Can someone HELP me with this.. Spark Plug gap??

[steamroller]

correct Instant, everything was fine meaning that I didn't have the rough idle that I currently have.

After looking for vacuum leaks (and not finding any) I DID notice what sounds like an exhaust leak coming from the area under the drivers side exhaust pipes. I'll check more and tighten the bolts later today.

I also pulled some "Live Data" information, and noticed that the MAP(inHg) ranged from 7.4(inHg) at 1853 RPM to 10(inHg) at 1472 RPM and I thought that should be higher??

Hopefully I'll have this thing figured out or have some more useful data to share later this afternoon.

---------- Post added at 11:00 AM ---------- Previous post was at 10:58 AM ----------

Thanks Faze, Those are on my "To Do" list today

Whats the MAP reading at idle? It's gonna fluctuate alot depending on throttle angle, it should be in the high teens @ idle unless you do have a vacuum leak somewhere

Since this started with a cap and rotor change make sure the plug wires are fully seated on the spark plug and cap terminals, they can be a pain in the ass sometimes.

Since you have a scanner check the CMP offset/crank cam correlation if it has that parameter, it should be + or - 2*. The slightest movement of the distributor can throw this off, you may have pushed it out of whack changing the wires

 

[Bamba]

Whats the MAP reading at idle? It's gonna fluctuate alot depending on throttle angle, it should be in the high teens @ idle unless you do have a vacuum leak somewhere

Since you have a scanner check the CMP offset/crank cam correlation if it has that parameter, it should be + or - 2*.

Strangely enough my MAP readings are at around 9.7 at idle and at different RPMs?? Are you sure about the MAP fluctuations?

Here is some freeze frame data associated with the P0300 error code

P0300 Random / Multiple Cylinder Misfire Detected

View Freeze Frame
DTCFRZF P0300
FUELSYS1 CL
FUELSYS2 CL
LOAD_PCT(%) 11.0
ETC(°C) 151
SHRTFT1(%) -5.5
LONGFT1(%) 0.0
SHRTFT2(%) 14.1
LONGFT2(%) 2.3
MAP(kPa) 9.5
RPM(/min) 2053
VSS(km/h) 0
MAF(g/s) 3.303
TP(%) 12.9


I also went ahead and replaced ALL the plugs..... Sounds a LOT BETTER! .. even better than it did before I initially took the old plugs out to clean them.

I also did a vacuum test and "surprisingly" it was STABLE at 20.5 inHg.

The scanner still shows the P0300 error but... I can't help but wonder if I did "something" to muck up the plug when I cleaned it, and I can't help but wonder if the errors I'm still seeing on the scanner are related to the pre-existing noise which sounds like an exhaust leak??

Question... Could a leak near the driver side exhaust manifold cause that P0300 error? I also just started receiving a "Pending Codes
P0141 O2 Sensor Heater Circuit Bank 1 Sensor 2"

If the rough idle symptoms STAY GONE... I'll consider this post resolved and open another one related solely to the "Pending Code/02 error"

Thanks for all of the help ALL you guys have given me... It really means a lot.

 

[steamroller]

Strangely enough my MAP readings are at around 9.7 at idle and at different RPMs?? Are you sure about the MAP fluctuations?

I also did a vacuum test and "surprisingly" it was STABLE at 20.5 inHg.

My bad I misworded my post, if you've got 20.5" of vacuum at idle you're good. The map sensor and engine vacuum are related though. I'll just post this it explains it better than what I can put into words, but yes it will fluctuate depending on load, throttle angle, elevation changes, etc


http://www.aa1car.com/library/map_sensors.htm

 

[Bamba]

Friggin P0300 code resurfaced again a couple days ago ... I'm going to close out this thread and open one solely for the P0300 error, as it has nothing to do with spark plug gap.

The 02 error has NOT returned... I guess I do have "something" to be happy about.

On 2nd thought... you guys have given me a lot or great information and there are a few things I have yet to do so I'll hold off on creating another thread for now... If I find what's actually causing the problem I'll let you guys know... Thx

 

[95TwinTT]

I would revisit some of the trouble shooting basic’s. If you all of a sudden have a miss and the only thing that has happened is the plugs were cleaned, I would look very close to see if some other wiring was disturbed.

If it happened after changing the dist cap, I would suspect wires in the wrong holes. If the distributor was removed, I would suspect it might not be back in the same tooth on the cam.

Another area that should be examined is the control for the EGR. Make sure all electrical and or vacuum lines are secured.

Stop chasing the spark plug gap. The correct gap is what is listed on the radiator cover. I run my gap at .024, but it is for other reasons. The manual states to refer to the info stated on the individual truck. In general terms the early versions to 1995 was .035 and the later models were .060. GM has a lot of brain power coming up with these settings.

It is very possible that you are chasing two or more problems. If you have a exhaust leak at the manifold, it can screw up the O2 readings. Any exhaust leaks before or between O2 sensors can mess up the OBD2’s reaction to mixture.

You might want to compare O2 readings between 1 & 2 on each bank. They should be pretty much the same.

 

[Bamba]

I would revisit some of the trouble shooting basic’s. If you all of a sudden have a miss and the only thing that has happened is the plugs were cleaned, I would look very close to see if some other wiring was disturbed.

Another area that should be examined is the control for the EGR. Make sure all electrical and or vacuum lines are secured.

Stop chasing the spark plug gap.

It is very possible that you are chasing two or more problems. If you have a exhaust leak at the manifold, it can screw up the O2 readings. Any exhaust leaks before or between O2 sensors can mess up the OBD2’s reaction to mixture.

You might want to compare O2 readings between 1 & 2 on each bank. They should be pretty much the same.

I'm inclined to agree with you on all points... Thanks for your input. I'll have some time to look things over more tomorrow evening and should have something to add late Sun

 

[Bamba]

I feel totally stupid.... not for making a simple mistake but for "somehow overlooking" it when the problems started showing up.

For the sake of anyone as silly as myself "sometimes"... I FOUND the problem!

I switched two of the spark wires when I initially took the distributor cap off! I believe it was the #2 and #4 wires. I reattached them "correctly this time" and NO MORE ERRORS

Note to anyone and everyone..... If you do any work, and problems arise as a result.... CHECK EVERYTHING you touched... chances are THERE will be the problem.

Thanks for all your help guys... The silver lining is.. I "learned a LOT about Fuel trim values and some general performance indicators.

As a side note... I also found the exhaust leak, and have replaced the donut gasket at the exhaust manifold.