94 GMC Jimmy hesitation problem

[MT-2500]

If OBD 1
Jumper pin A & B turn on key and read codes on check engine light.

[shanes76]

ok, cleared codes this morning and I have these codes now
23
35
43

[MT-2500]

You have never posted back your fuel pressure readings.
What are they?

Code 23 is intake air tempt sensor code.
35 idle speed problem.
43 knock sensor problem.

Have you got the air intake sensor pluged in?

[MT-2500]

Also you have never told us about your idle speed RPM?

To be able to help you we are going to need info

[shanes76]

Im not sure where the idle air temperature sensor is, I have no way of getting the feul pressure readings, no gauges and dont have the money to buy them. Im not sure of the idle speed RPM's, but I can tell you when your idling you go about 20 mph

[blazes9395]

The air temp sensor is located on the rubber boot for the incoming air, at the throttle body. Make sure it is plugged in and not damaged, this sensor is easily damaged if your not carefull. This can cause a rich/lean/hesitating problem. After getting some more info and thinking about it, I tend to think you have a fuel problem, maybe a leak at the injector, or the regulator. You do need a fuel pressure guage to check. You could take the upper part of the intake off and check for washing, but you run the risk of breaking the upper intake gasket, and if money is short, then that would make your truck run real bad, if at all. Generally, when you remove the upper intake, its a good idea to just replace this gasket, it becomes brittle and cracks causing vaccuum leaks. As for the knock sensor, check your wiring and make sure its connected properly, if that checks out and the wire is not damaged/burned/broken, then your next option is to replace the sensor.

[shanes76]

ok, just replaced the IAT sensor and Im down to one code now its 43 which is the knock sensor- my old IAT sensor was hollow, you could see right thru it and the end was pretty carboned up

[MT-2500]

How isthe fuel pressure doing?
Have you checked it and checked for fast leak down?
How is the idle doing?
How is the hesitation doing?

Have you cleared codes and look to see waht comes back?

[shanes76]

yes I have cleared the codes and the only one that came back is 43
I havent got to test drive after installing new sensor so I will post those results tommaro evening, but it did seem to idle better sitting there and it did start right up
I havent got the fuel pressure checked yet, but it seems fine to me, before after starting the motor and giving it some gas it would, it would seem like it hesitates just giving it throttle, now it dont fter the new sensor so hopefully with some good luck it might be fixed

[MT-2500]

You are gaining.
Let us know how it goes.

[shanes76]

I definatly will MT, I still may end up cleaning the IAC sensor since the IAT sensor was pretty black, but it does seem to have an improvement just sitting there running, and I should probally do some new plugs after it was running rich and cutting out or whatever it was doing, or what do you think, should I get new ones just to be on the safe side?

[MT-2500]

I would go a new set of AC Delco plugs.
It has been my experience when a plug get black gas fouled they are done for or hard to clean.
Check that fuel pressure and leak down for sure.
Let us know how it goes.
On the knock sensor code save it for last.
First thing on it is check the wiring and voltage to knock sensor or sensors.
Good Luck

[shanes76]

knock sensor is the only thing left throwing a code, it did run a little better, didnt hesitate or cut out as much, but now it has a small surge

[shanes76]

MT I have been thinking, I didnt have the surge until yesterday on the way home, which I drive an hour to work then an hour home, I replaced the IAT sensor on the 25th, just started it and let it run maybe 2 minutes and that was it, the intake hose and old sensor are pretty carboned up, when I was on my wayto work yesterday I had a cup of coffee and noticed what looked liked a bunch of carbon deposits(like in the intake hose) on the lid of my cup and is it possible that the EGR got clogged up from it? I never had this until I removed the intake hose and put in the new sensor. And also what if my EGR valve was stuck, would that cause the hesitation and slight back fire? Or maybe its no operating right, it hasnt throwed out any codes, when its cold it idles pretty good and now when it warms up, still doesnt idle right really, but I did read that an EGR valve can cause pinging so maybe thats why my knock sensor threw a code. And I also read it can cause a misfire which could be my hesitstion im getting? And also after getting ready to leave from work yesterday it had to roll over about 7 times to start, but in the mornings when you hit the key it fires up- just a thought

[shanes76]

ok, just noticed this today, when I go out and start it and turn the heater on it dont blow nothing out but after it runs for 1-2 minutes it starts blowing, its like the vacum isnt strong enough to open the vent but as soon as it warms up it blows real good, would it have something to do with low vacum or something, I think its related to my hesitation somehow