I'm having issues with my stupid truck again, need some advice / ideas.

 Truck is an 89 Chevy 3500 (454) , throttle body injection.  Problem is, it runs rich.  Dropped it off at the mechanics because it was pissing me off.  Now its pissing them off.     So far we have tried, new 02 sensor, temp sensor, and computer, nothing has helped. The new computer did not come with a chip so we had to use the original one, could it be the chip ??  Mechanic said, or some reason it is staying in cold start mode and wont realize its warmed up.  It never switches over and uses the 02 sensor to adjust its self. Hooking it to the scanner tool thingy shows that it knows its warmed up.  Strange thing is, if you get it warmed up and shut it off, let it sit for a few minutes, then restart it, it runs better (still rich but better). But still wont switch over and read the 02 sensor.  I used this trick to get it to pass its smog test (barley), but I want to get it right before it destroys the new cats I had to put on it. 

 Any GM techs out there remember these things, and have an idea for me before I get really mad and do something bad. 

 Recent repairs (in the last few years) have included new distributor, new coil, new fuel pump / filter, new catalytic converters (both  ).   

 STUPID fuel injected computer controlled JUNK !!!!!!  What this thing really needs is a carb and a normal distributor.

TJS, this is all killer info.

To add to this, an exhaust and or vacuum leak will make you chase your ass around.

Do you know what the vacuum level is at idle? Also make sure the TPS is seeing .5 volts at idle.

How many miles are on this badboy. The last one of these that did something similar had severely retarded cam timing due to a worn timing chain, the first was a fluctuating ignition timing, the second was a pig rich condition but actually drove/ran OK.

Also, can you see the O2 sensor switching on the scanner? You should see an occasional and somewhat random 0-1volt DC switch, I have seen the early ones not set a code if the connector fails (this is not like the heated ones).

GT

What is the spray pattern of the injectors on top  of the throttle body?  I had kinda the same thing with my 87 Blazer with tbi 350 and it was just the injectors were worn and allowinig more fuel to be dumped in.  Just a thought, since it sounds like everything else has been looked at.  I dont think a chip would do anything cause on those modles there aint much the computer controls so its almost a waste of money.  Or maybe try another engine control computer?

WOW, lots of info, thanks guys. OK let me try to answer all the questions.

 No coolant leak and its not low.
 Distributor, not sure where it came from, the original one broke (shattered its guts in the driveway one day) and I picked this one up (new) from my mechanic neighbor.  It was changed about 3yrs ago, but I do remember that the trigger system inside it looked different.  They told me its a design change because the older ones shatter like mine did. It plugged right in and ran fine after that.   
 Thermostat is a 190 (I believe) its been in there for many years, no signs of anything strange on the temp gauge.
 Timing is correct, they check that now during the smog check. And it passed.
 Not sure how the injectors are firing, but they are noisy. 
 Also not sure of fuel pressure, there is no place to check it on this truck.  If I remember right its a low pressure system, its supposed to be something like 12lbs I think.
 I replaced the base gasket for the TBI a few years ago too, forgot to list that, sorry. It had the high idle issue and ran like crap.
 Not sure how rich it is, it did pass its smog test (barley), but both the smog tech and the mechanic looked at the test sheet and said its rich. I think the only reason it passed was because it has 2 brand new cats under it.  The old cats, front one was hollow, gutted its self and plugged the rear one. Exhaust guy said running rich can cause that, burning fuel in the cat (??).
 There is a slight exhaust leak on the pass side manifold, goes away once it warms up. but the 02 is on the driver side (I think).
 It has 116 k miles on it.
 TPS sensor was checked and is in spec.
 I think I did see the 02 sensor switching with the scanner (looking over a shoulder), nothing occasional or random about it, looked like square wave signal. 
 There are no trouble codes, and it never turns on the check engine light no matter how bad it runs.

