Hello guys. So I have been having this problem for quite some time, just didn't think it was this serious. There have been times in this past summer, when I start up my truck and it starts up fine. Then, if I shut it off, and start it up again, it starts like if its dying, and the rpm needle is going up and down, until it finally settles down, and the truck becomes stable. Now, I do have a K&N FIPK, and when I first had it installed, I got a SES light. My mechanic told me that it came on because there was more air than fuel. The light went away, but every now and then, I'll be at a red light, and the rpms will bounce up and down, causing the car to "jump" on me. Now after that being said, let me get back to the main question. I went to my mechanic, and asked him about why there are times that the truck starts up like if it is about to die on me. So, he decided to test the fuel pressure, on a valve that it has somewhere behind the air intake. He told me to start it, and then shut it off. After I shut it off, he showed me that the fuel pressure was dropping. I do not know what any of the readings were. All I know is that he told me that my fuel injectors are bad. I believe it is called "The Spider". It is going to be a big job, but I am going to have to do it. It will be about $700 with AC Delco injectors. Now I know why I have been wasting so much gas, and why my exhaust smells like gas. NOW, my question is, could the damaged fuel injectors cause my SES light to come on, and my RPMs to go crazy, because I am losing fuel, therefore being a lot more air than fuel? Or is it just the K&N intake that causes that?

 

its the fuel system that does that your intake wont effect that change your fuel system/injectors out and retest fuel pressure the same way k

 

ok, thanx. Btw, what do you think I might as well replace when taking all of this stuff apart? My mechanic recommended the intake manifold gasket set. Do you think I should also replace the fuel pressure regulator? Is there anything else, because I really don't want to have to pay double to replace something else again. I rather kill 2 birds with one stone.

 

yea if you have buildup around the intake manifold on the inner part of the head were it bolts to i would but if you take it all apart you might as well to get it outta the way its not that hard i did mine in my driveway there is a couple posts of step by step to do it my suggestion is felpro pinto gaskets for the intake and it comes in a set for the manifold,plenum,throttle body all that you need and if you have an autozone near you i think its only 30 bucks for the set. as for the regulator replacing that to would be preventive maintainence which would save you in the long run to have to it now with it all tore apart versus later and tearing more apart. good luck with the repairs let us know if you need anymore help.

 

Ok. Thanx a lot. You've been a great help.

 

Ok.. Let me start off by saying your mechanic doesn't know what he is talking about if he 'thinks' the SES light is caused by an aftermarket intake messing with the air fuel ratio. An intake will not change the AFR, period. The AFR is controlled by numerous sensors, but primarily by the MAF sensor (detects the amount of incoming air) and the O2 sensors (detects the amount of free oxygen in the exhaust). Between those two sensors, they compensate for any change in variables affecting AFR to maintain ~14.7 to 1 AFR (optimal for gasoline).

With the fuel pressure, you will have to fill us in on what it is doing. Grab yourself a fuel pressure gauge from your local autoparts store ($20-$30) and hook it up to the fuel pressure test port (shrader valve much like a tire air valve) that is located behind throttle body and slightly to the driver's side of the upper intake. With the gauge connected, turn the key on and wait for the pump to cycle. The pressure should rise to 55-60psi and hold steady. Turn the key off and watch the gauge, marking down the time it takes to drop a certain amount of pressure (2psi or 5psi depending on rate of leakage). Then let us know what the pressure leak down rate is (psi per hour, minute, or second depending on the rate of leak down) and if it levels off at some point.

If you find that your pressure leaks down, then you could have a few different things happening. #1 is a leaking FPR (fuel pressure regulator). #2 is a leaking electronic injector AND poppet nozzle. #3 would be an external fuel leak (pretty obvious). And #4 would be a check valve problem in the pump. #3 & #4 are long shots, but I have to mention them. #2 is not unlikely, but still requires two components to be faulty. #1 is the most common for the older CPI motors, but is still a possibility on the SCFI motors.

If you end up finding that the FPR is not leaking and conclude that one or more of the injectors are leaking, then the more economical approach is to replace the SCFI spider with the updated MFI spider which can be purchased for around $200. I was able to get mine from the local Chevy dealer for just over $200 in my hand which is cheaper than replacing 2 individual old style injectors.

Now, once you get the fuel lines off and the upper plenum off, you can reinstall the fuel lines and pressurize the system. This will allow you to pull each injector out individually and check for fuel leaks. If you notice that the FPR is wet on the underside, then the FPR is your problem and you should be able to replace it without removing the spider from the intake.

While you have things torn down, the lower intake manifold gaskets are not a whole lot more work (although it can be fun to get the accessory drive bracket out of the way). But if they aren't leaking, then there really isn't a need to tear it down that far unless you want to.

Hope this helps a bit more.

 

that accessory drive bracket isn't that bad kyle the biggest pain imo is the powersteering pulley to reach in there bent over for a while to get it off if it is haveing trouble coming off what a pain lol [8D]

 

No need to pull the pulley off although I find that a lot easier than loosening/removing the two hidden nuts that hold the pump to the front of the block. I know exactly what it's like.

 

how to install and remove fuel lines from fuel rail to fuel filter on 96 blazer 4wd help would accepted thanks

 

Blazer1996, you might want to create a new thread on this... Your problem doesn't really apply to the topic in this thread.