Tahoe issue??

macojoe

macojoe

Administrator
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
 
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.
 
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
 
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!
 
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.
 
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
 
I am going to try Ferms fix before getting into anything to deep, But going to have to wait a few days as we are going to get a HUGE SNOW STORM here tomorrow they are saying up to 2 feet!! I am also busy trying to get the new house ready to move in. I got all the ceilings painted today along with 2 walls, got a new vent in for the dryer , washed all the curtains, still have to paint the living room and kit chen and steam clean all the rugs. Busy Busy Busy!!

Wife still in the hospital, they say she doing good and will go back to the rehab place for 2 weeks after this, that will be 2 months since she will be home, and I should have us all moved by then??
 
You will know REAL quick if it is the throttle body carboned up. The colder it gets the worse it will be. When the engine is cold it needs more air, and if teh throttle body and IAC are carboned up it cannot get enough air in. Think of it like a choke on an old carbed engine. If the throttle body is carboned up, then the choke essentially can't work to allow it to stay running. If it doesn't want to stay running, give it a little throttle right after it starts to keep it running. After a minute or so it should idle on it's own.
 
Thanks ferm thats just what it needs a little gas to keep running for a few min.!! Thanks aussie I will tell her!
 
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!!!
 
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
 
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.
 
spareparts said:
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
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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.
 
Well it started this morning, and went right to high idle, but after a min or so started doing the same thing, but cleared up much faster then before also. So my son is going to do it again this week as it is snowing again now. We will see after the 2nd time if we can get it right//
Ferm I had that problem in my 02 truck and it was that purge thing, I had a friend change it and it was good after that,but the light would stay on all the time in that truck.. I am sure if its not fixed now that would be it, the ck light went off after a little while and has not come back on so far, we will see? Thanks for reminding me!
I am going to get a oil change this week, but when I had the other truck it also had the 4.8 and bot the same gas mpg.

My new question is I have called about getting breaks for the Tahoe and it has 4 wheel disc, they all ask me if it has one or two pistons, I will have to look to find out. But My other truck had 2 pistons, and I was wondering does it matter?? I would think the dual pistons would be better? So if I buy the dual instead of the single will they just fit in place of the single with out problems

Thanks guys!!
 
Not very well Aussie, 2001 Tahoe 2WD 5.3L here, wife's wheels. Poor girl it is asking for another change of engine oil, radiator is leaking, then I went to drive it and it feels like the shock on the right rear is broke. I forget the miles around 95,000 ? The Service Engine Soon light stays lit all the time. Some odd Computer Code that is saying their is a problem with the computer. Runs and drives like a top. The light has been on so long I am surprised it hasn't burnt out. So I dropped it off at the repair shop next door. Now if I could get the seat re-upholstered while it is down I would be a hero..
BTW I started using Mobil One 5-30 Synthetic at around 40,000 miles. Then I switched back to regular motor oil at around 85,000 miles. No sign of leaks or burning it out the tailpipe but she now uses 1 Quart in between oil changes (3,500 to 4,000 miles.) Valve stem seals maybe..
 
RidgeRunner said:
Not very well Aussie, 2001 Tahoe 2WD 5.3L here, wife's wheels. Poor girl it is asking for another change of engine oil, radiator is leaking, then I went to drive it and it feels like the shock on the right rear is broke. I forget the miles around 95,000 ? The Service Engine Soon light stays lit all the time. Some odd Computer Code that is saying their is a problem with the computer. Runs and drives like a top. The light has been on so long I am surprised it hasn't burnt out. So I dropped it off at the repair shop next door. Now if I could get the seat re-upholstered while it is down I would be a hero..
BTW I started using Mobil One 5-30 Synthetic at around 40,000 miles. Then I switched back to regular motor oil at around 85,000 miles. No sign of leaks or burning it out the tailpipe but she now uses 1 Quart in between oil changes (3,500 to 4,000 miles.) Valve stem seals maybe..
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Get me the code number, or swing it by as I have an ECM for it sitting on the shelf. I can flash that ECM to shut codes and such off, but I don't have all of the stuff here to do custom tunes for gassers(I don't have the money to spend on a wideband O2 sensor that I might use once every 2 years).
 
I may do that after fixing some of the other issues Ferm. If you were only closer you would have the entire job.
I think the plan is to keep it, I may need to upgrade the radio too. The sub isn't working and the speakers in front sound blown.
 
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