So... I know there have been a few different posts about a similar topic, but I haven't found anything quite like mine!

This has been going on for about a couple months or so, but it is continually getting worse!

Anyways, when I'm driving my truck, it will occasionally start to bog out and chug. If I lay on the gas, it will continue to bog out and there will be nearly no noise coming from my engine. However, if I let off the gas for a second and then jump back on the gas it will rev hard and take off. If I stop at a stop light or stop for too long it will really start to chug and stall and I will hear a loud air sucking noise. The RPMs drop down to like 400 or so. Sometimes when I tap the gas while its doing that it will jump the RPMs back up to like 1200 and idle high for a couple seconds before coming down to normal numbers.

When this problem originally started it would happen maybe once every week or two and go away with just a tap of the gas. Now it happens damn near every time I drive and just after I get it to go away it starts to do it again.

I know it can't be a bad cat as I had that removed a few years ago. I also know it can't be related to my exhaust because about 2 weeks ago it cracked in half right before where the cat would be and the problem still resides (although now louder to hear and more noticeable! haha). I originally thought that it was my Torque Converter lock-up solenoid, but if I tap the brake or take it out of OD it still does the same thing.

I am nearly positive that my plenum IS blown (My truck continues to burn a little bit of oil on a consistent basis) but I am not sure if this is my problem or not. After looking on the forum quite extensively I have also seen that some think similar problems are caused by either a bad IAC or a bad TPS.

I haven't had a chance yet to tear the throttle body off the clean it and check those out, I was just wondering if anyone has any ideas or better ways to diagnose this. I am just trying to invest as little as possible into this truck so that it runs decent enough to sell to someone looking for something slightly better than a "beater". Any advice would be helpful! Thanks in advance!

 

I'm thinking its the IAC, you can pull it out and clean it. I believe there is a link in the DIY section for that.

 

Check the codes. Clean the IAC as mentioned and try it. I'm thinking o2 sensor though.

 

if you're having a problem while the gas pedal is depressed a little or a lot, then its not the IAC, since its only purpose is to allow idle air past the closed throttle plate. once you crack open the throttle, the IAC is out of the picture. so if you 're having problem while gas pedal is pressed - consider replace the throttle position sensor TPS.

if you are having a problem with idle RPM, replace IAC. f*** cleaning it. do poke out the hole in the TB at the end of the IAC well, and don't forget the o-ring.

could be lots of things, including O2. if you have any CEL codes and didn't tell us then why not...

 

That sounds to me like an oxygen sensor failing. A blown plenum gasket will coat the sensor with burnt oil, so you'll probably want to conduct the test found in the plenum gasket TSB, fix that if it's indicated, and swap out your oxygen sensor afterward whether the gasket is shot or not.

 

I'm pretty sure I'm throwing trouble codes, I just haven't checked them yet. My CEL light on my dash is actually burnt out. I'm gonna try the on-off-on-off ignition trick to figure out which codes I'm throwing. I'm sure there will be a hefty list! I'll post back my findings tomorrow. Thanks for the quick responses fellas!

As far as the 02 sensor, are you talking pre or post cat? Isn't the pre for fuel mixture control and the post for catalitic converter diagnosis?

 

Yep, pre-cat sensor, and your understanding is correct.

 

So... After some work, my cousin welded my exhaust back together and she is now purring like a kitten. I replaced the IAC and it is almost like a new truck. The only trouble code left is a bad pressure/vacuum leak. I started tearing into my intake and got it out and it was pooled with oil (pictures to possibly come). The only problem was that I broke 3 intake bolts in my heads so now those are on their way out to get drilled! Thanks for the help guys

 

you need to order the hughes kit for the plenum....which is the plate at the bottom of the intake....dont just replace gasket, it will blow again.