I have an 85 Coupe.When I start it cold,it idles rough and sputters some when driving.But when it gets up 160 degrees it runs fine.
Whats up with this?
I have set the minimum idle as described in this forum and also reset the TPS.No change

 

Do you have any codes? Do you have the factory service manual from www.helminc.com? Chances are you're cold start injector has some problems with it and will need to be diagnosed.

 

Per above or the Coolant Temp Sensor might be indicating a higher than actual temp so the ECM isn't delivering enough fuel. A new one is about $9. Simply unplug the harness from the old one and plug it in to the new one (no need to install it). If it runs ok, replace the old one.

 

I dont have a service manual.It did through a egr code back in mid summer.I unhooked the battery and reset the ECM.No codes since.
I will get a coolant sensor and try that.Does that sensor not feed the readout on the dash?

 

kg63 don't throw parts at it without diagnosing the problem. Not what you want to hear I know but that factory service manual is going to be worth its weight in gold so getting one is in your best interest. Check ebay or the for sale section of this forum.

 

The cold start valve (CSV) is not the problem. It is only active under 95*f engine temp. It is only needed for cranking bleow 95*f and not idling. The EGR is not active at idle or WOT and only under acceleration and cruising. The CTS located on the front of the intake manifold next to the thermal temp sensor for the CSV. The CTS can be ohmed to see if it is good or not. Unplug the (yellow and black on my 86) connector and use an ohm meter, putting the red and black lead touching each of the two terminals. Post what the ohms were and what the engine temperature are. I/we can use the FSM to tell if it's correct or not. That sensor does not feed the dash readout and only the ECM for proper fuel among other things. There is a sensor (one green wire) in the right cylinder head on my 86 that sends the engine temp to the dash guage...not sure if it's in the same place on your 85 though. Sounds like a vac leak and you might want to clean and reset the IAC is you have not. Also have you ohmed and leak tested the injectors?

 

I have cleaned and reset the IAC.Have not checked injectors.Thanks for the info.Its pretty busy around here and I probaly wont get to do any of the troubleshooting until this weekend.

 

Let us know after testing a few things.

 

Just ohmed the CTS cold.It was 3.1.
It was dam hard to get to.Had to remove some of the air pump crap.

 

Good the CTS ohmed at 3.1. You also have to give us the engine temperature or if the car hasn't been cranked since last night..the outside air temperature. The resistance changes on the CTS with changes in temperature. Without the engine/outside temp it will be hard to tell. I didn't have to remove anything but the air intake (accordian) the MAF is in.

Might want to repeat ohming it with both CTS ohms and engine temp.

 

When I ohmed it the car had not been started since last night.Air temp this morning was 65.
Also, I had checked the TPS voltage before and it was .54.Well I decided to check it again,it was still .54.But I had already bought one a while back and hadnt put it on because I thought the old one was fine.Anyway,I put the new one on and set it @.54.Then the engine starting running better cold,Whats going on here.I guess maybe the TPS was giving poor signals once it was moving.

 

O.K. my FSM says that at 70* engine temp the CTS should ohm 3,400 ohms. You probably had your ohm meter in a different setting at it is really 3,100 ohms you got, which means the CTS is ohming correctly. Not exact on the spot, but close enough. As the temp rises the resistance dereases or a decrease in ohms and vise versa.

Key on, you can do a test for the TPS by watching the voltage as you slowly manually open the throttle plates. As the plates open the voltage should increase without any hang ups/or hesitation. It should peak out at WOT greater than 4.0v minimum and less than 5.0 maximum.

Hope this info is useful.

 

look closely at your tps. there is a center on one side where they stick this thing together. If your old tps hasn't got sealant on this parting surface, there's probably moisture building up inside, and miniscule debris is fouling the feedback voltage.
it happened to mine. before I got it, someone changed it, and the thing was really wierd in the mornings.
well one saturday I took it to the do-it-urself carwash, and sprayed everything down.
It wouldn't idle below 2000 rpm
I changed it and voila! all better

 

OH BTW
when I changed the injectors, all the o-rings were hard and shrunk down and came out with lots of difficulty.
also check the pvc hose..mine was cracked on the under side where it slides on the TPI.
Also there is a little T cannister at the firewall on the left side near the distributor that governs the vacuum to the heater controls and the cruise control.
mine was great from the top but the bottom side looked like gas vapors melted the plastic and opened that vacuum hose up to atmosphere.
over by the battery, the cruise control vacuum hose was compromised by the battery acid. it was all smooshy.
the hose at the charcoal cannister was cracked and whistled when I squeezed it.
also under your car,in front of the rear wheel on the left side is a small vacuum hose that goes to the gas tank. I guess when GM put the line in, it was easier to do it in 2 pieces, and theres a short 2 inch piece of vacuum hose just before the floor goes up to clear the suspension.
rattle your pvc valve and make sure it's not stuck wide open
start your car, take the carpeted cover off the right side covering your engine computer and listen for vacuum leaks I had 2 there.
now really far out, do your gauges work when the engine is cold??
when mine was cold, the gauges were all funny readings. someone at the car show said change your computer. I laughed, and they said I mean it. I did, and the engine ran ok when cold. Apparently a cracked circuit board. you might be able to borrow a friend's computer for a night to see if things change.
make sure the clamps on the MAF are tight, check the screws on the top of the throttle body too
check under your plenum and make sure those little plastic vacuum lines aren't cracked and broken. the heat bothers them, and add up all the vacuum leaks, the iac couldn't help after it closed and the manifold was still getting outside unregulated air, leaning out the mixture.
Remember the O2 sensor doesn't have fulll authority until the temp sensor tells the computer the engine is warmed up
Phew!!
try all of that before your buy anything!