87 Mustang with a miss when it warms up

[twfs]

I have a 87 lx 5.0 5 speed with gt40p heads and tfs stage 1 cam maf conversion. Got the thing together and ran great. I was letting sit there and idle for a while and noticed that the idle dropped down and started loading up and wanting to die. Gave it some gas and went and ripped it a little and it was cutting out. Shut it off and let it cool down all the way runs fine no miss but as soon as it starts warming up to operating tempature it starts missing again. It is kind of a random miss not a even one like plug wire on a header or anything like that. If you hold it at steady speed driving you can't even notice it but when you get back on the gas it is definitely there bad. Did a koer test and it gave me a 91 left side 02 sensor changed it and clened the plug to it and it is gone but still have the problem. The car had ran fine for about a month and then I sit there and let it idle there for a while and now I have this problem. Puzzles me to death the idle doesn't realy surge or anything spout connecter is in and checked the timing with my light got it set at 12 with spout out put it in back in to make sure the puter was changing it and it was up to about 17 at a idle. I do have slight vaccum leak that i think is coming from the plenum gasket or in that vacinity ordered a new 1 today. Any ideas guys Im kind of lost if the vacum leak doesn't fix it. Thanks

 

[liljoe07]

91 the ONLY code you got?

 

[twfs]

sometimes a 33 and a 44

 

[liljoe07]

Fix the vacuum leak first.

 

[jrichker]

The TFI module mounted on the distributor is usually the culprit for a high speed miss on a warm engine. If the problem does not occur when the engine is cold, the TFI module is definitely suspect. You may need a special socket to remove the TFI module, but most auto parts stores will have one for $5-$7.

Be sure to use plenty of the heat sink grease on the new TFI and clean the old grease off the distributor.

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See Automotive Tools Specialty | Auto Mechanic & Technician Diagnostic, Testing Equipment | Thexton

Many auto parts stores will test your TFI module for free. Bring along a hair dryer to get it hot while testing it and run several test cycles, since it often gets weak when it heats up. The test tends to spot some TFI modules while others sneak by and still cause problems.

 

[lincoln+ford]

Do what he said with the hair dryer or when you drive there in another vehicle leave it on the heat vent for a min or 2.