P0300 code has emptied my checking account. Help!

[BigAl]

Ok bought a 2002 astro AWD in Kentucky when I was up there in Jan. Van has 142k. Seems to have been maintained ok but for the SES and ABS lights. Scanned the codes and was showing a P0306 (misfire #6) and a P0300 a few rare times. Seems the van would throw one of these codes right at 2000 rpm no exceptions. So I changed the oil, Installed AC Delco cap-rotor, wires and plugs. Still trowing a P0300 @ about 2000rpm. Also noticed the rpms jump up about 200 when a code is thrown, I'm thinking the torque converter is un locking. I pulled the distributor, gear was slightly worn but not bad, I installed a rebuilt dist...still same problem. Fuel pressure is around 54. Have run two tanks with chevron tec, still no improvement.

Ok here's where it gets stupid.

Out of frustration I jumped on it one day and spun a rod bearing, no I'm not 16, but I can sure act it on rare occasions.

Lifted the body and installed a GM remanufactured 4.3 direct from the local chevy dealer. While the van was apart I installed new O2's, new fuel pump, radiator, water pump, tested the injectors they all fired and sprayed fuel, pcv, thermostat, idler pulley, tensioner, flushed the brakes, new trans filter and fluid, cleaned the MAFS, new vacuum, radiator, heater hoses.

She runs nice but still throws P0300 codes every time I now make 1600 rpm. It really dose run well, the only indication of probles is the SES light and the unlocking of the torque converter. It will throw a P0300 while in park as soon as it gets to about 1600 nomater how slow I ramp it up.

Ive got way more into this van then is reasonable and it wants MORE! Any suggestions to nail down this P0300 would be appreciated!

Oh I did get the ABS light fixed, opened and re soldered the ebcm.

BigAl,
Pensacola Fl
2002 Astro, X mtr AWD

[BigAl]

Chasing a P0300 code that comes up every time the engine makes 1600+ rpm. My scanner (andriod Torque app) is showing a timing advance of 15.5° at idle, that goes up to 46° when accelerating. Is CMP the same as Timing advance?

[LiftedAWDAstro]

I merged the 2 topics so we can keep a running tally of the issue. As for the CMP being the same as advance, I don't know but I do remember seeing the advance changing a lot when driving depending on load and speed. All I would do is look at the cap and rotor to make sure they are in good shape even though they are new. Any chance the GM reman'd engine has a run-ability warranty where you can take it to a GM dealer for assistance? The next best thing might be to PM v8famvan as he is a superior GM master technician superhero and he will give troubleshooting pointers.

[BigAl]

Thanks Lifted, the van has had 3 caps and rotors since I bought the van 3 weeks ago, only one new but still chucking a misfire code. BUT I think I'll try them again as this was before I smoked the original mtr and tben I was getting a P0306 under the same conditions, now with the new mtr Im getting a P0300 and at 1600 not 2000 rpm. Dont know bout the dealer thing, tomarrow Ive got to stop by there to inquire about my core credit and I'll ask.

[v8famvan]

Al,

I am not exactly sure what information your Android Torque app scanner is giving you but the key piece of data that I would be looking at is some thing called the 'CMP Retard' parameter. The correct spec for this is 0 degrees +/- 2 degrees. This parameter is not adjustable from the factory, however as time and age accumulate, the reading can go out of spec. To adjust this you have to remove the hold down 'fork' from the distributor and grind the inside edges of it to allow for adjustment. The data parameter is updated on the data stream once the rpm is over approx. 1500. If it is still out, adjust again & rev up to recheck.

The 2nd thing that I would suspect on this is the injectors. For reference check out the information in the thread '96 - '02 4.3 CSFI to MPFI Injector upgrade kit.

[MountainManJoe]

If you're still desperate, trying checking the coil. It's not an expert opinion, but I'll throw it out there because it's easy to check and you can cover all your bases.

viewtopic.php?p=77818#p77818

[MountainManJoe]

@ v8famvan

I always thought that on the newer engines the distributor's only job was to deliver the spark to the correct cylinder, and that the computer used the camshaft position sensor and hall effect sensor to deliver the proper timing. So what is actually happening when the distributor is out of spec as your describe?

