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I have a 2001 3.8 Mustang with about 113,000 miles. Bought the vehicle, replaced the fuel pump & battery, and it started right up. From that day, there is definitely something wrong. It idles pretty good, but when you get to around 1300-1800 rpm, you can feel vibration, almost like a slight misfire. No codes, other than the ABS light being on (pretty sure module is toast, can’t connect to it with my scan tool). I initially though it was a clutch issue, as when you were accelerating from a stop, there would be hesitation, almost like a slip for a little while, along with if you were to WOT from around 2-3K, you would feel a slight hesitation, like a slip, and then take off. So I replaced the clutch/pressure plate/pilot bearing/throwout bearing/flywheel, was original clutch, and when I had it apart, the throwout bearing was toast, so it needed to be done. After that, clutch worked better, but still had that hesitation.
This hesitation is mainly noticed under load, going up a 6% grade, I can hear, what almost sounds like an exhaust leak, WOT accelerating up the grade. When under low load, can’t hear it.
I have new plugs i’m putting in, again, original plugs, so 100K is Ford’s recommended replacement window, so replacing them now, but I have a very good feeling that is not the issue, but I will find out soon enough. Also replaced the air filter, but again, just because it was scheduled to be replaced anyway.
No codes, looked at mode $06 data on my scan tool, and saw it had some misfire data recorded on #4, but was not increasing, and after I cleared the ECU, it did not add any more misfire data on any cyl’s after a quick drive, so that’s not much help.
I looked at o2 sensor data on my scan tool, looked good. Both upstream sensors were fluctuating with the short term fuel trim.
I have to say I am by no means an expert on using the scan tool, so some data I may be interpreting as good might be bad. I would be happy to get any readings of PID’s you want.
Thanks all, let me know if you have any questions.
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here is a link to help you.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
I have read that. Definitely some things to look into. I did change all the spark plugs with OEM Motorcraft, seems to help a bit on startup, but the main issue is still there. I did some more work with my scan tool, and found some interesting results. When looking at FORD.ENGINE.INJ(x)_f, that monitors the injector circuit for faults, I did notice on injector 1, a very rapid switch from fault to no-fault. I have attached the data, and will try to paste it here to see how it looks.
I only posted 2 of the cyl, normal reading and abnormal reading, 4 seems normal, 1 seems odd. I suppose the next order of business is to switch injector 1 and injector 2, and see if the problem moves. Again, no code, but just my findings with the scan tool.
Frame Number FORD.ENGINE.INJ4_F FORD.ENGINE.INJ1_F Frame Number Injector #4 fault (open/short) Injector #1 fault (open/short) Frame Number INJ4_F INJ1_F Frame Number Frame Number INJ4_F INJ1_F 0 No Fault No Fault 1 No Fault No Fault 2 No Fault No Fault 3 No Fault No Fault 4 No Fault No Fault 5 No Fault No Fault 6 No Fault No Fault 7 No Fault No Fault 8 No Fault Fault 9 No Fault No Fault 10 No Fault No Fault 11 No Fault No Fault 12 No Fault No Fault 13 No Fault Fault 14 No Fault No Fault 15 No Fault Fault 16 No Fault No Fault 17 No Fault No Fault 18 No Fault No Fault 19 No Fault No Fault 20 No Fault Fault 21 No Fault No Fault 22 No Fault No Fault 23 No Fault No Fault 24 No Fault No