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1990 tbi 350 hard starting! Help!

3K views 19 replies 7 participants last post by  Iggy 
#1 ·
I have a 1990 ex cab chevy that starts up fine when it warm out. But when it starts getting cold you have to crank and crank on it for a while to get it to start. It will fire right up if you prime the throttle body with a little gas. And it also has fine throttle response and no hesitation when it's in high idle. But when it kicks down in to low idle it has a hesitation when you first push on gas. It will also stall sometimes if you in the gas hard and let out of it fast. Any one had a problem like this before? Any help would be appreciated!


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#4 ·
My truck would do some of the same things, it would run like dogshit and sputter below 2000 rpms, but normal above 2000 rpms. If you put your foot on brake and gave it some gas while sitting there in gear(simulate a load) it would die, also shifted hard and funny and idled high. Also check the wires, I bought the truck the guy said he put a new tps in, but the dipshit used a butt connector on one of the wires, anyways that's what was my problem was. That's where I would start your search. Should have 5v at the sensor.
 
#6 ·
It will continue to get worse until you get to a point where when you let up on the pedal at all it you will have next to no power.
This is your egr sensor and I have replaced it 3 times now on different trucks due to the previous owners giving up.:fish:
It is a expensive part at around $150 compared to the other $20 electronics. The line leading to the sensor fills up with oil and eventually ruins the quarter sized piece of foam the sensor quickly follows.

It could be one of the cheaper ones such as the tps or the wires going to the sensors. But once you check your lines for cracks, replace all these which is a good maintenance practice anyway, and are still not getting any new codes, consider replacing the EGR sensor. For some reason I never have received a code for a egr sensor(also known as a vacuum switch). But, I know the symptoms and replacing the egr sensor has fixed them easily enough.
 
#8 · (Edited)
Just wondering if you still needed any help on this. Im surprised no one told you to replace the fuel filter. I work at a shop that works on mostly chevy trucks and you would not believe how many times we just change the fuel filter and it fixes most the problems. But just for future reference on that truck you do not need these parts to make it run...EGR or EGR vacuum solenoid, the oxygen sensor, ESC, or EAC. In theory these parts can be removed without any issues except maybe throwing a check engine light. Hope this helps.
 
#14 ·
Well the tps fixed it! But have another question for you guys. I'm running open headers and notice that one side of the motor is running normal. But on the other side has lots of oil on the collector. You can take your finger and run it around the inside of driverside collector and its has the normal black like a tailpipe would. You do the same on the passenger side and has a good amount of oil. Any one have a idea of what would cause that?
 
#16 ·
It had a slight stumble and when you would be in it hard and let out it would stall out. But for the most part it was drivable. I did some research and figured out how to do the obd I code reading and got a TPS sensor low voltage code. So I put a new TPS on it. At the same time I put some headers on. It is my offroad play truck so I am running them open. Now it is running like crap super rich! To get it started have to give it gas when cranking. And when I do get it started in runs crappy smoking and smelling like gas and spits oil out of the collector on the passenger side header. I replaced the coolant temp sensor TPS and tried a diffrant used IAC and throttle body I had off another truck. Still no luck it runs the same. All the research I have done sounds like only other thing it could be as far as sensors is a MAP sensor. But I dont have a check engine light or any codes showing. So I'm at a loss what to try next.
 
#18 · (Edited)
With a 1 wire o2 sensor it needs to be within a certain distance from the cylinder head or else it won't register correctly because it is too hot or too cold. I'd be willing to bet because of the proximity of the sensor to the open collector that it is not getting warm enough. If you can I would put a cheep muffler on and see if that helps, I'm thinking the muffler will hold enough heat to be adequate for the sensor.

Something else to point to the o2 sensor is that I don't believe the o2 sensor comes into play untill it comes out of hi idle **I might be wrong about this**
 
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