hard starting c4
Thread Starter
Drifting
Joined: Jun 2013
Posts: 1,590
Likes: 60
From: ft myers FL/Munising MI
hard starting c4
hello everyone....I'm new here...I have a 85 c4 that I'm trying to bring back to its former glory and have been here as a guest and got really good advice...thanks all....recently I cleaned the throttle body and installed a new IAC valve. now when cold, I have to crank it awhile to get it going, then the check engine light comes on....if I shut it off, and restrart, it goes off and starting is no longer an issue for the day..what did I do??? It idles and runs fine after initial start up.
also, I installed a hypertech power chip...really fun considering where the computer is, but it works great. Now I was thinking I would install new injectors and I'm wondering if I use the bigger injectors available, would that chip mix the fuel appropriately?
since I'm on a roll, let me ask one more stupid question...I use a 160 degree thermostat and would like to know when that little fan in front comes on....can I force it on??? the fan in the engine compartment comes on ...I live in s fl....it's hot always...trying to keep it cool...Paul
also, I installed a hypertech power chip...really fun considering where the computer is, but it works great. Now I was thinking I would install new injectors and I'm wondering if I use the bigger injectors available, would that chip mix the fuel appropriately?
since I'm on a roll, let me ask one more stupid question...I use a 160 degree thermostat and would like to know when that little fan in front comes on....can I force it on??? the fan in the engine compartment comes on ...I live in s fl....it's hot always...trying to keep it cool...Paul
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
The little fan in front is useless. Its the "last chance" fan that was installed by dealers when early C4 customers could not come to terms with a car that ran NORMALLY at 225 degrees...or more.
That fan will not come on until 238? more or less...then it does not do much.
Main fan come on at 228 unless the hyper-theft chip is a thermo-master chip then they come on at 180 IIRC.
No, you cannot just put bigger fuel injectors in there unless you add some more Cubic Inches displacement to use the fuel. A blower will also need more fuel. A 350 ci semi stock engine would just choke on more fuel.
Don't fall victim to the aftermarket BS. You don't need 75% of the stuff you will see advertised.
Your cold start issue could be the coolant temp sensor, the fuel relay or the injectors. These fuel injectors DO NEED to be replaced...but with new ones same size. Ohms test each both hot and cold.
Fuel pressure test.
Verify TPS setting. Clean/replace plugs & wires as needed. Dist parts as well.
There are many reasons why its hard to start when cold but the most common are listed somewhere above. MOST of all, check and clean any & ALL electrical plugs, connections and wiring under the hood. The wire harness is the nervous system of the C4...take care of that and most of the performance issues will go away.
BTW....you are setting trouble codes if the Check eng lite is coming on. Read the codes and report back. Until then, do the elec system cleaning and check the fuel relay. Turn the key to ON, listen for the fuel pump to run 2 seconds. Or, use a DVM or test lite on the relay to see if its sending power across. If the relay is bad that causes extended CS cranking.
Cool is related to the geographic location you are in. I see folks come in here that live in San Diego and they cannot understand what all the talk is about !
Try the gulf coast or the Arizona dessert in july...
Cool to YOU, means <230. Hitting 235 with a/c on sitting in traffic is nothing to be alarmed about. These are designed to run hot and they will without harm. Just do the cooling system maint and keep the hoses in good shape and it will be ok. Many of us fight that battle when we invest a bunch of money in a built engine. I have. Right now Mine will hit 240 with a/c when its 97 outside sitting in traffic. Tx gulf Coast area. (sweaty hell on earth) It drops as soon as I move again. Not a big deal. That's after $1000 worth of upgrades....things were much worse before the money spent. Before, if it hit 235 it would stay there...now it will drop to 200 soon as I get it moving again.
That fan will not come on until 238? more or less...then it does not do much.
Main fan come on at 228 unless the hyper-theft chip is a thermo-master chip then they come on at 180 IIRC.
No, you cannot just put bigger fuel injectors in there unless you add some more Cubic Inches displacement to use the fuel. A blower will also need more fuel. A 350 ci semi stock engine would just choke on more fuel.
Don't fall victim to the aftermarket BS. You don't need 75% of the stuff you will see advertised.
Your cold start issue could be the coolant temp sensor, the fuel relay or the injectors. These fuel injectors DO NEED to be replaced...but with new ones same size. Ohms test each both hot and cold.
Fuel pressure test.
Verify TPS setting. Clean/replace plugs & wires as needed. Dist parts as well.
There are many reasons why its hard to start when cold but the most common are listed somewhere above. MOST of all, check and clean any & ALL electrical plugs, connections and wiring under the hood. The wire harness is the nervous system of the C4...take care of that and most of the performance issues will go away.
BTW....you are setting trouble codes if the Check eng lite is coming on. Read the codes and report back. Until then, do the elec system cleaning and check the fuel relay. Turn the key to ON, listen for the fuel pump to run 2 seconds. Or, use a DVM or test lite on the relay to see if its sending power across. If the relay is bad that causes extended CS cranking.
Cool is related to the geographic location you are in. I see folks come in here that live in San Diego and they cannot understand what all the talk is about !
Try the gulf coast or the Arizona dessert in july...
Cool to YOU, means <230. Hitting 235 with a/c on sitting in traffic is nothing to be alarmed about. These are designed to run hot and they will without harm. Just do the cooling system maint and keep the hoses in good shape and it will be ok. Many of us fight that battle when we invest a bunch of money in a built engine. I have. Right now Mine will hit 240 with a/c when its 97 outside sitting in traffic. Tx gulf Coast area. (sweaty hell on earth) It drops as soon as I move again. Not a big deal. That's after $1000 worth of upgrades....things were much worse before the money spent. Before, if it hit 235 it would stay there...now it will drop to 200 soon as I get it moving again.
Last edited by leesvet; Jun 20, 2013 at 05:46 PM.
Thread Starter
Drifting
Joined: Jun 2013
Posts: 1,590
Likes: 60
From: ft myers FL/Munising MI
thanks for the quick reply and info....this trouble did not start until I changed the IAC....I have already installed new plugs/wires/ dist...
the hyper tech chip is a thermo ....I never go over 200 anymore, so it works great...helped to install a brand new radiator too....
I heard that you could get a manual switch to turn the little fan in front on....I also ordered a vortex ram air system but now I'm wondering if it will do any good....is it worth putting on???
the hyper tech chip is a thermo ....I never go over 200 anymore, so it works great...helped to install a brand new radiator too....
I heard that you could get a manual switch to turn the little fan in front on....I also ordered a vortex ram air system but now I'm wondering if it will do any good....is it worth putting on???
Thread Starter
Drifting
Joined: Jun 2013
Posts: 1,590
Likes: 60
From: ft myers FL/Munising MI
I'll have to put the stock chip back in to find the code....but...this didn't start happening until I installed a new IAC....wouldn't you think that has something to do with it????
