very rough running when cold 85
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Intermediate
Joined: Jan 2005
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From: Clearwater Beach Fl
very rough running when cold 85
Hi guys, well been looking at this forum for a long time and solved many a problem here thanks to your advice but this is the first time i have ran into a situation that doesnt quite fit problems OTHER owners have had! Here is the scoop, i have an 85 vette with a mid range jasper crate engine, i have a commercial performance chip, modded the MAF, changed the exhaust (still original manifolds) to twin pipes with flowmasters, bypassed the coolant flow to the throttle body, have the 168 degree thermostat, have replaced ignition modual, plugs, wires, cap, rotor, pcv, pickup coil, IAC and fuel pump. everything else is stock. when i start it cold it runs like crap until it hits about 168 degrees then it seems to run a little better. when i say it runs like crap i mean it idles rough (the tach jumps 2 to 400 RPMS back and fourth and its not all cam related! it accelerates fine but cruises and idels with a miss not so bad you cant drive it but bad enough it is emberassing! once it hits 180 it runs like a brand new car. i have had it pro scanned and there are no codes and no trouble anyone can seem to find HELP ME lol Thanks in advance!
Grant
Clearwater Beach Florida
Grant
Clearwater Beach Florida
Melting Slicks
Joined: Jun 2004
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From: rochester n y
idle
Hi Grant, See my anwser at post "hunts for idle". Your chip could be not compatible with thermostat, map sensor could be wrong, but that should give a code.Let me know. Good Luck Save the Wave.>George
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From: Clearwater Beach Fl
George,
Very good thoughts The chip and thermostat are matched and had been running finr for a year or more. i did forget to mention that this trouble seemed to come on all at once, i had to take a friend to the airport and on the way back the ignition seemed to cut out from time to time so i did the whole tune up then plugs wires cap module, pick up coil etc it all seemed to run fine prior to the cut out problem no indicvations that somthing was going bad or anything (i firmly beleive the problem was the ignition modual at the time but it needed a good tune up anyway)after i replaced all that stuff it ran like new for about a month then we got hit with the hurricane and it seemed to go down hill fast from that point on *lol* i dont think the hurricane had anything to do with it but thats a point of referance for me. I pulled the plugs and 2 of them number 6 and number 8 were splash fouled BAD they were bosch double plats and i read here a lot of you guys dont like them so i put in AC Delcos but it has not seemed to make any differance. I pulled them yesterday after am onth of service and they were clean and normal.
Grant
Very good thoughts The chip and thermostat are matched and had been running finr for a year or more. i did forget to mention that this trouble seemed to come on all at once, i had to take a friend to the airport and on the way back the ignition seemed to cut out from time to time so i did the whole tune up then plugs wires cap module, pick up coil etc it all seemed to run fine prior to the cut out problem no indicvations that somthing was going bad or anything (i firmly beleive the problem was the ignition modual at the time but it needed a good tune up anyway)after i replaced all that stuff it ran like new for about a month then we got hit with the hurricane and it seemed to go down hill fast from that point on *lol* i dont think the hurricane had anything to do with it but thats a point of referance for me. I pulled the plugs and 2 of them number 6 and number 8 were splash fouled BAD they were bosch double plats and i read here a lot of you guys dont like them so i put in AC Delcos but it has not seemed to make any differance. I pulled them yesterday after am onth of service and they were clean and normal.
Grant
Last edited by clearwater_shark; Jan 11, 2005 at 11:24 AM.
Melting Slicks
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From: rochester n y
corvette C4
Hi Grant, Did you put in the stock A/C Delco plugs or the A/C Delco professional platinum(rapid fire) ? How about all terminals going in and out of ECM, all tight and no signs of being dirty. All grounds clean ? what injectors are you running.? I think you can use the turbo style Grand National Buick injectors. Very important too is your fuel filter. Is it new ? (clean). If you're not too sure about when or if it's been changed that could have effected your electric fuel pump. Is the fuel pressure stong ? I'm kind of shooting here. Hope you get it taken care of to get your Corvette running stong again. Let me know.Good Luck.>George
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From: Clearwater Beach Fl
the injectors are the original's with 120 thousand miles on them, yes the fuel filter was changed and i have not checked the ECM connections i will try that today 
thanks for the ideas! Oh this morning i tried unplugging the o2 sensor but it made no differance and didnt trhow a code either (isnt that odd?) the fuel pressure is unknown but i cant see that changing when it warms up to normal operating termp can you? could it have been a mistake to bypass the throttle body coolant flow?
thanks for the ideas! Oh this morning i tried unplugging the o2 sensor but it made no differance and didnt trhow a code either (isnt that odd?) the fuel pressure is unknown but i cant see that changing when it warms up to normal operating termp can you? could it have been a mistake to bypass the throttle body coolant flow?
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From: Clearwater Beach Fl
lol man this is getting the best of me here I am running out of ideas coil maybe? i DID notice the miss is there under cruise when its hot too but barely noticable and not at all under acceleration. Fuel injectors? ECM? if the ECM is bad wouldn't it refuse to throw codes? i tried unplugging the MAF and i got a check engine light and it stored a map code... just not shure what to think! runs AWFUL help lol I just cant help but feel it is in the ignition maybe im wrong but it sure does not present like fuel problems...
I am running out of ideas coil maybe? i DID notice the miss is there under cruise when its hot too but barely noticable and not at all under acceleration. Fuel injectors? ECM? if the ECM is bad wouldn't it refuse to throw codes? i tried unplugging the MAF and i got a check engine light and it stored a map code... just not shure what to think! runs AWFUL help lol I just cant help but feel it is in the ignition maybe im wrong but it sure does not present like fuel problems...
