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Hard start

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Dcalebaugh

Guest
Any advice on what to check for this problem? I have an 86 that starts great when the ambient air temp is cool, but starts hard when the temp is high. Even if I have already run the car, if it is cool out side it starts easier. I also notice a slight hesitation off idle, do not know if the two are related. Just bought the car and am learning. Also what should an auto idle at in park? Mine seems high 1000 to roughly 800, sure clunks when you put it in drive at that rpm.

Thanks
Dave

Just a side note, when it starts hard it appears to be flooded and blows smoke with a strong smell of gas.
 
F

Fastvette86

Guest
Dave,

My 86 does the same thing. I changed all of the injectors when I installed a Big Mouth manifold and it helped some. I've narrowed it down to the cold start injector leaking. Unfortunately it's no longer available. I just give it 1/4 throttle when its hot and been sitting more than 5 minutes and it starts lots faster.

This winter I'm going to take the cold start injector out and see if I can find someone that will test and clean it.

Your slight hesitation off idle - does the fuel level in the tank affect it? If it is worse as the fuel gets lower, then your sock filter on your in-tank fuel pump is probably dirty. Pull your pump and replace it. You idle is too high if it is 1000 rpm when the engine is hot, you might try resetting your minimum air on your throttle body.

Dennis
 
S

Shadowing1985v

Guest
yeah never touch your tps sensor unless u think u know what u are doing

tps should be .54 volts in park
air control should be 1 inch and 1/8

o broke my cold start valve
it cos tme 46 to buy one
they say, but it never cam ein
they said something happend as if it doens't exist, ehe,, i guess they dont' make it anymore anyways

i welded the pipe and no wim going to put a gasket on it caus ei put it on and it started leaking a little

anyways

make sure you are at top dead center

1000 is way to high your auto should idle at 400 rpms in drive

i have a 85 and mine idles at 550 and i have auto i havn't been able to get mine down to 400 yet,, but im getting closer, i still have thigns wrong with it,, im slowly fixing it,, i have replaced alot of things,,
 
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Shadowing1985v

Guest
oh yeah one more thing

this is for everyone,,, a corvette with tune port injection

should start so easy.. i mean really easy,, no mater what condition your cold start valve is in,
i dont' even know why they put it on there

if u go and buy spark plugs
alot of people do this they will go buy spark plugs and stick them on there car

with out checking the gap on them
i did this, and learn that i had to tap thema few times to make them .035 or what ever the book says,, then after that my car started really easy
 
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Shadowing1985v

Guest
gaping your spark plugs

its the messurement gap inbetween your spark plugs

when u buy them they arn't pre taped
 
C

c4ever

Guest
Dave,
Are you pulling any codes?
Idle when at running temp in park under 600rpm (auto)
Transmission in D: 520 to 550rpm

Carlo
 
D

Dcalebaugh

Guest
OK, here is what I have done so far. I cleaned the throttle body. This seemed to help its starting problem, as a side note I see that the previous owner installed one of those units in front of the tb to improve airflow, I cleaned that also. I then, following the hayes manual jumped the diagnostic link and then unplugged the Idle air control and then started the car. When I started the car the idle went from around 800 before to around 4-500, perfect I thought. I then shut the engine off plugged the aic back in and restarted, you guessed it, back to the old idle speed. The only other thing mentioned in the manual was to check the tps. I dont have a jumper to put in so I can get my probes on the terminals and read the voltage. I tried to push the probes in from the end of the connector but no luck. Am I heading in the right direction or did I miss something? If I need to adjust the tps how is that done, I see the two tork screws, do I remove them completely? The Hayes is a bit vague on that. Thanks in advance.

