mass air flow sensor

[biggsteve97]

I have an 03 Tahoe with the 5.3L, it has a slight stumble at idle as well as low power from idle to 3,000 rpm however from 3000 rpm to red-line no power issues. This is not as noticeable when the engine is cold it becomes more noticeable the longer you drive it. I have change intake gaskets, spark plugs, air filter, cleaned the throttle body, all four O2 sensors, fuel pressure regulator, fuel pump, and the evap vent solenoid and hose assembly. All of this changed nothing, still has a slight stumble at idle and low on power until 3,000 rpm. I have only had 2 codes in the past 2 months a P0101 mass air flow sensor circuit issue (2 months ago) and a P0430 bank 2 converter efficiency code. The P0430 code only came on after an hour of stop and go driving below 30 mph. That was 5 days ago and has not come back. On a tech 2 the mass air flow sensor is slow to respond but not slow enough to set a code. I can find no other faults. Could the mass air flow sensor cause all of this or am i possibly looking at a faulty cat or both? I am stumped and so are both Local gm dealers.

[biggsteve97]

I just got a Jet Performance Mass Air Flow sensor and it did wonders. No more miss or stumble at idle and lots of power. No sluggish take of performance now either. However, my girlfriend drove the Tahoe all week because of the foot of snow we got and the engine light came back on with P0430 again. I have NO drive-ability issues now so I do not understand what is happening. Does anybody have ANY ideas? The sensor is only 6months old.

[Sicklajoie]

You running stock air filter setup?

[biggsteve97]

yes, I am running the factory air intake setup. The oxygen sensors are only 6 months old. I do have an update since my last post on the fourth, starting yesterday (February 6th) the stumble/hesitation at idle has returned though the engine still runs great unlike before.

[fxdxharley]

any updates to what your problem was? i have a 2000 6.0L that has pretty much the same problem. idles rough and no power. also seems to back fire sometimes when w.o.t excellerating. no codes at all.

[biggsteve97]

Well I installed the header/exhaust kit that replaces the factory converters and that helped immensely as well as I installed an air raid throttle body spacer. The best I can tell is that the passenger side catalytic converter had started to melt but I do not think this was my entire problem as occasionally it still hesitates and does not feel up to the power it should be at lower rpms. I am starting to think the factory muffler may have some internal failure because I drove it before reconnecting the muffler and it had way more power and throttle response than it does now after reconnecting the exhaust. Your problems sound exactly like failed or failing catalytic converters. Beware of the factory ones you will have to replace them again and at almost $800 a pop that is ridiculous. The kit I bought was only $275 on ebay from dna motorsports and you will never have to replace another cat plus you get way better flowing headers. There are two things I have noticed with the kit one is that you will have to either use o2 sensor spacers on the after cat sensors to keep the engine light off or do a custom tune to turn them off and second the number 3 spark plug wire might be too short to route around the funky bend on the driver side header. I used summit racing boxed msd race wires that where longer and had adjustable boots to clear everything. That cats are wide open and built more like a resonator. There is a blog on here about these headers and I have lots more pics on there as do others. Hope this helps.

[biggsteve97]

ebay longtube header install is the blog name

[fxdxharley]

Steve, did those headers resolve your problems? iyou said power was still an issue with stk exhuast, so did you go after market? I like that header set up and not a bad price either. What exactly is the o2 spacer? just a spacer you put on to keep sensor up out of the tub more or? I will go read the posat on these headers. thanks for your input. o any more pics would be great. send me a pm and i can give you my email.

[biggsteve97]

Well I would have to say yes they pretty much fixed my problems. I have recently found out the sluggish take off from a dead stop that is annoying to me is unfortunately inherent to the Flex Fuel motor and they way it is programed. The Tahoe is definitely a rolling start vehicle. This kit made a night and day difference in the way the motor ran. Much stronger performance, almost makes the lag on take off bearable now. I will be going with a dynomax ultra-flo cat back exhaust kit soon. but that depends on money and when I get it since fuel keeps going up and up and up.... Oh and the spacer looks like a long spark plug extender, thats probably all it is anyway. It moves the sensor out of the pipe enough to change the way it reads and hopefully keep the light off.

[biggsteve97]

I have more pictures on car domain. http://www.cardomain.com/ride/385971...hevrolet-tahoe

[fxdxharley]

thanks alot. maybe i will get mine to run good and have power again. plus i sure hate to have to buy new cats.

[60ratrod]

hey biggsteve, i would also try doing a port and polish on your throttle body. i just finished doing one on my 01 tahoe's throttle body and whorrry throttle response batman! i had to run to the store shortly after reinstalling the throttle body and got on the on ramp to get on the interstate on my way back to really test out the throttle response and at a slow 15mph rolling WOT acceleration i broke the rears loose til about 45mph when they caught again(it didn't help that the roads were wet from some rain we are getting)! this might help with your off the line acceleration. and it was simple enough to do. i used both a cordless drill and a dremel. just do a google search on it.

[biggsteve97]

I will have to look into that thanks. At one point I had thought about getting a 78mm throttle body but they are running about $200 right now so doing this would be way cheaper.

[60ratrod]

78mm is the bore on the stock throttle body so it wouldn't have done much
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[biggsteve97]

actually the stock throttle body necks or tapers down to 72mm the one i was looking at is bored completely through to 78mm adding 350cfm of flow. here is the link. http://cgi.ebay.com/ebaymotors/ws/eB...%3D1&viewitem=

[60ratrod]

never mind, i was thinking of the earlier cable throttle bodies. their bore stock is 78mm

[biggsteve97]

i wish I had a cable controlled throttle body instead of that drive by wire. The pedal does not have the same resistance as the cable controlled so when I am having fun in the dirt and get into the rough stuff if i get to bouncing or some whoops or dips my foot moves slightly and the engine responds to quickly causing a challenge. I will get used to it one day but for now it is a bit aggravating