Fault 25 No Fault Fault 26 No Fault No Fault 27 No Fault No Fault 28 No Fault No Fault 29 No Fault No Fault 30 No Fault No Fault 31 No Fault No Fault 32 No Fault No Fault 33 No Fault No Fault 34 No Fault No Fault 35 No Fault No Fault 36 No Fault No Fault 37 No Fault Fault 38 No Fault No Fault 39 No Fault No Fault 40 No Fault No Fault 41 No Fault No Fault 42 No Fault No Fault 43 No Fault No Fault 44 No Fault No Fault 45 No Fault No Fault 46 No Fault No Fault 47 No Fault No Fault 48 No Fault No Fault 49 No Fault No Fault 50 No Fault No Fault 51 No Fault Fault 52 No Fault No Fault 53 No Fault No Fault 54 No Fault No Fault 55 No Fault Fault 56 No Fault No Fault 57 No Fault No Fault 58 No Fault No Fault 59 No Fault No Fault 60 No Fault No Fault 61 No Fault No Fault 62 No Fault Fault 63 No Fault No Fault 64 No Fault No Fault 65 No Fault No Fault 66 No Fault No Fault 67 No Fault Fault 68 No Fault No Fault 69 No Fault No Fault 70 No Fault No Fault 71 No Fault Fault 72 No Fault Fault 73 No Fault No Fault 74 No Fault No Fault 75 No Fault No Fault 76 No Fault Fault 77 No Fault No Fault 78 No Fault No Fault 79 No Fault No Fault 80 No Fault No Fault 81 No Fault No Fault 82 No Fault No Fault 83 No Fault No Fault 84 No Fault No Fault 85 No Fault No Fault 86 No Fault No Fault 87 No Fault Fault 88 No Fault No Fault 89 No Fault No Fault 90 No Fault No Fault 91 No Fault No Fault 92 No Fault Fault 93 No Fault No Fault 94 No Fault No Fault 95 No Fault No Fault 96 No Fault No Fault 97 No Fault No Fault 98 No Fault No Fault 99 No Fault No Fault 100 No Fault Fault 101 No Fault No Fault 102 No Fault No Fault 103 No Fault No Fault 104 No Fault No Fault 105 No Fault No Fault 106 No Fault No Fault 107 No Fault No Fault 108 No Fault Fault 109 No Fault No Fault 110 No Fault No Fault 111 No Fault No Fault 112 No Fault No Fault 113 No Fault Fault 114 No Fault No Fault 115 No Fault No Fault 116 No Fault No Fault 117 No Fault No Fault 118 No Fault Fault 119 No Fault No Fault 120 No Fault No Fault 121 No Fault No Fault 122 No Fault No Fault 123 No Fault Fault 124 No Fault No Fault 125 No Fault No Fault 126 No Fault No Fault 127 No Fault Fault 128 No Fault No Fault 129 No Fault No Fault 130 No Fault Fault 131 No Fault No Fault 132 No Fault No Fault 133 No Fault No Fault 134 No Fault No Fault 135 No Fault No Fault 136 No Fault No Fault 137 No Fault No Fault 138 No Fault No Fault 139 No Fault Fault 140 No Fault No Fault 141 No Fault No Fault 142 No Fault No Fault 143 No Fault No Fault 144 No Fault No Fault 145 No Fault No Fault 146 No Fault No Fault 147 No Fault No Fault 148 No Fault No Fault 149 No Fault Fault 150 No Fault No Fault 151 No Fault No Fault 152 No Fault No Fault 153 No Fault No Fault 154 No Fault Fault 155 No Fault No Fault 156 No Fault No Fault 157 No Fault No Fault 158 No Fault No Fault 159 No Fault No Fault 160 No Fault No Fault 161 No Fault No Fault 162 No Fault No Fault 163 No Fault No Fault 164 No Fault No Fault 165 No Fault No Fault 166 No Fault No Fault 167 No Fault No Fault 168 No Fault Fault 169 No Fault No Fault 170 No Fault No Fault 171 No Fault No Fault 172 No Fault No Fault 173 No Fault Fault 174 No Fault No Fault 175 No Fault No Fault 176 No Fault No Fault 177 No Fault No Fault 178 No Fault Fault 179 No Fault No Fault 180 No Fault No Fault 181 No Fault No Fault 182 No Fault No Fault 183 No Fault Fault 184 No Fault No Fault 185 No Fault No Fault 186 No Fault No Fault 187 No Fault No Fault 188 No Fault No Fault 189 No Fault No Fault 190 No Fault No Fault 191 No Fault No Fault 192 No Fault No Fault 193 No Fault No Fault 194 No Fault No Fault 195 No Fault No Fault 196 No Fault No Fault 197 No Fault No