I just got a realy good deal on a 87 T-Bird Turbo Coupe 5 speed. I bought it to put the drive train into a Pinto, but until I find a suitable car for the transplant, I figured that I will drive the T-Bird as a backup car. In order to transfer and register it, the car must pass a smog check (California #$%&^) Check engine light during test = automatic fail.
So here's the situation: The car runs excellent but below about 20 mph, and at idle the 'check engine light (CEL) comes on. It goes back off less than a minute after getting up to speed, and never comes on at hiway speed. The continuous memory code is something like HEGO rich or not switching (I forget the number) no other stored codes. It passes the KOER test. Fuel pressure is about 38psi, and does not drop for 5 minutes w/ engine stopped. The previous owner had the base idle and TPS out of adjustment, but I have that straightened out.
I hope a turbo 2.3 expert can help me; I want to get this engine running good before I try to transplant. it.
tia
mike
The first thing I would do is a FULL tune-up, clear the old code(s) and make sure everything is connected the way it should be, including the engine to body ground and see if it still does it. The next thing I would do look at things that directly relate to mixture (by the code you mentioned), the O2 sensor and the Coolant Temp. Sensor : install another ground to the O2S to the body (small hose clamp a wire to it then to the body). The next things I would do, in order: replace the CTS on the intake (with a new one), replace the O2S (with a new one), replace the VAM (with a KNOWN good one). replace the ECU (with a KNOWN good one). KEEP IN MIND: I have the luxury to have a stockpile of ECUs and other sensors to swap out when I work on these cars (sorry). Re-check after each thing you do, and also keep in mind that these are fairly primative systems and I have had wierd codes and the fix had nothing to do with that part of the system.
Bill
the only thing I can think of is maybe vacuum lines?
Thanks for the replies. I am trying to figure out what is happening without buying too many parts. I have the Ford shop manual, so I started running the tests. I checked the ect and vat voltages are normal. The output of the VAF is .99V at idle,which maybe a bit high. At idle the HEGO is at 0.75 V which means rich. The book suggests to open a vacuum line at the vacuum tree and see if the oxyegen sensor voltage drops meaning Lean. When I did that, the Oxyegen sensor voltage started switching high and low, like it should during closed loop, and the check engine light went off! I even drove it around with the small vacuum leak, and the check engine light stayed off. I suspect that my Vane airflow meter may be the problem, but its over a hundred bucks, so I want to be more sure. Does anyone know what the VAF voltage should be at idle?
mike
This might sound stupid, but did you think about have it tested with a vac line dissconnected? (J.K.)
Bill
Have you ever thought about dumping the stock ECM and going with a megasquirt?
I`m wiring one up for my 2.3 turbo and it looks promising..
The link below shows the out put voltages for the large VAF. Another site mentioned that at rest (engine off and key on) the VAF voltage should be 0.246V (unfortunately I did not write down the web address when the page was printed).
http://binary.uta.edu/EEC/html/VAF.html
Since a small vacuum leak fixes things, maybe one of the intentional leak systems is not working properly, i.e. PCV, EGR.
This is unlikely but an easy check. Since the fuel pressure is staying up after engine shut down, the injectors probably do not have a major leak. There still is a possibility the injectors are not balanced (maybe some one replaced a injector with an incorrect one). Check the spark plug colors for any major differences.
Quote from: 77turbopinto on August 02, 2008, 12:48:26 PM
This might sound stupid, but did you think about have it tested with a vac line dissconnected? (J.K.)
Bill
Not dumb at all, Bill- that's what I plan to do; if I can't straighten it out, I will put some hose on my 'vacuum leak' and hide the other end somewhere!
Oldkyacker, the shop manual did mention low PCV flow, and I bought a new valve- which looks different than the one in there now. Maybe someone installed the wrong one. I plan to change it next week and see what happens.
This is the first time I drove a turbo T-bird, and I'm impressed with the power. Can't wait to get that motor into a lighter car!
mike
for turbotbird specific info,(and lots of it) go here....
http://www.turbotbird.com/
Years ago when I bought my Turbo Coupe (used) I had the light come on. It proved to be the throttle position sensor. As I recall it was only at slow speeds too. Basically it's just a rotating potentiometer and due to the throttle range of typical driving it wears a lot in the lower range of travel.
The sensor does have some degree of movement in the slotted holes. You might try rotating it forward to put it in a less worn position. I have no proof, but I was told that the computer would compensate for just about anywhere in the slot it was rotated to.
Mark the old position so that if this doesn't change anything you can set it back to the original position. It's a free way of seeing if it makes a difference. Even if this doesn't work, the throttle position sensor might still be bad. You can also try ohming it out on a meter, but as I recall my bad one didn't show that much.
Tom
Quote from: Wittsend on August 03, 2008, 11:14:18 PM
.....The sensor does have some degree of movement in the slotted holes. You might try rotating it forward to put it in a less worn position. I have no proof, but I was told that the computer would compensate for just about anywhere in the slot it was rotated to.....
Yes it is true that some newer cars have a self calibrating TPS, but the T/C does not. It needs to be correctly adjusted to about .9 volts at idle (IIRC).
Also, they do wear and will have 'flat spots' where the voltage either spikes or drops.
Bill
thanks to all for the help; oldkayacker, you nailed it- the PCV valve had been replaced with the wrong one apparently. Seems like the ECU could not adjust for that much air flow thru the VAM at idle- it needed more cfm to bypass the VAM thru the PCV. I replaced the PCV valve, turned down the base idle, adjusted the TPS to 0.9 Volts, and now the check engine light stays off. Passed the smog test today, so the turbo coupe is legal. Its actually a nice running car now- plenty of power, and good on gas too.
Until i find a Pinto to swap the drivetrain, the TC should be a decent work-car. Between all the folks here, and the Turbo web sites, plus the shop manual, I learned a lot about the EEC-IV system, so thanks again.
mike