MAF sensor or intake gasket? Runs rough idle-2200rpm.

[TBizzle98]

My 1998 Silverado has a 4.3 Vortec. I drove it and it was fine and it sat for 8 hours then it had a serious rough idle issue. I have replaced the plugs and wires, and I did the cap and rotor less than a year ago. It seems to send me several different symptoms. It's difficult to diagnose one. I had it scanned by Auto Zone, and as you all know one little engine probelm can send back numerous different sensor issues. The one thing telling me it is the MAF sensor is that I can unplug it and it doesn change anything about the way the engine runs. If I drive the truck it stumbles all the way up to 2200 RPM then it begins to smooth out if I will lift the accelerator just a touch to increase vacuum. Is there any positive way to test that sensor and find out what it's problem is.

Also.....I put an Air Hog air filter in this truck almost two years ago and my Check Engine Light has been on since. Any coorelation there that anyone knows of?

[MT-2500]

Originally Posted by TBizzle98

My 1998 Silverado has a 4.3 Vortec. I drove it and it was fine and it sat for 8 hours then it had a serious rough idle issue. I have replaced the plugs and wires, and I did the cap and rotor less than a year ago. It seems to send me several different symptoms. It's difficult to diagnose one. I had it scanned by Auto Zone, and as you all know one little engine probelm can send back numerous different sensor issues. The one thing telling me it is the MAF sensor is that I can unplug it and it doesn change anything about the way the engine runs. If I drive the truck it stumbles all the way up to 2200 RPM then it begins to smooth out if I will lift the accelerator just a touch to increase vacuum. Is there any positive way to test that sensor and find out what it's problem is.

Also.....I put an Air Hog air filter in this truck almost two years ago and my Check Engine Light has been on since. Any coorelation there that anyone knows of?

Welcome to AF
If the check engine light is on what are the code no.
Any engine miss or miss fires?

Does the check engine ever flash when driving?

[TBizzle98]

Troubleshooting codes are: P0420, P0102, P0301

That is a number of possibilities. To my understanding a mechanical issue such as the intake gasket could cause a number of ill-reading sensors which will kick out several codes. Not sure, but that's what I have gathered from all this computer stuff. I did the extrenal vacuum leak checks, the plugs and wires are new. #1 is showing a misfire. I THINK the #1 plug had some water on it. It kind of looks like the intake was seeping water across from the water passage to #1. May be an issue. I have my fingers crossed.

[MT-2500]

Originally Posted by TBizzle98

Troubleshooting codes are: P0420, P0102, P0301

That is a number of possibilities. To my understanding a mechanical issue such as the intake gasket could cause a number of ill-reading sensors which will kick out several codes. Not sure, but that's what I have gathered from all this computer stuff. I did the extrenal vacuum leak checks, the plugs and wires are new. #1 is showing a misfire. I THINK the #1 plug had some water on it. It kind of looks like the intake was seeping water across from the water passage to #1. May be an issue. I have my fingers crossed.

No 1 first.
If the intake gasket gasket is seaping or leaking fix that before you drive it.
If the air hog fiter tripped the light or set a code I would pitch it in the trash can and put the AC-Delco air filter back on it.
Have you tryed cleaing MAF sensor or is there any air leaks in ar intake system?
MT

[gmvortec]

Originally Posted by TBizzle98

Also.....I put an Air Hog air filter in this truck almost two years ago and my Check Engine Light has been on since. Any coorelation there that anyone knows of?

If you over oiled the air filter when you install/clean it can cause problems in the intake tract, one of which is coating the Maf with oil, if this is the case,try cleaning it with some carb cleaner.

http://www.framairhog.com/cleaning.html

[TBizzle98]

I replaced the intake gasket. It appears to have been seeping from the front water passage into intake 1. That explains some of the slightly rough idle before this HUGE miss materialized. It also tells me why there was a nasty looking plug in #1.

I also discovered a problem with my ditributor cap which I just replaced a year ago. I stuck my probes on my ohm tester to it and found #1 & #2 were showing 30 ohms. Not cool. I just bought a new cap.

The water neck in the intake (I bet all of you are familiar) was also seeping antifreeze so I bought a new one. The old one broke off in the intake and I am currently in the middle of trying to get that removed, what a pain! I hate pot-metal. I can't even get the E-Z-Out to grab it enough to extratc. BS man! What was GM thinking there? Pot-metal with threadlocker into aluminum??????

[TBizzle98]

Fixed! As far as i can tell the problem is gone! Whoo-Hoo! My Check Engine light is even off! I think it runs better now than it has since I bought it.

Just out of curiosity.....has anyone ever replaced their converter on a '98, or even gotten brave and removed it? I've been told several times that you cannot effectively remove the converter on '98's. Supposedly it cannot be bypassed or anything along those lines. Any info there?

[legbreaker]

Originally Posted by TBizzle98

The water neck in the intake (I bet all of you are familiar) was also seeping antifreeze so I bought a new one. The old one broke off in the intake and I am currently in the middle of trying to get that removed, what a pain! I hate pot-metal. I can't even get the E-Z-Out to grab it enough to extratc. BS man! What was GM thinking there? Pot-metal with threadlocker into aluminum??????

I know quite a few GM techs and they have always told me that the best way to get those heater fittings off the intake is with an impact. I know that sounds weird, and you would that it would just bust it off, but because of the impact not putting angular force (right wordage?) on the fitting like a wrench or hand rachet would, it decreases the likelyhood of it breaking. I know this doesn't help you now, but maybe it will for next time.

[MT-2500]

Originally Posted by TBizzle98

Fixed! As far as i can tell the problem is gone! Whoo-Hoo! My Check Engine light is even off! I think it runs better now than it has since I bought it.

Just out of curiosity.....has anyone ever replaced their converter on a '98, or even gotten brave and removed it? I've been told several times that you cannot effectively remove the converter on '98's. Supposedly it cannot be bypassed or anything along those lines. Any info there?

I is illegal to operate it on a fedeal highway without a cat.
And the engine will not run as good with the cat removed anyway.
MT