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Thread: 98 S10 V6 Runs rough when cold after 5 miles runs great?

  1. #1
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    Angry 98 S10 V6 Runs rough when cold after 5 miles runs great?

    98 S10 V6, when started ( cold ) runs with hesitation /stumbling, most apparent on slight throtle, if i give it more throttle runs ok, if its a warm mourning ( fine ). only cold start first thing in the mourning...a few weeks ago replaced the enging temp sensor in the block seemd to correct problem ( or deminis it) now thats it in the 50 s in the mouning more apaerent .............. only occurs when stone cold, i have no codes ............. if i go on the HWY when cold at sligh throttle condition most appparent especially if i use cruise controll , if it was a carberator would think it was accelrater pump >> have replaced , New pulgs , new dist cap, new wires was thinking to replace the ox sensors , i am originial owner , almost 10 years old has 72,000 ,miles runs great all day after reaches operation temp .any thoughts
    Last edited by STRAYDOG; 09-11-2007 at 06:43 AM. Reason: spellin
    Semper Fi

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    Let er be, my friend. If it really bothers you, you could have a remote starter installed or just run outside and fire it up 5 mins before you leave.
    Chevrolet. . . . . . The Heartbeat Of America!!!

  3. #3
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    Unfortunaely the colder the mourning is the more severe the driveability problem , yestertday was 55 degress........... in January in my parts it can go down below zero F , The funnny thing starts immeditely no smoke , just when starting from a stop , stumbles, if I park for a couple hours & start her up runs fine, driveability only first thing in the AM ?? ......... its got to be a sensor ?
    Last edited by STRAYDOG; 09-11-2007 at 11:25 AM. Reason: spleelin
    Semper Fi

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    have you checked vacuum lines to make sure that you dont have a leak??

  5. #5
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    Quote Originally Posted by bradrhale View Post
    have you checked vacuum lines to make sure that you dont have a leak??

    will take a look ....................
    Semper Fi

  6. #6
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    Vac lines OK, Have replaced #1 PCV, & hose , #2 coolant temp sensor ( in block) , when to Nappa to get a manifold intake temp sensor unfortunatly out of stock .will be in Monday after noon ........basicly changing emissions components one by one , next will be the throttle position sensor then (2) oxegen sensors .... she runs great after 6 miles ( cold start am ) no smoke idles smooth ????

  7. #7
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    I would test TP, then MAP then EGR. You don't have ECT wiring such that it's heating with engine, do you ?

  8. #8
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    Crabtruck , yesterday was 42F degrees in the mourning ( much colder than it has been ) ran perfect when accelerating from stop , untill after about 4 /5 miles then a mild pproblem ( acellerating) till reached operating temp.then fine therafter , so if it is the 40s ( colder) problem not as bad , or severe as cold starts in the 55 deg range >>.seems she ( S10) isnt reading temp correctly when cold..picking up NEW temp sensor ( located near MAF) this mourning ......... regarding ( TP & ECT wiring) ? huh ? please advise >>> guess I understand my 66 Vette BB , totally & all this elecrtonics is greek to me . & i truly appreciate any help
    the Dog
    Last edited by STRAYDOG; 09-17-2007 at 06:59 AM. Reason: clarification

  9. #9
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    For ECT wiring I meant do the basics of looking at its routing and condition - nothing fancy.
    Faulty wire can work different as its temp changes.

    Did not catch that you had replaced the ET not the ECT,
    the first being for your gauge and the latter for the PCM brain.
    Probably a ECT defect, but make sure the contacts are clean
    since the full scale is only about 3v, just a little counts.
    For ref, I think the resistance is about 7300@40deg,5700@50,1675@100, and 240@195deg.

    For the TP look for a smooth change of voltage from idle through WOT.
    Changes I believe from about 1v to 4 or 5v at wide open.

    Intent was to look for problem and hopefully not replace parts that are not bad.
    Check the EGR is not sticking or dirty. Just some ideas before you go shopping.

  10. #10
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    Crabtruck ........ first off thanks for you help , I have replaced the following

    #1 new coolant temp sensor ( that gives information to ECM )

    #2 new air temp sensor located in plastic housing supplying air to engine

    #3 replaced throttle position sensor.......TPS

    #4 replaced PCV ( vac line ok)

    Check all connections everthing clean & tight, unfortunatly problem still exists.......... the EGR Valve looks very easy to remove , can it be cleaned via removing & cleaning with wire brush............. & check via applying vacum ? Note owned my S10 about 10 years bought it new, 76,000 miles my winter driver ..................The check engine light has never gone on

    any assistance resolving this problem is very aprecited
    Semper Fi

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