ENVYMYSS

just installed pacesetter long tubes and off road y pipe now im getting a misfire under load and a po300 and po400 code. no rear 02's and runs fine at idle but if im cruising in gear and accelerate in gear it shakes. ANY IDEAS??? HELP

car is a 96 ss z28 otherwise all stock

ThoR294

iTrader: (6)

p0400 is EGR failure (I assume you got the race style headers, with no EGR hookup)

P0300 is random misfire.

double triple check your spark plug wire routing.

MasterTomos

iTrader: (15)

Did you replace the front o2 sensors when you did the swap? People have reported that their sensors go bad during header swaps, even though they worked perfectly beforehand.

cardo0

P0300 is random radom/multiple cyl misfire and P0400 is EGR flow.

Headers will lean out the mix but random misfires sounds more like burnt plug wires or bad plugs. I think u can get lean misfire though. Fix would be a PCM tune or maybe just to test u could use a adj fuel press reg and increase the fuel press for a test run.

The EGR flow would be a bad solenoid as i think thats all the PCM can see. It dont measure flow or have any position switch on the EGR vlv. All it knows is if the EGR solenoid gets energized. Unless it can use O2 sensor output to see EGR flow results - i doubt it.

ENVYMYSS

Cyl 6 has high misfire counts under load but few present on 3,4,5 also. Egr codes i have read are common after lt install due to lack of backpressure but just came on today sop i thought that was odd. The lt's do have air/egr and everything is hooked up. Also when i was monitoring with tech 2 while driving the temp[ has been higher since install and fans dont kick on until about 232 degrees then the low speed comes on but have yet to have the high speed come on. Cruising is fine and i can command them on with tech 2 but before install the temp usually wouldnt get up to half temp any ideas?

ThoR294

iTrader: (6)

check your plug wires

ENVYMYSS

i did check them by feel cause i could not get under vehicle and it does not seem melted anywhere but i will look better this weekend.

Anyone know anything about temp issue? Any way i can lower fan kick on temps without tuning? If not does the jet dst work well and is it user friendly?

MasterTomos

iTrader: (15)

Only way to have the fans come on at a lower temp without tuning would be to run a toggle switch to them. A couple different companies sell them right around $65-80 usually, but what does heat have to do with this issue?

SS#502

If the car runs really hot and rough you could have some plug wires in wrong position, like #5 and #7. It'll run all jacked up but it will run. I would definitely check to see if they burned on one of your pipes and check your O2 wires also since they sit really close to the headers.