truck wont start, getting spark and fuel, turns over wont catch on 2004 Chevrolet Silverado 1500

will act like its going to run, holds 200 rpm and spits out the carb. changed all tune up parts. changed crank sensor. once it get running it will run fine for a day or 2. worst time is a cold start. acts like its out of time.

by in Saint Louis, MO on October 23, 2012
3 answers 5 comments
ANSWER by on October 23, 2012
ddc, your truck acts like it is going to run at 200rpm??? it is barely idling at 400! did you modify this vortec engine? there is NO carburator! and seriously...did it actually run fine for a day or two? any check engine light on? if so, please let me know what the code(s) are...thanks...
COMMENT by on October 23, 2012
its sputters at about 200rpm but wont fully catch, only for 5 to 10 seconds before it spits out of the throttle body"carb". its normal idle is 700. no modifications to engine, only has 60k. and yes it ran well for several days after changing the crank sensor. no check engine lights. wondering if it could be the cam sensor now. about the only part in electrical system not changed.
ANSWER by on October 24, 2012
The last part of your question, you say it acts like it's 'out of time'. Have you checked to see how much slack is in the timing chain? Checked 'base timing' with light? Are both mass air and MAP sensor readings correct? No leaks between MAF and TB?
COMMENT by on October 24, 2012
no i have not to all your questions, that is probably above my skill level. i have now replaced the cam sensor. no difference. wondering if crank sensor i changed is bad, ran fine for a week after changing it?
COMMENT by on October 24, 2012
probably best to get a shop to look at it. may be less expensive in the long run.
COMMENT by on October 24, 2012
took icm and coil to have checked, both were ok(icm was replaced 2 years ago). changed pcv seeing as it was only thing not changed now. put it all back together and it started, rough, then smoothed out, still has a slight flutter in rpm. now wondering if i have a bad wire somewhere. so yeah, if it stops again i think it will be time for a pro. but thanks everyone for the advice.
COMMENT by on October 25, 2012
Persistance is a good thing most of the time , and in your case , sounds like it was worth it. Internal vacuum leaks/resrictions can be hard to diagnose in person , online is even more fun. As for the remaining 'flutter' , maybe re-check plugs (my opinion-OEM is best) for any fouling that might have occurred prior to replacing the PCV valve and replace as needed. Again- my opinion- don't waste time cleaning there's more to a spark plug than meets the eye-litteraly.
ANSWER by on November 10, 2014
I recommend 2 places to go take it auto zone /tell them your problem /ask the to plug that diagnostic machine into the plug inside of your car.this machine will give a codeor codes describing the problem .if that don't work go to a mechanic shop or a electric shop.a mechanic shop might cost you from $60to $200 to do a full engine diagnosis.and electric shop could cost you $40 to $70 to get a diagnosis.