Need some imput stat

[brian022687]

So my Tahoe started giving me issued on Wednesday. Coming to a stop at an intersection the engine starting running incredibly rough, and the check engine light began flashing. The code was P0300 multiple cylinder misfire. I did a little looking around and found that the gasket around the fuel spider at the intake manifold was leaking. I replaced that gasket but it's still running exactly the same. Tonight I snapped a bunch of the plastic clips for the fuel spider so I sucked it up and bought a new one, I assumed the problems were coming from the spider because last year I replaced it with a junk yard one, and no change what so ever in the performance. It runs rough at idle in park or neutral, in any of the drive gears it's fine when I am accelerating, however at idle it runs very rough and begins backfiring. I was just looking to see if anyone out there could give me a little advice on where to look next. The fuel spider is brand new, and I check the distributor cap and it was good, the plugs and wires were replaced less then 6 months ago and all the wires look to be in good shape. Can anyone think of anything that I missed?

 

[ccapehartusarmyINF.(ret)]

what year is your tahoe? have the pressure checked in your fuel system that leaky gasket may not be the only leak, also its possible your idle air control valve is bad
the IAC controls the idle speed of your engine

 

[brian022687]

Its a 97 Tahoe, and no I have not checked the fuel pressure yet I don't have the equipment I have to borrow it tomorrow. Any idea where the idle control valve is?

 

[ccapehartusarmyINF.(ret)]

i pulled this up on the net for yah
the first thing id probably do is disconnect the battery for about 5 minutes what this will do is reset the PCM then when you reconnect the battery start it up and let it run for like 20 minutres then take it for a drive now it may run a little funny at first because the PCM has to relearn your driving habits
there is several youtube videos that explain how to check the IAC to see if its bad

 

[SunlitComet]

wrong engine.

so all the gaskets or seals are in place from the work? on the spider it will give resistance to mounting the plenum down so you have to work the spider out of the oval for the plenum to mount properly. you crack a vac line somewhere perhaps? also who made the parts you got?

 

[brian022687]

Yes I double checked the gaskets for leaks after I installed the new spider last night. I didn't find any cracks in any of the vac lines either but I will take another look today. As for the parts the gasket kit was made by Dorman and the spider was made by GP Sorensen. Both from auto zone.

 

[ccapehartusarmyINF.(ret)]

oh duh hes got the 5.7 liter my bad

 

[ccapehartusarmyINF.(ret)]

this be it

 

[SunlitComet]

damn you! still the wrong engine setup. brian, you will find the iac valve on the left side of the throttle body it is the component on the rear. the sensor in front of it it the tps and is directly inline with the throttle shaft. (1997 reset procedure) you can try to reset the iac by turning key for 5 seconds, then off for 10 then start it again. this will only help to control idle speed. other sensors in the system change the fuel ratio to keep it correct in any position. so if it is running like the mixture is off then look for any pinched wiring that was damaged or not plugged in. for that job there was the maf, iac, tps, map, evap purge, iat and most importantly two ground wire for the computer which must be attached to the thermostat housing.