Fault 198 No Fault No Fault 199 No Fault No Fault 200 No Fault No Fault 201 No Fault No Fault 202 No Fault No Fault 203 No Fault Fault 204 No Fault No Fault 205 No Fault No Fault 206 No Fault No Fault 207 No Fault No Fault 208 No Fault Fault 209 No Fault No Fault 210 No Fault No Fault 211 No Fault No Fault 212 No Fault Fault 213 No Fault No Fault 214 No Fault No Fault 215 No Fault No Fault 216 No Fault No Fault 217 No Fault No Fault 218 No Fault No Fault 219 No Fault No Fault 220 No Fault No Fault 221 No Fault No Fault 222 No Fault No Fault 223 No Fault No Fault 224 No Fault Fault 225 No Fault No Fault 226 No Fault No Fault 227 No Fault No Fault 228 No Fault No Fault 229 No Fault No Fault 230 No Fault No Fault 231 No Fault No Fault 232 No Fault No Fault 233 No Fault No Fault 234 No Fault No Fault 235 No Fault No Fault 236 No Fault Fault 237 No Fault No Fault 238 No Fault No Fault 239 No Fault No Fault 240 No Fault Fault 241 No Fault No Fault 242 No Fault No Fault 243 No Fault No Fault 244 No Fault No Fault 245 No Fault Fault 246 No Fault No Fault 247 No Fault No Fault 248 No Fault No Fault 249 No Fault No Fault 250 No Fault Fault 251 No Fault No Fault 252 No Fault No Fault 253 No Fault No Fault 254 No Fault No Fault 255 No Fault No Fault 256 No Fault No Fault 257 No Fault Fault 258 No Fault No Fault 259 No Fault No Fault 260 No Fault No Fault 261 No Fault No Fault 262 No Fault No Fault 263 No Fault No Fault 264 No Fault No Fault 265 No Fault Fault 266 No Fault No Fault 267 No Fault No Fault 268 No Fault No Fault 269 No Fault Fault 270 No Fault No Fault 271 No Fault No Fault 272 No Fault No Fault 273 No Fault Fault 274 No Fault No Fault I have a 1997 model of the 3.8 L with 105,000 miles on her. Overall, my engine runs pretty smoothly but it does have some gimmicky shudders now and then. It’s an old beater, I don’t mind it too much.
Here is my anecdote:
One thing that threw me off for a quite while though has been a mysterious vacuum leak. It’s only just audible under the right conditions and only enough to throw the fuel trims off a bit. Then, just recently I think I have discovered the source…the lower intake manifold gasket because in the cold weather this year it decided to noticeably leak coolant.
I suspect the lean condition caused by the vacuum leak is causing a slight knock in one/some of the cylinders. My engine runs smoother on high octane than regular gas which gives some support to this theory (though this could be for other reasons as well).
A faulty fuel injector certainly could cause a mis-fire as well as your data suggest. Switching the injectors seems like a reasonable test. Though you may want to also check for a vacuum leak, it should be a quick and easy test.
Hello Silveram, thanks for your input.
I do have a slight lean condition, mainly on bank 2, drivers side. I have around a 13% long term fuel trim at idle, that drops at RPM raise. I know I have an exhaust leak on that bank, I believe to be in the exhaust manifold. I have yet to get under and verify 100%, but I am pretty darn sure. I need to fix that before I can go after any other issue. I have a feeling my scantool is giving me false data on injector 1, and that there is no open or short in that injector wiring or computer driver, but it could be, have to get another, better scan tool to verify.
Once I fix the exhaust leak on bank 1, and replace the small grommet that the PCV hose connects to that is a bit loose on drivers side valve cover, I will be able to further diagnose the issue.
I don’t see how higher octane fuel would help if you have a lean condition.
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