2000 Chevy Astro 4.3L CSFI Vin W

ASTRO

MEMBER
2000 CHEVROLET TRUCK

Po302, po507: Replaced all of the following: fuel pump, cat. Conv, fuel injectors (no.2, no.6, no.5), fuel pressure regulator, pcv valve, IAC sensor, HEI coil, plugs, wires, cap, rotor, fuel filter, all three O2 sensors, VSS, Ignition control module check was good, EGR valve stem clean, new vacuum lines, no.2 spark plug replaced again just to rule out a factory defect, TPS check good, CPS check good. I've given her lots of love. All work has been completed within the last 8mo. I should have a lean machine at this point. Exhaust doesn't really seam to have any tell-tale signs of water (white smoke) Hope to avoid replacement of head gaskets. Could the intake manifold gasket be a cause of the misfire, and not the head gasket? Since there is a PO507 with a PO302 wouldn't this be more likely?

6 Replies

SERVICE WRITER

MECHANIC
9,123 POSTS

If you have been losing any coolant:

Let the truck set 12 hours, Have it jacked up enough to have access to the oil drain plug. Slowly back out the drain plug so there are drips coming out and catch them in a clear jar until you can confirm any coolant iis or is not present in the oil. IF not obvious, just fill the container a few inches high and allow it to set another 12 hours. Completely drain the oil. Then pressure test the cooling system with the drain plug out and catch the drainage into another clear container, letteing it set under pressure for 8 hours or so. The coolant will settle to the bottom of the container.

IF you have not been losing any coolant. Compression test the #2 cylinder.

SPONSORED LINKS

Was this

answer

helpful?

Yes

Monday, March 19th, 2007 AT 5:45 PM

ASTRO

MEMBER
12 POSTS

1st stroke=90
2nd=100
3rd=110
4th=about 120 and this is where it topped out.

Was this

answer

helpful?

Yes

Tuesday, March 20th, 2007 AT 6:47 PM

SERVICE WRITER

MECHANIC
9,123 POSTS

Good results. I should have looked at the po507-high idle. Typically this is a vaccum leak source. There are couple ways to go about this. One is using an un lit propane torch and running it around the intake gasket areas, the # 2 cylinder and injector, or spraying a combustible liquid like carb cleaner. Listen for an idle change and then focus in that area.

My hunch is an intake manifold gasket problem.

Was this

answer

helpful?

Yes

Tuesday, March 20th, 2007 AT 7:09 PM

COUDRIET

MEMBER
2 POSTS

What was the end result or what fixed the problem?

Was this

answer

helpful?

Yes

Monday, April 2nd, 2007 AT 4:49 PM

ASTRO

MEMBER
12 POSTS

Replaced intake gasket. Engine performance improved. BUT. Went on a road trip (1100 miles round-trip. 30 miles from arriving home, started to misfire (constant). After compression test (#6 and #4 bad), decided to replace the head gaskets. And what fun it was. Had two bent valves, HEAVY carbon build up on valves. Cleaned and inspected heads for cracks. Installed two new valves, lapped all valves, replaced valve seals. Everythings back together, fired her up, tap. Tap. Tap (when you lightly touch the gas pedal there is also an intermittent knock. Sounds like something is hitting the bottom of the intake. What am I looking at hear, bent push rods? Did the bearings go on the balancer shaft? I feel pretty sure some valve adjusting will clear-up the tapping, but the Knock sounds bad.