99 Tahoe Idle ruff on cold start

[99hoeon33s]

Well lets see imma start from the top I got my tahoe in august of last year and all the maintenice was not tooking car of so far Ive replaced distrubutor cap and rotor spark plugs (not autolites)LOL! wires fuel pump fuel filter updated spider injector seafoamed it trans fluid exchange coolant exchange differential fluid change new air filter but I still get a rough idle on start and poor i mean poor throttle response compared to other vortecs i have drove i have pulled the codes and it said
P1441 Evap system flow during non purge
P0155 OSB2S1
P0430 Catalatic effeicency bank 2 below threshold( gutted cats)
and thats it some advice would be helpful thanks....

99 Tahoe 4x4 4dr 5.7

 

[lesterl]

p0155 is O2 heater circuit bank 2, sensor 1. I would check that out....

Whats the fuel pressure like?

Any vac leaks?

 

[99hoeon33s]

Nt any vac leaks i know about and what do you mean about the o2 sensor i checked it per all data instructions with a scan tool it failed just haven't changed it yet i probably will tomorrow and do you have any idea about 1441 code

 

[SouthJerseyTahoe]

O2 sensor heater wont cause any idle issues. Very common to have intermittent heater codes. All the heater does is get the o2 warmed up faster. Does it ever back fire upon starting? Worn distributor gear will cause hard starting and rough idle, surging. If you had a significant vacuum leak it would set a lean code.

 

[99hoeon33s]

Well I changed the 02 sensor and that code is not showing up anymore but i dont have a lean code or surging I just have ruff idle upon starting for maybe the first 10 seconds then goes away but when driving it just doesnt seem to have the power or response some of the other vortecs have now maybe it could be the distributor gear but would that set a camshaft position sensor code???

 

[SouthJerseyTahoe]

Just throwing out some ideas and facts here. These engines dont run well with under 50 psi fuel pressure. Under 45 they dont run at all. Fuel pump connectors are common to melt, plastic timing covers warp and create cold start and misfire issues with the crank sensor. Make sure your MAF sensor isnt installed backwards because I've seen that more than once. (They fit both ways and their is an arrow pointing in the direction of airflow). I spent half a day tracking that one down. I also spent another slow afternoon playing around with the timing on a well worn dist gear just to see and it wouldnt start over 5 degrees retard and backfired and kickbacked at 5 degrees advanced but wont set a code until given a good drive cycle. It did run ok once it was started though. I have seen dist gears that were sharpened down like knives and the engine still ran. Unfortunately you need to have a diag tool capable of checking your cam retard. The spec is 0 degrees + or- 2 degrees and anything more creates problems.
On another note MAF codes are stubborn to set. I've seen an over oiled K&N filter contaminate a MAF and set a lean code or make it stall out and once on an older Ford Explorer 5.0 a small piece of fuzz got into the airbox and planted itself right in front of the hot wire causing it to idle like crap. That isnt likely on a Tahoe but needless to say that was a hard one to explain to the customer and now Ford has screens in front of the air intake. You can get a can of cleaner just for the MAF that wont leave a residue but unless I see some freeze frames or screen captures from your live data stream I'm only taking educated guesses.

 

[SouthJerseyTahoe]

The code 1441 could possibly have a vacuum leak through your purge valve because thats not a common code on a Vortec. You should also get a lean code but just check around the top of the intake for a disconnected or broken vacuum line. normally you can hear it but being its only during purge it might be intermittent depending on what side of the purge valve the leak would be on. You can try spraying starting fluid or carb clean/ gum cutter here and there around the top of the intake to find a vacuum leak that will cause a noticeable change in RPM. just dont go crazy and soak it or you could cause it to ignite. just a spritz here and there and lsiten to the engine.

 

[99hoeon33s]

Imma check the degrees on my lunch and will update as soon as i found out

 

[99hoeon33s]

Is this what i should be looking at?

 

[SouthJerseyTahoe]

No ignition advance is different from cam retard. but your fuel trims look ok although I really need to see them once the engine is fully warmed up. How many miles on the truck? How long have you owned it? Has the distributor ever been changed?

 

[99hoeon33s]

Its got 190000 on it i have had it since August and it hasnt been replaced as far as i know

 

[SouthJerseyTahoe]

My truck has 180,000 and as far as I know its the original distributor. At a steady cruise I can feel a slight surge/buck which could be mistaken for a misfire and my cam retard is only out by 3 degrees. Under load or acceleration you cant feel it. It did backfire on startup a couple days ago and was tough to start. This is all due to the worn distributor gear but I just havent had the time to swap in my spare. the Suburban I just did intake gaskets on had a gear thats teeth were sharp as a knife and worn halfway through. if they get bad enough they just plain stop meshing with the cam and the truck stops running.
Without seeing your data stream in person or driving your truck I cant guarantee this is your issue but it is an educated guess. You're gonna have to get access to a real diagnostic tool and not just a code reader to see what your cam retard is at. In addition I would need to see your fuel trims once its fully warmed up and in closed loop.

 

[99hoeon33s]

Ok I will post a link with a video I will take of obd wiz on my computer while idling and driving my truck at full temp tommorrow thanks for all your advice it is greatly appreciated and do you know a good scanner program to use with the pc

 

[SouthJerseyTahoe]

I'm not really accustomed to using pc based diag programs. Right now I'm using a SnapOn Modis and a SnapOn Vantage but we are getting a new Launch this month. The datastream is still the same though provided your pc can keep up. Some screen captures at idle and under load or whatever rpm range you are having your issue will help.

 

[99hoeon33s]

It seems better since i change both upstream o2 sensor but still real slow throttle response

 

[SouthJerseyTahoe]

Placebo.

 

[99hoeon33s]

Huh?

 

[SouthJerseyTahoe]

I would like it if you can see what your cam retard is. Even my old SnapOn brick can read it so your pc based software should have no problem.
I looked at my neighbors Ford F350 tonite and his long term fuel trims are high on bank 1 telling me its running rich on the passenger side bank but Fords dont like to set misfire codes until the cat is melted so until I bring it to the shop and read the cylinder contribution to see what cylinder is suspect I wont know what injector is stuck open and leaking from the bad gas thats been sitting in it for the last 5 years. Point being... everything is explainable but you dont let your wallet figure it out. Sometimes its cheaper to swallow your pride and find a good tech and spend an hours diag time to give you the answer that you have been stressing out, losing sleep and money over. just my 2 cents.

 

[SouthJerseyTahoe]

You spent how much on 2 new upstream sensors? They arent like spark plugs they dont go bad all at once. They do get lazy but even if one takes a **** altogether it doesnt affect fuel control to the point of noticeable power loss. At some point if I cant help you solve this you're gonna have to take it to a good tech.

 

[99hoeon33s]

I do work on cars but i have just done everything i can think of with no changes