Rough Running After Warm Startup
Thread Starter
Heel & Toe
Joined: Jan 2006
Posts: 16
Likes: 0
Rough Running After Warm Startup
Hi, I'm having trouble with my 85 Vette...
So my car seems to idle slightly rough (but never stalls) and it just seems like for a V8 it should be running a lot smoother than it does. I've done some work to it in the past couple months to try to fix it:
Replaced: Timing Chain, Valve Seals, Plugs, Rotor, Cap, Plugs Wires.
I've adjusted the rockers several times in hope that was part of the problem after I did the valve seals but it doesn't seem to run quite right still.
The first start of the day it couldn't start any better and it usually runs great. Turn the key for half a second and it's running. The subsequent starts if it's even remotely warm you have to crank for 5+ seconds to get it to start and then it sputters up to idle. It then blows smoke and reeks of gas and will miss for a little bit. As the car heats up to 200 degrees the better it will run usually..
I've search around a bit but finding what I want is rather daunting and I'm not sure where to look as my problem could come from a number of places. Just looking for some advice..
I'm going to measure the injectors next to see how they read.
Any help or advice would be greatly appreciated.
So my car seems to idle slightly rough (but never stalls) and it just seems like for a V8 it should be running a lot smoother than it does. I've done some work to it in the past couple months to try to fix it:
Replaced: Timing Chain, Valve Seals, Plugs, Rotor, Cap, Plugs Wires.
I've adjusted the rockers several times in hope that was part of the problem after I did the valve seals but it doesn't seem to run quite right still.
The first start of the day it couldn't start any better and it usually runs great. Turn the key for half a second and it's running. The subsequent starts if it's even remotely warm you have to crank for 5+ seconds to get it to start and then it sputters up to idle. It then blows smoke and reeks of gas and will miss for a little bit. As the car heats up to 200 degrees the better it will run usually..
I've search around a bit but finding what I want is rather daunting and I'm not sure where to look as my problem could come from a number of places. Just looking for some advice..
I'm going to measure the injectors next to see how they read.
Any help or advice would be greatly appreciated.
Racer
Joined: Dec 2004
Posts: 470
Likes: 0
From: Phoenix Arizona
Almost the identical problem with my '90 vert, replaced the 02-sensor and then needed to replace my injectors after they were tested. They were faulty beyond repair and I understand you cannot repair Multitec injectors regardless. I do not believe your '85 has the same injectors, however I would test them yourself or have someone knowledgeable you trust to test them.
Hope this helps
Hope this helps
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
It would be interesting to see those injector coil resistance numbers. It sounds like that is where the problems is. You also need to check and see if any of them are leaking. You can use a fuel pressure gauge and pull the plugs to check.
Attach the fuel pressure gauge and remove the gas lid and rubber boot at the tank. As soon as you turn the key on to prime the fuel system, quickly pinch off the fuel feed line (top line going to the right). If the pressure drops of fairly quickly, take the vac line off the FPR and look for signs of fuel in the line. Pull the spark plugs and look for raw fuel.
None of this is necessary if the injectors ohm way off.
Attach the fuel pressure gauge and remove the gas lid and rubber boot at the tank. As soon as you turn the key on to prime the fuel system, quickly pinch off the fuel feed line (top line going to the right). If the pressure drops of fairly quickly, take the vac line off the FPR and look for signs of fuel in the line. Pull the spark plugs and look for raw fuel.
None of this is necessary if the injectors ohm way off.
Thread Starter
Heel & Toe
Joined: Jan 2006
Posts: 16
Likes: 0
Checked the injectors..
So I checked the injectors which was surprisingly easy. All of them read 17.9 - 18.1 ohms hot. I'm assuming that means their good (ha ha, or their all bad) since they are all pretty close.
I haven't tinkered with fuel yet. I know that I need to get a fuel filter. It didn't seem like lack of fuel to me although I admit I know jack about these motors. I'll definitely try all your suggestions.
I also bought some injector cleaner tonight as well as going to clean the TB and the MAF as well and clean the IAC like I did on my old GM's.
Thanks for all the useful tips so far. It's nice to be on a forum with helpful people even though I'm sure I'm asking a question that others have asked before. You search for just about anything on here and you get 6 billion posts that have nothing to do with your problem. :-)
I haven't tinkered with fuel yet. I know that I need to get a fuel filter. It didn't seem like lack of fuel to me although I admit I know jack about these motors. I'll definitely try all your suggestions.
I also bought some injector cleaner tonight as well as going to clean the TB and the MAF as well and clean the IAC like I did on my old GM's.
Thanks for all the useful tips so far. It's nice to be on a forum with helpful people even though I'm sure I'm asking a question that others have asked before. You search for just about anything on here and you get 6 billion posts that have nothing to do with your problem. :-)
