Problem with Thermactor system?

JChalfan · Dec 19, 2006

Ok, first off I'm still running the stock catted h-pipe w/ flowmaster catback, and all smog equipment is hooked up. I've pulled codes, and I get an EGR code I've known about for a while, but I don't remember the exact number. I could figure it out if it's relevant. I don't have any thermactor system codes.

So this is really more annoying than a problem...

When I'm coasting down hill in gear, everything sounds normal at first. Then after about 10 seconds or so, all the sudden the exhaust gets really loud (lots of popping through the pipes). If I give it gas for a moment and let back off, it is quiet again, but then after another 10 seconds or so it gets loud again.

When it gets loud, it's instantanous, like a valve opened. I'm suspecting some part of the Thermactor system is pumping air from the smog pump into the exhaust when it's not supposed to.

I've found some posts on here describing the basic operation of the Thermactor system, but I didn't find anything indicating when and under what conditions the system opens the solenoids. I did read that it pumps air into the heads when the car is cold, and into the cats when it's warm.

Any suggestions? This isn't really causing any drivability problems, it just annoys the heck out of me. I usually just push in the clutch when coasting downhill to avoid this, but I would like to fix it if possible.

Thanks.

Jeff

jrichker · Dec 19, 2006

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on. The Thermactor codes if present, will help troubleshoot your problem.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829 – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $35.

JChalfan · Dec 19, 2006

No thermactor codes, just 67, 31, and 24. The 67 and 31 have been around for a while, I know I need to replace my EGR. This was the first time I have seen the 24, which I think is the air temp. sensor. I'm not going to worry about the 24 unless it pops up again, since I've never seen it before.

Thanks.

Jeff

HISSIN50 · Dec 19, 2006

Jrichker is a lot smarter than I am, but the AIR system would not be first on my list.
An EGR issue is a little more likely IMHO. Even an IAT/ACT can cause a bit of richness (which might only really show it's head during closed throttle decel). If that line of thinkin sounds decent to JR, he might post a list of the ACT-values-per-temp that you should see (so you can see how far out of calibration the ACT is or isn't).

Good luck Jeff.

jrichker · Dec 19, 2006

The 67 code will prevent you from doing the engine running tests.
Right now, I would want to know that there weren't any engine
running codes before I started spending time checking all the
thermactor wiring & plumbing.

ode 67 - clutch not depressed (5 speed) or car not in neutral or park
(auto) or A/C in On position when codes where dumped. Possible
neutral safety switch or wiring problem. This code may prevent you
from running the Key On Engine On tests. You can generally ignore
this code, since it has no effect on engine performance.

Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

dragnazz5.0 · Dec 19, 2006

do what jrichker said but im leaning towards the diverter valve. it could be sending air into the back of the heads all the time which is causing a backfire with the extremely hot exhaust gases which is from the egr not functioning properly. dumping the air into the heads is also giving the o2 sensors a false lean signal which the computer is taking and dumping more fuel. and if the iat sensor is bad (ford defaults to -40 on iat i believe) it will also go to a default rich mode. so figure out the egr and iat problems before you start dealing with the smog pump issues like jrichker and hissin said

JChalfan · Dec 20, 2006

Thanks for the suggestions. I'll see what I can figure out tomorrow, and post the results.

Jeff

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