2000 Vortec misfire help

[Static]

I know this isnt a s10 forum but I know theres alot of very intelligent minds here that might have some ideas. This is a motor swap I did around 2004. Engine is a 2000 4.3 v6 with 50k transplanted into a 1985 Olds Cutlass using a Painless harness and an oem fuel injected tank from a Monte Carlo TBI car. Ongoing misfire codes throughout the years, and 50k. Ive managed to fix them all but recently has started again, p0300, and is affecting driving at freeway speeds. Car is quick from stop to 60 ish but on the freeway above that it misfires badly, complete lack of power. Sometimes it will recover and drive fine for a while then misfire heavily again. Heres the history of what has been done.

Used an OEM vortec pump for the swap in tank
Lower and upper intake gaskets- within 3k of swap due to coolant leak on #6
Plugs, wires , cap, rotor- within 10k of swap
Updated poppet injector spider to the revised injector design- within 10k of swap
New High pressure fuel pump Summit Brand I think- October 2010
Plugs, wires, cap, rotor, coil, fuel pressure regulator- within 500 miles
Pulled distributor, checked for wear on the gear, looks very good no sharpened teeth

MAF, both o2 sensors, and the cat are original to the donor engine. I have an OBDII code reader that can display some data. I am at a loss of where to look next.

 

[bshaw1979]

Re: 2000 Vortec misfire help

A scan tool that displays misfires per each cylinder is very helpfully. I would start with a cap though.

 

[Static]

Re: 2000 Vortec misfire help

Cap is new. It is multiple random misfires code p0300.

 

[midnightbluS10]

Re: 2000 Vortec misfire help

You'd be suprised at what some code readers will show compared to others. My Actron scanner always showed the specific cyl code, ie p0304. The Tech2 at work showed p0300 and allowed me to see which one was misfiring. Confirmed #4 was the culprit.

 

[bshaw1979]

Re: 2000 Vortec misfire help

Also...sometimes you can narrow it down to cylinders on one bank misfiring.. It help so much to know exactly which ones aren't firing. As for the cap. I replaced one in my shop on a blazer that was 2 months old.

 

[IGottaSy]

Re: 2000 Vortec misfire help

Got to replace it all not just the cap. Could be the rotor, spark plug, injector/wiring harness, coil or spark plug wire. If the problem persists, I'd check static compression of the cylinder.

 

[Static]

Re: 2000 Vortec misfire help

I am using an Actron Scanner Model #CP9145. In the past its shown specific cylinders misfire like when coolant was in #6 or when #3 wire cooked the boot due to a bad connection. Sometimes it would throw a random misfire code but its never hesitated this bad. Its like its running on 2 cylinders. Im suprised its not throwing o2 codes lean/rich as its either not combusting the fuel or theres no fuel to combust. Or am I wrong in thinking that?

 

[The Bronze]

Re: 2000 Vortec misfire help

I am using an Actron Scanner Model #CP9145. In the past its shown specific cylinders misfire like when coolant was in #6 or when #3 wire cooked the boot due to a bad connection. Sometimes it would throw a random misfire code but its never hesitated this bad. Its like its running on 2 cylinders. Im suprised its not throwing o2 codes lean/rich as its either not combusting the fuel or theres no fuel to combust. Or am I wrong in thinking that?

The OEM data from a quality scan tool will give you the specific number of misfires per cylinder currently (and history). That, along with fuel trim for each bank will get you going in the right direction.

You won't get O2 sensor codes when there are active misfires. The PCM is smart enough to realize that the O2 sensor data won't be valid and will not set the code. The data will be available for review though....

The distributor reluctor also is prone to cracking that will cause the same kind of problems you are experiencing.

Also, if for some reason your vehicle is not able to give you misfires for a specific cylinder, you should perform a crank relearn. Procedure as follows (requires OEM compatible scan tool):

Install scan tool, apply parking brake, block wheels. Start engine and let it idle until it reaches 150*F. Initiate crankshaft learn. Press and hold brake pedal (or it won't work), bring engine up to 4000 rpm until the engine rpm begins to fall. Turn off engine and wait 15 seconds. Crank relearn should have completed.

 

[jeepruby04]

Re: 2000 Vortec misfire help

This is very interesting, I have a 2000 s10 that has very similar problems. I have went through the complete ignition system trying to get rid of it. I've checked all the ground wires I could find also. Mine only does it now when there is a lot of moisture like rain or very high humidity. Please post if you find a fix because I'm stumped and ready to put a bullet in this thing. :rant:

 

[Static]

Re: 2000 Vortec misfire help

Ready to put a bullet in this thing too. Had to loan my car out so I can have it at the house and work on it when I have time. Finally get it over here and the hood cable breaks. Spent most of the daylight hours getting the hood open. Pulled the distributor apart and reluctor ring is not cracked. If I get time over the weekend I will check to see if the timing chain has too much slack so I can eliminate that as a possibility. Pretty much waiting on a hood release cable, until then I cant do any load testing.

 

[midnightbluS10]

Re: 2000 Vortec misfire help

Ready to put a bullet in this thing too. Had to loan my car out so I can have it at the house and work on it when I have time. Finally get it over here and the hood cable breaks. Spent most of the daylight hours getting the hood open. Pulled the distributor apart and reluctor ring is not cracked. If I get time over the weekend I will check to see if the timing chain has too much slack so I can eliminate that as a possibility. Pretty much waiting on a hood release cable, until then I cant do any load testing.

All you had to do was pull the grille out enough to get a wrench on the hood latch bolts and unbolt it. The hood comes right up. Took me all of 30 mins after figuring out a plan of attack.

