Engine Stumbles only in gear and only at idle

[YUOnDaGround]

My engine when I first start it up idles fine but when I put it into gear it stumbles every 5 seconds. I do not have any codes. So I don't think it is an intake gasket. FYI I just changed sparkplugs (gapped to .040") to AC Delco Iridium and I have a K&N CAI. Any ideas?

Yes this just started after the plug change and the intake. I have unplugged the battery to let the computer reset so any thoughts on how to get rid of the annoying stumble?

 

[Thumper8302]

first off 2 things

1. tell me u didnt gap the plugs urself... u dont gap those urself.. u can and will scrape off the coating on the diode.. Hopefully they were pre-gapped in the box...

2. i know this may sound dumb but did u plug ur MAF back in? alot of people believe it or not do it.... now on the stumbling issue with the CAI's... make sure all hose clamps are nice and tight especially on the throttle body... they can easily get pinched and leak...

now when u installed ur CAI did u inspect the butterfly on ur intake? and also did u clean ur MAF? I would recommend cleaninh ur throttle body and ur MAF 2-3 times a year sine u are usin an oiled element air filter... many people have had MAF issues from the oil comin off the filter and caking the sensor... get u a can of MAF sensor cleaner and clean it and get u a can of deep creap for the throttle body and if u gapped ur plugs urself ur gonna need new plugs...

also how many miles do u have, what make and model, 2wd or 4wd?

 

[YUOnDaGround]

first off 2 things

1. tell me u didnt gap the plugs urself... u dont gap those urself.. u can and will scrape off the coating on the diode.. Hopefully they were pre-gapped in the box...

2. i know this may sound dumb but did u plug ur MAF back in? alot of people believe it or not do it.... now on the stumbling issue with the CAI's... make sure all hose clamps are nice and tight especially on the throttle body... they can easily get pinched and leak...

now when u installed ur CAI did u inspect the butterfly on ur intake? and also did u clean ur MAF? I would recommend cleaninh ur throttle body and ur MAF 2-3 times a year sine u are usin an oiled element air filter... many people have had MAF issues from the oil comin off the filter and caking the sensor... get u a can of MAF sensor cleaner and clean it and get u a can of deep creap for the throttle body and if u gapped ur plugs urself ur gonna need new plugs...

also how many miles do u have, what make and model, 2wd or 4wd?

1. I verified the gap on the plugs with my feeler gauges, a couple were off a little so they had to be adjusted (one was too wide and one too narrow). My feeler gauges are incredibly smooth and couldn't scrape off the coating IMO. - I don't use the 'gauge wheel' type.

2. The MAF is plugged in and all connections are tight.

3. I did not inspect the butterfly in the TB.
I did clean the MAF Before I installed the K&N about a week earlier.

4. 2002 Tahoe Z71 4WD with 163,000miles

 

[Thumper8302]

do u still have the plugs u took out... i can understand ur feeler gauges are smooth but u dont gap iridiums... if u have ur old plugs slap those back in and see if it goes away and hit that throttle body up

 

[tybardy]

sounds like a vacuum problem... any lines pop lose while working on the truck? Check around for a disconnected vacuum line

 

[radkon]

I had a similar issue:

So my 03 5.3 Tahoe (Z flex fuel) always had a weird issue with idle after I would disconnect the battery. Found out last year after the original battery died. Every time I would come to a stop it wouldn't hold a steady idle. It would bounce up and down then die. At first I thought it was a dirty MAF (via K&N oil) cleaned it and no change. I then looked at the voltage regulator/alternator so I had the alternator tested and it was fine. After a few days the issue went away (with no additional work or parts). So I have to disconnect the battery the other day to do some work and the idle issue returned. Worse than ever. Never threw a code or set the check engine light. I noticed if I held the idle with my foot at 750 it wouldn't stall. So I used HP Tuners to set the idle at 750 (up from 550) and it still wouldn't hold the idle. At this point I thought IAC (Idle air control) only to remember that the 5.3 is throttle by wire. Did some searching and folks were saying to clean the throttle body. Surely it couldn't be that easy! Well it was. I pulled the TB and saw a very nice build up of oil/carbon/dirt/grease and what not. I used some carb cleaner sprayed on a rag. Do NOT spray the cleaner into the TB since there are a lot of electronics in there. After 15 mins of cleaning, slapped that bad boy back on and viola! Perfect idle. Reset it to 550 and still fine. Hard to believe such a little thing could cause such a headache.

CLIFFS: Bad idle? Check your throttle body for nasty build up and clean it before you waste too much time and money fixing other things.

 

[andrew383]

Try cleaning your MAF again also..It may have got some oil on the sensors after you installed the CAI...

Did you damage the plug wires when you pulled them off??

You hooked the vac hose back up to the intake ???

 

[YUOnDaGround]

Plug wire still intact.

Vac hose installed and working properly