JohnBlazeLTZ

Hey guys...how do you know when the TBI needs a rebuild?

My Caprice has about 210K on it...so I imagine that is does but here's the issue:

When I start up my car...the engine runs fine...but when I put it in gear and press the gas...it starts sounding like its misfiring a little bit. I am thinking that the diaphragm in the TB may be worn out and the car doesn't stop misfiring until the fuel pressure builds up enough to fill the diaphragm good enough. Its usually only at start up where I have the problem and after about 5 minutes idling there is not issue after its warmed up. Say for instance...I just started the engine up and the engine is still cold...if I rev the gas a little bit...it actually sounds like its gonna stall/kill and you can hear it sounding a little raspy in the exhaust tone and I actually smell an excess gas/exhaust smell.

I'll also admit that I may be due for a new set of plugs, cap and rotor...and a general tune up may be needed also...but for me...I feel that the the TB needs a rebuild. I won't make the ultimate decision on the TB rebuild till I give it the tune up parts first but if you guys have any advice on this I would really appreciate it.

Thanks a bunch,

JB

eschevyrda

this is a dam good question

JohnBlazeLTZ

LOL...thanks man! Where's Fast when we need him?

studdmstr

Seriously it might not be a bad idea to rebuild it with that many miles
While it's disassembled you'll probably want to get the throttle shaft rebushed and the injectors cleaned. If the area where the throttle shaft sits is worn, you'll end up with a vacuum leak. I just redid mine a week or two ago and I think the total cost was about $180, with me doing the disassembly and reassmbly. It was $80 to have the throttle shaft rebushed, $50 ($25 x 2) for injector cleaning and about $50 for a gasket/rebuild kit. As a bonus I did some of the ultimate throttle body mods while everything was apart.

JohnBlazeLTZ

Cool man. That's the kind of input I wanted. Did you have any sluggish driving conditions at all? Did you feel a difference at all? Some have said cleaning the injectors alone makes a noticeable difference. Where did you get the throttle shafts rebushed at? Did you mail it out some place or was it local to you?

BronYrAur

iTrader: (1)

I just go by looking at the spray pattern, if you have a good conical spray pattern, no drips, and they don't leak while the engine is off then you're ok. Rebuild kits around here are about 30 bucks, certainly can't hurt, I've done a few, but just to correct leaky injectors or bad spray patterns. But, keep in mind, the kits come with new filters for the injectors too, which are probably pretty old and dirty judging by your mileage

goldens98

My car had 180000 miles on it. I got it rebuilt when it started to hesitate it would run as if it had bad gas for about a week. I took it to the mechanic and he took it off. It had all kinds of gunk in it. which is normal for the miles. He rebuilt it and it ran as good as new.

studdmstr

I noticed that on initial throttle tip-in the throttle would stick a little. My idle also wasn't very smooth and the spray of the injectors didn't seem to be as fine as it should have been. Now when I press on the throttle it's silky smooth all the way from idle to the floor and my idle is much smoother as well. It's hard to say if I felt an increase in power from just cleaning and rebuilding because I did some of the ultimate throttle body mods and installed an open element, but it does have a little more power now and pulls farther into the rpm range.

I think you will feel a noticeable difference by doing the full rebuild and clean, especially if it hasn't been touched in 210k miles

I got my throttle shaft rebushed locally at a carburetor repair/rebuild shop and had them recommend another local shop that did injector cleaning. The injectors came with new O rings and filters.

Tbi-MAX

im sure its a fuel problem, ill start 1st, with a new fuel filter, spark plugs, wires, rotor, cap, then ill move to the pod, and rebuild that... how does your fuel pump act? has it been changed?

I highly recomend the pod rebuild, after you check the things above... the filters in the pod for the injectors get gunked up from bad gas.. this is how Fast355 just lost his 350 monster.. 1 of the filters was bad, and giving less gas to the bank of 4 cylinders... this is not got at all.. also the regulator spring maybe bad or broke, or even you may have a bad regulator... just open the pod up and inspect everything, im sure the gaskets have melted and have to be scraped off with that mileage. The rebuild kit is like 30-35$ check napa..

like 1 of the guys above said, just check it for a spiral spray, and make sure it dont leak in the on position with engine off.. you can also point your timing light at them to see the spray pattern better.

with that mileage, i would not clean the injectors, but just put some new ones in... but then again these injectors last forever almost.. so its up to you. but I wouldn't want to do the rebuild more than once, since its already going to be opened up..

Fast355

iTrader: (2)

John,

The only reason I can think of to rebuild the TBI unit are as follows.

A.) Unit is heavily gunked up, beyond using carb cleaner on the outside
B.) Injectors do not spray properly
C.) The TBI injector pod is leaking
D.) The throttle shafts are worn

Other than that, they do build up some carbon underneath that tends to block the MAP sensor vacuum passage. The IAC ports also gunk up pretty badly.

At 210K miles, I highly suspect a dying O2 sensor and a bad CTS. Both are common failures on a high mileage vehicle. Both will cause problems when the vehicle is cold, but go away when it warms up. The other thing I see wear out in ALOT of TBI vehicles is the TPS. The TPS can develop a "bad" spot in it and cause problems.

JohnBlazeLTZ

Man you guys are mint.

After reading all the recent replies I feel that this may be the culprit. I don't have time right now to reply throughly but will check back later today. I got a bunch of stuff I need to do before I go to work today and have to get it in gear right now. Thanks to everybody that has replied so far. I will be back a bit later.

Thanks a Mill....

JB

85 camero

i have a 5.7 tbi motor in my truck that has 256,000 miles and i ran seafoam in it and it helped alot.also i puit in new injectors.