Very hesitant cold start
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Joined: Oct 2001
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Very hesitant cold start
Hi Everyone,
This is my first time posting. I found this site yesterday. Hopefully someone can help.
I have a '85 Coupe Gt that I have started basic performance mods on (H&R springs, Bilsteins, front and rear sway bars, strut barce, cat-back exhaust). I still have a way to go. Ther is a big problem that I can't figure out. In the mornings or after sitting for a while (8 or more hours on a warm day and 3 or less on a cold day) my car will hesitate on start. The first couple of cranks it seems like ther is no combustion at all, then it wants to turn over but still can't. After numerous cranks and holding the gas pedal down (full throttle), it finally turns over (very rough, backfiring, hesitating, surging and dark smoke from exhaust). Once the engine smoothes out, it idles like a dream and the engine is very responsive to the throttle (NO HESITATION AT ALL).
I have already changed the sparkplugs, wires, rotor, dist-cap, ignitioncoil, airfilter, fuelfilter, and fuelpump (all with BOSCH or OEM). None of this seemed to help.
Has anyone else encountered such a problem? PLEASE HELP.
Bal
"85 Coupe GT
This is my first time posting. I found this site yesterday. Hopefully someone can help.
I have a '85 Coupe Gt that I have started basic performance mods on (H&R springs, Bilsteins, front and rear sway bars, strut barce, cat-back exhaust). I still have a way to go. Ther is a big problem that I can't figure out. In the mornings or after sitting for a while (8 or more hours on a warm day and 3 or less on a cold day) my car will hesitate on start. The first couple of cranks it seems like ther is no combustion at all, then it wants to turn over but still can't. After numerous cranks and holding the gas pedal down (full throttle), it finally turns over (very rough, backfiring, hesitating, surging and dark smoke from exhaust). Once the engine smoothes out, it idles like a dream and the engine is very responsive to the throttle (NO HESITATION AT ALL).
I have already changed the sparkplugs, wires, rotor, dist-cap, ignitioncoil, airfilter, fuelfilter, and fuelpump (all with BOSCH or OEM). None of this seemed to help.
Has anyone else encountered such a problem? PLEASE HELP.
Bal
"85 Coupe GT
AudiWorld Uber User
Joined: Dec 2000
Posts: 41,093
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The warmup regulator is probably not working.
The vacuum advance on the distributor might also not be working. The smoke and sputtering when cold and smooth running when warm indicates to me that it's the warmup regulator, or maybe the thermo-time switch that's gone bad.
AudiWorld Member
Joined: Jan 2001
Posts: 252
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From: Roswell, GA
Re: Very hesitant cold start
Here is an informal procedure I used on my 4KQ - basically the same engine.
-When cold (it must be cold because you are testing the thermo time switch) put a test light in the plug for the cold start valve. If it does not blink then your thermo time switch is probably bad - it is located in the back of the head near the inlet from the heater core. If it does blink, put the connector back on the cold start valve. Then remove the valve and place the nozzle end in a container and turn the engine over a few times - did I mention to disconnect the coil??? If it does not spray fuel into the container then replace the cold start valve. If it does spray then you have some serious diagnosis to be performed. Also it would be a good idea to thoroughly clean your ISV.
-When cold (it must be cold because you are testing the thermo time switch) put a test light in the plug for the cold start valve. If it does not blink then your thermo time switch is probably bad - it is located in the back of the head near the inlet from the heater core. If it does blink, put the connector back on the cold start valve. Then remove the valve and place the nozzle end in a container and turn the engine over a few times - did I mention to disconnect the coil??? If it does not spray fuel into the container then replace the cold start valve. If it does spray then you have some serious diagnosis to be performed. Also it would be a good idea to thoroughly clean your ISV.
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