shadetreemech

Hello, I'm new to this forum and and have read and searched the forum for possible solutions to my problem and have had no luck. I'm working on a 1988 gt. The car is running very cold and the gas mileage is less than 8mpg.
The owner of the car had a coolant leak at the bottom of the timing chain cover and added a bottle of copper colored leak fix which stopped the leak.

I've changed the tstat several times, two tstats were stuck open.
Third tstat seems to work and stays closed until engine warms up.
I purged the air out of coolant system, the upper radiator hose is hot and I can feel coolant running through the upper radiator hose.
The coolant in the overflow tank does not change temp and the coolant level does not change.
The temp gauge reads on the low end of the scale. The heater air is somewhat warm but not toasty.

The first KOEO scan was a 23 and I adjusted the TPS to read 0.85v.
I then cleared the codes by removing the jumper during the KOEO testing.
The next KOEO test was 11.
The KOER test codes are 92 34 22 42. My eyes were burning from the rich fuel mixture.
The next KOEO test was 11 34

The voltages with the EVP harness tested fine, then with the harness connected the voltage at the EVP SIGRTN was 0.66v.

Does anyone have any ideas? I will test the MAP sensor next.

Thanks

houtex

Codes are here:
http://www.troublecodes.net/ford/eec-iv/

After code clearing...
92 - HO2S Circuit Indicates Rich
Sounds right. Heated Oxygen Sensor isn't lyin', it's rich according to your testimony.

34 - EGR Valve Position/Pressure Feedback EGR Voltage Above Closed Limit (Others)
Sounds like a bad EGR valve or EGR solenoid.

22 - Manifold Absolute Pressure/Barometric Pressure Sensor Out Of Self Test Range
Bad MAP sensor.

42 - System Indicates Rich
Duh, ya think, car?


Next set:
11 - All's well... at first...
34 - Back to the bad EGR.

Sounds like you have EGR control and MAP sensor that's bad. The MAP will definitely screw things up, I had one go out. This is what it looks like:

https://lmr.com/item/DY527/1987-88-M...-Sensor-Map-Se

EGR could be the valve or the solenoid. I'd replace both.

THAT said... a leaking injector or two isn't outside the realm. The extra fuel being delivered *will* cool down the engine and make it run cold... but that assumes it's not being asked for, which without the EGR and MAP known good, you cannot actually know. So fix those codes and see where you are. Also continuing to run it around like that will wash out the oil rings of the pistons and that's not good.

For what it's worth, I had a similar thing happen on my 97 HoopTbird V6, and it drove me *nuts*. I did the EGR, the MAP, and that helped, even found a disconnected tube for the MAP (that was fun) but at the end I wound up replacing all of the injectors... problem solved!

But the damage was done, and shortly after I was also replacing the cats because they wound up melting and clogging from the fuel buring in them. Yay emissions controls! I mention this because... well, because. I hope it doesn't happen to your car, truly.

So if it doesn't clear up from the EGR twins or the MAP sensor, you might be looking for injectors. Looks like a couple hundred to get 'em.
https://lmr.com/item/LRS-37262/musta...ype-3-8604-ev1
(If you want 'stock.' There are higher lb ones to consider if you want... probably don't need 'em though.)

Chasing gremlins aren't fun, but those two (overall) issues are going to need clearing first before you know where to go next.

Hope that helps. Good luck!

Edit: Oh, that's interesting. Keywords are being linked elsewhere. I didn't pick those, so fair warning if you click them.
"Bad form, TMS, bad form!" - Kids of Neverland.

shadetreemech

I found some links for testing a ford MAP using an o'scope and a vacuum source. Apparently a ford MAP generates different frequencies based upon the amount of vacuum that it receives.
The following link has some great info:

http://troubleshootmyvehicle.com/for...e-map-sensor-2

I will check the vacuum source hooked up to the MAP.
Then check the wiring connector to the MAP.
Then bench test the MAP.

The following link has some great info regarding ford EGRs:

http://www.tomco-inc.com/techinfo.html

If I find a solution to either or both problems I'll post here, perhaps it may help others.

shadetreemech

Well I checked the wiring to the MAP sensor and the 5v and ground at the harness are good but I didn't check for continuity of the grn/blk wire going back to the computer. Replaced the MAP sensor along with the EVP (5v and ground checked ok on the harness).
Reset the memory and drove about 25 miles and the scan codes are exactly the same.
I guess the signal wire of the map sensor could be hosed. From what I've read the EGR and MAP are closely linked. I'll check the signal return wiring of both systems next week.
I think the gas mileage went from 5mpg to 10mpg. I don't notice a lack of power on acceleration and the idle sounds fine except for a slight surge at idle of maybe 50rpm. The idle is at 900rpm. If anyone has any ideas I'm all ears.
Thanks

shadetreemech

I forgot to mention that the vacuum hose to the map sensor had a strong vacuum but I didn't check with a gauge.