stalling

[Sbrown0221]

I have a 89 chevy 1500, 5.7 pick up. I beleive it's referred to as the c/k series.

Recently I've been having some issues with stalling. When the engine is cold everything runs fine but after warm up I've noticed the problem start occurring.

When I'm doing a slow turn ( any direction) , backing up, or in stop and go traffic, the truck want to stall when I touch the gas pedal. Once I get past the intial slight throttle it picks up and does fine.

I've replaced the distributor cap and rotor, plugs and wires, fuel filter and even the fuel pump( mainly because it never gauged fuel correctly but I thought it might have a pressure issue).

Nothing seems to work and I'm not getting any codes.

Any suggestions ?

[Schurkey]

The usual diagnostics:

What is the manifold vacuum at idle?

What is the fuel pressure?

What is the cranking compression of all eight?

Connect a scan tool, (not a POS code-reader) and tell us
a. what the coolant temperature sensor is showing BEFORE the engine is started, (better be about the same as the weather outside) and as the engine warms up.

b. Does the throttle position sensor operate smoothly from idle to WFO?

c. Does the IAC work? Passage clean of carbon and varnish?



Those distributors have a nasty habit of destroying the magnets around the teeth of the pickup coil/reluctor; mine started out as a high speed misfire that got worse and worse until the engine completely died and wouldn't re-start.

[Sbrown0221]

Schurkey, thanks for the reply and sorry it took so long to reply back.

I don't have a manifold vacuum tester nor anything to test the fuel pressure.

I removed the egr valve and checked for carbon build up. Also checked for any vacuum leaks but everything looked fine.

[Schurkey]

Originally Posted by Sbrown0221

Schurkey, thanks for the reply and sorry it took so long to reply back.

I don't have a manifold vacuum tester nor anything to test the fuel pressure.

I removed the egr valve and checked for carbon build up. Also checked for any vacuum leaks but everything looked fine.

If you don't have tools, 'bout your only option is to throw parts at it and hope you replace the defective one before you spend too much money.

I'd be looking first at the TPS. An automotive multimeter could work to diagnose it.

[MT-2500]

Originally Posted by Sbrown0221

I have a 89 chevy 1500, 5.7 pick up. I beleive it's referred to as the c/k series.

Recently I've been having some issues with stalling. When the engine is cold everything runs fine but after warm up I've noticed the problem start occurring.

When I'm doing a slow turn ( any direction) , backing up, or in stop and go traffic, the truck want to stall when I touch the gas pedal. Once I get past the intial slight throttle it picks up and does fine.

I've replaced the distributor cap and rotor, plugs and wires, fuel filter and even the fuel pump( mainly because it never gauged fuel correctly but I thought it might have a pressure issue).

Nothing seems to work and I'm not getting any codes.

Any suggestions ?

Any check engine lights?
You can get codes by grounding pins A and B together.
If any codes post back code no.

[Sbrown0221]

No codes showing.

[j cAT]

Originally Posted by Sbrown0221

No codes showing.

idle problems after engine warms is usually the vacuum/IAC/PCV crankcase venting system/hoses. especially those at the intake manifold ports.

so how did you check for vacuum leaks with no vacuum gage ?

[Sbrown0221]

I removed each vacuum hose individually and inspected. There are only like four vacuum hoses. I'm not familiar with any other way. Is there a tool that will do this?

thanks for all your input, it is apprecaited.

[j cAT]

Originally Posted by Sbrown0221

I removed each vacuum hose individually and inspected. There are only like four vacuum hoses. I'm not familiar with any other way. Is there a tool that will do this?

thanks for all your input, it is apprecaited.

the vacuum guage measures vacuum. a good running engine will have 17-21 inches of vacuum. the hoses develop cracks. this then causes the vacuum to decrease. by placing the guage in series of the vacuum line then pinch the side that goes to the intake manifold you will see if the vacuum holds or drops to zero.