[v8famvan]

@ v8famvan

I always thought that on the newer engines the distributor's only job was to deliver the spark to the correct cylinder, and that the computer used the camshaft position sensor and hall effect sensor to deliver the proper timing. So what is actually happening when the distributor is out of spec as your describe?

You are not alone in thinking this. Back when these vehicles were new that is what we were told & accepted that as fact. However, as I was doing the driveability issues that came into the shop, I was presented with issues like this under warranty and had to fix them. After some discussion with the GM Technical Assistance Center, it was determined that the concept of how the system actually worked was not as perceived.

Initially what we were told about the system is that the computer monitors the crankshaft position sensor & used only this information to calculate the cylinder to fire - injector & ignition. We were also told that the camshaft position sensor was only used to for misfire monitoring and was not considered in the calculation of timing. However, this (& this was the new bit of information) the computer did use the camshaft position sensor to calculate timing adjustments. I do not believe that they had built the system to allow for changes - due to wear - in the indexing of these 2 signals even though the computer could register the variation. Simply grinding the 'fork' & resetting the variance back to the base spec allowed the system to once again be within the range it was designed to operate in. I also believe that GM has learned from this as most of the vehicles since then have a 'Crankshaft Variation Relearn' procedure available to be done on them which is essentially a software program which electronically allows you to reset the variance due to mechanical wear.

[BigAl]

Ran out of time so dealer has it now. They did a relearn but say its still thowing a P0300 random misfire so there looking into it....$$$ still adding up.

[MountainManJoe]

OK so if I understand correctly, the problem arises when the engine parts wear down to the point that the camshaft is no longer in sync with the crankshaft, and you are compensating for this by rotating the distributor? If this were true, wouldn't the valve timing be out of spec also?

[BigAl]

Update: Day 3 at dealership still no fix. They reset computer, did relearn but still throws P0300. They let it sit for 2 days and finally put it in the shop yesterday. Going to check with them this morning. Unfortunatly Im going to need the van for the reason it was purchased sooner than expected. MS. just declared FEMA disaster area and I'm likley to be deployed there this week. Be nice to have the van, I purchased it to do this type of work after having to live out of my Prius for 16 days on Long Island when working Huricane Sandy untill I found a room 2 hrs away from where I was working.

[LiftedAWDAstro]

If it runs fine and is getting average fuel economy, drive it! What do you do for disaster areas?

[BigAl]

It's fixed. Got it back from dealer still trowing P0300 at about 2k rpm. Decided to remove 1/16" spacer I'd installed on the crank position sensor back with the old engine because the sensor showed some light rubbing on the end, at the time thought that might have been the reason I was getting a P0306 at above 2k rpm. After removing the spacer and reinstalling the sensor the engine was throwing a P0300 at about 1200 rpm now. decided to do a CMP relearn again and the problem is gone. Halalua!

[BigAl]

If it runs fine and is getting average fuel economy, drive it!

Well problem was when ever it threw a code the torque converter would unlock, my rpm's when up by about 300 and my HiWay MPG would not get better than 15mpg. Now I'm getting 20 mpg HiWay.

What do you do for disaster areas?

I inspect homes, cars, private roads and bridges.

[BigAl]

Now I can get down to configuring the van for my use. I've removed all seats except for driver seat, put a very dark tint on all windows except driver, passenger and wind shield. Made and installed block out curtains for all windows, installed four 5v 3A USB chargers in the doghouse. Now to add a gel house battery, inverter, isolator, low voltage auto start, alarm, 8,000 BTU 110 v air conditioner, replace the radio with a 7" Samsung tablet with GPS and cellular chip built in and a amp. Add a cot, 12v Cooler, 12v Microwave, porta potty, some storage bins, 22" flat screen TV / computer monitor, bluetooth speaker phone, rear view camera, front frame mounted retrieval D rings, a class III modified hitch with the typical 2" center receiver and two 1 1/4" receivers welded on each end to accommodate a aluminum 60" wide truck tool box, the outside 1 1/4" receivers provide support to the tool box making it very sturdy and provide for a steel tube bumper behind the tool box. This locking box will provide much additional storage when I'm deployed and still provides a 2" receiver behind the tool box for towing a trailer with the tool box installed. Air shocks to be installed in rear for extra weight of tool box and view shocks in front. Hopeful it will be finished before hurricane season.