94 GT: Temp guage wags & car sputters?

[SGTMack]

Has anyone had a similar problem? Do you think my mods and the eronius temp signal are screwing with my computer and making the car stall? HELP! (I will be forever indebted to the person who has the answer to my problem. I WILL PAY YOU! I don't have much - I recently became disabled in a full contact fighting course [called Combatives] for the Army and they haven't cleared me for living expenses yet - however, I will give you what I have. I just don't think that taking my car to the dealer, and having him charge me $185 to read my OBD codes (something I already did, with no luck), is worth it (nor, do I have the liquidity to do so). Please, I'm desperate. I need to drive 412 miles to Madigan Army Medical Center in Ft. Lewis on Vallentines Day for my Fitness for Duty Exam (where they will probably kick me out and finally pay for my living expenses ), but I don't think the car will make it. Any information you can provide will be much appreciated. I just don't want to keep chasing this problem (ex. having to buy a new fuel filter, new battery, new alternator, new ECT sensor, etc.). If I can get a definitive answer (hopefully from someone who has experienced the same thing), I can have my OMS shop (military vehicle repair shop) fix it. Thanks for you consideration.

Sincerely,

Mak

Anyway, here's the gist of my problem:

Car:

1994 Mustang GT 5.0 HO

Upgrades:

K&N Cold Air Intake System
BBK Performance H-pipe (no cats)
New Clutch

Problem: Car’s temp gauge “wags.” Causes car to sputter/misfire/die for one rotation. (Also of note: Car can take a few (up to 4) turns to start.)

Symptoms:

This usually happens when the car has warmed up (driven for more than 20 miles), however, it happened to me today, while the car was warming up (during the first mile)

Generally, what signals the start of the problem is the temperature gauge starts to wag. Sometimes it jumps. The temperature gauge will start to wag as soon as the car warms up and sometimes it doesn’t result in any problems with the car. (The car used to only have the temp guage problem, it just recently starting dying.)

The battery light comes on when the temp gauge wags, however, it only comes on when I am accelerating.

Lately, the Tach has been wagging as well. Sometimes, it shows the wrong RPM (stays at a high RPM, even though I know I am not revving to 3000RPMs). This is recent, before that, the only symptom was the temp gauge wagging.

Anyway, when the temp guage wags, and the battery light comes on, the car sputters. It feels as though it dies for a second, however, it immediately resumes accelerating. This happens, off and on, the entire time the gauges are wagging. The sputtering is a choking feeling - like the car has hiccupped. It only lasts for a turn of the engine, however, I don’t want the car to die on me while I am on the freeway, so it scares me.

The car sputters, reguardless of whether I am accelerating or not. If I am just holding the gas in, to maintain a constant speed, it will sputter then too.

Solutions Tried:

I have tried replacing the battery.

I have tried higher-grade fuel. (I was using 87, now I use 92.)

If you can give me any idea as to what my problem could be, it’d be much appreciated. I have run the OBD I scanner on the car, however, I did not get into the Engine Running tests. I figured the holdover memory would keep the code, if there was one to begin with. The OBD I did not give me any warning codes.

 

[HISSIN50]

Sorry to hear about your injury - best of luck getting healed up and things taken care of.

Did the battery light issue arise after the other gauge issues started? If not (it all started at once), I would think that perhaps the battery voltage might have something to do with your gauges. FWIW, the gauge has NOTHING to do with the engine management. There is the gauge sender (it is located behind the dizzy, with one wire on its lid) and there is the ECT (which does relate coolant temps to the computer, controls your fan, etc. It is on the heater tube on the pass side).

Were it me, I would install a mechanical aftermarket temp gauge (even if just a parts store cheapo) to get a handle on what is going on with the temps. You can remove this gauge once other issues are fixed, or leave it installed. I might also install a voltmeter or put your DMM in the car where you can see the display (if you can safely do it, see what the DMM reads when things start to flip out).

If you can get the battery light to start doing its thing, does it keep repeating? If so, with what frequency? I am trying to think of a way for you to be able to get components tested reliably (parts stores do free in-car and bench testing in most places).

It can be worthwhile to look at the regulator wiring at the alternator. There are about 4 wires of small gauge at the alt, plus the power cable.