Dave

PS I just checked and no codes were stored
 
S

Shadowing1985v

Guest
go buy like a foot of wire

make 2 inch wires

and make 3 of them
strip both ends

shove each end in from the tps to the female connector
then on the top two "a and b" it sould read ona ohm meter .54 volts


check the cap on your spark plugs, im telling u this gave me hard to start problems
 
F

Fastvette86

Guest
Dave,

Sounds like your minimum air setting is OK since it idles at 450 or so. Your heading in the right direction by checking the TPS. I bought a TPS test harness from Corvette Central and it worked great. You only need to loosen the 2 torx screws to adjust it. You need to adjust it to .54 volts and then check it at wide open throttle and make sure it gets to 4.5 volts. It took me a couple of trys to get it right.

I checked out www.cruzinperformance.com yesterday and they said that they can clean cold start injectors and stop them from leaking.

Hope this helps.

Dennis
 
D

Dcalebaugh

Guest
Dennis,

Thanks for info. I am either going to buy or make a jumper. One question though, once you lossen the tork screws how exactly do you adjust the sensor? What part gets adjusted?

Thanks
Dave
 
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Fastvette86

Guest
Dave,
The TPS body rotates around the two screws. It will also move up and down, so that's why you have to check the wide open throttle voltage too.
Dennis
 
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Shadowing1985v

Guest
wow wait a minute

wid open throttle i never check that,, hmm

4.5 u say.. i will go check that out on mine as well
and come back and tell u guy's what mine reads
 
D

Dcalebaugh

Guest
I finally was able to get some fine point probes and measured the tps voltage at idle it measured .53. I can not get it to idle at the proper rpm with the IAC connected. I followed the steps to a tee and as soon as the idle is adjusted to the proper idle, plug the AIC back in, start it up and back up to 1000 rpm's. Am I to assume the AIC valve is bad? Also with the AIC unplugged it idles great, so is there any harm to running the car without this valve until it is replaced?

Thanks
Dave
 
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Shadowing1985v

Guest
hehe i have that same problem, i got curious

i unpluged my AiC

and it shot up to 1500 rpms

then i unplug it and it goes to 550


my car is doing the exact oppsite of yours

i have a automatic
it should idle at 400
havn't seem to get it there yet, im still trying,, doing the valve adjustment sunday
 

WhalePirot

Well-known member
Joined
May 9, 2002
Messages
2,942
Location
SoCA
Corvette
1984 White Z-51/ZF6-40/Shinoda body
leaky injector?

I think one or more injectors is leaking. The 'rich' start points to it, and the unprogrammed fuel may be screwing up what the ECM's 'reads'.

I don't know what the 'bleed down' fuel pressure specs are. If an injector is leaking the fuel pressure drop, as teh ignition is shut off, will be too rapid. Methinks the pressure should hold for a few minutes, minimum, with no leaky injectors. BMW has a spec for this, and a test. i know of no such animla for Chevy, but the disassembly verbiage calls for bleeding off the pressure, safely.

Vacuum leaks can do similar weird things, and can be found audibly or with WD-40 sprays at suspect leak areas.
 
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Fastvette86

Guest
Dave,

Sounds like your IAC may be bad or dirty. Try unscrewing the IAC and cleaning it and the passages for it in the throttle body.

Other than that, the only thing I can think of that would cause a high idle is a bad coolant sensor. If it's bad, then the car will keep it at high idle and it will run too rich. That could be the casue of your hard start too.

Good luck,

Dennis
 
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jnsampson

Guest
I have the same problem in my 85. It's been diagnosed as either a leaky fuel injector or the so called 9th injector (Cold Start Valve). As previously written by another member, the CSV is no longer manufactured. GM stopped it in either 88 or 89. There is a kit out there to plug the CSV. But that requires a new EPROM upgrade.

Most likely it's a leaky injector or two. You can definitely smell the fuel dump when you start it when it's been run earlier.

I just picked up a set of slightly used (19,000 miles) 24# injectors off of eBay for $76.00 for the entire set. GM charges somewhere in the vicinity of $125.00 PER INJECTOR. Ecklers has a set for $309.99 for the whole set. Mid America has a set of Accel injectors for $399.99.

If you have any more questions, give a shout.

:cool
 
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Shadowing1985v

Guest
hmm

i have two small puddles of liquid under my runners that gets there


on both sides in the middle
i don't know what it is
 

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