Wonky Turbo Coupe - Looking for Advice - TCCoA Forums
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post #1 of 6 (permalink) Old 11-05-2011, 10:57 PM Thread Starter
Adam Mc Laughlin's Avatar
Join Date: May 2011
Location: Santa Rosa, CA
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Wonky Turbo Coupe - Looking for Advice

Hi Everyone,

Pulled a 1988 Turbo Coupe out of a field last month. Changed the fuel pump, fuel filter and installed a battery and it runs.

Got some quirks: Wanted to know what you guys thought of this:

Codes are:

The fans seem to come on MUCH more early than I think that they should. The engine seems to be weak, the check engine light comes on right away. ( bad sign on an OBD 1 Ford )

Also, the engine stumbles hard when the fans kick on.

Any ideas? What do these codes suggest on the Turbo birds?

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post #2 of 6 (permalink) Old 11-08-2011, 02:41 PM
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Lets see .. codes for OBD1 Ford ..

21 - Engine coolant temp sensor out of self test range
25 - knock not sensed during dynamic response test
34 - egr valve circuit out of self test range
74 - Brake on/off circuit open
77 - breif wide open throttle not sensed during test

Looks like its failing a few self tests .. may need to get a wiring diagram to check these circuits to verify its not a problem with the PCM itself. Coolant temp sensor can cause a lot of problems.
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post #3 of 6 (permalink) Old 11-09-2011, 12:04 AM Thread Starter
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Location: Santa Rosa, CA
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WELL, I got a new Bosch ECT sensor. That will go in this weekend with the new plugs, wires, cap, rotor, valve cover gasket, etc.

The fan comes on as soon as you start the car, it has to mistakenly believe that the engine is hot.

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post #4 of 6 (permalink) Old 11-13-2011, 09:57 AM
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Well... sorry. Dont know how I missed this thread except I was spending too much time on blazerforum.

How to fix, depends on key element WHERE TO START:
What do all these things have in common> Black wire w/ white stripe to respective sensors.
- the WOT code doesnt matter if you didnt kick the throttle to floor during that self-test. Likwise, perhaps, Knock sensor.

Where do they converge? Pin 46 of the ECM That wire could be the problem but it may be deeper than that*.

Historical anecdotal issues: Fox Tbird notorious for passenger side cowl leaks, down A-pillar or firewall to Power relay and ECM grounds.

Pull pass kick panel and the evidence should jump at you.
Along with fixing the rain leak, replace all relays there - ECM power relay may be hiding above and to right of ECM-, and when you install them install Base down.

* Not to mention fixing the corroded ECM grd terminal you likely find is the problem.* even if there's no apparent leak. Check the block to chassis ground strap at firewall, as well.

___________________Obligatory Anecdote _________________________________

- I once ran across a guy with a TC in parking lot would not start after torrents of rain. HE thought he was an expert on his car and said the FP didnt prime and no check engine on key-on, so there was something seriously wrong.. I tried to tell him about that relay but .. NO.. he would let his trusted shop take care of it.
I knew the shop owner and happened to have a tire in there being fixed. {about all other than towing I would trust the guy with after a major engine replace but that's another story}

Went in to pick up my tire next day and there laying on the shelf is a rusted out relay and what was a water stained though probably perfectly good ECM. He'd no doubt screwed yet another trusting customer.

I learn more about cars every day!
I do it just because I still want to know HOW and WHY!!! Quit learning=die. Be informed as to WHAT, rather than learn,=brain-dead already.
1993 Silver LX 3.8L My Bravadiva's 'go store-fetch me parts' girl

Last edited by pettyfog; 11-13-2011 at 10:24 AM.
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post #5 of 6 (permalink) Old 11-14-2011, 11:41 PM Thread Starter
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Location: Santa Rosa, CA
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Hey Pettyfog,

You and I had some similar thoughts! When I got these codes, I pulled out my Helms book and I too noticed that these items did have a common connection. I had initially wondered if the black wire / white stripe was something that had a fusible link in it that was done, but didn't investigate this any farther when the phone rang.

I did pull the ECM and I found that the ECM had been replaced already. Spray painted black chassis with a blue sticker? Hummm... No noticeable corrosion on the ECM connector, but I didn't investigate grounds or relays in that neighborhood.

You can bet that I will be attacking these later in the week!

The car has idled through about three gallons of fuel so far. Got it nice and hot, and now it starts much easier. Car only has 71 K on it. Fan still comes on when it wants, check engine light comes on and off as it desires, and sometimes both fans are on even though there is no A.C. running?

REALLY looking forward to ironing out the mechanical and electrical; I want to paint the Turbo Bird!! Leaning towards a cream, but still open to other choices. Brandy Wine looks nice BUT is too sunlight sensitive.

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post #6 of 6 (permalink) Old 11-17-2011, 06:07 PM
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The codes you pulled are normal except 21. Failing or failed ECT. It helps to control the fans.

The ECT is located under the upper intake on the intake manifold. A 1" sensor socket 3/8 drive with a swivel works the best. Just enough room and you will only have to remove the pcv hose. There is also a bung under the intake that feeds coolant by the ECT. It gets clogged. Pull it off and see if it is clear of rust. A hose is attached to it. These hoses fail when they get old and brittle. If I remember correctly it is a preformed hose and is not available anymore but you can just use a normal heater hose to replace it. It is a small hose and don't remember the size.

25 is when you don't tap on the exhaust manifold during the KOEO test.
34 is due to a recall that ford installed a check/delay valve. Always comes up on my 88 TC as well. There is a way to tell if the recall was done but I forget. I could look at my car and take a picture of the check valve so you could compare.
74 is also a code during the test that you apply the brake pedal during the test. if you don't it will set that code.
77 I think that is also a part of the test when you apply the throttle and if you don't apply enough it will set that code also.

Good luck!
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