no idea what was going on so I kept my foot on the brake as I had a car parked in front of me (in hindsight I probably should have just gotten the hell out of the car). I started yelling as I had 2 people there working on another vehicle. They came out and yelled for me to shut it off. In my desperation, I pulled the key out of the ignition and held it up to show them I couldn't turn it off and the shaking, noise, attempts to turn on continued. Looking back now, that was kind of funny. They yelled for me to take my foot off the clutch. I guess in my panic and confusion I still had my foot on the clutch. The car then made a loud banging sound and the engine literally shook, you could visually see it kick to one side, then the car stopped and started smoking. I was crushed! We then disconnected the battery which was red hot.

You guessed it. Stuck starter. Related to the misfire and popping. Have no idea. High ho, high ho, it's off the LMR I go. Now, I'm paranoid this car may start on fire at some point as I seem to have some really wonky electrical issues going on.



Tiffany
 

mustanggarage

Active Member
that sucks. I wish I had some great information for you so that you could fix this with a quick 1 component replacement make the car brand new kind of magical insight. unfortunately all I can offer is commiseration. Electrical problems are my nightmare. I hate them. I am currently dealing with my all my gauges not working properly. anyway. the only suggestion I can offer is to have someone who is good with electrical problems look it over and see where the short in your circuitry is. I would however suggest replacing your solenoid. it is relatively cheap and is a common source of the stuck starter problem. anyway good luck.
 

i.playhard

New Member
It's the starter solenoid on battery side fire wall check wires may have some how messed up Changing battery or its just defective good thing is its cheap Auto zone it's like 15 bucks if that's not it then the eec maybe jacked up due to bad ground wiring and it's shorted out but either way should have a car mechanic check all the power and ground wires and replace any that look iffy Good Luck!

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i.playhard

New Member
It's a ground wire issue I have had same issue with my 88 gt I ran new from battery to frame and also added additional ground cable from under a compressor to frame and issue stopped hope this helps you can Google adding additional ground wire to my 5.0 fox mustang and see a lot how to do videos

Sent from my SGH-M919 using Tapatalk

It's the starter solenoid on battery side fire wall check wires may have some how messed up Changing battery or its just defective good thing is its cheap Auto zone it's like 15 bucks if that's not it then the eec maybe jacked up due to bad ground wiring and it's shorted out but either way should have a car mechanic check all the power and ground wires and replace any that look iffy Good Luck!

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Tiffany

New Member
Thank you for all the help and suggestions......keep them coming.......I compiled this.....the history of this Mustang to the best of my knowledge....

Okay, so here it is........just the facts maam........

Parts that I have replaced since purchase August of 2016

Solenoid
Ignition switch (2nd replacement as it was replaced on recall as well)
130 amp Alternator/wiring harness
Battery cables positive and negative
Battery
Coolant reservoir/tank
Rear brakes and cylinders
Sun visors

Previous Owners Mods

K and M filter/stock cold air intake
Hurst shifter (24 years old)
3 piece American Racing Wheels/lowering springs
3 chambered Flow Master exhaust/cat back
Suspension Techniques (25 years old) with original struts/shocks


Currently has stock radio and after market alarm (read that alarms can cause electrical issues)

What I found in receipts (there were a few I couldn't read, but this is most of them)

EFI fuel pump 2013
filter
tank sending unit
filler neck seal
oil level sensor
oil level deal
mass air flow sensor and clean

O2 Sensor 2005
O2 Sensor
Diverter valve upstream/downstream
Diverter valve solenoid

Replaced fuel injectors and valve cover gaskets 2002

8 fuel inj 19lb 2002

Sensor assy-eh gas recirc 2001
sensor as-ego (heated)
valve and actuator asy

Clutch 2001

Radiator 2001

Pump assy exh a. 2000

Shifter 1991

Heater core 1994

Cat convertor 1994

There is a lot of documentation on emissions as this was a CA car.

One of the rear quarter window motors is not working properly. Motor worked and drive gear didn't when purchased. Motor started cutting out after a few weeks of driving. Maybe there is an electrical issue there?

We also increased the timing from 11 to 14 to see if the car would drive better or have additional pep. The misfire worsened after the increase, but I don't know if there could be any correlation. If we backed the timing off would the misfire be less like it was before the car was garaged? It is still at 14.

I also can't help but wonder if there is any correlation with the battery issue, starter issue and the new higher amp alternator and new wire assembly? The new alternator was installed in March and the increased misfire was present on the first drive (with headlights) a few days ago. I also had the starter stick and burn and the battery bulge and leak all over.

I ran an error code (paper clip) test when I first noticed the misfire. It threw no codes at that time. I am going to rerun the test.

I wanted to post of picture of my Mustang for you all, but I still keep getting a file is too large error message. I was able to post the same pic on another forum where the layout looked identical?

Thank you everyone for your time and help!

Tiffany
 

Tiffany

New Member
So, I can't post a pic in my reply, but I was able to post it as my avatar. Not sure why it's showing 2 pics layered?
 

broncojunkie

Well-Known Member
Your avatar looks fine to me. I post my pics to photobucket and then link directly to it in my posts because I have the same "file too large" issue. The problem is that I've started having issues with photobucket lately, so I don't post as many pics. It seems my phone hates photobucket's new layout, so I have to post pics from my laptop.... which I'm rarely on.

As for your car troubles, it does sound like you have some wiring issues. As stated above, I would check ground wires. You can always add more grounds. You need a good ground from motor to body. Check ground from your battery and your ecm. I think the ecm has a ground near it... just behind the kick panel on passenger side. Another ground that is easily missed is an orange (iirc) wire with a ring terminal just behind the motor. It comes off the injector harness and grounds to firewall.