 Heres a little description of how it runs and what it does.
 Truck cold, hasnt been driven in a few days, get in start it and drive away, after a few blocks it will develop a slight stumbley miss at cruise speed, this goes away at full throttle. If I shut it off (once its fully warmed up) go into a store to get something come back out and drive home the truck runs better, not perfect, but better. If you dont shut it off, lets say you just jump on the freeway and drive, it runs like crap. It misses and has no power, sounds and feels like a lack of fuel (plugged fuel filter). But as soon as you hit full throttle it clears right out and runs good (no missing). Back to cruise and it starts all over again.    This is worse in the winter, not as bad in the summer.
 

Propman,
 You need to take the cap off that dist. If you see green fuzzy shit that kinda looks like moss you have a bad pickup coil (hall effect) in the dist. I know you said the dist. was replaced 3 years ago and that is about how long it takes for the windings in the pickup coil to start messing up. Also, the original dist. had issues with the magnets cracking.

Also is the primary coil in this truck original too. As GT said wires, cap, rotor, coil and coil wire.

 OK guys, I brought it back home tonight so I can check some of the things you guys have mentioned.  Kinda late and dark tonight but I'll get on it right after work tomorrow.

 TJS, I'll pull the cap off first and look for anything funny.  Not sure what broke in the original dist, there was just lots of broken little metal parts all over the place in there.  The coil is not original, it was changed a few years ago. Actually it was after the trip down south to pick up my old Blue Eliminator.  Truck ran like crap on that trip and wouldnt start the next day, coil was dead. The basics, plugs, cap and rotor where changed last year when it started this crap (no help), maybe I'll pick up some wires for it too.

 I have the smog check paper now, it was in the truck.  It shows ...
 Idle speed test = 808 RPM,  %C02 = 14.4,  %02 = 0,  HC(PPM) = 70 (max is 220, ave is 51),  CO (%) = 1.37 (max is 1.50, ave is 0.20) this why they keep telling me its rich. 

 Upper RPM test = 2699 RPM,  %CO2 = 14.4,  %02 = 0,  HC(PPM) = 23 (max is 200, ave is 34),  CO (%) = 0.34 (max is 1.60, ave is 0.30).  Its blowing flowers out of the exhaust at RPM. 

 To me this is looking kinda like the vacuum leak issue you guys mentioned earlier, I'll check that out tomorrow, again. If it was ignition related, wouldnt it still show up in the upper RPM test ?  And why do the upper RPM #s look so good but it runs bad at that RPM going down the street. 

 BTW, the smog test on this truck is still done off the rollers (like in the old days), so there is no load on the motor. 

I have the smog check paper now, it was in the truck.  It shows ...
 Idle speed test = 808 RPM,  %C02 = 14.4,  %02 = 0,  HC(PPM) = 70 (max is 220, ave is 51),  CO (%) = 1.37 (max is 1.50, ave is 0.20) this why they keep telling me its rich. 

The low HC (hydrocarbons) would be an indication that there is not actually missing too bad....you should be GTG as far as ignition stuff. I think you may have a lazy o2 sensor or the plugs are gapped narrow (too tight). The CO (carbon monoxide) is an indicator of a somewhat rich condition especially with new cats...You need to check for vacuum leaks like you mentioned, check the intake manifold and the TBI base gskt., don't forget the EGR base gasket too if is equipped....

Upper RPM test = 2699 RPM,  %CO2 = 14.4,  %02 = 0,  HC(PPM) = 23 (max is 200, ave is 34),  CO (%) = 0.34 (max is 1.60, ave is 0.30).  Its blowing flowers out of the exhaust at RPM. 

Again with the low HC, the higher CO could be a response of trying to clean itself up, or again a lazy o2...Just my .02c, its been a long time

To me this is looking kinda like the vacuum leak issue you guys mentioned earlier, I'll check that out tomorrow, again. If it was ignition related, wouldnt it still show up in the upper RPM test ?  And why do the upper RPM #s look so good but it runs bad at that RPM going down the street. 