Another thing I would do is to clean the power distribution box connection (this is where your alternator hooks up to the underhood fuse box). More than a few of us have had issues with that connection getting corroded, etc and causing issues.
Take a look at your temp sender wire. Make sure it is tight and clean.

I will stop for now and see if you think it is worth me trying to think of more stuff.

Others will have good ideas for you too. Best of luck Mak.

 

[HISSIN50]

Also, when it 'dies', do you think the ignition actually cuts out for a second and then the car somehow catches/restarts itself after the burp? This could be why the battery light comes on................

 

[SGTMack]

HISSIN50,

Thanks a lot for the quick response. Here's what I've got for you.

Did the battery light issue arise after the other gauge issues started?

Yes, the battery light issue started a few days after the gauges started flipping out. The first thing I noticed was the temp gauge. Then the battery light, accompanied by the misfires/dying and tach misreadings.

If not (it all started at once), I would think that perhaps the battery voltage might have something to do with your gauges. FWIW, the gauge has NOTHING to do with the engine management. There is the gauge sender (it is located behind the dizzy, with one wire on its lid) and there is the ECT (which does relate coolant temps to the computer, controls your fan, etc. It is on the heater tube on the pass side).

I checked the ECT sensor, and the PCM sender that attaches to it, (as per my Hayes manual) and both were working properly. I, also, had a brand new battery put in. And had it tested, along with my alternator, today. Tomorrow, I am going to take the car into a local electronics repair place ...the guys who sold me the battery (Les Schwab) refered me there, stating that they have better testing equipment and can test more stuff than the Les Schwab equipment handles.

Were it me, I would install a mechanical aftermarket temp gauge (even if just a parts store cheapo) to get a handle on what is going on with the temps. You can remove this gauge once other issues are fixed, or leave it installed.

Looked into it. But, I would have to disconnect the factory one in order to tap into the original sender. I may just take you up on that tomorrow...hopefully I'm not damaging the engine!

I might also install a voltmeter or put your DMM in the car where you can see the display (if you can safely do it, see what the DMM reads when things start to flip out).

I should hook the DMM up to the temp. sensor (the one that feeds the dash gauge)? That sounds like a good idea. However, I won't be able to read it until I stop. Although, I just bought the thing, and still have the option to take it back. Radio Shack, who sold me this one, has another one that records the readings and downloads them to your computer...it's about $30 more, but if you can tell me what to look for, I'd be willing to make the upgrade... (Hell, if you can solve my problem, I'll send it to you when I'm done!)

If you can get the battery light to start doing its thing, does it keep repeating?

Yes, it repeats whenever I push on the gas. I noticed that the battery light will come on, and the car dies (momentarily), ONLY when I am pushing on the gas. It used to only happen on the freeway, however, now it happens all the time. It's really annoying, especially when you're trying to get out of a standing stop (I have a M/T, and it's kinda hard to match revs/steadily accel. when your tach is going nuts, and the car keeps jerking/misfiring).

If so, with what frequency? I am trying to think of a way for you to be able to get components tested reliably (parts stores do free in-car and bench testing in most places).

Frequency: Every time I push the gas. It's been happening a lot lately, even when the car is cold. However, it only happens when the temp gauge is jumping. Sometimes, NOT lately , the temp gauge doesn't freak out....and, I don't have any misfires. Oh, those were the days. (I just bought the car a month ago, from a private seller...so, I may just be SOL [no lemon law for private sellers]. I pray everyday [please don't jinx me just yet..lol.]...I used my reenlistment money for it [gave up another 3 years of my life, but they will probably kick me out anyway...so....]...lol. And, since the military hasn't started giving me disability, I really have no income to spare...on a new car...lol. Ugh...help.)

Tomorrow, I am going to a local alternator/electrical repair shop. They have diagnostic tools which can [hopefully] diagnose my problem.

It can be worthwhile to look at the regulator wiring at the alternator. There are about 4 wires of small gauge at the alt, plus the power cable.

I checked the wires leading to the alternator...and the ignition and spark plug wires. They're all tight, and in good condition. Plus, the guy at Les Schwag, checked my alternator with a battery tester/AC thingy, and found no faults.

