Newb Needs Help

qws · September 8, 2008

Hi guys.. I'm new and looking for some of your help.I have a 2001 savanna 3500 that has the random misfire code. PO300... lucky me!What happens is when only on a higway and only when you let off the gas the SES lights blinks. (Random Misfire)Had the truck tuned up by a mechanic... still had the problem.After there tune up it ran fine for a week then the code came back. This time I took it apart and found a burnt wire that was left on the exhaust manifold.Ran it again and the same thing. Took it aprt again regapped all the plugs. Now I get PO300, and cyls 2,4,and7. The coil was never replaced. Does anyone know what the resistance should be for testing? or have any other ideas what may be causing this? O2 sensor? Injectors?Thanks in advance for your help. All info is welcome.

Draenor · September 8, 2008

What was the burnt wire?

qws · September 8, 2008

The burnt wire was a spark plug wire that they didn't put back in the loom and was laying on the exhaust manifold

Shaners · September 9, 2008

My buddy has a 2500 Avalanche with the 8.1L and he has gotton the random missfire code too... It doesn't seem to affect the drivabillity of the truck.

The dealer wasn't able to figure out the problem under the factory warranty so he got GM to give him a 100K mile warranty on his engine for free.

Kodiak450 · September 9, 2008

My buddy has a 2500 Avalanche with the 8.1L and he has gotton the random missfire code too... It doesn't seem to affect the drivabillity of the truck.

The dealer wasn't able to figure out the problem under the factory warranty so he got GM to give him a 100K mile warranty on his engine for free.

8.1 in an Avalanche? Was that a factory option? Didn't know Avalanche came in a 2500 series.

2000DV4.8 · September 9, 2008

My buddy has a 2500 Avalanche with the 8.1L and he has gotton the random missfire code too... It doesn't seem to affect the drivabillity of the truck.

The dealer wasn't able to figure out the problem under the factory warranty so he got GM to give him a 100K mile warranty on his engine for free.

8.1 in an Avalanche? Was that a factory option? Didn't know Avalanche came in a 2500 series.

Yup, they did for a few years, not sure of the exact years, but it was '01-'03 or something like that...

qws · September 9, 2008

Intersting... for being a newb I expected something more in the lines of "welcome aboard""great to have you"" Have you checked this, this and that?"

Never did I expect to be hijacked so quickly.

After years of being on a variety of forums this is a first.

For those that may be following a bit and looking for answers to your own problems I guess we'll just have to use the search feature.

If anyone would like to chime in with some worthwhile advice to me in regards to the problem I'm having with one of my service trucks please feel free I'm always willing to learn something new from those of you with experience.

2000DV4.8 · September 9, 2008

Intersting... for being a newb I expected something more in the lines of "welcome aboard""great to have you"" Have you checked this, this and that?"
Never did I expect to be hijacked so quickly.

After years of being on a variety of forums this is a first.

For those that may be following a bit and looking for answers to your own problems I guess we'll just have to use the search feature.

If anyone would like to chime in with some worthwhile advice to me in regards to the problem I'm having with one of my service trucks please feel free I'm always willing to learn something new from those of you with experience.

Sorry dude, didn't mean to jack your thread, but take it easy, it's only been a few hours, someone will have the answer to your question. I don't, but I'm sure somebody will.

Don't let this turn you off to the site, there's a ton of knowledgeable people here. We do BS a lot, but usually only after the question at hand has been answered. New members are always welcome, so stick around, hopefully you'll have some helpful input too.

minibike132 · September 9, 2008

Welcome to the site Ed. It's pretty hard to diagnose a P0300 on the computer but let's give it a shot. First off I'm not sure what kind of plugs were put in (not the brand, what the electrode is made of) we don't check gap on most plugs anymore because that dammages the electrode on most modern plugs. Second what was done as far as "tune up" because everyone has a different idea of what goes into a tune up anymore. Third if your mechanic is in the habbit of leaving wires out of the looms I would get another mechanic. Can you feel a missfire or are we going by the light? What are you checking the code with? It would be real cool if you had a good scanner, we could be of alot more help to you if you do. If not the best you are going to get is guesses which is going to cost you more in the long run but we can do some base testing without one to narrow things down and get an educated guess and not a "well I had a miss fire and replaced these parts which cost a grand before I got lucky". As far as coil resistance I don't remember the last time I checked one and I don't see the spec off hand but it may come to me, if not I'll check one when I get a chance. Or someone will come in and let us know. Don't be put off by your hijack, this is a good site but usually newb intros and questions go into separate pages and people get a little geeked when they don't. Plus your asking about a van and for some reason we don't take kindly to G bodys. Just kidding, anything bigger than a impala is welcome here and the random question about those is too.

davzog · September 9, 2008

We have seen lots of newbees on this site and never had one slam us for not being socially adept. Folks on this forum are ALWAYS interested in offering super advice and many are very knowledgeable. This is, however, a forum that allows folks to offer opinions and "shoot the breeze" on occasion....hyjacking a thread does happen, but most times everything falls back in line.

