Truck idles rough at start up only.

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I have a 1994 with a 350 engine. I have replaced the distributer, IAC, TPS, coil, temp sensors, o2 sensor only had one and I removed the catalytic converter, tank and fuel pump are new and tested for pressure all good, fuel lines are new, cap and rotor, wires and plugs are new. Recently it started doing this. On a over night cold start it starts fine then immediately starts to idle rough for around 45 seconds then smooths out after that all is good and it drives fine. 2 days ago it did the same thing at my work only sitting for 9 hours. All the grounds have been replaced and are good. I just replaced the plugs a week ago and the old ones were around 5 months old and they all looked good. I thought it may be the valve seals so I changed the oil and put a additive in but so far with 75 miles on it nothing has changed. I also added some Sea Foam in the tank but like I said nothing has changed. Any thoughts would be appreciated. Thank you.
was the replacement distributor from carquest/advance auto? the reason i ask is because i replaced my distributor in my 1994 k1500 and my truck was doing the same thing running very rough at startup on a cold start but only for the first 30 seconds or so with no other driveability issues. it would start with no issue if i unplugged the timing connector in the cab directly below the glovebox. just recently i decided to put my old ignition control module back on the distributor and no more rough idle at startup. i have had very poor luck with most carquest/advance auto electrical parts and this discovery just adds to the list of reasons i tend to steer away from them.
 

JACK34

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was the replacement distributor from carquest/advance auto? the reason i ask is because i replaced my distributor in my 1994 k1500 and my truck was doing the same thing running very rough at startup on a cold start but only for the first 30 seconds or so with no other driveability issues. it would start with no issue if i unplugged the timing connector in the cab directly below the glovebox. just recently i decided to put my old ignition control module back on the distributor and no more rough idle at startup. i have had very poor luck with most carquest/advance auto electrical parts and this discovery just adds to the list of reasons i tend to steer away from them.
Yes it was. It's at my mechanics shop right now. Thanks for the info.
 

JACK34

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was the replacement distributor from carquest/advance auto? the reason i ask is because i replaced my distributor in my 1994 k1500 and my truck was doing the same thing running very rough at startup on a cold start but only for the first 30 seconds or so with no other driveability issues. it would start with no issue if i unplugged the timing connector in the cab directly below the glovebox. just recently i decided to put my old ignition control module back on the distributor and no more rough idle at startup. i have had very poor luck with most carquest/advance auto electrical parts and this discovery just adds to the list of reasons i tend to steer away from them.
If that is the case what parts dealer/part make would you recommend?
 

JACK34

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was the replacement distributor from carquest/advance auto? the reason i ask is because i replaced my distributor in my 1994 k1500 and my truck was doing the same thing running very rough at startup on a cold start but only for the first 30 seconds or so with no other driveability issues. it would start with no issue if i unplugged the timing connector in the cab directly below the glovebox. just recently i decided to put my old ignition control module back on the distributor and no more rough idle at startup. i have had very poor luck with most carquest/advance auto electrical parts and this discovery just adds to the list of reasons i tend to steer away from them.
I just talked to my mechanic. He said it's the fuel pump, fuel pressure regulator on the TBI and the car quest distributors are junk. So he's going to replace them and I will get a refund on the distributor. The fuel pump is from LMC 2 years old. 9 pounds of pressure. He said LMC stuff is junk as well. So we will see how it turns out.
 

Supercharged111

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I just talked to my mechanic. He said it's the fuel pump, fuel pressure regulator on the TBI and the car quest distributors are junk. So he's going to replace them and I will get a refund on the distributor. The fuel pump is from LMC 2 years old. 9 pounds of pressure. He said LMC stuff is junk as well. So we will see how it turns out.

I'd rebuild the TBI unit before going after the pump to try to get the pressure right. And throwing new junk parts at the truck will create more problems than it will solve as you've seen. I'd put all the factory sensors back in that you replaced so you don't end up chasing your tail down the road.
 

JACK34

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I'd rebuild the TBI unit before going after the pump to try to get the pressure right. And throwing new junk parts at the truck will create more problems than it will solve as you've seen. I'd put all the factory sensors back in that you replaced so you don't end up chasing your tail down the road.
I will let him know what you said thank God for your wisdom. Thank you.
 

Supercharged111

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I will let him know what you said thank God for your wisdom. Thank you.

The thought occurs to me he may have already pinched the return line and not seen a jump in pressure, which would indicate a weak pump. But if the TBI hasn't been rebuilt it's still a good thing to do, the regulators are notorious for sucking.
 

tayto

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9 psi is still in spec, though not ideal. I would put a TPI or vortec pump in it is a mandatory upgrade IMO.
 
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