Chevy 350 Another Puzzle to Solve?

[steve hughes]

If you are sure it is timed correctly then pull the throttle body off the manifold. TBI chevies are bad for the tb gasket coming apart. If that looks good make sure the vacuum ports on the tb are not clogged with carbon, another common problem. When you timed it did you unplug the timing connector? If not your timing will be about 30 degrees off. If all that looks good it most likely is the coolant temperature sensor located in the manifold by the thermostat housing. The sensor sometimes goes out of range and makes the engine thinks it's cold when it's warmed up making it run rich. This is also a very common problem on tbi chevies.

 

[acoen]

If you are sure it is timed correctly then pull the throttle body off the manifold. TBI chevies are bad for the tb gasket coming apart. If that looks good make sure the vacuum ports on the tb are not clogged with carbon, another common problem. When you timed it did you unplug the timing connector? If not your timing will be about 30 degrees off. If all that looks good it most likely is the coolant temperature sensor located in the manifold by the thermostat housing. The sensor sometimes goes out of range and makes the engine thinks it's cold when it's warmed up making it run rich. This is also a very common problem on tbi chevies.

Agreed, I replaced the gasket with a new one when I put the manifold back on. Cleaned the TB with carb cleaner when I put it back on. Yes I unplugged the harness timed the truck to 0 degrees then plugged it back in. Now if the sensor is out of range would it make the truck run horrible in open loop or cold? I've heard of this before as well.

 

[Junior Samples]

ahh the ole coolent sensor.. but you mentioned it ran crappy from the get go correct? im getting more confused by each post..lollol

 

[acoen]

ahh the ole coolent sensor.. but you mentioned it ran crappy from the get go correct? im getting more confused by each post..lollol

Yes ran horrible in open loop and cold.....So the coolant temp sensor wouldn't be the culpret?

 

[Junior Samples]

kinda what i thought but once again here goes the keyboard diagnostics and i suck at it, i say lets eliminate your ign module, and can always check temp sensor while your at it.

Arron whats your cell? if your at home, i cant type as fast as i can talk or just call me when ya get a min 810-845-0350...im heading back out to garage

mike

 

[acoen]

kinda what i thought but once again here goes the keyboard diagnostics and i suck at it, i say lets eliminate your ign module, and can always check temp sensor while your at it.

Arron whats your cell? if your at home, i cant type as fast as i can talk or just call me when ya get a min 810-845-0350...im heading back out to garage

mike

Will do!

 

[Junior Samples]

well thats factory ground location for ecm and coolent sensor
check ground connection

 

[acoen]

well thats factory ground location for ecm and coolent sensor
check ground connection

Apparently I didn't have a good ground....I think that is a bad place for it. I placed on ground on the front of the intake manifold on driver's side for ECM and the other is some other ground I placed on the other side There are bolts with studs. Still have fast idle....I bet it is a good idea now to readjust the IAC. Runs good no smoke unless I nail it full throttle then it is gray. I may run a ground strap from that location to the block somewhere, since I have RTV on every bolt......Moral of the story check your grounds. Now it did hunt and seek a little on start up but I had the A and B still jumped. I will check again in a couple of hours, see if she cranks up.

 

[Junior Samples]

yeah it doesnt seem to bright an idea, I dont know if them bolts run through the 88/89 intake or if there sealed, if they run through and touch the water wouldnt that be just like grounding to your radiator?
you'll get electrolysis and corrosion, but thats a good way to test for defective ground straps, ground ohm meter and stick other end inside coolant..i think its something like 0.10 volts will tell you theres electrical current running through the system.

Anyway i'll check in morning to see what ya found

 

[acoen]

yeah it doesnt seem to bright an idea, I dont know if them bolts run through the 88/89 intake or if there sealed, if they run through and touch the water wouldnt that be just like grounding to your radiator?
you'll get electrolysis and corrosion, but thats a good way to test for defective ground straps, ground ohm meter and stick other end inside coolant..i think its something like 0.10 volts will tell you theres electrical current running through the system.

Anyway i'll check in morning to see what ya found

I think there is a water jacket there, but I will run another ground strap from that point to another just to make sure the ECM has a good ground. I'm going out in a few minute to start the thing. I hate to start her late at night because it has dual open chamber flowmasters....sounds like a race car.....Nice truck though for 1500 bucks. keep your fingers crossed hope it still runs good.

 

[acoen]

this sounds like the same problem my buddy has on his 1991 camaro 305 tbi. Let me know if you figure this out because we have replaced everything on his car and it is still not running right.

Check the ECM ground, I had mine grounded to the stock location but wasn't getting a good ground. Changed the location and TaaaaDaaaa! Truck runs and starts better than ever.

 

[Junior Samples]

Fantastic, the phone call worked. Alot easier talking to human then typing on screen sometimes.

Mike

 

[acoen]

Fantastic, the phone call worked. Alot easier talking to human then typing on screen sometimes.

Mike

Again thanks Mike (especially you) and many others who made great suggestions. All of the suggestions made me think a little. Funny how a couple of good nights of sleep will clear your mind. Mike thanks again for the phone conversation, photos and diagrams (over the top help)....helped me nail this puppy down. Greatly appreciated and thanks again

Aaron

 

[T Rubble]

thanks for the tip, mentioned it to my buddy and he is going to check the ground.

 

[larry33kc]

My truck pulled something about like your ( it's an 89 also) I did everything I even pulled the motor It ended up being the computer HTH