Where is the throttle position sensor?

[bnoggle]

Can someone please tell me where the throttle position sensor is located on a 1983 chevy 250 integral head. The truck has a very rough idle, poor shifting, and feels like it wants  to stall every time you go near the gas. Any other suggestions would also be appreciated. A brief list of what has been recently (past three months) replaced/rebuilt are

Head gasket
Exhaust gasket
Thermostat
Plugs/wires/cap/rotor
All vacuum hoses
Carb rebuild
Tv cable
Electronic ignition
All Vacuum fittings
Transmission filter
EGR
Water pump
Belts
Alternator rebuild



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[1967KaiserM715]

Shouldn't be a tps. As far as I know

[bd]

Verify the firing order 1-5-3-6-2-4.  Did you spray for vacuum leaks using B12 or other aerosol carburetor cleaner, including all around the integral intake manifold, carburetor, etc?  What procedure did you use when adjusting the valves?  Did you verify valve motion on all cylinders?  Did you have the cylinder head Magnafluxed (checked for cracks) and rebuilt while it was off the engine or simply replaced the head gasket?  Did you run a dry/wet compression check beforehand and after?  What were the pressures?  Have you checked engine vacuum?  What carburetor float level setting did you use to adjust the float? 

[bnoggle]

Verify the firing order 1-5-3-6-2-4.  Did you spray for vacuum leaks using B12 or other aerosol carburetor cleaner, including all around the integral intake manifold, carburetor, etc?  What procedure did you use when adjusting the valves?  Did you verify valve motion on all cylinders?  Did you have the cylinder head Magnafluxed (checked for cracks) and rebuilt while it was off the engine or simply replaced the head gasket?  Did you run a dry/wet compression check beforehand and after?  What were the pressures?  Have you checked engine vacuum?  What carburetor float level setting did you use to adjust the float?

I used the float level setting included in the kit I purchased from mikes carb parts

Engine vacuum levels all read normal around 17 ft lbs at the intake manifold

Ran a dry compression test when lashing the valves. From 1-6 the values were 135, 145, 140, 145, 150, 140

Cylinder head was checked for cracks, and milled flat

I used the propane torch method but never found any leaks except at the vapor canister.  It has since been replaced.

Just verified, firing order is correct and TDC is at firing positions 1&6

When lashing valves I found tdc and then tightened valves on cylinder 1 until there was no more up and down motion. I then tightened them 1/2 turn more. Next I turned the engine 1/3 a turn to get to cylinder 2 and repeated the process. Once I finished tightening valves I ran the engine with the valve cover off to check that everything was ok. It ran smooth for about 5 minutes and then the problem described above began again. I shut it down and replaced vacuum lines. It ran smoothly for about 5 minutes again and then the problem came back. Etc.


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[bnoggle]

Would there a a cam position sensor?

Do you think it could be an ignition control module?


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[1967KaiserM715]

It's been a while since I done a inline six, but I thought there was supposed to be some lash? I am pretty sure when I did my brothers 292(same basic motor) it had a lash setting of .004"

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[bnoggle]

Did that motor have hydraulic lifters?


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[bd]

The 250 L6 uses zero lash hydraulic lifters.  Greater than zero lash adjustment is for solid lifters.  In 1983, Federal emissions vehicles didn't use feedback emissions systems, so there are no sensors linked to an ECM for fuel and ignition control. 

Vacuum isn't measured in "ft-lbs."  Did you mean "in Hg?"  Was the vacuum gauge needle steady, floating, bouncy, or _________? 

Although safe, the propane method is not as reliable for discovering difficult vacuum leaks.  Check again for vacuum leaks using Berryman's B12 spray, but be careful since it's very flammable.  Spray all around the Varajet carburetor and intake, especially where the fuel bowl attaches to the throttle plate and around the throttle shafts.  With the engine off, open the throttle about 1/4 and move the throttle shaft side-to-side to determine the amount of side play between the shaft and plate.  There should be no more than ~0.005".

Unplug the EGR valve and plug the vacuum hose while the engine is running rough to determine whether there is noticeable improvement.  With the engine at operating temperature and the air cleaner removed, while idling rough hoover the carburetor using a clean shop rag to enrichen idle fuel mixture to determine whether there is any improvement. 

[Irish_Alley]

why did you have head work done? did you have this problem before the head work?

[bnoggle]

why did you have head work done? did you have this problem before the head work?

Three reasons, first I was trying to solve this problem. Secondly the head gasket was 34 years old and had 88,000 miles on it. Third, I had an exhaust leak between the manifold and the head.


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[bnoggle]

Checked for leaks again with spray, and found none. Spraryed all around the carburator, adn the integrated head intake. Also sprayed aroud vacuum lines, egr, pcv, and any other vacuum component I could find. Next i tried enrichining the fuel air mixture, the engine bogged down and smoke came out of the tailpipe. I suspect it has become an electrical problem, since my last post I have noticed a constant static in the radio. I checked wirng and there are no problems there. Multiple antennas have the same problem. I also noticed the noise gets worse with the hood up, so I am convinced there is an electrical component malfuinctioning somewhere. I checked the alterator boot, distrubutor cap, spark plug torque, and spark plug wires. All are installed correctly. Could it be the ignicion control module? I have heard they go out fairly often.

[Irish_Alley]

i dont know. what your saying is your issue reminds me of my mud truck when i first got it and was learning about everything. i want to say it was an issue between timing and carb adjustment. first thing i had to do was adjust the timing (mind you this was on a sbc) and hook the vacuum advance to manifold vacuum instead of ported. then adjust the carb till it ran great.

but i didnt have any smog stuff on mine, do you have any? or a cat?

[bnoggle]

The truck has all the exhaust equipment that came standard in 1983, including a CAT. I was told by someone today to start replacing sensors until I find the one that is causing the truck to run rough. I also picked up a new condenser unit today thinking that could possibly be part of the problem. I have not gotten time to go install it yet but will post again tomorrow after I do. Please keep the ideas coming.

[Irish_Alley]

the sensors on your truck should be very limited and none should effect the truck due to not having an ecm. a condenser for the ac? have you tried to remove the exhaust? before you replace anything you should try to eliminate what you can and if that can be done cheap or free then thats even better. unless you have spare cash just to be tossing at the truck

[bnoggle]

the sensors on your truck should be very limited and none should effect the truck due to not having an ecm. a condenser for the ac? have you tried to remove the exhaust? before you replace anything you should try to eliminate what you can and if that can be done cheap or free then thats even better. unless you have spare cash just to be tossing at the truck

It's a condenser like in the traditional sense of points and condenser. I'm not sure what it is actually called, but the package calls it a radio condenser. It sits in the distributor next to the ignition control module. I did remove the exhaust, well actually it rusted through, it still ran rough though. Originally I thought it was running poorly because of no back pressure from the exhaust, but that apparently isn't the case. Unfortunately under the current laws in Pennsylvania I must have all emissions equipment connected, and present to pass inspection otherwise I would disconnect all of it. They don't really care if it works or not so I guess  I could make it look like the emissions equipment is connected. I will try disconnecting what few sensors I have tomorrow.


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