I guess with your explaination of how you checked for vacuum leaks you are not instructed as to the proceedure.


then you would check for any intake gasket/cracks in the intake etc.

with this test you watch the vacuum guage for changes as you use a propane touch not lighted but with a hose on the touch end and with some propane gas coming out the end of the hose if you pass this over a leak the vacuum gauge will react. you can test this with creating a leak using a vacuum line by making a leak and observe how it will change the vacuum.

some have stated I checked for vacuum leaks . I did not hear anything leaking . this is also not the correct method.

what also is funny when they say , I checked the fuel pressure it squirts really good !

[Sbrown0221]

LOL, well i guess that's what happens when we learn all we know from WWII era mechanic as I did. Bless his heart he doesn't know today's cars but has tought me enough to not ignore a issue and to maintain a vehicle.

I really apprecaite the detailed expaination and I will do as advised. I 'll keep you updated as to my progress through this issue.

I was thinking though, if it is a vacuum leak wouldn't it be doing it all the time, even when it's cold, which is not the case?

also, is it okay to replace those hard plastic vacuum lines with straight vacuum hose, or are they hard plastic for a reason?

[j cAT]

Originally Posted by Sbrown0221

LOL, well i guess that's what happens when we learn all we know from WWII era mechanic as I did. Bless his heart he doesn't know today's cars but has tought me enough to not ignore a issue and to maintain a vehicle.

I really apprecaite the detailed expaination and I will do as advised. I 'll keep you updated as to my progress through this issue.

I was thinking though, if it is a vacuum leak wouldn't it be doing it all the time, even when it's cold, which is not the case?

also, is it okay to replace those hard plastic vacuum lines with straight vacuum hose, or are they hard plastic for a reason?

rubber lines can be replaced with plastic tubing or even metal.

with many angles best stick to rubber.

my vacuum troubleshooting is actually a 1960-1990 era proceedure for vehicles with carbs.

with fuel injection you can get away with some vac leaks. looking at the new vehicles not many vacuum lines at all. mostly vacuum leaks on the newer engines is the intake gaskets.

with a carb if you have a leak the engine cannot suck fuel out of the carb as well. then the lazy mechanic or DIY messes with the carb mixtures to get it running smoothly to compensate for the leaks.

this causes many problems and reduces engine life. with fuel at 50 cents a gallon burning some extra fuel was not a big concern back then by not locating ALL these leaks.

I have been lucky I guess over the years with engines/vehicle performance. I get over 10 yrs on my vehicles and shoot for 200,ooomi.

if you do your own work and have the ability to follow the OEM shop manual you will know more to keep your vehicle running properly and the proper proceedures to do it than the pro's .

these forums are not a place to get all the info needed to properly keep your vehicle running as best it can . its a start to get you moving in the correct direction.

when the engine is cold the computer control is not that critical on the fuel mixture. you can get away with a vacuum leak. as the idle drops then you get these issues.

the crankcase venting system PCV / hoses can also cause this. the IAC adjusts to maintain idle speed. if the air/mixture/vacuum leaks are to great then the idle cannot be controlled by the computer/IAC etc...

[Sbrown0221]

I apprecaite all the help in resolving this. I actually am pretty dilagent on maintaining my vehicles. This 89 chevy c/k1500 has 380000 miles on the original motor and my 95 Ford escort just hit 240000.

Anyway, I went to take the IAC off to look for carbon build up and to see if the plunger moves freely, when I went to unscrew it from the throttle body I noticed it was only finger tight. I removed it the rest of the way and inspected and cleaned it with some throttle body cleaner. Reinstalled, tightened down and ran till warm... Runs like a champ with no stalling on slow turns, reversing or stop and go traffic.

[j cAT]

so what you had was a vacuum leak . strange how those screws were loose ..very strange....

[Sbrown0221]

Was strange since the whole thing is one big screw. I've never removed the IAC so it had to come loose by normal engine vibration.

Is that considered a vacumm leak in the throttle body?

[j cAT]

Originally Posted by Sbrown0221

Was strange since the whole thing is one big screw. I've never removed the IAC so it had to come loose by normal engine vibration.

Is that considered a vacumm leak in the throttle body?

that is the point where the air/vacuum are blended to adjust the engine idle speed. not a good place for a vacuum leak.