I think you are on the right track

Thanks Rusty, any help / ideas are appreciated


 I'll check out the ign system (just to be sure) and check for vacuum leaks (I'll get a vacuum reading too) when I get home tonight.

 I had another strange thought pop into my head this morning though.  What if the fuel pump is making to much pressure ?  Maybe it cant deal with it at low RPM.  I'm fairly sure there is no way to check fuel pressure under the hood on this thing (or nobody around here had a fitting for it). I remember once before when I had a fuel pump issue I had to unhook the filter and put a gauge on it under the truck to see what it was doing.   I've had many many fuel pump issues with this thing, its always one of my first suspects when something isnt right.     

It's easy to check the fuel pressure on these..You need one of these..  http://www.actron.com/product_detail.php?pid=16175 I may still have mine, gotta go to my dads to see if it's there (he is at Lake Shasta again  ) and I would say there is a better chance of the fuel pressure being too low as apposed to too high. There is a fuel pressure regulator on the very top of the TBI unit, stupid easy to replace, there is a spring and a diaphragm under there and they do fail occasionally.

You can pinch off the fuel return line to see if it runs better, this increases the pressure to the injectors..

Another simple test is to pull the connector on the o2 sensor and put a jumper wire on the signal lead then hold the other end in your hand and go from + to - terminals of the battery with the other hand using your body as the conductor), you should be able to drive the engine rich then lean to see if she ever cleans up.....

Good luck, I'll let you know if I have the test gauge, I know I have a noid light kit here at my house. (again, been a while)

GT

 GT, That little adapter that comes with the tester is what nobody had, watched 3 guys go through there boxes looking for that thing.   

 Heres what I found tonight.

 Everything looks OK in the distributor (no green moss), timing is correct. 
 Vac at idle is 18
 Injectors look to be misting nicely, no dribbling or anything strange.  Like little shower heads, those thing spray alot of fuel.
 
 When first started (motor completely cold, hadn't run all day). I checked for vacuum leaks by spraying starter fluid all around the TB, and all the hoses, as well as the edges of the intake, and around the EGR.  There was a vacuum leak around the rear of the base of the TB (under the hot water plate thingy), again.    As soon as I hit that area the idle would drop.  Once the motor warmed up (5 min running), it didnt do it anymore.    So, once warmed up there are no vacuum leaks.

 

The low HC (hydrocarbons) would be an indication that there is not actually missing too bad....you should be GTG as far as ignition stuff. I think you may have a lazy o2 sensor or the plugs are gapped narrow (too tight). The CO (carbon monoxide) is an indicator of a somewhat rich condition especially with new cats...You need to check for vacuum leaks like you mentioned, check the intake manifold and the TBI base gskt., don't forget the EGR base gasket too if is equipped....

 GT, the 02 is new, 4 days old. As is the temp sensor and the computer.  I swear, now that this thing passed its smog test, its going on craigslist next week and getting sold.  I'm getting something old enough so I dont have to smog it ever again.  I'm sick of this stupid truck !!!  I want a good old fashioned carb and ign system, standard caveman stuff that always works.  And if it does break you can fix it with a screw driver and a hammer. 
 

I will give ya 50 bucks for the truck.  LOL!

 LOL, I should have seen that coming (the standard SoCal Jet Boats offer). 

"Fix it with a screwdriver and a hammer"    Do all jetboat guys think alike when it comes to fixing things?   

At least he di not say with a stick and a rock     

 Something odd happened with the truck today.  I used it to move some firewood around at moms house, it ran great all day.  On the way home I came to a stop and it wouldnt idle.  Had to keep my foot on the gas to keep it running. Ran fine going down the road, just realy rough at idle and would die if I didnt catch it.  Went out and checked it out after it cooled down, still wouldnt idle.  Turns out the EGR was stuck partially open.    Messed with it a bit and everything went back to normal.   Do you guys thing this could be the problem, or is it just an unrelated issue ??  Maybe even when its closed its still letting some exhaust through, and messing with everything.