Very "lazy" '88 350 TBI help - Hot Rod Forum : Hotrodders Bulletin Board
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Old 11-30-2003, 08:05 PM
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Very "lazy" '88 350 TBI help

Hello all...this is my first post to this list and it's been more than ten years since I've pulled a head, swapped a carb, fine-tuned a Holly, etc....and all I've done in the past was on late '60's & early '70 Pontiacs & Plymouths so please forgive my ignorance before I even start. I just purchased a somewhat tired but still strong '88 Suburban 4x4 with a 350 TBI motor. I honestly know nothing about these systems. I do understand the vehicle is very heavy (5000 lbs) but the truck starts from a dead stop like a snail. It seems to take forever to pick up speed and has very little punch. I'm thinking about a swap to a carb setup (only because that's where my previous experience is) but I don't want to go too crazy...and I hate to rule-out the TBI before even getting to know it. The truck is & will remain a family "car" so I'm not looking to race or anything. I was hoping someone out there might be able to provide a starting point to the completely uninitiated on how to "spice" up an '88 350 TBI. I sincerely appreciate any and all help or comments. Thanks. Russell
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Old 11-30-2003, 08:35 PM
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First off, I would do a tune up, plugs, wires, dist cap, rotor, air filter, fuel filter etc.

If that doesn't help do a compression test. Maybe it is just plain worn out and needs rebuilt. Does it burn any oil?, smoke badly?

Also, put some fuel injection cleaner in it, the injectors may be clogged.
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Old 11-30-2003, 08:48 PM
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hmmm.. All that a throttle body injector is, is a carb with injectors instead of the normal cherries you see in a carb. These could be clogged. Also, fuel injected computer controlled cars have throttle position sensors that electronically control the amount of fuel that is mixed with the air coming in. This part may be bad. They get carbon deposits on it and will not mix the air/fuel mixture correctly. Try dumping some sea-foam in the gas tank and directly into the intake. If the injectors are gummed up this will help. Is there a check engine light on?? Problems with computer controlled engines are a lot of trial and error with sensors and switches that go bad. If you are planning to put a carb on it, you have to fool the computer in the car since it is always sending and receiving signals from the injectors. So, if you bolt a carb on the engine light will always be on because it is not getting a signal from the injectors that were once there. This is bad because if there really is a problem with the engine, you won't know because the light is on all the time anyway. It will make it almost impossible to decode computer codes to pinpoint other problems.
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Old 11-30-2003, 08:53 PM
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if it has high mileage, check the cat converter, it could be stopping up due to exhaust heat melting it`s internals. if your truck checks to be really quiet, this is one clue. if it checks out okay, i`d agree that tune up would be the next step, and if high mileage is a factor it`s likely the timing chain is slackish, this too can cause somewhat sluggish performance.
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Old 12-01-2003, 06:29 AM
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you might want to clean the top end before you change the plugs. the sea foam mentioned above works well. last time i checked autozone and advance didn't carry it but napa and car quest did. when you get it, warm the motor, pull the vacuum line off the brake booster and funnel enough in to make the motor stumble a couple of times then enough to make it stop running. wait about 1/2 hour then restart. some people recomend changing the plugs after making it stop running before restarting. i usually kill the motor twice and change plugs after the second time. i would also run some marvels mystery oil in the crankcase as the oil drain back holes get a little sluggish with age. as far as what you put in the gas i use lucas.
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Old 12-01-2003, 09:43 AM
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Here is a link to a website that has a lot of good info on the GM TBI setup and how to get it back into good tune. They also have a very good assortment of bolt-on parts.

CFM-Tech
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Old 12-01-2003, 11:59 AM
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Thanks

Thanks for all the help....I'm going to do the tune-up with the sea-foam first as my starting point. I do have a service engine light on....I was told it is a bad O2 sensor...could this have a significant effect? After all this...and if it all checks out OK....any suggestions on going to the next step? On older engines all I used to do as a first "performance" step was to put on headers, an Edelbrock, and a 4-barrel (I know that's real simplified....but for a street-rat like I had it was all I really needed until a performance rebuild) I see suggestions for these 5.7 TBI engines like different injectors, a spacer plate, computer chips....any ideas any of you might be able to validate as "worth it" without losing low-RPM power and sacrificing much fuel-economy?

Thanks for the CFM-TECH link...it looks good although I haven't jumped into it yet

Many thanks again for all the information!!!
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Old 12-01-2003, 01:32 PM
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since that light is on your priority's may have changed. if you have autozone in your area they will pull the codes and print out the possible causes of said codes, for free. if it were me i would find out why the light was on and do what it took to turn it off as my starting point. if the oxygen sensor is bad it will cause the car to run bad along with several other things covered by check engine light like the throttle position sensor.
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Old 12-01-2003, 02:22 PM
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Thanks minesblown...will do. I'll start there and work my way up. Many thanks again.

Russell
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Old 12-01-2003, 05:57 PM
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tbi injection is solid but sluggish i had a 95 with 45thousand and it was a dog no matter what i did so i only did whats natural i sold it a bought a camaro
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