99 burb running rough

Recently replaced my intake manifold gasket and cleaned out the upper intake, things went well and it ran smooth for a few miles, until it warmed up, typical behavior in the past.

I have a few questions about the sensors on a 99 burb.

If I unplug the CPS cable from the distributor shouldn't it throw a code?

I found that when I unplugged the CTS when warm it ran very rough.

How long can I safely run the truck with the EGR unplugged? This is the digital type just 4 wires no vacum hose. When I did the manifold I took this off and it seemed to move OK, it's black but it moves and there doesn't seem to be anything in it based on shaking it. Is this item serviceable? Didn't want to hit it with brake cleaner thinking it might screw it up.

My problem is after driving on the highway for 20 minutes or so when lightly applying throttle it skips, hesitates. It's worse with the AC running.
When I get on the back roads it really show up as a real stumble, especially after going down hill coasting and then lightly applying the gas to climb, I'm only talking a 75' hill not the mountains. In the Summer it does a real chitty chitty bang bang while the ac is on and I'm stopped a light.

I wonder if the EGR is opening when it should not be? Could that cause this type of problem? That's my current theory. It did all of this prior to the intake job, at least it's not leaking coolant anymore.

Here's something else that really weird. When it's really acting up I pull into the driveway, put on the AC, turn the wheel all the way to the left, have my wife keep her foot on the brake and put it in drive and that gets it to stumble pretty bad, has to be in drive though. If I don't get this thing running right I think she's going to let her foot off the brake one of these days.:eek: Anyway, it make this intermitent ticking sound, like a spark arcing, not all the time but I can't for the life of me figure what that is, it sounds like it's coming from near the PS pump. not a click or a wrap but like the sound of a gas grill ignitor. Must be spark right?



I'd also like to extend a huge thank you to everyone who has contributed to the board, it's a fantastic resource, the intake job would have been a lot tougher without all the great info on here.

when you did intake did you clean egr ports? is the mil on?usually a missfire like that would pull a code if driven enough.

I cleaned the ports on the manifold with brake cleaner and then air. Just hit the EGR itself with air.

How did you reset the timing after you took out the distributor? The timing is computer controlled, but it has to be manually adjusted for the computer to make proper adjustments.

Just marked the rotor position & dist position and put it back as it was. I really don't know where to take it to get the timing set. The whole reason I've done the job myself is that I just don't have a mechanic that I trust to do it right at this point. I know there's many good ones out there but I've just had a really bad run of luck taking it to shops. I have not tried the dealer yet, that might be the best route but I'd rather pay for a tool I can use in the future than just a one time fix.
I have seen people mention the autoxray scanner but when I called them to see which model would set the cmp retard they said I'd have to move up to the sister company and something ~800+
Can anyone tell me what model autoxray they've used to get the cmp retard?

I also now realize that I may not be getting the SES light with the cam position sensor removed is that true? I have not put a code reader on it while removing the leads to the distributor.

It sounds like a plug wire is arcing out on the head. If you can, try running the engine at night, and see if there is a lightning show around the area you hear it. Sometimes a slight misting spray with water will aggravate the condition. The method you used to reinstall the distributor is good for getting in the ball park, but you will have to have a scan tool that is capable of reading the CMP retard. It must be at 0 degrees. It is possible to have the distributor off 20+ degrees even if the marks line up. I have done it myself, but I have the GM scan tool to set the timing. I am not sure if or which aftermarket scan tools are capable of this. The GM one cost me $2500, but I have seen them on Ebay for half that. If you disconnect the connector at the distributor, the ECM will not have a cam position reading, after a while the check engine light will come on, if the engine seems to run better with it unplugged you are closer than you think. On some of the sensors, the ECM will substitute a fixed value if it loses a true reading, this value will be closer to what it really should be receiving. That might be why it runs better with it unplugged. Hope this helps, and is not confusing

That is very helpful, thanks a bunch for your time. I'll have a peek at night and get a scan tool on it.
Will post results when I get them, still need to get my hands on a scan tool or load up some software on a laptop.

I got a laptop on it with software from obd-2.com, I've got to say this scanner software is good for the money < $150. No nonsense and it's got much of the extended data that you pay extra for from say autotap or auto enginuity.

I could see mis fires and a P0122 from when I unplugged the TPS - cleared that and went for the cmp retard figure. I was off a few degrees negative so I adjusted the distributor position, figured I'd swap the rotor and cap and do the plugs. Here's where I encounted several nasty suprises. The plugs were Autolite AP605 swappped for AC delcos.. On the cap I went with the Napa store brand, copper contacts, I think they said it was made by erland. The next problem was the distributor base was cracked where the screw goes in, this is a real enginering marvel in all of it's cheap plastic glory. Got a new distributor for $150 a rebuild that actually looked better than the ACdelco stock piece of crap.

Thanks again for the feedback and I'm happy to report the truck is running smooth so far. I know I've heard many people recommend the stock wires - the guy at Napa said their quality HD set was made by Delphi. I notice Delphi on the boots of the wires on the truck - stock and Packard on the wire itself. I'm now wondering if the Delphi at Napa is the same as the GM stock wire. I'm going to get a look at some at the dealer parts counter and compare them to the Napa. I'll report back if I purchase the Napa wires and let you know how they work, I may wimp out and just go with the GM wires online.