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1987 Convertible - Poor Performance

 
Old 05-09-2019, 02:42 PM
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Jveino
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Default 1987 Convertible - Poor Performance

My first post, so apologies for redundancy with other threads. I wanted to share the symptoms and fix for what was VERY poor engine performance with my 87 auto trans. The symptoms were sluggish acceleration, would not shift to 3rd under acceleration while engine topped out at approx. 2,400 RPM's, at times under acceleration and in 2nd gear when RPM approached approx. 2,400 RPM I experienced a sound similar to shaking a beer can with a couple of nuts/bolts inside it. Also, and I know C4's run hot, mine ran very hot.
The experienced owners know that I had a clogged catalytic converter. I replaced the stock exhaust with a Flowmaster solution. I used their part #2020028 front Y, which eliminated the pre-cats and a their part #17153 cat back with D50 mufflers. I know I could have eliminated the cat altogether as I live in FL, but the mechanic felt that we may be reducing back pressure too much.
The car now runs GREAT, as it now has "push you back in the seat" acceleration and will keep going till you let up on the pedal. Also, the shifting is now much more smooth in all gears and the car does not run as hot as it previously did. The bonus is that I love the Flowmaster sound. The D50's are not too loud and do not resonate in the cabin, but still sound very throaty.
Hope this helps someone wrestling with the same issues as me.
JV
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Old 05-11-2019, 01:04 PM
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Y-bodluvr
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Originally Posted by Jveino View Post
eliminated the cat altogether as I live in FL, but the mechanic felt that we may be reducing back pressure too much
Not so and take in mind the catalytic Converter is 32 years old with xxxxxxx miles on it at this point I would either replace with a high flow, put a test pipe in place or hollow it out which is the cheapest route but you will get some drone especially with the Flowmasters if you delete or hollow it out...

Last edited by Y-bodluvr; 05-11-2019 at 01:06 PM.
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Old 05-11-2019, 05:48 PM
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cuisinartvette
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yup if that hot exh cant get out somethings going to bake.
Delta Flow 50s arent bad....theres a FM system made forthe C4 its pretty quiet
The DF sound great at WOT. Not a fan anymore but they did sound good on an 89 I had.
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Old 05-12-2019, 08:11 AM
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Thanks for the reply - The Flowmaster front Y included a high flow Cat so I went with a new one instead of hollowing out the old one. Love the sound. The only thing I don’t like are the plain tips on the muffler. Looking for a solution to that.
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Old 05-12-2019, 08:14 AM
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You didn't mention how many miles on the car or if all other maintenance is up to date. Post a few pics, too!
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Old 05-13-2019, 09:30 AM
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The car has 46,800 miles and maintenance is up to date. The AC has been changed over to the new Freon and as far as I can tell from the old service records (I am the 4th owner) the worst it has encountered is a number of bad alternators.
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Old 05-13-2019, 11:20 AM
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Originally Posted by Jveino View Post
Thanks for the reply - The Flowmaster front Y included a high flow Cat
I see didnít see that in your post it sounded like your mechanic was telling you to keep the original cat on and just eliminate the pre cats 46k miles is pretty low for cats to clog but as youíve found out itís not just miles itís age also

my 89 has only 27k on it but I will be getting a front y without pre cats and deleting the main very soon as Iíve just given it a complete tune up and thatís next on my list
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Old 05-13-2019, 12:07 PM
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One issue, at least with the 87 - don't know about the 89, is that there is an AIR system that pumps air to the main cat while the car is warming up. So if I eliminated the main cat, then I either had to eliminate the AIR pump and it's associated plumbing and wiring OR figure out a way to deal with the air line going to the cat. I assumed that I couldn't just plug it off. The new cat was cheaper that dealing with all the other issues.
Also, I can't say enough about how much cooler the car runs with the new set up.
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