Replaced the fuel filter, car has been chugging or jerking at cruising speeds. When I give WOT its good till about 4000 rpm and then starts cutting out. Had a guy replace the fuel filter which he said had some brown dirty gas in it hoped it would fix the problem but it didn't soooo what next (bad gas, person who bhanfed the filter didn't think so, fouled plugs, what?) I missed a gear a few weeks ago while power shifting but I have all the top half of the motor redone, (heads cam intake MAF pushrods headers chip, etc) so I don't know if thats part of the problem or what. Cars only got just over 30k miles.
Rick


99 SS, M6 Plenty mods 33K miles

 

Fuel pump cutting out or fouled plugs...... Oh yea, O2 sensor?

When were your plug wires replaced? I had one that the boot had touched the header and melted down to the shield and it did something similar to what you are describing.

Call Chris on Monday, I sent you his number in a PM. He should be able to use a Tech2 and help diagnose the problem. He has done wonders for my car.

Bill

 

Im on vacation next week but I'll give him a call. I was kinda hoping it was something simple

 

Sounds ignition related.

 

Chris is a good guy and did some work on my car as well.

 

Is the SES light flashing on & off when it is chugging? If so, it's going to be a misfire. So, o2, spark plugs, plug wires, maybe the MAF. What MAF did you switch to when you did the heads? Did you just switch the ends?

Start with changing the plugs, then the o2's. I might be the fuel pump, but not if the SES light is flashing. One sign of a bad pump, is that it starts harder then normal. Meaning, it doesn't start right up when you turn the key. It would crank over more than normal before starting.

Good luck. Let me know if you want to switch MAF's, coils, etc. I should be on layoff in about a week.

 

broken or weak valve spring

 

Above 4,000RPM, it's calculating fueling solely on MAF feedback. Chances are if you feel it go down hill right at that threshold, it's MAF related. Either your MAF is dirty or your tune is not calibrated for your aftermarket MAF correctly. It's fairly common for the MAF to become dirty - especially when switching to a K&N type oiled filter. Go down to the local Autozone and pick up a can of MAF cleaner (QD Electronics Cleaner) and spray out the inside of the MAF.