350 accelerates roughly and sometimes idles roughly

[benscharlotte21]

Hey new member here. First off I have a crate 350 with about 15 thousand miles on it. Here's the unfortunate series of events...

Got the truck during the summer in pieces and built her up.
Began running like junk a month and a half ago. Got a 44 code and tested the MAP sensor and throttle position sensor. Both appear good. Replaced O2 sensor, got a little better for 20 miles but then went back to her old ways. Then went through vacuum lines. Didn't help. Earlier today I replaced the fuel filter and did a throttle body rebuild. No improvement. Then tested EGR and thats good too.

Couple sidenotes: When I do the diagnostics with the OBD the IAC valve clicks and makes a vibration noise. Also at idle sometimes there is a whistle, however simply touching the throttle without even changing any RPM makes it go away.

The issue seems to be spurratic. Once in a while it will drive perfectly but usually I can tell not all the horses are there.

HELP!!!!

 

[Boone83K10]

What does the book say for code 44? Never assume it looks good, always assume it's the problem.

 

[benscharlotte21]

Code 44: "Lean Exhaust... Check ECM wiring connection terminals, have the fuel pressure checked, check the oxygen sensor wire, Check the carburetor throttle body gasket, vacuum hoses and intake manifold for leaks, replace oxygen sensor*"

Im about to go out and check the ECM today, maybe Ill find something there.

 

[89Suburban]

The injector wires look ok under the air cleaner collar? Not damaged or pinched, missing insualtion etc?

 

[Irishman999]

A couple things lead me to believe you have a vacuum leak. The whistling sound is probably a vacuum leak. Vacuum leaks cause the engine to run lean so that explains the code. You mentioned that you rebuilt the throttle body, did it just get a rebuild kit or did you have the shaft fixed? The shaft will wear out the body and cause a vacuum leak. The fix is drilling out the throttle shaft holes and installing bushings.

Today, go find a can of either (starting fluid). With the truck running spray the either all around where the intake meets the heads, all over any fittings that go into the intake manifold, all over any vacuum lines and lastly spray it around the throttle body itself to check the base gaskets and throttle shaft. When either finds its way into a vacuum leak the engine will rev up a little bit.

 

[Boone83K10]

Code 44: "Lean Exhaust... Check ECM wiring connection terminals, have the fuel pressure checked, check the oxygen sensor wire, Check the carburetor throttle body gasket, vacuum hoses and intake manifold for leaks, replace oxygen sensor*"

Im about to go out and check the ECM today, maybe Ill find something there.

so you are running lean. you said 1.5 months ago this started happening.. so when it got cold. it ran better for 20 miles because it took that long for the O2 to lean foul/gather the info for the computer. you didn't say what fuel delivery you have but I assume TBI since you rebuilt it.

did you check the fuel pressure?

 

[benscharlotte21]

I'm going to check fuel pressure later today. And yes it's TBI.

There is nothing that looks bad around the injector wires all insulated well.

What are you referring to as the shaft irishman? The throttle itself?

Thanks


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[Irishman999]

I'm going to check fuel pressure later today. And yes it's TBI.

There is nothing that looks bad around the injector wires all insulated well.

What are you referring to as the shaft irishman? The throttle itself?

Thanks


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Yeah, that thing that goes through the throttle body that has butterfly valves screwed to it. One end is connected to your throttle cable and the other has some springs and stuff on it.

 

[benscharlotte21]

As I am spraying starter fluid on it right now I seems to effect the engine. I think it may be sucking mist in the intake directly though so I will have to get creative


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[Irishman999]

As I am spraying starter fluid on it right now I seems to effect the engine. I think it may be sucking mist in the intake directly though so I will have to get creative


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hold the can close to the throttle body, just use short little blasts. If you spray it directly into the throttle body it usually slows down the engine for some reason, not rev it up.

If the idle is increasing as you spray that stuff on your throttle body that is a good indication of a vacuum leak. Part 2 of this is finding a vacuum gauge. You might be able to barrow one from orileys or Autozone, plug it in and see if the needle is steady or bouncing.

 

[benscharlotte21]

I determined the source of the whistling is the drivers side port of the throttle body. Suggesting that it is sucking air through it at idle. Isn't the IAC valve supposed to open and close to allow air at idle or am I mistaken? I put the air cleaner on and sprayed starter fluid around the shaft and as I suspected it didnt change the RPM or anything. Also when I connect the terminals in the plug for the OBd and scan the IAC clicks rather loudly.

 

[Irishman999]

Im going to be away from the computer the rest of the day so I will leave you with this.

Check everything again, all vacuum lines, connectors, fittings and even the gaskets. Make sure the bottom of the throttle body itself is flat. Grab the throttle shaft and see if you can move it around, if it wiggles around you should get bushings installed.

The tool to install the bushings is a couple hundred bucks, if you look around online you can find rebuilt throttle bodies for a few hundred usually. What I did with mine was put it in a box and send it to our buddy on here Jims86.

 

[89Suburban]

http://www.gmsquarebody.com/forum/showthread.php?t=1570

 

[benscharlotte21]

Just an update: I upped the fuel pressure a little bit, replaced the cap and rotor, and plug wires (for ***** and giggles). The increase in fuel pressure seems to have helped a little bit. Next question is... when I depressed the EGR valve at idle nothing changed. Looking in the Haynes manual it should drop RPM. Also if this is the issue that could cause a lean condition right? And rough acceleration/idling? I appreciate all of the time and help.

 

[89Suburban]

Yeah if you pressed that valve by hand it should just about kill the motor at idle. Hesitation on initial acceleration is another possible sign of it not functioning properly. This is a subject I still have not gotten a full handle on after a lot of research. Here is everything I found so far if it helps, you can browse through, some troubleshooting stuff in here too.

http://www.gmsquarebody.com/forum/showthread.php?t=6902



If you have a vacuum gauge check this out as well for troubleshooting:

http://www.gmsquarebody.com/forum/showthread.php?t=1570