hard starting when hot, maf sensor

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wallster - 14 Jul 2006 16:17 GMT

Hello everyone. My '88 C4 starts great when cold but when she's hot I
have to pump the accellerator pedal to start it. I originally thought
that I had a leaky injector or two but I believe it's the mass air flow
sensor or burn off relay(s). The engine was hot and I removed the maf
sensor and sprayed throttle body cleaner through the sensor (thinking
maybe it was dirty) and the car started without any problem afterwards.
That only lasted so long and now she's doing the same thing. How can I
test the maf sensor before I spend the cash on a new one? Also, how can
i test the burn off relays as well?
Thanks in advance.

walt
'88 conv

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wallster - 14 Jul 2006 16:37 GMT

i forgot to mention that i pulled the codes from the car and a 32 code
popped up. The service engine soon indicater light came on a few days
ago on the thruway but hasn't been on since. I installed a new battery
yesterday (battery was old and dying) so i cleared the codes when i
changed it. 32 is an EGR code i believe, any thoughts?

walt
'88 conv

> Hello everyone. My '88 C4 starts great when cold but when she's hot I
> have to pump the accellerator pedal to start it. I originally thought
[quoted text clipped - 9 lines]
> walt
> '88 conv

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'Key - 14 Jul 2006 20:13 GMT

>i forgot to mention that i pulled the codes from the car
>and a 32 code
[quoted text clipped - 8 lines]
> walt
> '88 conv

would be leaning towards the mas sensor myself..

I got away from that computer all together.
got tired of my 84 c-4 always throwing codes.
all I have to do now is watch the gages,
like the good old days :-)

my2¢

Signature

"Key"
=====
---snip---

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wallster - 14 Jul 2006 19:58 GMT

this looks weird (that i keep replying to my own question) but the more
i dig into the problem, my thinking changes. I found a service bulletin
from '91 regarding the MAF relay (or relays with the bosch MAF set up
that this car has) that the relay can take a dump and still test okay
as well as not produce an SES code.
The relays are $11. so i'll change them first. They might not be
resetting the mass flow sensor thus producing a false fuel
signal/reading.
As far as the 32 code (EGR), the car idles fine and runs strong so i
doubt the valve or switch is faulting. I've driven the car over 200
miles since that SES was shown (at thruway speeds) and the SES hasn't
come on. This could have been a false code (or the beginning of
something to come... D'OH!)
I'll post later if the relays fix the problem for future google
searches.

walt
'88 conv

> Hello everyone. My '88 C4 starts great when cold but when she's hot I
> have to pump the accellerator pedal to start it. I originally thought
[quoted text clipped - 9 lines]
> walt
> '88 conv

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wallster - 14 Jul 2006 23:06 GMT

Here's a good article explaining how and what a mass air flow sensor
does. It also explains what the relays do.
OEM relay stock number is 14089936 (for those who are looking for parts
numbers)
http://corvettebuyers.com/c4vettes/maf.htm

walt
'88 conv

> Hello everyone. My '88 C4 starts great when cold but when she's hot I
> have to pump the accellerator pedal to start it. I originally thought
[quoted text clipped - 9 lines]
> walt
> '88 conv

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wallster - 15 Jul 2006 15:05 GMT

I changed both MAF relays (burn-off and power relay) as well as the air
filter and she fires right up. I drove it about 25 miles and between
this morning and yesterday it hasn't started hard once, just turn the
key.
Autozone stocks the relays (part# MR44 @$10.99ea.)
Hope this helps anyone else with the same problem.

walt
'88 conv

> Here's a good article explaining how and what a mass air flow sensor
> does. It also explains what the relays do.
[quoted text clipped - 18 lines]
> > walt
> > '88 conv

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Brad - 18 Jul 2006 00:05 GMT

I have an '85 with a similar problem, hard starting when warm. Starts great
in the morning but will give me trouble even after it sits 8 hours at work.
I've looked everywhere I can think of and no one lists these sensors for an
'85. Does anyone know if it takes the same ones as the '88? Thanks in
advance. Brad

>I changed both MAF relays (burn-off and power relay) as well as the air
> filter and she fires right up. I drove it about 25 miles and between
[quoted text clipped - 28 lines]
>> > walt
>> > '88 conv

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