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david craig
david craig, Auto Mechanic
Category: Chevy
Satisfied Customers: 3748
Experience:  owner/mechanic at 3D Automotive
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After replacing head gasket 350 Vortec is a pig to start and

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Hi...after replacing head gasket 350 Vortec is a pig to start and delays acceleration
JA: Is this your first time dealing with this issue? What size is your engine?
Customer: small block 5.7 thanks. Yes started fine before just damaged head gasket on one cylinder
JA: What is the model/year of your Chevy?
Customer: 1998 CK
JA: What can I say?
Customer: Fault code says crank/cam or Maf sensor
JA: What can I say?
Customer: thinking perhaps advance the timing a little..what do you think?
JA: What year is your Chevy?
Customer: 1998
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: timing is correct..cleaned the MAF and the CPS
JA: Anything else you want the mechanic to know before I connect you?
Customer: engine low miles ..

Hi Im David, thanks for visiting the site. What are the fault codes?

Customer: replied 1 month ago.
Hi David sorry for the delay in answeringP1345
Customer: replied 1 month ago.
We have cleaned the MAF and crank sensor

no problem, thanks

Customer: replied 1 month ago.
Are you still there?

yes im here, please have a little patience

Customer: replied 1 month ago.
sure..sorry

thanks

try adjusting the distributor. I have attached the complete diagnostic for the code, but adjusting the dizzy would be the first thing I would try.

Customer: replied 1 month ago.
Thanks david..shall i advance it a little

try advancing yes

Customer: replied 1 month ago.
Ok thanks..i will get back to you shortly DavidCarl

Ill be here

Customer: replied 1 month ago.
Hi david...tried advancing and retarding the distributor..still just about impossible to start.
revs to the high range ok but chokes on accelerating

ok, standby

this is a failure of the cam and crank sensor working together. a scan tool is going to need to be used to troubleshoot this to see what sensor is reading offset from the other.

Customer: replied 1 month ago.
Thanks...maybe i will buy both sensors ..good idea you think..as a short cut?

I never like to replace anything until I know its bad.

Customer: replied 1 month ago.
Understood but we used a different diagnostic tool and it came up with the same code P1345.
Does that fault code not include the MAF sensorWe are also unable to clear the engine warning light.

its definitely a hard fault for sure. maf sensor has no input to the code whatsoever

it doesnt matter what scan tool you use, the code is the code. it needs to be diagnosed accordingly.

if you want to take your chances by replacing both sensors, have at it. but I would check the power, ground and signal at the sensors.

Customer: replied 1 month ago.
Ok..the crank sensor has 3 pins..what should i read from them?
Similarly how do i test the cam sensor and MAF
Thanks

ok, please give me a while to get those tests together for you. thanks.

cam and crank schematic for reference

more info for you.

http://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-cam-sensor-1

Customer: replied 1 month ago.
Good stuff David..i will leave in [peace for a whileRegards
Carl

ok, if you follow that information, you will determine if its a wiring issue or a component issue for sure.

please accept the answer and leave a 5 star rating for me if you are satisfied with my assistance. just remember, by accepting the answer and leaving a rating doesnt mean we are done. im here to help you until the vehicle is fixed.

david craig and 2 other Chevy Specialists are ready to help you

thank you much and let me know if theres any more information or assistance that you need.

Customer: replied 1 month ago.
hi David..replaced cam and crank sensors.
The difference now is that we can clear the engine warning light and no other codes.
Still a pig to start and excessive cranking brings up the engine light again.
My mechanic thinks its an air leak symptom?
The only gasket we did not fit new when doing the head gasket was the inlet manifold one.
What do you think?

the lower intake manifold gasket wasnt replaced?

Customer: replied 1 month ago.
No..just cleaned and reused the old one with some silicon.
When you say lower gasket..is there not just one?
Customer: replied 1 month ago.
My apologies the lower ones were replaced new..but the upper one between aluminium and plastic was not replaced

spray around the intake manifold and plenum, all vacuum hoses and connections and the brake booster with carb cleaner and check for an rpm change

Customer: replied 1 month ago.
Fire risk?

not with carb cleaner

Customer: replied 1 month ago.
no surge with applying carb cleaner.
Car starts fine first thing and engine warning light stays off.
Restart after 5 mins max and reluctant to start . The engine warning light comes on.
We have checked the timing ..perfect.
Replaced the crank and cam sensors.
No fault codes...does this leave the MAF at fault> ?

if the maf was faulty it would code. but you can test it.

http://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/how-to-test-the-maf-sensor-2

hows it going?

Customer: replied 1 month ago.
Hi David..i dont have a digital meter with Hertz

are you talking about checking the signal from the maf?

Customer: replied 1 month ago.
thats right

just use the voltage to check the signal by back probing the connector while cranking the engine

Customer: replied 1 month ago.
to be clear..cable A should pulse some sort of voltage?

yes you should get a dc voltage reading

Customer: replied 1 month ago.
Cheers..will try it

ok

Customer: replied 1 month ago.
David..we tested the MAF sensorBlack wire has a good earth
Red wire is grounded with ign off...12.7 volts with ign onYellow wire (with engine running) fluctuates between 0-4.2 volts about every second
Yellow wire ..when unplugged from MAF fluctuates between 0-5.0 volts about every second

well that tests good.

is it still taking a long time to start?

Customer: replied 1 month ago.
first start is fine.
second start even after 3 mins is hard

how about doing a fuel pressure leak down test

Customer: replied 1 month ago.
How do i do that please

standby

fuel pressure test and leak down test,