hello everyone, new guy to the forum and to fieros! my name is Josh and i bought an 88 gt, red, five speed, leather seats with 82,000 about two months ago. im a military guy who loves his rides and talking on forums. so, can a fiero correct its self? this is why i ask.....while i was deployed for six months i found a deal on my fiero and bought it two months before i returned. when i got home i drove the car around a few times and didnt have any trouble other than the temp gauge not working and an oil leak. the oil leak was from a rusted out oil pan which i had replaced and the gauge i guess is bad because the last owner left another in the car for me. the plug on the temp sensor on the engine was busted, so i had it replaced as well. i have been getting code 15 from the computer for the temp sensor, but other than that...nothing. THEN....it started to idle high around 2100 rpm. i replaced the IAC, the MAP sensor, and the EGR valve because it was rusted out bad and leaking. did that fix my high idle? a little.....its dropped to around 1700 rpm, but after the second time i drove it after replacing the EGR valve. before i replaced the egr valve nothing else helped. it would eat through a tank of gas in about 100 miles and after it was warm it was hard to restart. it would sputter for a min or so and then smooth out to its 2000 rpm range. any who, as i said it seams to have dropped a few rpm sense the egr valve was replaced.....is this because the pcm is slowly correcting all the problems it was seeing?

thanks

Welcome to the Forum!

The stock Fiero ECM is primitive by today's standards, but still pretty impressive. It is re-thinking stuff all the time and probably did change some things.

A high idle can also be caused by a vacuum leak, and as high as it is it would probably be a pretty big leak. Take your air filter pipe going into the throttle body off and with the car running stick your hand completely over the opening into the throttle body. If the car doesn't die, you have a vacuum leak. Its worth trying since it will probably only take you maybe 5 min.

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First off welcome to the Forum.....Sounds like the car must have been a northern card being you mention rust seveeral times....If your temp sensor is not reading correctly then that will cause your fuel issue....it is reading the engine is cold at all times and dumping way to much fuel...I would say that would be the issue on the excessive fuel use......The idle could be a vaccuum leak..common problem areas there would be EGR tube, plastic vaccuum lines under top plenum, ect....Idle should be around 900 or so I think...There will be others come in with much more knowledge of the 2.8 then me so they will expand on what I have stated....Also I will be in your area in a few weeks and could take a look at the car if you would like..

[This message has been edited by MstangsBware (edited 05-28-2011).]

thanks for the replies everyone! ill be sure to try the throttle body trick this morning. i drove the car last night after i made my post to put gas in it and cruse the town a bit...during which i got a rolling complement from an old string ray vett that someone had been taking care of the car (the vett looked BAD...ha). any way, when ever i punched the gas i could see the fuel in the air behind me in others headlights...also, when i get second or third around half throttle it would start loosing power and sputter some. when i got home i checked my trip meter which i reset after my fill up's and i had driven 20 miles in stop and go and a little high way driving.....i had use a HALF tank of gas! and my average mph on the last tank was 10mpg!!! so that temp gauge could really cause it to run this rich? thats amazing, but i believe that could be the case sense the plug was broken. im thinking i may want to replace the fuel pressure regulator as well just as a fail safe sense i have done the fuel filter already. more thoughts?

thanks!

[This message has been edited by javojjaaf (edited 05-29-2011).]

The Fiero has two temperature sending units. One is in the cylinder head, just on the left end and down from the ignition coil. This sending unit is for the gauge and temp light, only. It doesn't send any information to the ECM and has no effect on the car's operation. It's for the driver's visual information only.

The other is on the passenger end of the engine, beneath the thermostat housing. It senses engine temperature and sends that information to the ECM. The ECM then processes that information to adjust the air/fuel mixture. This could be a cause of poor gas mileage and hard starting. If it has defaulted to the cold side, it will cause the engine to run rich.

These two temperature sending units aren't interchangeable in their function nor will one harness plug into the other.

quote Originally posted by fierofool: The Fiero has two temperature sending units. One is in the cylinder head, just on the left end and down from the ignition coil. This sending unit is for the gauge and temp light, only. It doesn't send any information to the ECM and has no effect on the car's operation. It's for the driver's visual information only. The other is on the passenger end of the engine, beneath the thermostat housing. It senses engine temperature and sends that information to the ECM. The ECM then processes that information to adjust the air/fuel mixture. This could be a cause of poor gas mileage and hard starting. If it has defaulted to the cold side, it will cause the engine to run rich. These two temperature sending units aren't interchangeable in their function nor will one harness plug into the other.

so my code 15 is most likely coming from this temp sensor and not the other one for the gauge....added to the list of replacement parts. thanks

As stated before the two have different functions and different connectors. If the parts store tries to sell you one with the wrong connector and tells you that you need to replace the connector on your wiring harness they are wrong. The correct sensor WILL have the correct connector on it.