I doubt that rudly complaining on first post will draw a lot of favorable technical insights. If the technical information is needed so immediately that a little discussion is not acceptable, I suggest going to a dealer and paying for the information....they work pretty quick, sometimes, without all of the fluf.

By the way, welcome to the forum...

tobias · September 9, 2008

Intersting... for being a newb I expected something more in the lines of "welcome aboard""great to have you"" Have you checked this, this and that?"
Never did I expect to be hijacked so quickly.

After years of being on a variety of forums this is a first.

For those that may be following a bit and looking for answers to your own problems I guess we'll just have to use the search feature.

If anyone would like to chime in with some worthwhile advice to me in regards to the problem I'm having with one of my service trucks please feel free I'm always willing to learn something new from those of you with experience.

Welcome to the site. Now, breathe deep and relax. If anyone had direct knowledge of your problem, they'd tell you, rest assured.

As for having to use the search feature to find answers, that's always the best place to start anyway.

qws · September 9, 2008

Thanks guys.. I never mind a bit of small talk and have been very thankful for these types of forums. Over the years I've learned an awful lot about a few vehicles and its saved me a lot of money. This particler truck was always a good service truck for me until recently. I bought it with 27k and it now has 170k. All miles have been from upstate NY to NYC to the surrounding New England areas. Even been to MI a few times, so yes it has served its purpose. All my trucks are serviced often and anything that needs replacement gets fixed. (They don't make me money when there not in service). My mechanic for this truck has always been very good and reasonable until this last time. I think one of the younger guys may have done the "tune up" and forgot to put wires 6 and 8 back in the looms. 8 is the wire I found that was burnt. This truck has been down for almost three weeks now and is our main truck since it has a 10ft box on the back and delivers our big equipment.Orginal problem: Blinking service light on highway ONLY when letting off the gas pedal. At this time also got a code of low voltage to MAF sensor. By the way I'm only using a Actron OBD2 reader. I cleaned the MAF sensor and that code went away. So far we have gone through and cleaned the MAF, Throttle Body, Went through the plugs and gapped them, checked the remaining wires and replaced the burnt one. Ran some very good cleaner through the injectors twice and used up 2 tank fulls of gas. After this one done we have the same code plus now the added codes of the three cyl's I've listed.I was hoping to find out the resistance of the coil so I could see if that was bad. Oh.... let me add that we noticed when trying it yesterday that when we press the pedal and get the rpms up to around 2000 the voltage drops and then comes back. Alternator was replaced less than a year ago with the belt. This is one of the reasons I'm thinking maybe the coil. After doing some searching on here I've also come up with looking into the fuel pressure reg and egr. ( fuel pump replaced last year by a dealer)I completely understand the difficulties with the PO300 code and the billion things it can be, but do try to look into the basic stuff first.I do apologize for the slam. Thanks guys for your understanding with that. I'm looking forward to being a part of this community for years to come.

minibike132 · September 11, 2008

Sorry we didn't get back to you sooner, I lost your post and had to get some help finding it (thanks Jim).

My mechanic for this truck has always been very good and reasonable until this last time. I think one of the younger guys may have done the "tune up" and forgot to put wires 6 and 8 back in the looms.

I shouldn't have made that comment about your mechanic. I have had many an apprentice make me look bad but we all have to start somewhere and make some mistakes along the line. Do you feel a miss or is it just the code. Does your scanner show missfire counts or just cylinders. In the firing order 7 and 4 are opposed, 2 is after 7 so if it isn't a hard miss I would count it as false because of the 7. Alot of times if you feel no miss but still get a light and especially if you get two cylinders that oppose eachother it is because the crankshaft variation needs to be relearned. Has this been done? If you actually feel a miss then this isn't the problem and should not be performed.

pennzoil29 · September 11, 2008

Welcome to the forum, and alway's remember, you have to put up with a lot of BS from all of us. I'm confident someone will get your issue resolved. Goodluck.