Post Reply 
 
Thread Rating:
  • 0 Votes - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
93 GMC Suburban K 2500 7.4L
10-06-2013, 04:24 PM
Post: #1
93 GMC Suburban K 2500 7.4L
here is my dilemma I have a sensor on the passenger side of the engine on the head just under the valve cover single wire lead.

the guts of it came out it does not leak (anything) but my temp gauge does not work. and have replaced the coolant sensor in the front of the engine. and now on idle it want to chug at about 200-300 rpm but when I press the accelerator it runs fine.

help where i can leave the rest up to the everybody else
Visit this user's website Find all posts by this user
Quote this message in a reply
10-06-2013, 04:35 PM
Post: #2
RE: 93 GMC Suburban K 2500 7.4L
Sounds like it might be the sensor for the temp gauge because GM usually has them on the side of the cyl head, although recalling driver's side. Could just be because it's a big block or maybe they have changed something over the years. (don't see too many big blocks these days)

Typically that sensor has no bearing on the engine running so you are probably looking at more than a single issue. What I would do first is the easy stuff. Make sure the air filter and it's related plumbing are clean and free of debris then while you have that apart clean the throttle body plus the IAC passage, which controls the idle speed. They get dirty / gummy and few people think to maintain that area. Most parts stores handle throttle body cleaner for a few bucks and that likely needs doing anyway. Being 10 years old you may also want to carefully look over all of the vac lines too. You'd be amazed at how a simple thing like that can screw up the works.

If that doesn't solve the problem then head to someone with a scanner and see if there's any stored codes or odd readings, which maye help us identify the culpret.

Let us know how you make out.
Find all posts by this user
Quote this message in a reply
10-06-2013, 07:19 PM
Post: #3
RE: 93 GMC Suburban K 2500 7.4L
ok well I was out in the rain and I unplugged one of the throttle body injectors and the idle came up to normal, so it seems to be running rich but cant drive it like that, so well I was out bought a bottle of sea foam to see if it could dirty injectors so far does not seem to be helping could it be the fuel filter.

just replaced the distributor cap and rotor about a month ago along with wires plugs about 5 months or so, and where is the iac located. over looked the vacuum lines and all seem to be in good condition and in place

help where i can leave the rest up to the everybody else
Visit this user's website Find all posts by this user
Quote this message in a reply
10-06-2013, 08:09 PM
Post: #4
RE: 93 GMC Suburban K 2500 7.4L
This is where a scanner would come in handy but let's stick with the hunt & peck method for the moment. You say it's rich because you pulled the wire off one of the injectors and it got better. There could be several reasons for it being rich but the basics are either electrical or mechanical.

Starting with the mechanical side, I would guess the injectors are not stuck open because obviously one closed when you pulled the wire. You could verify that by pulling the other wire. It's also a good guess the fuel pressure is not up to the sky because I don't think it's possible for it to go high enough to cause what you describe, which puts us to the electrical side of things. IOW, something is commanding it to be rich via the ECM / PCM. (engine computer) This is where a scanner is probably the best thing. Not only will it tell you what codes are in storage but it can see the O2 sensor readings of what is going out the exhaust plus all of the input sensors including that other engine temp sensor which is a prime suspect. (usually near the t-stat) The computer uses temp to set the fuel mix based on temp the same way an old fashion choke on a carb does. OTOH, it's more complex because the ECM also uses RPM, load (via vac readings), throttle position, and a few other things.

Back to where the IAC is located... if you can see the injectors and throttle area look to one side just above the throttle plates and you will see a hole about the size of your pinky nail. Inside that bore is a plunger device that allows air to go around the throttle plates while they are closed. It's controlled by the ECM to hold the idle speed within a preset range, usually around 800 RPM or so regardless of load from PS, AC, being in gear, etc. This plunger gets dirty so it can't move back and forth. It's something few people even think to clean during service work. Just use a generous squirt of the cleaner through that passage after doing the rest of the throttle bore. Start the engine to clear it out (will run like it's flooded) then repeat if necessary. Usually twice is all that's needed if that's the problem. It's starting to sound as if that is NOT your problem but it certainly can't hurt and it's one less thing to do later.

BTW, some of your testing will set trouble codes, especially if you run the engine with things disconnected. You may need to have the codes cleared then drive it to see what new codes come back. Even if the dash light goes out the codes will still be in memory for a long time. Post those code numbers here so we can see what's going on.
Find all posts by this user
Quote this message in a reply
10-06-2013, 09:19 PM
Post: #5
RE: 93 GMC Suburban K 2500 7.4L
If I read through everything correctly I have another suggestion. It sounds to me like you are saying it ran OK before you changed that front temperature sensor, right? If so, put the old one back in and see what happens. The one on the side is for the gauge. But I am also guessing that you changed the one on the front trying to fix the gauge? It sounds like something went wrong when changing the front one. Check for broken wires, loose connectors, corrosion, etc. on that front sensor before doing a lot of other work.

If that fixes your problem you could still clean the IAC just to prevent issues later on.

Let us know what you find.

Thanks for using the forum,
Garner

Interested in Mining? Look here: Coal Mining, PA
Visit this user's website Find all posts by this user
Quote this message in a reply
10-06-2013, 11:51 PM
Post: #6
RE: 93 GMC Suburban K 2500 7.4L
Good eye Garner. My brain has been full for a few days and I glossed over that part. (oops)
Find all posts by this user
Quote this message in a reply
10-07-2013, 09:18 AM
Post: #7
RE: 93 GMC Suburban K 2500 7.4L
Got your back buddy, just like you always got mine! Team Work! Now if it pays off & helps Tommyboy???

Thanks for using the forum,
Garner

Interested in Mining? Look here: Coal Mining, PA
Visit this user's website Find all posts by this user
Quote this message in a reply
10-07-2013, 06:25 PM
Post: #8
RE: 93 GMC Suburban K 2500 7.4L
ok after all the turmoil and guessing and a whole can of TBI cleaner and playing around took it to a friend and he spotted what I did not, the EGR valve rotted away from the base and is floating on the rubber so now all I have to do is replace it thanks for all your help and hope this helps you in the future

but since cleaning the iac my truck does run smoother and looks better

help where i can leave the rest up to the everybody else
Visit this user's website Find all posts by this user
Quote this message in a reply
10-07-2013, 06:33 PM
Post: #9
RE: 93 GMC Suburban K 2500 7.4L
Thanks for the update. Please let us know how it works after you replace the EGR.

Thanks for using the forum,
Garner

Interested in Mining? Look here: Coal Mining, PA
Visit this user's website Find all posts by this user
Quote this message in a reply
10-07-2013, 09:17 PM
Post: #10
RE: 93 GMC Suburban K 2500 7.4L
Just a pointer there Tommyboy... When you remove the EGR valve there will be lots of carbon built up in the manifold holes. Scrape them, clean them, and blow or vacuum them out or the chunks may break lose and get stuck in the new EGR valve causing it to stick open, which will have you pulling your hair because it will act like a vac leak but you wont be able to find it externally!
Find all posts by this user
Quote this message in a reply
Post Reply 


Forum Jump:


User(s) browsing this thread: 1 Guest(s)