1997 305 vortec cant fix miss!!!

[Jay P]

How many miles? I would look at the fuel pressure regulator. If the diaphragm is bad it will suck extra fuel when vacuum is high. Extra fuel will have more effect on a warm engine than a cold engine. It would also cause the O2 sensors to look bad.

 

Jay

[Jsdirt]

I couldn't make heads or tails out of which o2 sensor was what, but you should have 2 staying steady (downstream, cat), and 2 switching (upstream, engine) high and low. Your fuel trim goes off the chart and is all over the place - something going on there.

 

I'd be investigating fueling issues as mentioned, and if that doesn't turn up anything I'd be checking spark/ignition issues, regardless of what's been recently replaced.

[cameronc]

All the fuel system has been replaced. I replaced fuel pump and 2 different spiders. It has 70psi key on engine off and 55psi running. The regulator isn't leaking in intake either, over tried 2 different distributors and caps. New plug wires and plugs. The only thing I haven't replaced is the coil and control module. Literally nothing I've done has change the problem better or worse.

[cameronc]

Well guys I replaced all the oxygen sensors today and I drove it about 10 minutes and it didn't miss one time. I'm gonna drive it to work tomorrow and I'll know for sure. It that fixed it I'll be the biggest moron on the planet!

[Jsdirt]

Nice!

 

Nothing is ever that easy at my place ...

[cameronc]

I put 150 miles on it today and never missed a beat. Still have high idle between shifts and got codes po507 and po420.

[Jsdirt]

The 0420 is a catalytic converter code - the misfiring probably smoked it. Hopefully you live where they don't test for emissions.

 

The other code is the high idle you described:

 

A P0507 DTC trouble code may be caused by one or more of the following:

 

A vacuum leak

 

Leaking air intake after the throttle body

 

EGR valve leaking vacuum

 

A faulty positive crankcase ventilation (PCV) valve

 

Damaged/failed/dirty throttle body

 

Failed EVAP system

 

Failed IAC (idle air controller) or faulty IAC circuit

[KLRV6]

Did you set the cam sensor when you put the distributor in? What did the distributor gear look like?

 

My 99 vortec ran much, much better after adjusting the cam sensor (in the distributor). You can use a infrared thermometer to check each exhaust port at the manifold to find any cylinders not firing correctly at idle. I had a brand new set of AC plug wires that had one bad wire which made it run bad.

[cameronc]

The distributor was new with a new gear.Replaced iac today and still won't idle right while driving. I can be rolling and put truck in neutral and it will idle around 3K but once I come to a complete stop it will idle down normal. As long as the wheels are rolling it idles way high???I have checked and checked for vacuum leaks and new pcv also

[Jay P]

You need to data log to find out if the ECM/PCM is telling the IAC to stay open keeping the idle high. It's possible you have some type of transmission issue (bad sensor) that is causing the ECM/PCM to not know it's in neutral.

 

Jay

[KLRV6]

The distributor was new with a new gear.Replaced iac today and still won't idle right while driving. I can be rolling and put truck in neutral and it will idle around 3K but once I come to a complete stop it will idle down normal. As long as the wheels are rolling it idles way high???I have checked and checked for vacuum leaks and new pcv also

Did you set the CMP Retard Offset on it? It does make a difference. http://www.gmtruckcentral.com/articles/distributor.html

[cameronc]

It's a manual transmission and yes I set the cam retard to 0° when I installed it.