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Ignition Problems???

JTGF88MUSTANG

New Member
I have a 1988 Mustang LX with the 5.0L engine, AOD transmission. It is mostly stock with no real modifications, I am the original owner. I have been trying to figure out a problem that has me stumped. I do not like to buy parts and just throw parts at it trying to fix a problem. I parked the car back in the summer and it was running good when I parked it and it cranked easily when I would crank it and move it. Then one day I went out to move it and it cranked but did not want to idle unless I kept patting the gas. A few days later the thing would not start at all. I checked the fuel pressure and have 39 psi on the fuel rail. I checked the coil and I did not see any spark at the coil. On the primary side of the coil I had good voltage reading and a good signal, but my spark tester did not show any spark. The coil reads good with a multi-meter, and with a test light, but still no spark on the secondary. I went out there today after just letting it sit for about a month and I still was not getting any spark with my spake tester, so I tried to see if I had spark using a test light with a gap between it and the secondary connection of the coil and I got some spark, but it was not much. I put the coil wire back on the coil and the engine started but the idle was rough. I know that 15 or so years ago I had the distributor replaced because the pick up on it was bad and that may be what is causing the problems now. Has anyone ran into this kind of problem or know what to try, short of buying parts and hoping to get the right thing fixed? Any information is greatly appreciated.
 

broncojunkie

Well-Known Member
There's a couple things you can check that won't cost you anything. Pull the tfi module and take it to one of the parts stores. They can put it on their machine and bench test it. Have them run the test a few times.

Second, pull your ecm and open it up. Look for capacitors that have leaked and corroded away from the board. I believe there are 3 total. They'll be obvious upon close inspection. If you're good with a soldering iron, you can replace the capacitors yourself. Or there are guys that do it for a fair price. You just have to ask around. You can try and match the capacitors individually or I've got them as a kit on ebay specifically for our cars.
 

347HO

Active Member
If the car is parked outside... Check all accessible wire bundles first mouse chewing.

Another issue is low voltage.
During cranking, if your voltage drops to 10.5 vdc, the current ramps up and weakens or destroys circuits in the ecu, and ignition.
You'll have to visually check circuits.

Good luck.
 

JTGF88MUSTANG

New Member
Thank you both, broncojunkie and 347HO, for the information. I have a new tfi module I purchased years ago and that I did not need, the coil in the distributor was my problem then. I have heard people say that they have gotten new tfi modules that were bad out f the box, I am getting the pulsing signal to the coil from the tfi module. I remember not long after I bought the new tfi module, I did find out that some of the local auto parts store could check them and I had my original checked then and it was good. I have called around and I have not been able to find any stores that still are able to test them.

I have thought about the ecm, but I have been hesitant about pulling that out because I was thinking that if the coil was getting the signal to fire that the ecm was doing what it is supposed to do. I guess that I will pull it and see what it looks like. I do not think that I would have a problem with soldering, I have had a lot of experience there. You mentioned ebay having a kit with the capacitors in it, do you remember exactly what you searched for when ordering the kit?

The car is parked outside and I checked all the wiring when I first started having a problem and everything looked good. I cannot say that my battery has not had a low charge at some point when I have been working with it, but I try to keep it charged up. I will take a closer look at the wiring and also check the ecm and go from there.

I really appreciate both of your suggestions and I will check them out. I love my old Mustang and need to get her back on the road again.
 

broncojunkie

Well-Known Member
I just realized your car is an 88. That was an odd year. If it was a California car, it would have been mass airflow. If not, it's speed density. I've never repaired a non-maf ecm. I presumed they would be similar, but I'm not really sure. A replacement speed density ecm should be cheap and easy to find. In fact, I'm pretty sure I have one. They're not worth a whole lot because most folks do a maf swap.Screenshot_20211206-205440_Gallery.jpg
 
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JTGF88MUSTANG

New Member
It is not a California car, I bought it brand new in Birmingham, Alabama. I do not know if it has a mass air flow sensor or not. Are you saying that if it is not a California car that it does have a mass air flow on it, if so what would you suggest then? Thanks again for the information and the help.
 

broncojunkie

Well-Known Member
California cars went to maf in 1988. All others switched to maf in 89. If you are in need of repairing your non-maf ecm, then I can't help you as far as the repair. If they have capacitors like the maf units, then the fix is going to be the same. If not, you should probably just find a good used one. I found my old one. If you think you need it, let me know and you can have it for whatever shipping costs. If you don't need it, I'll just hold onto it in case I need it in the future.
 

broncojunkie

Well-Known Member
I just re-read my last post. I think I made that sound more confusing than necessary lol! I apologize. Let me know if it doesn't make sense. Basically, let me know if you need a replacement ecm.
 

Blueknights75

Active Member
If it was converted to mass air you will have an electrical module attached to your air tube going from your air box to your throttle body. As a side not because I went through hell with my 87 Speed Density and electrical parts such as TPS sensors, only use Motorcraft parts. Between Autozone and Advanced Auto you can still find pretty much everything Motorcraft. FoxResto in Locust, NC rebuild the ECMs and rebuilds the distributors if OEM with new PiP sensor. Just an fyi….keep us updated!!!
 

JTGF88MUSTANG

New Member
I really appreciate that broncojunkie, I am going to get out there and take a look at my ecm as soon as the weather permits. From what Blueknights75 has told me I don't think I have any wires going from the air box the throttle body. The only wire going to my throttle body is the throttle position sensor that comes to my mind without looking at it.

Blueknights75 I agree sticking with Motorcraft parts is best. I know for sure that my car has not been converted to anything, I have owner the car since it came off the dealers showroom. I appreciate the info you have given me about the place that rebuilds the ecms and distributors and your letting me know how to tell if my car is a mass air flow setup.
 

JTGF88MUSTANG

New Member
I have been unable to do anything with my Mustang in a while. Every time I am planning on doing something to it something else has come up or it has been raining. I did have time to check and it does not have a maf sensor, it has the map sensor located on the firewall. I also tried and it does not start at all, the last time I looked at it, it would start but did not idle, now it is back to not starting. I am going to try to test the maf sensor and look at the ecm and go from there. If anyone else has any other suggestions I will be glad to get them. Thanks for the help so far and I am sorry for not getting back to those who have given me suggestions sooner. I am hoping to get to get back to my car in the next couple of weeks if not sooner.
 
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