Tuning Problem???
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Joined: Oct 2008
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From: Canton Michigan
Tuning Problem???
NEWB HERE LOL...I don't know if this would be a tuning problem or not so i thought i would get as much input as possible. But the car seems to have a terrible time keeping the RPM's steady when its idling and its getting extremely annoying specially in this DC traffic. On start up the car will idle fine right around 900rpm but after the motor warms up the RPM's will bounce from 400-1500 and sometimes stalls when it drops down. My cam is a 244/248 114lsa with a bit over 600 lift. My shop insists its the cam but i thought i would see what you all have to say. Wheather its the CAM or not this needs to get taken care of ASAP cuz its absolute hell to drive in traffic. I dont know if this is related but ever since i got my car back from the shop with the new motor it seems like shakes itself to death off the line sometimes when im just driving normal(it feels like wheelhop), what could cause this? Thank you before hand for all your help
Melting Slicks
Joined: Dec 2003
Posts: 2,857
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From: pawleys island sc
of course that cam is big enough to cause idle problems but guys are running bigger cams without any real problem. you say you got the car back with a new motor. was the car tuned after the engine work was done? I mean by someone who KNOWS how to tune - anyone can put a big cam in but it takes some talent to tune the car to run properly.
I think you need to give a little more background info on what was done and when before anyone can offer a reasonable suggestion.
I think you need to give a little more background info on what was done and when before anyone can offer a reasonable suggestion.
Pro
Joined: Oct 2008
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From: Hayward Wi
for your tired have them balance checked some one at the shop could have knocked one of balances off it while working on it.
as for the engine sounds like its over compensating try putting some load on it from like the AC and if it over reves then its over compensating for RPM drop and increase
as for the engine sounds like its over compensating try putting some load on it from like the AC and if it over reves then its over compensating for RPM drop and increase
Le Mans Master
Joined: May 2006
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From: Hillsboro OR
I have read that if the blade on the throttle body has got a dirt build up on it, it can unbalance it mechanically. This could cause the PCM to struggle to keep the idle steady. It's worth a look.
My $0.02 HTH
My $0.02 HTH
Tech Contributor
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
I sure sounds like a tuning issue. I have a simular cam and had the same issue. I had the PCM tuned (by a professional) and it made a world of diference. Still has a very slight idle issue but it just needs a little fine tuning.
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Joined: Oct 2008
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From: Canton Michigan
The car was dyno tuned after the motor swap but we had an issue with one of the pulleys breaking off so we had to wait till a new one came in then had to get it pinned. So the car never really made a full run on the dyno. After we got the new pulley the car was re-tuned(without a dyno). All tuning was done by Vector Motorsports. We took it to him about a week or so after and he changed some stuff with just his computer and said we "should" be ok. Its now a month later and the car is not any better. Its garaged now but were going to get this taken care of ASAP. Thanks for all the input so far
Burning Brakes
Joined: Feb 2007
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From: Kansas City Missouri
St. Jude Donor '09
Well did it do this before? If the car ran smoothly after tuning but then picked up the problem then it is not the tune. If it has done this from the beginning I might suggest finding a new tuner.
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Tech Contributor
Joined: Apr 2007
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From: Forney Texas
I am +1 on taking it to a different tuner. There are some good tuners in your area I'm sure. Haven't heard of your guy, so can't comment. Just consider it getting a second opinion from a different doctor. Your car and mods aren't worth squat unless you can go out and enjoy it!
Safety Car
Joined: May 2007
Posts: 4,812
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From: Taylorsville North Carolina
I just did a 402 with the MS3 (237/242)cam. I know my tuner spent a lot of time working the idle thing, but I have no issues with mine so far. Sounds like tune to me. If it was something mechanical, seems like it would show up during the tune. HTH.
Le Mans Master
Joined: Jul 2005
Posts: 7,405
Likes: 353
From: New Castle Del.
St. Jude Donor '09
NEWB HERE LOL...I don't know if this would be a tuning problem or not so i thought i would get as much input as possible. But the car seems to have a terrible time keeping the RPM's steady when its idling and its getting extremely annoying specially in this DC traffic. On start up the car will idle fine right around 900rpm but after the motor warms up the RPM's will bounce from 400-1500 and sometimes stalls when it drops down. My cam is a 244/248 114lsa with a bit over 600 lift. My shop insists its the cam but i thought i would see what you all have to say. Wheather its the CAM or not this needs to get taken care of ASAP cuz its absolute hell to drive in traffic. I dont know if this is related but ever since i got my car back from the shop with the new motor it seems like shakes itself to death off the line sometimes when im just driving normal(it feels like wheelhop), what could cause this? Thank you before hand for all your help
Thats deff in the tune. We have tuned cars with bigger cams on smaller motors and they idle fine. It takes some time to get them to idle but it can be done. If you would like to bring it up to my shop i gurantee i can get it running correctly. Thats not all that huge of a cam for a 408 cu in motor.
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Joined: Oct 2008
Posts: 74
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From: Canton Michigan
Its a Profession Products 96mm Intake Manifold that i got from Maryland Speed. "Tony's Corvette Shop" in Maryland is going to diagnose and re-tune the car. I have heard nothing but good things about them and they concur with all of you that its a tuning issue and that they have done many corvettes with bigger cams and they idle just fine. Thanks everyone for the help this forum makes car problems a million times easier with all the knowledge from owners and tuners i should have done this a long time ago.