help - loss of power in '85
#1
Burning Brakes
Thread Starter
help - loss of power in '85
hey everyone
I went to take a short run today with the '85 (4 + 3 ). and it started right up ready to go - then as I started up the street - it seemed to be sounding much more rough then before - almost heavy and more thumpy(I believe that's a technical term used in some lesser circles of knowledge and the English language). I drove for a while hoping it was due to sitting for about a month (my apologies to the Vette gods - back injury). as the drive went on it did not improve - if I tried to give it extra gas it tried but did not come close to feeling like it wanted to - very sluggish, heavy and yes thumpy. So I stopped turned around and headed home.
I did some searching but as soon as I mention power loss - it blames the L98. I was looking forward to a couple of days off to enjoy the ride -
Temp gauge was normal -
any thoughts opinions, etc would be greatly appreciated
Sean
I went to take a short run today with the '85 (4 + 3 ). and it started right up ready to go - then as I started up the street - it seemed to be sounding much more rough then before - almost heavy and more thumpy(I believe that's a technical term used in some lesser circles of knowledge and the English language). I drove for a while hoping it was due to sitting for about a month (my apologies to the Vette gods - back injury). as the drive went on it did not improve - if I tried to give it extra gas it tried but did not come close to feeling like it wanted to - very sluggish, heavy and yes thumpy. So I stopped turned around and headed home.
I did some searching but as soon as I mention power loss - it blames the L98. I was looking forward to a couple of days off to enjoy the ride -
Temp gauge was normal -
any thoughts opinions, etc would be greatly appreciated
Sean
#2
Zen Vet Master Level VII
Spark-air-gas
Sounds like you have spark and air so I'd check your fuel pressure. Lack of pressure can make a car feel sluggish. Put a gauge on your fuel rail and see what ti says.
Sounds like you have spark and air so I'd check your fuel pressure. Lack of pressure can make a car feel sluggish. Put a gauge on your fuel rail and see what ti says.
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sb66 (06-17-2018)
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sb66 (06-17-2018)
#4
Burning Brakes
Thread Starter
I did not see a code - they will show up visibly on the dash - correct? (I know probably a moronic question - I have not had any before)
I will see what gauges I have -
thanks
I will see what gauges I have -
thanks
#5
Burning Brakes
Thread Starter
no error code lights up on the dash
#6
sb66 are you willing to get your hands on a few basic tools like the fuel pressure gauge suggested? it will be something simple and basic most likely. we can guide you through a series of elimination.
if your fp is ok, my bet is on the icm. but u have to stay methodical and do this stuff in steady succession.
VT
if your fp is ok, my bet is on the icm. but u have to stay methodical and do this stuff in steady succession.
VT
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sb66 (06-18-2018)
#7
Burning Brakes
Thread Starter
thanks - Yes I am going to see what I have - If I need to I will get a fuel gauge tester. Is there any specific kind I should look for ? or is there a "general" tester for this?
"icm" ? sorry still learning stuff.
thanks - really appreciate everyone's willingness to help guide me through this
Sean
"icm" ? sorry still learning stuff.
thanks - really appreciate everyone's willingness to help guide me through this
Sean
#8
You can rent a fuel pressure tester at autozone or the other store like that. Just tell them the which car you're testing.
You could have some bad tune up parts, sounds like its misfiring.
You could have some bad tune up parts, sounds like its misfiring.
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sb66 (06-18-2018)
#9
Burning Brakes
Thread Starter
https://www.summitracing.com/parts/a...model/corvette
icm?
not buying anything yet - just making sure I understand stuff
thanks
icm?
not buying anything yet - just making sure I understand stuff
thanks
#10
Burning Brakes
Thread Starter
#11
https://www.summitracing.com/parts/a...model/corvette
icm?
not buying anything yet - just making sure I understand stuff
thanks
icm?
not buying anything yet - just making sure I understand stuff
thanks
When the car loses power, does it feel choppy, like you are having a misfire, or is it smooth, and just doesn't pull? If its missing, ICM, plugs, and wires would be my first items to check. If it feels smooth, then I would check knock sensor/knock sensor connector, replace the gas in the tank (I siphoned all but 1 gallon out, then went and got gas), then check the ICM.
It is especially important to replace the gas if it is older than 6 months, in my case the car would knock, the knock sensor would pick it up, and timing would be pulled which resulted in low power.
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sb66 (06-18-2018)
#12
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sb66 (06-18-2018)
#13
Race Director
Basic tuneup, plugs, wire, cap, rotor. Check the fuel pressure, then a compression or preferably a leakdown test.
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sb66 (06-18-2018)
#14
Burning Brakes
Thread Starter
Yep, that's an ICM. In my experience, the ICM either works, or doesn't - but I've heard of ones that fail partially. Assuming fuel pressure checks out, and there isn't a vacuum leak, then I would start with the ICM.
When the car loses power, does it feel choppy, like you are having a misfire, or is it smooth, and just doesn't pull? If its missing, ICM, plugs, and wires would be my first items to check. If it feels smooth, then I would check knock sensor/knock sensor connector, replace the gas in the tank (I siphoned all but 1 gallon out, then went and got gas), then check the ICM.
It is especially important to replace the gas if it is older than 6 months, in my case the car would knock, the knock sensor would pick it up, and timing would be pulled which resulted in low power.
When the car loses power, does it feel choppy, like you are having a misfire, or is it smooth, and just doesn't pull? If its missing, ICM, plugs, and wires would be my first items to check. If it feels smooth, then I would check knock sensor/knock sensor connector, replace the gas in the tank (I siphoned all but 1 gallon out, then went and got gas), then check the ICM.
It is especially important to replace the gas if it is older than 6 months, in my case the car would knock, the knock sensor would pick it up, and timing would be pulled which resulted in low power.
I will do a visual check - and probably end up down the road buying a fuel pressure tester - sounds like it will be useful through the lifetime of the car
#15
the car is definitely not smooth - feels like it might be lacking compression - so I guess that would be missing? not very good with the diagnostic side of things - I am sure this should and would be easier for some -
I will do a visual check - and probably end up down the road buying a fuel pressure tester - sounds like it will be useful through the lifetime of the car
I will do a visual check - and probably end up down the road buying a fuel pressure tester - sounds like it will be useful through the lifetime of the car
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sb66 (06-18-2018)
#16
Burning Brakes
Thread Starter
thanks - really appreciate all the help
#17
Drifting
Member Since: Mar 2017
Location: Nashville TN
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2017 C4 of Year Finalist
had something similar when I had a fuse went bad (didn't burn out but looked like it almost did) for my MAF module. I thought the MAF was the issue but luckily the fuse just needed to be replaced. Forget which it is off the top of my head but maybe take a look at your fuses. ICM going bad is also another good place to start, as is fuel pressure (rent the pressure gauge at Autozone, you can return for a full refund).
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sb66 (06-18-2018)
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sb66 (06-18-2018)
#19
Burning Brakes
Thread Starter
fuel pressure - 43 key to on position
40 at idle, and increased when I pulled throttle cable
those numbers seem ok?
the only thing I noticed was a slight puddling of some type of fluid by the thermostat housing - but I think that has leaked slightly for a while - so that really is not anything new - not necessarily good but not new
thanks
Sean
40 at idle, and increased when I pulled throttle cable
those numbers seem ok?
the only thing I noticed was a slight puddling of some type of fluid by the thermostat housing - but I think that has leaked slightly for a while - so that really is not anything new - not necessarily good but not new
thanks
Sean