QuestionQUESTION: I have a 1988 Mustang 5.0 GT w/manual trans and 273 rear ratio. I installed a brand new long block crate engine from Ford, everything from intake to oil pan and from harmonic dampener to flywheel new as well.I also installed a Cobra upgraded transmission. I tried to keep the engine stock as possible for reliability and gas mileage. It has a cobra intake and edelbrock 65mm throttle body. New MSD pro billet distributor, MSD blaster coil, Accel wires etc. You get the point. While driving down the road at cruising speed, if I push the throttle down a little bit it stumbles and misses for a second or so no matter what gear I'm in. It does not do it at wide open throttle though. Occasionally if I run it up to 5000rpm and shift, it will shoot a big flame out of the exhaust as I shift. I have checked and rechecked the time and it is set at 14 degrees BTC. I have changed it from 6 degrees up to 20 and the only difference I have seen is in performance. It performs best at 14 degrees. Also, if you look at the coil at night it looks like a blue flame is "going around" the body of it. I contacted MSD and one person told me it was normal, and another told me to put more grounds on the car...batt to frame, frame to engine, engine to body. Did all of that and didn't help. I tried a factory coil and all it did was make me lose performance. I changed TPS sensor, IAC, fuel octane,I've exhausted everything I know. I do have experience with autos, especially Fords and Chevys but this one has me stumped and the local Ford dealership don't have a clue either. Any suggestions? Thank you
ANSWER: First things first.... since it is an 88 please remember that it is not as friendly to upgrades as a mass air car would be... as far as the MSD coil and the cross arrcing... get ridf of the MSD coil... the msd blaster tfi is a junk coil... (I have tried 3 of them and know a lot of other people that used that coil and they all have voltage leak... (Cross firing)) Second... switch out the msd distributor to a stock one... in my opinion the best thing to do is get the car running good with oem parts than upgrade... (Building a car with a bunch of add ons it is harder to troubleshoot a problem with a bunch of aftermarket stuff installed...) and please remember that because it is new... does not mean that it is good... also... try resetting the dizzy... (bringing #1 to TDC and droppimng it in... it could be a tooth or 2 off... ) also make sure to check the voltage on the tps... (Voltage as close to .9 volts as possable with the throttle closed and the key on... ) try those things out and let me know what you come up with...
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QUESTION: I totally agree with you that the MSD coil is junk...this is MSD coil #2 with same results. Can you suggest a good one I should try? I have pulled the distributor out numerous times, pointed the rotor towards #1 and turned the oil pump shaft with a socket so that when I dropped the disrtibutor back down in it would go right in and not turn the rotor. How do you check the voltage n the TPS...do you do as the Chilton book says and pierce the wires with a volt meter. Tell me how YOU do it. Thanks for your help.
ANSWER: the easiest way to check it is to use a streight pin through the wire and check voltage through it. a good aftermarket coil in my opuinion is ine of the black oil filled mallery coils... (I have been running one for the last fiew years with no problems...) also... when pitting the dizzy in make sure that it is absolutly on TDC... (the timing pointer sitting at 0 degrees with bolth valves closed... ) I have had frienda say that it is on tdc and be off 10 degrees or so... that is a good thing to do by turning the oil pump with a socket... let me know what happens... Rob
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QUESTION: Which wire do I pierce with a straight pin to check the voltage on the TPS? I deal with Summit mostly, so what is the name and /or part# of the Mallory coil that you suggested? Thanks for your help with this and my other migraine.
Answerthe tps is the dark green wire... the value should be less than one volt at idle KOEO... here is a chart with all of the KOEO values (Key on engine off)
Pin # Wire Color Connections for a 88-93 5.0L HO Mustang Value at Idle
01 YEL +12 Battery Voltage 12-14 volts
03 DG/WHT VSS + / Vehicle Speed Sensor Positive 55MPH = 125hz
04 DG/Y IDM / Ignition Diagnostic Monitor (TFI) 20-31hz
06 ORG/YEL VSS - / Vehicle Speed Sensor Negitive 55MPH = 125hz
07 LG/RED ECT / Engine Coolant Temp Sensor 0.5 volts = 200*F
09 TAN/BLU MAF RTN / Mass Air Flow Return < 0.1volts
12 BRN/YEL Fuel Injector 3 4.9-5.2ms duty cycle
13 BRN/BLU Fuel Injector 4 4.9-5.2ms duty cycle
14 TAN/ORG Fuel Injector 5 4.9-5.2ms duty cycle
15 LG/ORG Fuel Injector 6 4.9-5.2ms duty cycle
16 BLK/ORG Ignition Ground (TFI) -
17 TAN MIL / Engine Light & STO / Self-Test Output ON = GND
19 DG/YEL FPM / Fuel Pump Monitor Pump on = 12-14volts
20 BLK Ground < 0.1volts
21 WHT/BLU IAB / Idle Air Bypass 3.0 - 12.0 volts
22 BLU/ORG FPR / Fuel Pump Relay ON = GND
25 GRAY ACT / Air Charge Temp Sensor 3 volts = 70*F
26 ORG/WHT Voltage Reference 4.9-5.1 volts
29 DK GRN Right HEGO 0.0-1.0 volts
30 BLU/YEL Transmission Neutral Interface 0.0 volts in neutral
36 YEL/LGRN SPOUT / Spark Output Signal (TFI) -
37 RED EEC Relay +12 volts 12-14 volts
40 BLK Ground < 0.1 volt
42 TAN/RED Fuel Injector 7 4.9-5.2ms duty cycle
43 DK BLU Left HEGO 0.0-1.0 volts
45 GRN/BLK BP / Barometric Pressure Sensor 159hz = sea level
46 GRY/RED Signal Return 0.1 volts
47 DK GRN TPS / Throttle Position Sensor 0.9 volts
48 TAN/RED STI / Self-Test Input GND = Self-Test
49 ORG Ground < 0.1 volt
50 BLU/RED MAF / Mass Air Flow Sensor 0.8 volts
52 LT BLU Fuel Injector 8 4.9-5.2ms duty cycle
56 DK BLU PIP / Profile Ignition Pickup (TFI) -
57 RED EEC Relay +12 volts 12-14 volts
58 TAN/RED Fuel Injector 1 4.9-5.2ms duty cycle
59 TAN/ORG Fuel Injector 2 4.9-5.2ms duty cycle
60 BLK Ground < 0.1volt
Hope this helps
