Tahoe issue??

[macojoe]

When I start it in the morning, it runs real ruff, after it warms up it runs great! In the old carb days I would say it was the choke. Today I say its TPS or something like that?? OI not up to all this computer crap!

Thanks Joe

[THEFERMANATOR]

My bet is the throttle body and IAC are carboned up. VERY common issue on trucks with over 100K miles, and is relatively easy and cheap to fix. Get you a can of carb cleaner or throttle body cleaner(there both about the same stuff, but carb cleaner is normally cheaper), remove the intake tube from the throttle body, open the throttle and spray the throttle body down and wipe it out real good with a rag to get all that black gunk out, and if you have some torx bits remove the IAC from the throttle body and spray it off and teh throttle body where it goes in to get as much of that black gunk out as you can. Also you may want to check the fuel pressure regulator out, but that normally causes issues with a hot start.

[aussie]

have a look at the exhaust when you start it see if its got black smoke comming out of it ---that will tell you if its over fueling --leaky injection can cause that on cold start up or when the car has sat for a few hours
check your exhaust to eliminate fuel alot of other things can cause it but lets not jump the gun

[macojoe]

Thanks guys!! I bet the carbon is it as the person driving the thing was a women with 2 small kids its who life. The kids looked like they were 10 and 12 now and thats the age of the truck and they have had it since new.
I will have to get my son to look at it as I can't see my left han most of the time, LOL!
Any pic's of the area to look at?? He has no patience, and gets pissed fast!

[THEFERMANATOR]

The throttle body is dead center behind the fan. It has the black plastic tube coming from the air filter box over to the engine. This is a VERY common issue with cold starts. They're supposed to be cleaned every 30K miles to prevent them from gumming up, but most people don't know to do it, and most shops are to lazy to open them up and clean them out hwen they charge you to do an induction service. It doesn't take that long to clean it out, the hardest part will be getting the plastic intake tubing out of the way so you can clean it out. Just be sure when you put it back together to get the plastic tubing all put back together or else it won't run for crap afterwards.

[aussie]

if you have a phone take pictures of things you take of in stages and mac if you were close by i would came and fix it for you free off charge-- i do this for all my mates-- im sure there will be videos on you tube showing how to do it and maybe someone on here can video it and send it to you

your saying it runs rough on idle when cold and once its hot its good--yes it could be the throttle body blocked not allowing enough air at idle cause when the engine is cold the coolant temp sensor tells the computer the engine is cold so it alows injectors to stay open longer so if you not getting enough air due to a blocked throttle body it will run like have the choke pulled too hard on a carby engine

when you start the engine cold if you hold your foot on the gas just i tiny bit does it run better---


theres 3 things that can cause rough idle when cold

too much fuel
not enough air
vacum leak
head gasket leak or cracked head

i dont know too much about these engine and what they suffer from but they all work from the same princeable

with the crack head or gasket what happen when the car sits for long peroids water leaks back into one or more cylinders so when you start it will missfire till the water vapours are pushed out --once its hot the water that leaks in turns to a steam which dosent effect the cylinder just like old school water injection

there 2 ways i check for this
one--if its a v8 get 8 screw drivers remove all spark plugs while the engine is hot keep each spark plug in order to cylinder and check for difference in color of the spark plug usuall the one missfiring will look different colored --place a screw driver down each spark plug hole for 30 sec then remove one and check if there any water on the screw driver check all if there all dry then there no leaks

two you need some one who has a exhaust gas analizer --you remove the radiator cap you may need to empty some coolant from the radiator start the engine --place the probe in the radiator filler and cover with a rag and run the engine if you get a reading then you have exhaust gases on your cooling system

[macojoe]

well my son came down today, took off the hoe and said that thing looks brand new, I said did you push ope n the choke and look in?? he did it and said WOW there the problem its loaded with crap! he used 2 cans of carb cleaner and cleaned everything. After that I started it up and got the cleaner o run thur, purrs like a kitten. Got on the highway and it has even more power!went to the zone and got some Lucas fuel injector cleaner, a big bottle enough for 30 gal of gas, put the hole thing in there and get that injection system clean. It says for carbon build up?
I looked at the air filter with my son it was ok but the zone did not have the one I needed. My son said thats not bad I have seen worse, I said it will be changed when I go by Advance this week, its a cheap replacement and I have seen some so plugged that the motor would not run, never mind the gas mileage, and I am getting 14 mph now!
Also every time I get gas the ck engine light comes on? I never leave the truck running when gassing up? So I got a new gas cap also and see if that helps? Light was on after we did the decarb, but I was betting that it was because of the cleaner and running like carp till I burned it up.
The real test is tomorrow morning and see if she runs good or still runs ruff on start up??
Now just a break job and she should be good!

I will let you know how she is in the morning!

THANKS GUYS!!!

[spareparts]

MJ, I was getting 14 out of my 02 Suburban when i first got it, I had been running 15w-40 in it. Some one told me to use 5w-30 like the manual said, i switched over and started getting 16 mpg on my next trip. I then switched over to Mobil 1 5w-30 synthetic and on our last trip to Florida, I averaged 18-19 on the highway running far faster than i care to admit

[phatdaddy]

same as spare, went to mobile one syn and picked up 2 mpg on the road. in town , no difference. also picked up a few oil leaks i did not have before.

[THEFERMANATOR]

Originally Posted by spareparts

MJ, I was getting 14 out of my 02 Suburban when i first got it, I had been running 15w-40 in it. Some one told me to use 5w-30 like the manual said, i switched over and started getting 16 mpg on my next trip. I then switched over to Mobil 1 5w-30 synthetic and on our last trip to Florida, I averaged 18-19 on the highway running far faster than i care to admit

Your a LUCKY man Spare. 15/40 in an LS engine was putting you in DANGEROUS territory with oil pressure. I bet it was hitting 100+ on a cold start. The LS engines are designed to hold GOOD oil pressure on 5W30 oil. As for your check engine light MJ, there is a bulletin about the fuel tank purge valve assembly back by teh tank. It sticks alot and causes teh check engine light quite often. Next time it happens run by autozone and get teh code number and I can let you know if that is it. The GM part to fix it is less than $40 if it is the purge valve, but changing it is a pain as it is up by the rear axle underneath.