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Followup To
Question -
I have a 1990 Mustang GT 5.0 HO 90,000 miles, that dies and surges at start up util it reaches close to 150 degrees. Then, until 180 degrees when I drive it, the engine sputters and has intake back firing at lower RPMS. After it reaches 180 degrees it 99% of the time runs perfect.
No check engine lights or codes from the ECU. I replaced the IAC, fuel pump, fuel filters, replaced the stock computer and MAF with Ford Racing product (ran the same with the stock ECU as well), BPS sensor, replaced stock headers w/ performance shorty headers, no cat converters, Flowmaster mufflers replaced O2 sensors, and have reset the computer many times during upgrades. I am not sure if there is a CAM upgrade or not and there is no hissing (vaccum leak).
Thank you for your time,
Don Carter
Answer -
Have you checked the timing? Is the base timing 10 degrees with the SPOUT disconnected? If you watch the timing with a timing light while it is acting up does the timing jump around erratically? Are any plug wires arcing?
I can't explain the temperature difference affecting this. Most times anything that would cause this would be worse with the higher temps. My first thoughts are to the ignition module and stator. Are they old or aftermarket? Most aftermarket, cheap brands can cause all sorts of problems because they don't last long.
Have you checked the fuel pressure hot and cold? Inspect the distributor cap for cross arcing between the terminals inside the cap. I'll think on this some more and see if anything comes to mind.
You have another question, Don?
I will try checking the timing. I know in the past I tried timing it with the SPOUT still connected.
None of the plug wires are arching, and no cross-arching between terminals in the cap. The ignition module is stock. The coil is aftermarket(bought it from shucks) could this be an issue? I also replaced and set the TPS to .99v.
At start up the trend is that it boggs down and dies 3 times, then the RPMs will surge at a slow rate between 1,000 and 500 until the temp starts to climb. Then the surging slowly will stop and it idles at 750RPM. When I drive it from this point it will sputter slightly and pop (intake backfire) between 1000 and 3000 RPM only for a short distance. Then it will surge a burst of power all of a sudden and run great.
Thanks for you advice,
Don Carter
AnswerI'm hoping that you meant the TPS is at .99V, in fact I don't think any of them will reach 99V:)!
Your base timing MUST be set with the spout disconnected or you will have too little advance and the PCM will not be able to control the timing correctly. 2 or 3 degrees retarded is usually not a problem, but setting it with the spout connected will retard base timing at least ten degrees.
You might want to look at fuel pressure just to rule that out.
