Like Seal said and I belive I said in my first post. Hook up all the stuf you took off. Test every part before you buy new. Use the book don't wing it.
The system works by getting data from sensers. Taking emmisions "stuff" of changes that data.
This is not a car from the 70s where you could block the EGR and make it run better. Also if your tranny is computer controlled it may not work right.

 

There are only a few things I have bipassed on the engine. Firstly, I have dual free flow cats, so the air pump is no longer useful, because it doesnt go into anything. The PCV and crankcase ventilation system is intact, but the solenoid bank is no longer operational. There are 3 solenoids, carbon canister, preheater and egr. All are based on controlling emissions, but none of them should effect either the fuel mixture of the timing as far as I know. All vacuum hoses going to or from the TB are disconnected and blanked with the exception of the MAP and break booster, and the only air lines coming off the manifold go to the vacuum gauge and my 4WD actuator. Apart from sensors on the TB, the only other sensors that control fuel and timing are the MAP, O2, CPS, and HE... am I right? The computer is always reviving information from other systems but it should't change the engine performance.

 

If CPS is Camshaft Position Sensor you don't have one. Other than that you are correct.

550 is low for an idle in gear. The ISC (Idle Speed Control Actuator) is used by the computer to control the idle under differing loads. Either the computer is getting bad info or the ISC is not reacting to the computer input or it is unable to compensate enough to overcome an abnormal load. Usually it is bad info to the computer. The normal idle of 800-850 suggests the ISC is working. If you have A/C you can load the engine without putting it in gear. This info might prove useful.

I don't know what you mean by a "hard pulling tranny" unless your torque converter is malfunctioning and causing an abnormal load. Your truck should have a 727 tranny I believe.

 

Ya, thats what I mean, I think the tranny could use a new TC, it always pulls pretty hard.... but is still functional. Should the ISC bring the idle back up when its loaded automatically? I dont have an A/C, so thats out.... but ideally when I put it in gear the ISC should prevent the revs from dropping right? Sometimes it will even stall when I drop it into gear because the revs drop too far.

 

The ISC has its limits on load compensation but yes ideally it should compensate automatically. It can only do so much. I will say it again eliminate ALL input problem possibilities before condemning the TC as it is very expensive and a major pain to replace.

 

I actually tried swapping one out last week, no real difference, but I have 3 or 4 of them laying around. Maybe its not receiving a proper input, perhaps I will try and test it to make sure its operating.

The isc that is not.... not the TC lol

 

Ok, so I just drove back from school, about 10 minutes, and Im starting to think its runs much worse once it hits temperature. It worked great until I hit operating temp, and then **** hit the fan.... it stalled at an intersection while i was waiting, and the revs were all of the place when I was idling, it wont even stay running long when its not in gear or under load. I popped the hood when I got to my house, and watched the engine. The ISC servo wasnt moving at all, and this is one I swapped in a couple weeks ago, even with the engine sputtering up and down it did not move at all. It hardly changed the sounds of the engine when I unplugged it. It seems to run great cold when its in open loop, but not once it heats up, so Im thinking maybe an O2 sensor or something, and then the fact that it cant compensate for the fluctuating revs because the servo is a no go. I have 2 more ICS motors on the bench, and I took a resistance reading through both. One of them was on my truck before, and the other is a off a wreck. On mine, when I touched the 2 left wires, I got no resistance, and when I touched the 2 rights, I got about half way up the scale, so about 7000 ohmes. On the other one, I got no resistance on the left 2, but on the right 2, I got so much resistance that the needle hardly moved. So obviously one is good and the other bad, but i cant find anything on how to check them.... I even tried applying a 5volt source to the pins, but nothing happened. Is there a schematic for them available, or how can I determine if this is a problem, because the last time I checked, the servo should be moving to keep the idle consistent, or at least TRYING.

 

I think when the isc moves the most is actually when you are starting up the truck when its cold.

Have fun pulling that o2 sensor. I still haven't found a tool the right shape to grab mine, but my truck does run fine in open loop, so I'm not overly ready to pay somebody else to get it out.

 

I ran the truck today with the O2 sensor unplugged, and it didn't really make a difference, but I have taken them out before, the best, if you know its junk, is to just cut the wire off as short as you can and then put a big socket on it.... worked for me....

 

Hey guys, after lots of work, and some money I have fixed the problem. I bought a new air emp sensor, egr valve and a O2, I put in the air temp, and nothing, I didnt even get to the o2, bu I put in the EGR. A while back, I blanked off my EGR valve using a multilayer gasket. It drove great for about 3 or 4 months, and then it went bad. Turns out, he gasket I used to blank it burned through, and was causing an air leak. I put the new EGR on and fired her up, and my vacuum pressure was up 5 points off the bat. Im glad this one is solved. Thanks for everyones help... its hard to diagnose a problem like this, especially when it was 100% stupid human error. Im just glad she is running right again, gotta pass e-test in 2 weeks.... fingers crossed!