Runs Rough, No Error codes

[Technocrat]

I have a 98 Safari 4.4 Vortec with 225,000 miles on it.

It is running rough with no error codes. It is hitting on all 6 cylinders.

It has a new distributor, cap & rotor.
Bosch Platinum plugs & plug wires are about a year old.

[94&92Astro]

Originally Posted by Technocrat

I have a 98 Safari 4.4 Vortec with 225,000 miles on it.

It is running rough with no error codes. It is hitting on all 6 cylinders.

It has a new distributor, cap & rotor.
Bosch Platinum plugs & plug wires are about a year old.

Make sure none of your plug wires are in contact or near contact with the exhaust manifold. Also a good idea to remove the doghouse and check out the engine while idleing at night to check for any errant spark. I stumbled upon a leaking wire this way which had come in contact with the manifold and was throwing an intermident spark into manifold. I wish I had started this way as I would have saved myself alot of time and money. Also alot easier to check vacumn hoses while doghouse is off.

[Technocrat]

Thanks!
I had not thought of looking after dark. I unplugged the wires one at a time while running & got a pronounced miss on all six so whateever it is does not seem to be isolated to a single cylinder.

I have checked for vacuum leaks & not found any.

[MikeS144]

I have a 94 with the vortec and had a similar problem. Does your exhaust smell of fuel? If so then you should look and your injector. I am not sure if yours has the same injector as mine, but the spider injector as it is called which I have has a history of causing problems like that.

BTW, how did the plugs look when you changed/pulled them?

[Technocrat]

Originally Posted by MikeS144

I have a 94 with the vortec and had a similar problem. Does your exhaust smell of fuel? If so then you should look and your injector. I am not sure if yours has the same injector as mine, but the spider injector as it is called which I have has a history of causing problems like that.

BTW, how did the plugs look when you changed/pulled them?

Thanks fir the input.
No, I am not smelling gas. I have tried running Gumout High Millage fuel system cleaner through it in case the injector was clogged, but to no avail.

The plugs just had a light ash color showing good combustion.

[old_master]

AC Delco 41-993 spark plugs will make a world of difference over the Bosch plugs. Usually they will set a DTC P0300, but not always. The only way you'd spot this problem is with an enhanced OBDII scan tool. Also, check fuel pressure and leakdown rate. Key ON, engine off, fuel pump running, fuel pressure must be 60psi to 66psi and must remain above 55psi for 3 to 5 minutes after the fuel pump shuts off. Insufficient fuel pressure can cause a random miss without setting a DTC.