Exhaust Cats Are Great, But Not Converters

Discussion in '1994 - 1995 Specific Tech' started by joetrainer31, Jul 15, 2013.


  1. joetrainer31

    joetrainer31 Member

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    Hello Brainiacs! I am almost done restoring my 95 GT. Today I ran a heat test on my Mustang's converters (live in CA gotta have them). I drove the vehicle for 5-6 miles in city conditions, came home, and immediately tested the heat before & aft the converters at idle. I suspect that a couple of my converters are bad/going bad. Below are the temperature numbers & some commentary. What do you all think?

    Drv Side Front (in = 369/out = 374) [seems normal]
    Pass Side Front (in =373/out = 362) [slightly concerned about the higher input temp]

    Drv Side Rear (in = 223/out = 170) [I suspect this one isn't even lighting off & the out seems to low]
    Pass Side Rear (in = 350/out = 306) [again, number out seems too low, & big diff from Drv Side]

    Does anyone have some insight into these results? Thanks guys!
  2. Bullitt347

    Bullitt347 man bewbs please...

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    Would like to see the numbers after a cruise at highway speed, or hold the engine at 2,500 rpm in park/neutral for 3 min and then test. The cats should be over 500 degrees if they are working.
  3. joetrainer31

    joetrainer31 Member

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    I'll give it a shot and report back. Also, I'm not sure if this is related to the numbers, but I also pulled code 311 & 314. These are new codes.
  4. joetrainer31

    joetrainer31 Member

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    Okay, I ran the car in neutral for 3 minutes at 2,500rpm & took temp readings after the initial 3 minutes with the engine still running at 2,500rpm. Below are the results:

    Drv Side Front: in = 367/out = 590
    Pass Side Frnt: in = 435/out = 545

    Drv Side Rear: in = 370/out = 359
    Pass Side Rear:in =479/out = 321
  5. Bullitt347

    Bullitt347 man bewbs please...

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    The front look normal, the rear are going to run a bit cooler as they are further downstream and there is less HC to burn off. The codes 311 and 314 refer to the secondary air injection system inop on bank 1 and bank 2. Basically it is saying that the smog pump is not injecting air downstream into the catalytic converters so that they can light off the HC better. (HC= hydrocarbons= unburned fuel)
  6. joetrainer31

    joetrainer31 Member

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    Okay. Front two look good. Thank you. I fixed the code issues. I forgot to secure the vac lines that are involved with the smog system and one of them (red one) say against the egr flow tube. Obviously it got melted so i spliced it to repair.

    Next, one of the rubber butt connectors was old and weak. It was popping off its connection, so I replaced it with a new connector.

    As far as the rear cats I'm suspicious. Especially since the inlet temp on the driver side is higher than the outlet. What do you think?
  7. joetrainer31

    joetrainer31 Member

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    Thanks again for your input Bullitt347. Thought I'd let you know about the resolution. Once I addressed the 311 & 314 codes, the cats were re-tested and they posted perfect numbers. Apparently, since there was a vac issue w/the codes the car was running too rich therefore the cats were reflecting that condition through their heat numbers. I took the car to a shop and had them test the cats. They said that there is nothing wrong with them and that they could not recommend replacing them. I trust that since they could have made money off of me.

    Thanks again Bullett347
  8. Bullitt347

    Bullitt347 man bewbs please...

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    Good to know you found a fix for the concern, and that it was not costly.
  9. joetrainer31

    joetrainer31 Member

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    Very true. It only cost me $13 in splices and butt connectors (I bought extras).

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