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!
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  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.
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  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.
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  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
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  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)
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  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?
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  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
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  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.
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  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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