----Stalling when in Op.Temperature??

[CaptainZoom]

I have a -89 5.7L Chevy Silverado k1500 Stepside.
When engine is cold it runs fine. Given gas whilst driving and it answers as it should.
When gear in "Park" or "Neutral", it revvs up and down as it should and works just fine.
-Until Operating temperature is reached, then it loses power dramatically and even stalls sometimes when I try to accelerate or rev it !!!
In idle, cold or hot engine,
-No problemo. Sounds like all 8 are running fine.
But as soon as I depress accelerator pedal, it stalls or almost stalls. It sounds like the engine is being smothered or choked...
But again, only when engine has reached operating temp.
So while it is cold (or has reached right op.temp) it runs just fine??

So I guess it is getting both spark and fuel enough?
When the choke is engaged, it enrichens the fuel/air mixture, and it obviously works fine then, it should get enough gas when in op.temp as well?
So it appears to have something to do with when the engine reaches the right temperature. Apparantly some sensor or something else tells the engine to start working with different settings? Or is there something else I have missed????

Please heeelp!!
BTW, It all came suddenly. One day it was working, the next day it was not.

[Bob B]

Originally Posted by CaptainZoom

I have a -89 5.7L Chevy Silverado k1500 Stepside.
So it appears to have something to do with when the engine reaches the right temperature. Apparantly some sensor or something else tells the engine to start working with different settings? Or is there something else I have missed????

Please heeelp!!
BTW, It all came suddenly. One day it was working, the next day it was not.

-----------------------------------------------------------------
Hi,
You might try to pull the vacuum hose from the EGR valve to see if it is being told to open when it shouldn't. Plug the hose with something like a golf tee.
Be aware that with no egr, you might get some pinging.
BTW, the computer uses only a few sensors while cold (open loop) then when the temp is up, it will look at all sensors after it goes into closed loop.
Bob B

[jveik]

vapor lock perhaps

[CaptainZoom]

Thanks Bob, Ill try doing so.
But can the EGR really make such a difference?
I had a -74 Blazer which I plugged the EGR hose on and I can't really say that I noticed any differance. But I understand the way You are thinking, and I'll give it a go.
If anyone else has any other suggestions, please let me know. I'm not the worlds best mecanic so all tips&tricks are more than welcome!

[CaptainZoom]

Originally Posted by jveik

vapor lock perhaps

What is that, and where do I find it...?

[CaptainZoom]

I got another thought, what about the choke?
Could it be stuck in "on" position, always mixing air/fuel ratio for a cold engine? And could it be causing this problem?

[roadrunner_70]

Listen to Bob. Your year and engine doesn't have a choke. Mixture through the throttle body is predetermined by program in your ECM while the engine is cold. When it warms up, several sensors come into play that allow for the system to run in closed loop. EGR, Oxygen, Coolant temperature sensor, etc. If your problem only occurs after it's warmed up, look to these areas as possible culprits.

[swingline]

the only difference between open loop and closed loop is the addition of o2 sensor input to the pcm because o2 sensors only work when at a certain temp, which is why obdII cars use heated o2 sensors, so closed loop can be attained faster and get those emissions down.

i would start my diagnosis at the o2 sensor.

[CaptainZoom]

Allrrright mates!
It would appear that You fellas know what You're talking about...
So I´ll do as suggested, and keep You all posted.
Thanks again!

[fatmacsumo]

loss of power did you change the fuel filter. next chk fuel pressure. if ok ohm out coil wire 5.0 per foot and pull off dist cap take a gander at rotor if ok
chk output of cateletic system. also make sure timing is ok and no vacumn leaks

[fatmacsumo]

p.s. also spark plugs cause this pull a couple and check them

[CaptainZoom]

But it runs fine when the engine is cold ?
(Winter here in Sweden means at least 8-12 minutes)
So it should'nt be either ignition or fuel supply since it runs fine on all 8, and revvs really good. Engine answers as it should, and there's no loss of power when driving, - As long as the engine is cold.

This should mean that all of these components are ok:
Ignition, plugs and cables
Fuel supply, filters etc.
Fuel pressure
...... or am I way off?

To Me, this means something is either:
1 TELLING the engine to change some setting when operating temperature is reached? -OR
2 FAILING to tell the engine to change some setting when operating temperature is reached?


(Unfortunately still on theoretical basis here,haven't had time to check it yet, but I'm aiming for this weekend.)

[fatmacsumo]

your fuel filter is easy to ck pull it off and blow threw it if there is any restriction or your cheeks blow up chng your filter you need to change your filter every 30,000 miles . you may have to do a complete tune up . check your coil ,egr ,dist and rotor. are you showing a code . please let me know

[CaptainZoom]

Originally Posted by fatmacsumo

your fuel filter is easy to ck pull it off and blow threw it if there is any restriction or your cheeks blow up chng your filter you need to change your filter every 30,000 miles . you may have to do a complete tune up . check your coil ,egr ,dist and rotor. are you showing a code . please let me know

Ok, I'd probably had better change it anyhow. Bought the truck 3 months ago from a trusty friend of mine. Worked fine until now. He had it in for a full service, approx. 1½ year ago. Plugs, oils& so on
Don't know if they replaced fuelfilter also...

I will check rotor and dist. How to check coil?
Where is the fuelfilter normally located? Next to the intake?
Is there only one filter to replace?

Is there anyway to get
faultycodes by myself (And if, how do I do it...?) or do I need special equipment?

Your inputs and effort is highly appreciated!

[fatmacsumo]

if it is throttle body injected the fuel filter is on the drivers side frame just in front of fuel tank,coil only fails 95% of the time. change fuel filter first
self test can be performed with a test light .
ground your test light or use a paper clip if you look at the ALDL connector insert the paper clip into
a & b in the right hand top corner then turn your switch on do not crank the truck it will blink 1 kwick time then 2 kwick times 3times that will be
code 12 which means you are entering diagnostic
after that read them the way you did code 12 for instance 1111 1111 1111 1111
1111 1111 = 44 it will blink the code 3 consecutive times to each code you have have a pen and paper ready sometimes you will have more than 1 code if you have a code call me back and i
will let you no what it is