Another thing I would do is to clean the power distribution box connection (this is where your alternator hooks up to the underhood fuse box). More than a few of us have had issues with that connection getting corroded, etc and causing issues.

I checked the fuses in the "Power Distribution Box," and found that a few of them were missing. I don't have the owners manual...nor does my Hayes manual have any information on it...so, I don't know if they're supposed to be missing. I'm going to look them up as soon as I'm done typing this. However, if you have any information on them, I'd love to hear it...

Here's what I'm missing (3 fuses):

Circuit Breaker 7
Relay 1
Maxi 17

Take a look at your temp sender wire. Make sure it is tight and clean.

I'll check the temp sender tomorrow.

Do you think that this could be damaging my car (aside from the car possibly overheating without me knowing it)? If that's the case, I'll stop driving it...

Also, when it 'dies', do you think the ignition actually cuts out for a second and then the car somehow catches/restarts itself after the burp? This could be why the battery light comes on................

That's exactly what I think is happening. The car catches itself immediately after it "dies." It happens every 3-5 seconds [ONLY while the accelerator is depressed]. Yup, that's why/when the battery light comes on.

Thanks again for your help. I really appreciate you taking time out of your day to help me. I really, really appreciate it!!! I just wish there was something I can do for you. I'm a marketing guy! Need any marketing advice? I'm a computer technician too (Mac and PC). If you have any computer problems, feel free to send me an email. I can build you a [professional] website...

Sincerely,

Mak

PS. I had another guy (on another forum) tell me to check out the MAF sensor.... I will be looking into that tomorrow. Gotta check my Hayes and see if there's a testing procedure for it... I can understand how the MAF could be screwed up - the previous owner put on a new H-pipe (no cats) and cold air intake... That could throw the car's computer off so much that it kills a sensor or two...right?

Anyway, thanks again. Here's the short version:

UPDATE [2-2-06]: I checked the ECT sensor, and the ECT-PCM sender, and both were working properly. Also, I took it to Les Schwab's (a large Northwest tire and battery chain) today - they sold me the battery (which I obviously didn't need). However, they have excellent customer service...and, if you have any problems (with the part they sold you), you can go back and have them run circles around your car (they have to run everywhere...lol.)... Unfortunately, they won't take the battery back...lol.

Anyway, I had them check the alternator and battery. No Faults Found (military terminology). Urgh.

I did look in the "power distribution box" and found that a few fuses (3) were missing. Is that normal? I'm going to look it up [online] as soon as I finish writing this. My Hayes manual didn't have a diagram of the fuse layout, and I don't have the owner's manual, so I don't know if I'm actually missing something.

3 Missing Fuses:

Circuit Breaker 7
Relay 1
Maxi 17

 

[SGTMack]

MAF sensor?

Here's what other people have been suggesting:

i had a friend w/ a '95 and his gauges where going crazy and the car ran like crap and he said it turned out to be the maf was bad, he put a new one and it fixed it
__________________________________________________

"If you want to test the MAF then tap it lightly with a screw driver and if your car starts to act up then you know thats your problem. But check the fuses and cleanout/replace your sensors. I forgot the name of the switch that goes into the radiator but you may want to check that. As for the sputter it really could be your fuel filter, air filter, clogged injetors sparkplug wires or even a vacuum leak. Even if the wires look fine on the outside then can be messed up on the inside. Start with the vacuum leaks, spray propane around the engine bay and if you hear it rev up then you can pin point the line. Also if you hear a clicking then check your manifold bolts and all the exhaust bolts. Good luck."
__________________________________________________

i'm not all too sure what the fuses are for but concerning your comment on the OBD codes. you dont need a scanner to check your codes. you simply need a wire long enough to run from one corner of your engine bay to the other.

LINK DELETED

hopefully this helps!

 

[HISSIN50]

Hello Mak,
I remember Les Scwab - I grew up in Seattle and they were up there.

Before I forget, this link should help with the fuses (info courtesy of Bikewiz).

This is a lot to sift through already. Did I ask if the trouble codes have been retrieved already? You can have a local parts store do it (most do it gratis) or do it yourself (my choice). If you have a store retrieve the codes, tell them that you have an OBD-I mustang. The 94-95's were wired with OBD-I (for GT's) and OBD-II (for V6's). Some places wont believe you (that it is OBD-I).
Contrary to what is noted in some write ups, the self-test connector is on the passenger side rear-strut tower area. Here is some info on retrieving the codes, and your manual can help with that as well. There are 3 pages in the link, IIRC. We use 3 digit codes. Like I said, I prefer to do it myself.

