87 C30 454 TBI Rough Idle and almost stalls out if you stand on it.

[Braden4]

Ok well first off I'm new to the sight so hello to everybody and I apologize for asking a question that might have already been answered.  Now for my question.  Like the title says I have a 87 C30 w/454 TBI and 400th.  I bought the truck and it was running rough.  Figured needed new plugs and wires.   Was still running rough after that so I sprayed for vacuum leaks with some WD.  No revs with that so I moved on to timing.  Keep in mind I do not have a timing light.  Ya not the preferable way but I advanced until it hit hard on the starter and then backed it off.  Still no improvements though.  I did have to move the wires one counter clockwise to get the timing even close.  This did help as it hardly had enough power to move before.  I have checked to ensure that all plugs are sparking.  Triple checked the firing order.  I'm running out of ideas.  I'm not real good on the electronics.  I'm about to the point of ripping off the TBI and throwing on a Q-jet.  When the truck is first started to be able to put it in gear you have to hold the brake and push the gas to idle it up so that it will not stall out when put into gear.  After it warms up that goes away for the most part.  At all times though you really have to feather into the throttle or else you will stall it out.  Any ideas would be great.

Thanks

[VileZambonie]

I'm about to the point of ripping off the TBI and throwing on a Q-jet. 

This is about the worst idea you came up with.

The way you timed it is unacceptable. You need a timing light and to put the EST in bypass mode. Triple check the firing order. You said you replaced the plugs and wires. What about the cap and rotor? Did you check for codes? How's your fuel pressure? Make sure the EGR isn't hanging open. Pull the vacuum hose off of the valve and see if it runs any better.

[Da67goatman]

I would bet on the fuel pressure spring being broken, it happens all the time, my aunt just replaced hers last month.

[Braden4]

Ok I will head out and check some of those things out.  I do appriciate the help as like I said the electronic stuff kills me.  I will try to get my hands on a timing light today even if I have to buy one.  Now for the bypass mode.  Where do you unhook that wire for the EST?

[Da67goatman]

Its a tan/brown wire with a black connector usually located around the master cylinder, it should be outside the wire loom, so it can easily be located.

[Braden4]

OK so I went to a guys house that I  know who teaches at the school in town.    He set the timing for me properly.   The truck was still running rough.   We or well he figured out  the timing is not advancing properly.  I  went  to the parts store and came up with codes 43 and 44.   43 is the  code for the  knock sensor.   Hunted all over the motor and low and behold no knock sensor to be found.  There is a bolt stuck in the hole where it should be.  Now I'm on the hunt for the wire its self.  My understanding is it is a singal wire?  If you have any help that would be great.

[Braden4]

I have  done some  hunting  online and I guess some of these do not  have knock  sensors.  Then I  would be stuck  wondering what would be my next step?

[topp]

If your computer shows a code for it, the computer is programmed to have it....

[VileZambonie]

Yes, it should have a knock sensor. That is not the cause of your rough idle problem though.

BTW your truck is an R30 not a C30

[Braden4]

Ya I'm tracking the R30 I figured that one out yesterday.  Problem is if you say R30 to some people they look at you like your crazy.  Thanks for the wiring diagrams.  Also tell me if you think this is a bit excessive.  When I was on the hunt for the knock yesterday I discovered a block heater.  I would imaging after market.  Thanks again.

[VileZambonie]

I'm not really sure what your question is or are you asking a question?

[Braden4]

Guess my question is  do I really need  the block heater also can you point me in the direction to finding that dang  knock wire.  I'm looking  at the diagram and I'm still struggling to find it.  I've pulled the starter nd  hunted all over the engine bay.

[VileZambonie]

Where do you live? You don't need a block heater.

Sounds like someone cut it or tucked it away. Maybe you should just start at the ECM and trace it out from there or run a new one. The connector end looks like this.



http://www.acdelcotechconnect.com/pi/wiring-connectors/gm/pigtails/1-cavity/male/

[Braden4]

OK I  chased all four of the blue wires off of the ecm.  One  goes to the driver side injector, one  to the throttle position  sensor, two of them go to the vacuum control mounted behind the throttle position sensor.  What should be mynext step. Thanks

[VileZambonie]

Sorry about that, I meant to say ESC module not ECM. Did you see the wire coming off of the ESC module in the picture I posted? Follow that wire to where the knock sensor should be.