So, I've made a thread or two on this before awhile back, but this time possible causes to my issue are more narrowed down.

To keep it short and sweet (somewhat), the following is all replaced.

- Plugs and wires (plugs are gapped properly)
- Cap & Rotor
- Fuel filter
- PCV valve
- 02 sensor, temp sensor, EGR valve
- Basically the entire cooling system

Also worth noting
- Fuel pressure good
- No vacuum leaks
- Voltage good

Despite these efforts, the motor continues to idle and surge quite roughly once warmed up, and seems to run pretty rich. No SES lights came on during a lengthy drive yesterday, so I have no way to check for codes. Car has hard cold starts, but starts immediately when warm.

The other interesting thing - The same cylinder continues to misfire, even w/a good plug and wire. Another one is slighty off at times too. A guy who's been helping me w/the car (Haven't had time to work on it due to dealing w/the aftermath of an accident I was in w/my daily) is gonna do a compression check on it in the next few days.

Anything else it could be? The last things I can think of are maybe a bad ECU, TPS, or MAF. But I'm losing patience w/the 305 at this point, lol

 

If the compression test is good the engine is most likely mechanically healthy.

 

Yeah, that's what I'm waiting to find out. But it's my understanding that low compression in a cylinder can cause a stubborn misfire from an incomplete combustion process too, am I right?

Definitely not interested in rebuilding the 305 if that is in fact the issue, so this thing might have to sit in storage for a while while I save for a 350 if compression is the issue.

 

Have you checked you injectors? I just went through this with my l03, start the car with the air cleaner off and put you finger under each injector and make sure there is a fairly steady mist of fuel coming from both injectors. If not there about $100 a piece. Hope this helps.

 

Could be the computer to? Id do a compression test even though I think its mechanically healthy if it runs fine until its warmed up which is what im getting at.

 

OK.

HOW do you know it's rich? Rough idle and surge indicate lean not rich.


Never mind codes. Put a scan tool on that thing right after you verify that the cranking compression on all eight is good. What are the O2 crosscounts, what is the short- and long-term fuel trim when it's misfiring? What is the manifold vacuum at idle, fast idle, cruise?

Lots of potential issues, starting with low battery voltage and going on to fuel pump priming failure. May suggest lean mixture.

HOW do you know it's the same cylinder? WHICH cylinder? Is there a vacuum leak into that cylinder? (i.e., is there a vacuum port on the manifold runner leading to that cylinder?)