 

[Static]

Re: 2000 Vortec misfire help

All you had to do was pull the grille out enough to get a wrench on the hood latch bolts and unbolt it. The hood comes right up. Took me all of 30 mins after figuring out a plan of attack.

That's how I ended up doing it. We had lost a grille at one time and ended up buying a pair off ebay that ended up being broken. So the grilles were installed then reinforced. I tried pulling the remainder of the cable but it ended up just breaking at the hinge point.

 

[Static]

Re: 2000 Vortec misfire help

Had a few minutes to tinker with it the other day. I pulled the distributor cap so I could see the rotor. I then rotated the crank until I could just see the rotor move, then rotated the crank the other direction. Very little if any slop in the timing chain. Put it all back together and drove it to the parts store to borrow their fuel pressure tester. Drove it for a while and fuel pressure was between 58-64 the entire drive even during misfire situations. On the drive it misfired so bad that it stalled. Took about 3 tries to get it started again, acted like it was flooded out. Once it was started it drove fine, took it on the freeway had misfire between 45-50 and at 70mph the car just surges. So fuel pump looks good at this point and the timing chain isn't stretched.

 

[The Bronze]

Re: 2000 Vortec misfire help

I am not sure how you would verify these correctly without a scan tool or scope, but my guess (based on the sharp stalls and no start) would be:

1) Crank Sensor (on front of engine) on a no start you should be able to read rpm on a scan tool to verify
2) Cam Sensor (in Distributor).
Cam/Crank Sync. (On scan tool, it should read 0* +/- 1*)

I would also caution you on the fuel pump, while I don't see being very likely, the fuel pump can cavitate (or cracked line, fitting or what-not) and induce air into the system. When checking fuel pressure, it is a good idea, to release the bypass and watch for a nice steady stream of fuel w/o air bubbles.

If this was mine, and I couldn't get scan tool information (and the CORRECT) procedure for resetting the cam/crank sync, then I would pay someone to check and adjust as necessary. It would only take a few minutes, especially if the setting was good right out of the box.

 

[The Bronze]

Re: 2000 Vortec misfire help

This was suppose to be an edit, not a quote. Please see the bottom.....

I am not sure how you would verify these correctly without a scan tool or scope, but my guess (based on the sharp stalls and no start) would be:

1) Crank Sensor (on front of engine) on a no start you should be able to read rpm on a scan tool to verify
2) Cam Sensor (in Distributor).
Cam/Crank Sync. (On scan tool, it should read 0* +/- 1*)

I would also caution you on the fuel pump, while I don't see being very likely, the fuel pump can cavitate (or cracked line, fitting or what-not) and induce air into the system. When checking fuel pressure, it is a good idea, to release the bypass and watch for a nice steady stream of fuel w/o air bubbles.

If this was mine, and I couldn't get scan tool information (and the CORRECT) procedure for resetting the cam/crank sync, then I would pay someone to check and adjust as necessary. It would only take a few minutes, especially if the setting was good right out of the box.

. If the sync is off, it would explain both the misfire and the inability to determine which cylinder. I really don't think it would cause an intermittent stall/no start, but it would be MY first step.

 

[SY2455]

Re: 2000 Vortec misfire help

I know that you check the distributor gear, but did you check the play in the distributor shaft Side to side? If the distributor housing is plastic like the 2001. Then the upper bushing might be worn out do to not enough oil getting up there. We had to replace the distributor in our van because of this. All of our miss fires went away.

 

[Giga]

Re: 2000 Vortec misfire help

Had the same problem with my 93 mustang. miss fired horribly to the point it would stall. Just went and replaced wires, plugs, coil, fuel pump, fuel filter and tested the pressure regulator. Ended up being 2 cracked injectors and one completely broken one. Dont know if that helps, but i never thought about the injectors until i pulled the engine for an engine swap...

 

[Static]

Re: 2000 Vortec misfire help

I am not sure how you would verify these correctly without a scan tool or scope, but my guess (based on the sharp stalls and no start) would be:

1) Crank Sensor (on front of engine) on a no start you should be able to read rpm on a scan tool to verify
2) Cam Sensor (in Distributor).
Cam/Crank Sync. (On scan tool, it should read 0* +/- 1*)

I would also caution you on the fuel pump, while I don't see being very likely, the fuel pump can cavitate (or cracked line, fitting or what-not) and induce air into the system. When checking fuel pressure, it is a good idea, to release the bypass and watch for a nice steady stream of fuel w/o air bubbles.

If this was mine, and I couldn't get scan tool information (and the CORRECT) procedure for resetting the cam/crank sync, then I would pay someone to check and adjust as necessary. It would only take a few minutes, especially if the setting was good right out of the box.

This is the next things to be looked at. I suspect cam/crank is somehow going out of sync at times. I would rather buy a good scan tool than pay someone to do it for me. That way I learn something. Can you recommend a good scan tool?

 

[Static]

Re: 2000 Vortec misfire help

Ok so I pulled the crank sensor and it looks like the reluctor has been riding on it. Also has a ding on it. I just happened to have one off another truck in the bottom of my parts pile. Looks to be a hair shorter. I swapped it out and took it for a test drive. Seems to shift better now and no misfire codes yet. Heres a picture of the old sensor.

 

[midnightbluS10]

Re: 2000 Vortec misfire help

If you swapped those out, you'll need to do a CASE relearn, IIRC. Takes about 10 seconds with a Tech2 or similar scanner. A Snap-On Modus can do it, so can the newest one, the Verus.