1990 TBI 350 refuses to start and idle nicely, I have log files.

[The_Joe]

So, I have tried everything on this truck before getting a cable, and now I have logs of this stubborn thing refusing to work. Im a newb and would love some other folks to look at this with me.

Fresh tune up, IAC, New map sensor, TPS, temp sensor, and vacuum leaks have been checked and fixed. I have a second complete throttle body with brand new injectors that hasnt given me any better results. Im not having any luck at all.

During these logs you can see me attempting to adjust the idle speed. All tests were at 0% throttle. To simplify the diagnostic I wanted to keep it in closed loop so during one test I unplugged the O2 sensor. The software reported the TPS at 15% so I attempted plugging in the new TPS without installing it, where it began reporting a negative 12%. You can see this in the log. My final test was to use a different ECU.

My goal is to get the truck running well enough to give it to my sister. I have access to a Moats Burn 1 but I have never fussed with custom chips yet. I would love any input you have.

Link to Log files hosted on GitHub.


If you are not used to downloading things from Github, here is a photo showing how to download it. Click "Clone or Download", as shown in the photo, then "Download as zip".

[The_Joe]

I guess my links didnt work, epic fail on my part. I have fixed my previous post and re-uploaded the files to github.

[GearGrinder]

Start by checking all fuses under the dash. Then check fuel pump relay under the hood behind the black plastic cover beside the coolant overflow tank. If all check good have some one crank the engine over and the other person spray a little carb cleaner in the top of the throttle body. If it fires up give it a couple more shots of carb cleaner and see if it runs for a little while. If it does you probably have a bad fuel pump. There are other ways to check that but if you don’t have a fuel pressure tester then the carb cleaner works good to. Don’t use to much. If it didn’t fire up then you probably spark issue. Bad coil or bad distributor.

[The_Joe]

Start by checking all fuses under the dash. Then check fuel pump relay under the hood behind the black plastic cover beside the coolant overflow tank. If all check good have some one crank the engine over and the other person spray a little carb cleaner in the top of the throttle body. If it fires up give it a couple more shots of carb cleaner and see if it runs for a little while. If it does you probably have a bad fuel pump. There are other ways to check that but if you don’t have a fuel pressure tester then the carb cleaner works good to. Don’t use to much. If it didn’t fire up then you probably spark issue. Bad coil or bad distributor.

Thank you for the reply!

I have tested the fuel pressure and it is within spec, (I dont remember exactly but I could check) and with a bit of starting fluid the truck will start but it cannot hold an idle under about 2000rpm.

Edit, I guess my title was confusing. I just meant that it doesnt start nicely, requiring starting fluid and such. I was unclear.

[GearGrinder]

Need a bit more info from your truck. How many miles? Is it a bone stock truck and no modifications? Has the distributor been pulled and reinstalled? Has the truck been sitting for a long time and was it running well when it was parked?Start by checking all connectors on the coil and distributor as the plastic over time gets brittle. I’ve seen a truck be hard to start and run like crap and die just like you describe only to find that the connector from the main wire harness to the coil pack. Just a guess but I would say you issue is with the distributor or coil or the connectors.

[brian617]

One of the most common TBI running issues is coolant temp sensor reading that is erratic. Log the temp sensor and make sure it looks normal. The fueling is heavily dependant on CTS. Examine pins in connector for corrosion.