Intermittent hard starting issue?

1988 CHEVROLET 2500
200,000 MILES • 5.7L • V8 • 2WD • AUTOMATIC
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MRCUTTINGCREW
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Being that it is an older truck and the parts are mostly inexpensive, I have new near everything in the truck. I did not replace the throttle body, but a mechanic replaced the seals and spring. Not all the time but sometimes when starting the truck, it is hard to start so I give it more gas, sometimes a lot more gas by pumping it. When it starts, I have to continue giving it gas and letting up slowly until I get it to idle. If something goes wrong, I ease off the gas too quickly, it sometimes backfires and doesn't start. I will hear a noise and smell gas. The new fuel injectors are still working throwing gas out until I put the key in the off position. The code says 33, MAP sensor voltage high low vacuum, but it has a new MAP sensor.
May 28, 2025 at 1:49 AM
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STRAILER
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It could be the engine has low compression which will give you the code 33, we should do a compression test, also I would change out the fuel filter in case it is clogged will cause a hard start issue, please go over these two guides to help us fix the problem or see why it is happening.

https://www.2carpros.com/articles/engine-cranks-excessively-before-starting

and

https://www.2carpros.com/articles/how-to-test-engine-compression

Please go over these guides and get back to us.
May 29, 2025 at 11:13 AM