See when this burp occurs, if it is TFI or PIP related, it might generate a code, and this will be very helpful in diagnostics. I agree that it sounds like an ignition burp and the car is shutting down for a split second. On a semi-related aside, I once had a very similar issue with a car (it was an old carbed roadster). It would cut out for a split second - sometimes it caught itself (like how you can open an electric clothes dryer door and close it real quick and the dryer turns back on automatically). Other times I had to restart it. Turned out I had a bad ignition connection at the ignition switch (there were two ignition connections providing key-on power, and one was bad - I was losing spark for a split second). I put a little light on the positive coil wire and wired it to the interior (grounding the other side of the light). When this burp occurred, my light would go out - that was how I tracked it down (I knew it was an ignition burp and went backwards). Silly tangenial anecdote.

Back to the ignition burp idea. The tach gets its signal from the ignition, so when a tach goes haywire, that is normally my first thought. But with all your gauges going haywire, I kinda wonder.

Most important sentence in this post and where I might even begin: Have you checked the TPS (throttle position sensor)? The fact that you say this happens when the throttle is pressed makes me want to explore this. A dead spot in the TPS CAN lead to a hiccup just like this! Here is some ubiquitous 5.0L info. Refer to your manual for what wire colors to hook your meter up to - you want to check them all (only 3 of them). Make sure you have 5.0 volts (+/- ~ 10%) on the VREF wire. Now for checking the TPS (it is a potentiometer of sorts), USE the supplied ground wire in the harness (some articles have you use a generic ground for your meter. The sensor uses its own ground, so I FEEL you should use that same ground for better testing (it is a more valid test that way). Look for around 1 volt with the throttle closed (dont fuss with resetting the TPS unless it is grossly off (like under .80 volts or over 1.2 volts). Now here is the hard part with a DMM. Slowly (I mean slowly) start opening the throttle, while watching your meter. The volts should rise linearly as you open the throttle (try to open it so slow that you see it rise by hundreths of volts - 1.31, 1.32, 1.33 volts, etc). Look hard for any dips or dead spots in the reading. Do this a few times if needed (I find it very hard to use a DMM - the old analog VOM is easier for this since I can see the needle fall). If you find a dip, I would do a little dance because you probably found the (or a large) issue. Now the TPS can be bad or the wiring, so make sure the wiring is sound, if an issue is found. New TPS's are pretty cheap too.

Oh, with the power distribution block: what I meant was to clean the connection on its side. You will see power cables (alternator, battery positive cable, etc) going to the side of the underhood fuse box. There is a little cap that slides up (you can actually remove said cap/lid). This exposes the nut that connects those cables (something like a 10 or 13 mm nut, IIRC). More than one stanger has had an issue with the car cutting out and cleaning this connection helped - esp up in the Pac NW, you know how corrosion is. It is worth spending 5 mins to remove each connection and cleaning each terminal and such. At the very least, break the bolt loose and squiggle the terminals around to break free possible corrosion, then retighten).

Ditto for battery connections, etc (I have stories about darned power connections and corrosion from up there).

That is what I can think of right now (I am way past tired). I will think some more, and maybe you can atleast get some codes and check the TPS. I have some great links from the wise folks on here, for troubleshooting given codes, as well as some decent personal knowledge for many of them.

Oh, the MAF. It would not be my first guess. Seems to me you can disconnect its wiring connection and the car will run in FMEM mode (safety mode). If the issue goes away while the connector is unplugged, I guess that could be an issue found.

A neat spark plug wire test is to spray the wires with a water bottle at night. If the wires are leaking, you will see blue pixie dust shooting around. DO BE VERY CAREFUL SINCE YOU WONT BE ABLE TO SEE MOVING ENGINE PARTS IN THE DARK).

Oh, about your DMM. I couldnt begin to tell you about that - I use a 3 dollar meter because I am poor. Other people can comment on which meter provides the best bang for the buck.

Best of luck Mak!

