I average bout 180 to 220 miles per tank.... Is this kinda low? I cruise probably 80% time 20% wot, tires all at 40psi, brand new paper filter, car is 99 z28 6spd with 145k on it...

I seafoamed it after getting a o2 sensor code and code has cleared it self, am I just masking the problem? And still need to change o2? I also have done maf cleaner , and have noticed for a long while now the motor either feels like it runs smooth or it feels like its almost missing motor gets louder and struggles....

Spark plugs r new, do coil packs or wires need change? There stock

 

First I'd put new wires on, then see how it runs.

 

Oem, msd, or other wires?

 

I have always run MSDs and have good luck with them. One of the main things I like is I can pull them off the plugs as many times and I want and they don't break. Always a good connection and never had any problems with them.

 

I roll about 270-280 mile and still have almost 1/4 tank.But around town i usaully 1st 3rd to 5th shift it as banging threw every gear is not nessasary.This seems to help it a lil with the MPG. I have 3.73 gears also.On the hwy it does great.

 

Any good wires will work better than wore out wires. I have always used the Accel universal cut to length wires....you can get several sets of wires out of one kit

 

Probably still needs those O2 sensors. I would also change the fuel filter if it hasn't been done yet.

 

Fuel filter done

 

what should good wires ohm out to?

 

If I remember right I think they should be around 2,000 ohms a foot

 

You can ohm out the wires to make sure they have continuity but, remember the normal use has more voltage going through it then your DVM.

 

Is this a recent change in mileage or has it always been this bad? If recent, back track on exactly what you have done.

I agree with above posters, start with wires and consider changing O2's. Might run a compression check to see if you have any low cylinders as well. Do you smell gas in exhaust? What did plugs look like when changed? You have to be pig rich to burn this much fuel.

I typically get 360 - 380 miles per tank in daily driving - not all highway either. That's on 87 octane gas too.

 

H/C/I 6.0 with a stalled auto and I usually average 180 - 220

If your car is stock there is deff something wrong. Sounds like you are on the right track though. No pending or stored codes right? Do you have an interceptor or anything similar to watch the missfire counters? A snap on brick will do it too.

I had a problem with it running rough now and then and spent TONS of timing trying to track it down, once I was able to see the misfire counters I found out it was isolated to cyl 5. I swapped the coil packs and found it moved with the coil packs, then swapped individual coils and found it did not move then. Turned out to be a wire rubbed through on the coil pack harness and was shorting out.

If you feel it missing you need to see the counters to tell which cyl it is. You may have a fuel pressure issue as well, pump could be on its way out. Only last idea I have is that your sender is going bad and showing the tank as empty when there is still fuel left. When you get gas on E how many gallons can you get in?

 

I got 270 miles to my first tank on 93 beating the crap out of it because of the newness to me. It's going for a tune up Thursday with more conservative driving planned minus the 3-6 passes I plan on making Friday night. I expect at least 300 miles this time.

 

I just got car bout month ago, bought from a friend, does have a zex wet nitrous system on it, which I do plan on pulling off...

Another note at lunch today I punched it and got up to 80 smoothly then got my food on way back to work I punched it and feels like its vibrating under me... It's been doing this a lot, not sure if its engine related or not, I already replaced motor mounts with prothane and energy suspension on trans mount, get rid of a lot of vibrations but still it feels ugly as hell sometimes when I gun it

 

If you wanna sell the kit complete, drop me a PM lol. I just want a small 50 shot.

 

It's a 100 shot kit lol and I'm returning it to the the original owner, good friend, heads up, the spark plugs are 2 steps colder , will this affect mpg?

 

Have 241k on 2000 z28. I get about 250 miles running close to 50% wot with a solid 2 -3 gallons left in reserve since im judging 250 based on when the light comes on. Highway i get about 25mpg runnig 70+ mph. (i live in south texas)