auto technician needed
 

HELP - I have a 2004 ASTRO van that is giving me fits. It runs rough at idle. I have changed the distributor cap, rotor, plugs and wires ( from GM ) NO CHANGE. I took it to a repair garage and they worked on it for two days.
They found that it was missing on 5 or 6 ( sometimes it is 5 and sometimes it is 6. If they turn off the injector on the one that is missing nothing happens. They did a smoke test of the vacuum lines and intake - no external leaks.
They changed the distributor, no change. They flow checked the injector and all of the flows were the same. They don't know what is wrong. When the engine is cold it is less noticeable. when the engine is hot it can stumble enough to stall sometimes.
Is it possible that the problem is caused by a lean condition due to a bad O2 sensor or could the crank position sensor go bad. They changed the distributor was changed because the gear was badly worn. ( they couldn't just change the gear.? )

Any ideas?????

Check for a leaking fuel pressure regulator. It mounts under the intake plenum and when they leak they will provide an over rich condition on 5 and 6. After it has been sitting, disconnect the air snorkel from the throttle body, open the throttle plate and sniff for fuel. If you smell fuel, attach a fuel pressure gauge, turn the key on to prime the fuel pump, and see how fast it bleeds down. It should hold steady pressure after the pump shuts off. A competent shop should have been able to pick up on that when changing the injector, sounds like they are throwing darts at the problem. Does the misfire go away when revved up?

The miss does seem to go away when reved up BUT it acts like it is not getting fuel. NOT flooded. If the injector for the cylinder that is missing is shut off there is NO change in idle. They didn't change the injector. They just checked flow.

Well it sounds like the ignition basics have been covered. Assuming a flow test was done with a scan tool and fuel pressure gauge activating and comparing flow of injectors, you can rule out wiring to the injectors and the injector driver in the PCM. My next step would be a cranking compression test and running compression check. If that checks out, I would start looking closely at the injector. I recently had a 96 5.7 liter that would pass a flow test, but misfired just the same. After ruling out everything else I popped the plenum and replaced the injector and my issue was solved. The trouble with these injectors is getting them out of the intake without snapping the retaining tabs to actually try and look at the spray pattern. The fact it is missing on 5 and 6 leads me away from an O2, as they are on opposite banks and are controlled by different O2 sensors.

I still think it is a lean condition because the engine runs and idles perfect when it is cold and the fuel enrichment is on. After the engine gets hot it starts to idle rough. The hotter the air temp gets outside it idles worse.

It 1 of 2 things. Either the valves are sticking or it's the distributor. You need to put the scan tool on it and go into data stream and look at CMP retard if its not 0 +/- 1 it needs a distributor it will probably be around 10 or 14. Go to the auto parts and get a new one for $75. It has to be dropped in perfectly and use the scanner to confirm it was dropped in perfect. There is no turning the distributor to get it right. If the gear was worn on the old distributor and the shop u took it to didnt pick up on this immediately they don't know what they are doing. You need to take it to someone that knows what they are doing so you don't keep waiting money. There is a chance that the gear on the cam is worn to bad to throw off the CMP retard along with the distributor. Your motor isn't lean or bad flowing injectors or injector harness the PCM is fine. Chevy doesn't have those issues.

The distributor to crank timing WAS off 7 degrees - The distributor has been changed. It is now 0*. Compression came out OK.

Sounds to me like the coolant temperature sensor.

any excessive smoke out the tail pipe? any power steering fluid leakinh on the ecm? hydra boost leaking? whats the milage?

Tink, verify the dist timing 1 more time with scan tool. If you are 100% confident the compression is ok (if one cylinder varies from the others 30 psi...) then you need to pull the distributor and examine the drive gear. It shouldn't be that bad since its a Van. Make sure u rotate the motor and look at the entire gear.

Black Baja is right. The distributor "Cam position offset" I think its called, needs to be set/checked via a scan tool. Its not like the old stuff where you can just throw a timing light on the balancer.

If the Distributor is like the one in my Vortec 454, they are plastic housings, and a throw away item. I replaced mine at 89k miles, the gear was worn. I replaced it with an aftermarket with a billet housing. I've heard of guys complaining about rough idle with certain aftermarket caps too. Some guys claim the Delphi cap is the only cap to use on these engines.

Does it have a MAF sensor?

some things for you to check,,
1st, remove the EGR and see if there is an carbon holding the EGR pintle open,
2nd,remove the Intake Manifold tuning valve and look inside the intake plenum for and puddles of fuel or any spots where it might look really clean (like fuel washing it clean) if you find signs of fuel remove the upper plenum and cycle the key so you get fuel pressure and check the fuel feed and return lines for leaks.
both very common issues

other than that you will have to check fuel pressure,scan data,read o2 data and remove the air intake temp sensor and spray some carb clean while engine is running and see if the o2 reading goes high (lean command because now it sees a rich condition)
if all checks out good and you still think its a bad o2 you can unplug the pre o2s (fronts) it than will read a fix 02 reading of 450mv and should run better but will tricker the check engine light on,

the ignition on that engine is pretty good,no real issues ,while its running take a spray bottle and lightly spray water on coil see if it starts arcing,

other than that the only other thing you could check is the crank sensor harness,it sometimes melts on the right exhaust manifold,

also dont over look fuel,,put a sample in a clear jar and let it sit for about 10 minutes and see what it looks like and if it separates,

if any of this were the case it would set a p1345 ''camshaft to crankshaft correlation code''

Not true

Im not here to argue with you,,i have done many distributor reset's that someone had just done lower intake gaskets on and everyone had a p1345 code...i weht in with a tech 2 to see where the timing was at and had to redrop the distributor then set the timing and the code went away..

Yes I've done the same thing many times fixing someone's screw up. But, whenever I've had them come in with a run problem and misfiring due to bad distributor or drive gear on the cam guess what? No correlation code. Ok now doesn't make sense at all. Only time I've seen it throw the correlation code is when it was already messed with. Otherwise no code. Only thing I can think of is because it is setting misfire codes that its not going into the part of the PCM's readiness for the correlation code. I've seen this issue atleast 20 times more so on the 4.3 with balance shaft but have seen on 5.7 and 7.4

yes i agree with you about the 1345 and cam gear not setting a code,,only when someone mess's with it..

check this out,,i got in a 2000 astro that kinda kicked my ass,,had a po401 403 which is the egr..it also had a po301 cyl 1 misfire..heres the kicjer,,fuel pressure at koeo 60 and koer 55 normal rite,,well it was blowing smoke rings out the tail with white smoke and a vary strong gas smell VARY STRONG.. was not the fp regulator or a cracked hose on the injector spyder..i did a compression check after the cylinder dryed out,,130 psi,,started it with a new plug still major smoke,,did another compression ck on cyl 1 now 90 psi,,cleared snapon compression gauge,,now 30 psi..i was like wtf???????? so i put the plug back in cyl 1 started it pulled wire off cyl1 and 3 no running change..pulled plugs in cyl 1 and 3 and put my leak down checker set on number one and ! tdc both rockers closed...i got air in 2 cylinders...blown head gasket..all the fuel is flooding cylinder #1...200 k going to scrap yard..