 

[94GTLaserRC]

WEll, without reading the 10,000 lines above...Sounds mainly electrical.. For about $40 you can get a batter charger at Walmart that also checks the alt. Make sure all the wires are coated and none are grounded anywhere, and that the wires are not bad

WELCOME to STANGNET!!!

RC

 

[SGTMack]

SOLUTION!!!!!!!!!!!!!!!!!!

I GOT IT!!!! I found the solution - totally by chance - on some obscure site, NOT dedicated to Mustangs, that wasn't even a "forum."... the link was buried between a bunch of other crap for Tempo's, Explorer's, Toyota's, etc....lol! Oh man, you know, I prayed to God last night....and, when I put in Black Sabbath this morning, all was well.... Well, almost all well. I did figure out the problem is purely electrical. I was on the freeway, the stuttering had stopped, and I was sure it wasn't going to happen again (the gauges were working fine). Then, when I turned on my blinker to pass a guy, the second the blinker connection hit, the problem started again...that clued me into the electrical problem. So, I took it into a local alternator repair place - the guy was a wiz with the voltmeter, and diagnosed it in a second.

SOLUTION:

What he did was take the charging measurement from the battery to see how many volts the bat. is getting from the alt. It looked small (3-something)...compared to the volts coming off the alt. (4-even)...so he ran a line from my battery's negative terminal post to the engine block. Every time he hooked up the jerry-rigged connection, the gauges stopped flipping out. Whew. So, as soon as I was done running around today, I added another (10-gauge) wire from the negative terminal (spade) to the chasis hookup (circle). The engine-to-chasis ground is still bad...but, that will have to wait till Monday. (The car works, though.) Only the Ford dealership can get me that part. It's a pretty funky cable, with a special connection that looks like it has a circuit breaker in it...it's close to the power distribution box...just follow the lead from the negative cable back to the power dist. box (fuse box) and it should be right there...

So, if you have a similar problem...I hear it's a pretty common one...here's the answer... It's the jank grounding cables Ford packaged with their cars....They NEED to be serviced every 50k. They don't tell you that.

Thanks again for all the help. I'll update when I complete the repair. I bet Ford charges me 200 bucks for the part!

Hold on HISSIN50....I've got something for you...

Thanks again to everyone... I really appreciate you taking time out of your day to help me.

 

[Chythar]

Damn! I should've read this post sooner, 'cause my guess was going to be a bad engine ground. I swear it was! Now I've lost out on MILLIONS....



Seriously, glad you found the problem. This board and its members are a wonderful resource of information. If it's happened on a Mustang, chances are this board knows how to fix it or knows someone who can.

 

[HISSIN50]

Great news - I am glad it was so simple!

If on the cheap, you can go to the parts store (Schucks, etc) and go to the battery cable section. Grab a 4 AWG or 2 AWG generic cable with ring terminals on each end. These make for nice ancillary motor grounds. I installed mine from the motor side of the passenger motor mount, to the frame near the ABS pump - there are a zillion places you can use. But ample (horrid excess) in terms of grounds never hurts.

In the future, you might wanna check your stock alternator charge cable. Mine was dropping 400 mV (.4 volts) from the alt to the distribution block. I simple ran a new bigger (4 AWG) cable in parallel to the stocker (add your own fuse protection) and disconnected the stock cable. With what you have done/are doing, and perhaps a little more, your primary power system should be in good order for some time.

Again, glad you got it and that it was relatively cheap (I know new battery cables from Ford are really expensive though - that is one reason I have not replaced mine yet. I am waiting for them to get bad before I hack up the stock battery terminal).

Now go enjoy and dont be a stranger - Chythar was right on about the members here.

Good luck with your injury!

 

[a_k]

thats awesome you figured it out. Mine over the summer was doing the same exact thing! Also turned out to be my engine to chassis ground..

 

[urban96]

after reading your first post i was going to suggest checking your alt/battery and all the connections, glad you have it figured out.

factory ford grounds are horrible

 

[94GTLaserRC]

So, if you have a similar problem...I hear it's a pretty common one...here's the answer... It's the jank grounding cables Ford packaged with their cars....They NEED to be serviced every 50k. They don't tell you that.
.

YES, I FINALLY nailed something
RC