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Your code 15 means the ECM is not able to sense the temperature of the engine. That means either the CTS is bad or the wiring to the CTS is bad. Easiest thing to do is replace the CTS. Do it with the engine cold. Don't drain the coolant, but have the new one ready. Take the old one out and quickly put the new one in. Do it quick and you won't leak too much coolant all over the engine. Yeah it's a pain to reach the sensor.

[This message has been edited by phonedawgz (edited 05-29-2011).]

alright, im gonna replace that sensor...but let me make sure i have it right. the sensor under the coolant line in the intake is the ecm sensor and the sensor in the head on the driver side of the engine is the gauge and light sensor? thanks a million, i hope this is the main issue!

Phonedawgz is right on the money with his advice. Have some pipe dope and some anti-seize ready. Put the anti-seize on the threads of the new sensor before removing the old one. If the adapter comes out, put some pipe dope on it when you reinstall it, then screw the new temp sensor into it. Be forewarned, the adapter requires a BIG socket. I think somewhere around an inch. Don't try putting a socket on the sensor to install both at the same time.

You will loose a little coolant, but if you don't open up the cooling system, it won't be enough to be noticeable.

Careful...

Idle will be off until ECM has reset the IAC. IE every time Battery or ECM reset has been disconnected, etc...

Yes. Once ECM reset, high idle most likely has a vacuum leak. Bad ECT sensor is next on list.

Note, ECM ECT sensor have been updated. 88 V6 should already have new version. If not, need a new plug too.

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(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

sweet, im picking up a new ecm temp sensor from o'reilly's now and this should do the trick. i have unloaded a entire can of throttle body cleaner on the top end looking for vac leaks with no luck, so im crossing my fingers on this to work! thanks guys, truly been helpful!

The most likely place for a vacuum leak is the EGR tube. If your new CTS doesn't take care of you high idle post here and we can give you a procedure to check it.

well gents, the ecu temp sensor was on the money! i was able to pull it off by myself by stuffing a rag in the hole while i put the new sensor in the brass adapter. idling around 900 rpm now with no running rich from what i can tell and starts back up after being warm with no trouble, almost had to put the peddle on the floor to get it to start back up before and it would skip real bad....to much fuel! any who, thanks a million for all the help! now, does anyone have a chart of what dash lights are in what place? the only ones i see are door ajar, break, and the engine light. i want to make sure they all work, but thats all that comes on when i turn on the key. thanks again

Left side, top to bottom:

Ajar
Left Turn Arrow
High Temp idiot light
High Beam
Brake

Right side, top to bottom:

Up Shift-circuit deleted in many Fieros
Right Turn Arrow
Battery-circuit deleted when optional center gauge cluster present.
Seat Belt
Service Engine Soon

thanks fierofool....now should they all light up for a test when you turn the key on? also, my temp gauge does't work. the previous owner left another in the car for me, but im not sure thats the problem. when you turn on the car the gauge jumps all the way up like i have heard they were bad about doing and gets stuck. i can tap the dash and it will swing back to where it should be when the car is cold, but it doesn't go up as i drive. the plug for the gauge sensor was changed.....could this be the problem or do you think the gauge is bad?

If the pigtail for the sensor was changed that means the wrong sensor is installed. They may have installed one for the ECM, instead. As said, the pegging is normal on a factory wired car. There's a repair procedure for pegging at www.gafiero.org In the left column click Tech Tips for the article, including pictures and diagrams. If you have a Haynes Manual, there's a test procedure for the gauge and circuit.

You might want to get a new sensor that looks like the one Phonedawgz posted above and go to a junk yard to get the correct pigtail. The 4 cylinders used the same sending unit, so it doesn't have to be from a V6.

All the indicator lights don't light at startup. The SES, Battery and Oil Pressure light in the gauge are the ones I know light up. These are sensor triggered. High Beam, Turn Signals, and I think Ajar don't light, but I'm not 100% sure.

where on the 4 cylinder is the gauge temp sensor located? i found two 85 SE's at a couple of U Auto Pull It's here in shreveport and bossier city. thanks

It's on the left front corner of the cylinder head. It stands straight up.

HOWEVER - They are not always in the same positions. Check the connector end - The temp gauge will match the temp gauge sender shown above. The CTS may not look like either of the above pictures. If so and you need to replace it you will have to also replace the connector on the harness.

BTW, just as a suggestion since you were running so incredibly rich from that sensor, I would change the oil. Running that rich can allow lots of gas to fall down in the pan and we all know thats not good. If you pull the dipstick odds are it will smell like gas.