simpsonracing

Very interesting. I appreciate all the info i just went out and baught a Chilton manual and was reading it I just noticed that it states everything you just said. The fuel pressure falls as soon as you turn the key off. Shouldnt it remain pressurised for at least a couple of minutes? Also last night i pulled a valve cover off just for GP and it doesnt have a flat cam. If the o2 sensors and the cats are bad together then pulling the exhaust appart or in my case of getting into a hurry and cutting the exhaust appart LOL would have no difference in the running of the motor right? Because the PCM cant get the right readings from the sensors.I also noticed last night when i opened the throttle body butterfly its got a lot of carbon built up on the injector lines and the intake plenum on the inside is black im assuming from backfiring. Another thing im wondering is if the timing chain were to get too much slack in it it would cause the same problem right? Because the crank sensor and the camshaft sensor would be out of sinc. To be honest with you thats almost how it sounds to me like the timing is way off and its really lazy. How would i be able to diagnose that kind of problem. With a timing light? I am definatly up for using the injector cleaner if my local GM dealership will sell that stuff to me. There a bunch of tighwads here about that kind of thing. Last night i drove it around and it was backfiring and spitting and sputtering and when i parked it the Cat was glowing red hot again. Im gonna get back to the Chillton and see what else i can find thanks again for the help.

maxxman04

simpsonracing, a red hot cat is usually an indication of not enough fuel, engine running lean, possibly out of time. what year is your rig? up to bout 94, some 95, gm used throttle body injection, the non vortec motor. 95up has the vortec 350, different pcm altogether. newer rigs, you need a scan tool that can read the cam offset. if it's only off slightly, turning dist will work, but if it's off quite a bit, then you'll have to take dist out, reset it right. it sounds more like a fuel problem tho. lack of fuel will cause backfires. check fuel pressure on rig against specs. you might have a bad fuel pump, pressure regulator, or even something as simple as a clogged fuel filter. start with the simple, work your way along. good luck.

tm4hammer

To check for timing chain slop pull the dist. cover, and turn crank pully clockwise until the rotor starts to turn stop mark the position of the crank pulley on housing and the pulley itself with some chalk now turn crank pully counterclockwise until rotor just starts to turn stop mark the position where crankshaft pulley stopped on the housing inline with the mark you put on pulley now measure how many degrees the two marks on the housing are apartare using timing light degree marks as a reference 10 or more degrees shows alot of slop! and yes the exhaust sensers and plumbing would effect how it runs if they are still active and sending a signal test the sensers but dont get ahead of yourself here slow it down test each of the systems i mentioned systematicly and completly dont bounce around start with the most obvious like plugs , wires , cap and rotor just because you have replaced them doesnt neccessarly mean that they are not defective go back and do a continuity check on the wires look for arcing , check the cap for cracks , the rotor for breakage i have seen a brand new rotor fall apart just from sliding it on the shaft and cause all these symtoms because it spun erraticly and then get into the heavy stuff one system at a time! if your checking the fuel system then go from start to finish not bypassing a thing the book you bought should tell you how to check each input sensor i mentioned and each of those systems could play a part in what you are experiancing! the GM cleaners i mentioned are available to the public simpsonracing and they sell them through their parts department just like any other part you shouldnt have any trouble buying them , if you get hung up on a proceedure send me a message and let me know and i or we will try to help you through it if we can one more thing when you start it up run it at about 2 grand for a couple a minutes to reset some of the systems ok ! burning day light time to get dirty LOL AND HEY MAXXMAN were you able to track down what was causing your problem
HAMMERGONE!!

maxxman04

waitin fer mother nature to cooperate. hopefully soon. i'll keep y'all posted and update with results. preeshyate yer time tm4hammer.

simpsonracing

Hey all found the problem. The Fuel Pressure regulator was bad but because its Sequintial injection (I think is what its called) has the fuel meter body inside the intake. Anyways it took out the fuel meter body injector lines and poppets from backfiring. Im not sure how much its gonna cost to fix but ill keep everyone posted. My friend at work said he went through the same problem but his was a rail style injection so his regulator is on the outside of the engine. thanks for all the help all.

tm4hammer

Good work simpsonracing! Takes a load off doesnt it! Ya MAXX the weather has kinda put a damper on my party as well ! Having to juggle other peoples projects in and out of my garage to stay warm and stay ahead of the game and work on mine too! LOL like that will ever happen ! I feel for ya brother ! later!
HAMMERGONE!!

maxxman04

update:
well, cap/rotor/wires that were on my rig, not so good. thought i changed all that, but from looks of everything, i'm in some other world. so, changed EVERYTHING, used that cleaner from gm dealer. seems to run alot better. did pull codes, misfire#5 cylinder, which i've been getting, o2 sensor malfunction, which after reading live data off scanner, it would appear that one of them is in fact not so well. so i'll change that out. initial road test, that miss at freeway speeds seems to have gone. still a real slight miss at idle, very slight, i'm hoping that cleaner, and some good ol' fashioned foot to the floor a few times, will burn out the crap in number five cylinder. gonna check plugs again in about a month. fingers crossed.

tm4hammer

Here is something you may want to give alittle thought to SR ! You may have come across what may well be the end result of a problem , but not necessarly the source or sources. Now ask yourself why and what caused this!
HAMMERGONE!!

tm4hammer

Right on MAXXMAN ! Sounds like you just about got it licked! And that other world you spoke of , I seem to frequent more often then not myself and it really isnt such a bad place after all, But then i have a good excuse in that im older than dirt! Thats my story and im sticking to it!
HAMMERGONE!!

maxxman04

UPDATE:
seems problem is fixed!!! just gotta replace one of the 02 sensors. ran awesome down the freeway. might also take to dealer to have the cam offset checked. otherwise, good to go!!! thanks guys for your help.