intake manifold completed - serv eng light on

[jak45]

I just finished the intake manifold gasket job on my '02 Montana-- quite the feeling of accomplishment. Unfortunately, when I started it, it ran rough and the service engine light came on. I checked the plug wires at both ends and they seemed secure. I struggled with the connections on the fuel injectors and I'm concerned I broke a connection/wire. My thought it to buy an OBD reader to narrow it down? Any thoughts?

[hufhouse]

I can only tell you my own experience. When the same thing happened to me, I took the car to a well-known good mechanic in our small town. Granted, it cost me $42 to find out that I had put the #5 spark plug boot NEXT TO the spark plug, but that would have probably taken me an entire evening to figure out. (With everything back together, it's nearly impossible to REACH the #5 spark plug.)

The $42 was worth having the van purring like a kitten and having an evening to nurse my cut up office-boy hands. :-)

It kind of reminds me of the story of the old mechanical engineer they brought in from retirement when a large piece of machinery stopped working. The factory was completely shut down because of the malfunction. He looked at the equipment for a while, took out a large red "Sharpie" marker, and drew a big "X" on one small part. He said, "Replace that part." The mechanics replaced the part and the machine started up again.

He then sent the factory a bill for $10,000.

The president of the company was livid. He demanded that the old engineer send an itemized bill detailing how he came up with $10,000.

So, he sent a bill that said:
- Sharpie Marker.......................$1
- Knowing where to mark......$9,999
- Total............................$10,000

I guess that relates here because it could take you a really long time to figure out what is causing the misfire, and also spend a good deal on the OBD-II reader. Or, you could drop it off in the morning with a good, reliable independent mechanic and spend just a little to have an evening to yourself.

If the independent says it's a fuel injector connection, then you can go ahead and fix it yourself if you want to spend the time. At least you won't be going down rabbit trails.

The intake manifold gasket is a great do-it-yourself repair. It's very obvious when it needs to be done, and it is very labor intensive. It doesn't require any special tools or diagnostics.

Figuring out why your Service Engine Soon light is on is almost the opposite kind of repair. It requires special tools and diagnostics, it's not obvious what is wrong, and fixing it could be far less labor-intensive than you think. That's probably a good repair to leave to an expert.

You could just have him do the diagnostics and call you with the results. Then, you can decide whether to fix it yourself or let him do it.

That's totally my opinion, but you have to understand that it worked out well for me.

[cdru]

Or save the $42 initially and go down to your local auto part store that will read the code for free. The come back here for free advice as to what might be the cause of that code if it isn't already apparent to you.

My guess is that you left a sensor connection loose or disconnected, or have a bad plug/wire.

[GTP Dad]

The advise from both cdru and hufhouse is sound. If you are serious about working on your own car spend the money on a good scanner. It will pay for itself many times over. I paid $150 for mine and it has saved me a lot of time and money. A friend of my sons has used it several times too when his CEL came on. A code reader is cheaper but that is what it does, read codes, you will still have to take the car to someone with a scanner to clear the code anyway. Of course it is your money so the choice is up to you.

[hufhouse]

Originally Posted by cdru

Or save the $42 initially and go down to your local auto part store that will read the code for free. The come back here for free advice as to what might be the cause of that code if it isn't already apparent to you.

I don't know whether it's true or not, but I've been told that the code readers at AutoZone are not as "specific" as the more high-end ones at a good shop. Someone said that they could only tell you it's a "misfire", not a "misfire on cylinder 5."

Again, I don't know whether that's true or not. Just what I've heard.

[cdru]

Originally Posted by hufhouse

I don't know whether it's true or not, but I've been told that the code readers at AutoZone are not as "specific" as the more high-end ones at a good shop. Someone said that they could only tell you it's a "misfire", not a "misfire on cylinder 5."

Again, I don't know whether that's true or not. Just what I've heard.

Yes and no. When your check engine light comes on, a specific OBD-II code is set in the computer. What that code means can be fairly specific, not fairly generic. If a misfire is detected on an individual cylinder, it will set code P0301 for cylinder 1, P0302 for cylinder 2, etc. If it is a general misfire across several cylinders, P0300 is set indicating multiple/random misfires. If say a MAF sensor was unplugged, P0100-P0104 could be set.

The computers that a shop can hook up to your car are definitely more sophisticated. They can get certian parameters or query the computer for more detail. However you obviously pay for it. The first thing that they are going to do is essentially what Autozone does, pull the basic codes and go from there.

I'm not saying you shouldn't go to a shop. But if it were me, I'd rather save the $42 for beer money and at least try to fix it myself for free. If you still can't figure it out, then spend the beer money. Get the code, come back here and we can help you out. GM has already taken enough of your money.

Here is a list of OBD-II codes. Not all are supported on all vehicles. I personally own this scanner and love it. No more having to go to the store to read a code, and it also has the ability to read a variety of real-time data readings from an engine while it's operating.

[jak45]

My local auto parts store didn't have a reader (at least for free use) so I went on-line. Checkers is running a sale on an Equus Innova, so I went to the store and purchased it. (I wish I had a Checkers in town) $150 down to $99 with a $30 rebate. I plugged it in and it showed P0302 -- a cylinder 2 misfire detected. This is exactly what I expected (not what wanted) as this was the injector I was concerned about. I'll have to take off the plenum and check the wire, but at least I'm confident where the problem lies. Thanks for your help -- I think this code reader will come in handy in the future.

[gmtechnician]

Quite often they start up with a miss because of lifter bleed down. This will set a misfire code and that is what turns on the SES light. The code just has to be cleared with a scan tool thats all. Nothing wrong with it. When they run rough when first started you should shut the engine off after about 20 seconds or so and wait 5 minutes to restart it. It will restart and run smooth and probablly not catch the misfire to set a code in the first place.

[hufhouse]

Unless, of course, you jam the plug wire between the plug and the engine block like I did.

There's no remedy for stupid.

[cdru]

Originally Posted by hufhouse

Unless, of course, you jam the plug wire between the plug and the engine block like I did.

There's no remedy for stupid.

We've all been there. Wait. No. I don't any of us have been that bad. Maybe close. But I think you take the lead.