Hi guys
I just changed the engine in my 97 Jimmy. Upon startup yesterday, the idle went right up to 3000+ rpm. After a few minutes, it settled down to 2500. I checked the throttle cable for binding but all ok. I disconnected the cable from the throttle body and idle went down to normal. When connected, there is approximately an 3/16" gap between the throttle lever and the stop screw . It looks like the cable is a bit short. Is this adjustable? What is the gap between the throttle plate and the bore? It seems excessive. The hood is not back on yet but, I did plug the vacum line that goes to the vacum canister attached to the hood.
This is the same intake and fuel injection system that was on the other engine. Aside from the fact that it had a few spun crank bearings, it ran good. Nothing was changed besides new gaskets for the intake and the usual tune up items: fuel, air & oil filters, plugs and wires as well as liquids. I did not notice if the throttle lever had this gap before dismantling it. All vacum hoses seem fine. BTW, it is an 4wd A/T so, I did not take it for a spin yet as I find 2500 rpm to be a bit high to engage the tranny. I thought of removing the throttle cable and recrimp the stop pellet near the accelertor pedal but, I tought I would ask more knowledgeable people first. I will try to find the problem again today but, help is more than welcome. I am pretty anxious to take it for a spin. Thanks
Don

PS I forgot to mention that no codes popped up on my code reader.

 

i just took off my intake manifold and reistalled it and i didn't have any problems with the linkage.

disconnect the battery for a few minutes to reset ecu.

what year is the motor out of.

u should check the idle air control valve.

did the linkage mount right on the motor?

i had a bad vacuum leak but it didn't run that high in the rpms.

 

Quick update. I put the hood back on so I could connect the vacum canister. No change. I had an exhaust leak at the Y pipe. Fixed that and I dont know if that helped or the fact that I disconnected the cruise control cable but, the idle is now at 1500 rpm. Can't seem to get it down any lower. If I force the throttle lever to close a bit, idle goes down but goes way back up to 3000 rpm when I let go of it.

The battery was out of the truck all the time the engine was changed. It did this upon startup yesterday.
1997 Jimmy brand new crate motor from GM.
Yes, right on with no problems.
I was thinking about that but hesitate to remove it since it was working fine on the other motor.
Thanks for your help and keep the info coming. I would like to be able to run this thing this week.
Don

 

The throttle plate should close fully for idle. It sounds like you have a problem with the throttle cable. Are you sure you mounted the bracket back on properly?

 

This is how it was on the old motor. The throtle plate is still open a bit.
Don

 

Are you sure that the throttle is open? The throttle blade does sit at a slight angle when it is closed fully.

 

Now that you mention it, I now it is at an angle. I figured is was open because I thought I saw a gap between the plate and the bore. I put the truck out yesterday night and now it is pouring like crazy. I will mesure it when it stops raining. On an a side note, if I disconnect both cables, the idle falls and I can shift it easily although there is not enough power for the truck to move. What bugs me is the fact that I just took the whole intake with T/B still attached, removed from the old and back with the new. Coud having cleaned the intake damaged a sensor and is there a way to test the sensors that are located on the intake with a multimeter?
I re read my first post and noticed that I did not mention the fact that I changed both upstream (pre cat) O2 sensors. They were given to me by a friend and they came out of a recent 4.3l truck. The connectors were not the same so I cut the wires and adapted the jimmy connectors. Could this have something to do with it? The one on my truck were Delphi and these are Denso and the computer does not throw a code although the check engine light flashes continually.
Don

 

I tried to find the problem again today. Here is what I did.
I cleaned and tested the IAC valve and cleaned the throttle body. Checked the tps. Cleaned the egr. Now with the cables correctly plugged in, I get 3000 rpm idle. If I unplug the cable that is to the left of the throttle cable (facing rear) idle goes down to 1500 rpm. If I put it in gear (A/T) the idle goes down to 1000 rpm, the truck shakes like crazy and dies. I unplugged the cts to see if the pcm would throw a code and it does., My MIL is always flashing when the truck is running but no codes. I took resistance readings on the coolant sensor as well as IAT sensor and all good. I unplugged the 2, O2 sensors upstream of the catalyst and let the truck idle at 1500 rpm for 30 min. No codes.
I really need help diagnosing this problem. Like I mentioned before, filters, fluids plugs and wires are all new. There are many knowledgeable people here so, please, help me with this. Thanks.
Don

 

Have you tried unplugging the battery for 10-15 minutes to reset the PCM, then turned the key on, but not starting the engine and waiting for another 2-3 minutes or so? This will allow the PCM to run the IAT all the way in and then when you start the truck, it may idle slower.

Have you made absolutely sure that there are no vacuum leaks? If you have to, disconnect all vacuum lines to the intake and plug the ports.

 

I did that and there are no vacum leaks as well as unplugging the battery as suggested. Like I mentioned earlier, I also replaced the O2 sensors with Denso models that were given to me and come from a more recent 4.3 of which, I have no detail about the truck. Checking auto parts on line, I see that the Denso I have are not the same # as the ones that should go on my truck (97 Jimmy). Could wrong O2 sensors be responsible for the truck idling to fast (1500rpm) and shacking when put in gear? It does not register a code even when I run the truck with both front O2 sensors unplugged. I don't want to buy new ones if I don't have to.
Don