I would also remove the alternator and have it bench tested asap, if you haven't already. Any parts store should be able to do it. It could be putting out too much power which could wreak all kinds of havoc. That would be a voltage regulator issue, which is attached to the alternator and can be replaced separately.

Just a few ideas.
 

i.playhard

New Member
Well I would either get a real OBD code reader or take it to say Auto Zone or some AAMCO Or PepBoyz and they can run eec code test for free usually? I would now after reading all the history say there most likely an issue with the Alternator Regulator is it a 3g upgrade or standard is it new or used? So cooking a battery like that is a bad sign get a volt meter and if you don't own one get a 10 dollar one at Harbor Frieght and test the out put it the voltage dash gauge pegged out in Red to max? This must be wired wrong to overcharge battery or defective regulator also did you pull the timing plug out when you advanced the timing ? If not that's going to definitely be an issue as timing maybe way off that will cause detonation which is the misfiring of the cylinder timing and that will damage your motor quickly! The black plug must be pulled out to set timing then reinstalled after its set. So I would definitely dbl check the alternator wiring get a proper code test done and also check the obvious like spark plug wires for proper connection or just replace them if they more then say 2 years old and do plugs at same time wires may be in wrong sequence as well and that will also cause all sorts of back fire issues as well! I would say whatever you did right before this issue with backfiring started is going to be where to look first! Assuming you did the timing correct it's possible you didn't tighten the distributor hold down bolt tight enough and the distributor moved after on its own after running from vibration and now timing is way off and or when you did timing I hope you didn't pull distributor up and only turned it to adjust as then the timing shafts gears will be off from TDC and back firing will be a given. It's most likely all electrical related but another easily overlooked cause of backfiring or pops in engine is a worn timing chain can also cause backfire and codes won't show that and most mechanics will over look easy to check by turning the crank bolt with a breaker bar and see how much play is seen and felt just Google checking timing chain late model 5.0 mustang to much play on YouTube! Good Luck!
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Tiffany

New Member
I am copying and pasting this here from another board I have been posting on. I wanted to update you all as it seems we have found and fixed the problem. This may help somebody else.

The Mustang Gods have smiled down upon us today! Hallelujah!!!!

We did the fuel pump trouble shooting today and everything tested good. We were sitting around and started talking about how the ignition control module went out in my last Mustang and had to be replaced. I lost all power one day when I was driving. No warning, nothing.

We decided just for the hell of it to pull the ignition control module and take it to the auto parts store and have it tested. We went to 5 stores.....this is why. It tested bad at the first store (the guy had an old archaic looking tester that he had to pull a manual out to figure out how to use). We decided to have it tested somewhere else. The second store it tested good. He gave us a paper printout and said that he tested it twice and got it nice and hot. We still weren't convinced. The third store, it tested good once then bad the next few times. Fourth store said they didn't have the capability to test it. The fifth store it tested fine once then bad the remaining times. We decided to buy a new module and he suggested testing the new module before we took it which we did.

Installed the module and took it for a spin around the block. Turned on the headlights, accelerated to shift and hot damn......no misfire.....no popping! Added the fog lights and blower and still no misfire or popping! I don't know if the radio is still losing it's presets. It may or may not be related.

Tiffany
 

Tiffany

New Member

  1. TiffanyGT
    Active User

    The Mustang Gods have smiled down upon us today! Hallelujah!!!!

    We did the fuel pump trouble shooting today and everything tested good. We were sitting around and started talking about how the ignition control module went out in my last Mustang and had to be replaced. I lost all power one day when I was driving. No warning, nothing.

    We decided just for the hell of it to pull the ignition control module and take it to the auto parts store and have it tested. We went to 5 stores.....this is why. It tested bad at the first store (the guy had an old archaic looking tester that he had to pull a manual out to figure out how to use). We decided to have it tested somewhere else. The second store it tested good. He gave us a paper printout and said that he tested it twice and got it nice and hot. We still weren't convinced. The third store, it tested good once then bad the next few times. Fourth store said they didn't have the capability to test it. The fifth store it tested fine once then bad the remaining times. We decided to buy a new module and he suggested testing the new module before we took it which we did.

    Installed the module and took it for a spin around the block. Turned on the headlights, accelerated to shift and hot damn......no misfire.....no popping! Added the fog lights and blower and still no misfire or popping! I don't know if the radio is still losing it's presets. It may or may not be related.

    Tiffany

    #3413 minutes ago
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mustanggarage

Active Member
Glad you got it sorted out. And, I am glad you posted your process for sorting it as well. I have spent a lot of years working on vintage mustangs and I know quite a bit about them. But my 89 is my first foxbody so I am learning all the happy little quirks and eccentricities of this car. I appreciate how well you described the problem and all you went through trying to figure it out. it will be useful to me at least if my car ever does something similar
 

broncojunkie

Well-Known Member
Glad to hear you found the problem! I went through the same thing with those modules on my old 92 F150 a few years back. I replaced it, but still had problems. Every test I did kept pointing back to a bad module. I finally talked the parts store into exchanging it. They had 3 in stock and all 3 tested bad right out of the box. The one I returned tested good the first time, but repeated tests showed bad. I think it would work properly until it heated up, which didn't take long at all. So when they repeated the test a few times, it would start testing bad. That little problem caused me tons of grief, however, I did end up with literally every single ignition part either new or upgraded (and new).
 

Seth85

New Member
Is your GT quipped with a voltage regulator under the hood or is it built into the alternator? If it's not built into the alternator could possibly be faulty voltage regulator

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