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Shop Night!!! Rebuild kit for tbi...Update 16.91 MPG!!!

S

smier

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I've got a '91 blazer with the stock 350 tbi. I've been chasing down a multitude of problems over the past year, and the one that's Been driving me insane is a low rpm miss or hesitation under light throttle, and the ocassional stalling out at a red light. I've been chasing down a string of Problems, and with each one fixed it's gotten better, but not right... I finally got off my rearend tonight and bought the BWD rebuild kit for TBI from advanced auto parts. $56 for the kit and 4 cans of throttle body spray and 3 hours of scrubbing and she's back together!!! Really easy to do and the kit I bought came with a new diaphragm for the fuel pressure regulator. Came with ok instructions, but has a great exploded view of the throttle body to use as a guide.
So once again here I am with another mixed success story. My truck now fires up instantly, has more power, smoother acceleration, and will now coast when I let off the throttle. I no longer notice the strong exhaust odor, and I didn't notice any of the rotten egg smell, but still has a slight hesitation at light throttle application which is most noticable when backing up whole parallel parking.
So far I've got new plugs and wires, cap and rotor, o2 sensor, TPS, IAC, coolant temp sensor, replaced the leaking intake manifold gasket( major vacuum leak there), new fuel pump after it crapped out on me one night, several new fuel filters, And probably a dozen more things I can't remember. I started with the obvious items that were throwing codes, and have gotten to this point. I'm thinking now that I probably need to tear into the egr valve as it is looking pretty dirty on the outside, and from what the inside of the throtle body and all the vacuum ports looked like, I'm willing to bet it's in sad shape. The other thing is I have a 180* thermostat and I've been reading that it can screw with the tbi systems??? Anybody had experience with this??? I'll be curious to see what kind of mpg's I get this week, so far I'm up to 15 to 16 around town... I was only getting 11 to 12 when I bought it.:waytogo:
 
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tbi should always have the 195 therm.... too cool a CTS reading will keep the ECM in open loop...

sounds like an EGR issue... most off-idle stumbling/stalling probs can be attributed to it...
 
You should be posting in the injection section... one thing you didn't do that's a very important part of a TBI rebuild is have the injectors cleaned. Every set I have ever done came out with 6 to 15% better flow. HTH
 
eagle mark said:
You should be posting in the injection section... one thing you didn't do that's a very important part of a TBI rebuild is have the injectors cleaned. Every set I have ever done came out with 6 to 15% better flow. HTH
Click to expand...

Or buy some new injectors......I just priced them at one store yesterday and they were $69 each for new ones (not remans). I'm thinking about putting some new ones in mine as well. I'm getting some hesitation during harder accelerations and right now, it won't start. Still working on it.....
 
MR injector here in town only charges $20. then I know what lb they are and are GM quality and not chiniese knockoff.
 
People always say that there will be problems with a 180 stat in a TBI application, even the fellas that really know there stuff. However, I've been running a 180 stat in mine for years with absolutely no trouble at all. There is never any trouble with staying in closed loop or anything. It keeps the temp cool enough that I can bump the timing a good bit without causing detonation, but it's still warm enough to have great heat in the middle of winter.
 
PO had a cooler thermostat in my Burb. I changed it back to the original specs and it definitely runs better. I think he towed with it quite a bit and maybe that's why he wanted it cooler.
 
we clean our own injectors in a pinch.... got a little rig setup for it on a plywood board... electric fuel pump, filter and marine fuel cooling canister filled with seafoam in a closed loop system.... wired with 2 alligator clips to hook it up to a booster pack.. turns on the pump and powers the injector... circulate seafoam thru it for a couple hrs.... usually clears up most issues... we only do this on something we need to get done that day and don't have time to send the injectors out, or get new ones in...
 
So I swapped the thermostat back to the 195* but I haven't had a chance to give it a good run yet. So far drivability is much better, I'm going to run it this week and see how things go. After this week, I'll decide whether to pull the injectors again and have them cleaned or swap in some new ones. Both the spray patterns from the injectors looked the same, but not as atomized and cone shaped as I was expecting? I was expecting a finer mist... I did a quick check of the egr valve and it seems to be working, but I'd really like to pull it off and clean it up and or maybe replace it with a new one. I'm too far in the hole on this truck that I don't mind replacing things anymore. I just want to get it right before I go into any mods. Oh, and I finally have some money to spare, so I'm finally going to join up so I can post in the proper forums!!! Sorry for that one guys, but my wife finally went back to work after being off for two years, so $25 was a lot some weeks... Thanks for all the info and advice.
 
when my tbi was still running, in the winter time it sounded like a diesel idling cold lol or a really cam'd out 350 haha ran like a champ once it got warm thow
 
The biggest problem with the TBI's are the throttle shaft gets some wear as does the throttle body itself so having throttle shaft bushings installed and either replacing or polishing the throttle shaft will do wonders.
 
If your setup still has OBD1, WINALDL is a useful program that can be download for free. Two screen shots and the interface cable I built are shown below.

JiminyData1.jpg


JiminyData2.jpg


DSC01338.jpg
 
Yeah, I actually picked up a laptop with the intentions of using it on my old '86 Camaro that had a TPI motor, I started building a 383 for it, but then kids and my wife bein off for 2 years ended that project... I still have the block, it sits all oiled up just waiting for all the new parts to go in someday! My current plan is to get this thing running how it did when it was new, so I have a nice baseline to work from. I don't want to go anything too radical as this is my DD and backup family car.
I drove it 38 miles yesterday and I can no longer get it to stall, but something is still not quite right, so I'm planning on cleaning or replacing the egr valve this weekend, overall I'm very pleased with the progress so far, the average person would never notice there's anything wrong at this point, and 4 mpg's in fuel savings adds up quick!!! I want to get a few more things fixed an cleaned up, and then it's off to be painted hopefully in a few weeks finally!!!! Now if I could decide on a color.... I'm really tired of the buff and gold two-tone paint it has now, my wife hates it, but 70 year old men really love it!!!
 
magik235 said:
If your setup still has OBD1, WINALDL is a useful program that can be download for free. Two screen shots and the interface cable I built are shown below.

DSC01338.jpg
Click to expand...

Wow!! Too cool...can you make a thread where you explain this more?
 
TBI goes into closed loop at aprox 165-170 F degrees. You can usually run a 180* stat with no problems. 180 is good if you are trying to make the most power on a TBI system where you have advanced the timing over stock setting of 0. The lower temps will help with detonation. So the knock sensor ESC does not retard timing.

195 is best if fuel milage and reduced emissions is your goal.

Re the EGR : Dont forget about the EGR solenoid. If its bad it can put vacuume to the EGR valve at idle/low rpms opening it up, and cause the troubles you are having.
 
Well, I normally wait until Friday (payday) to fill up, but curiosity got the best of me so I topped her off... 124.8 miles on 7.38 gallons =16.91 mpg!!! I'm curious what it would get on the highway. I wasn't Babying it either, I actually thought it might have gotten worse because I've been enjoying the smoother acceleration!!! Can't wait to dig into the Egr system this weekend and see if that's what's still causing the stumble on light acceleration. Hasn't stalled since I did the gasket kit and fpr diaphragm and cleaned all the crap out ob the throttle body. Still haven't decided about the injectors, I think I'll wait and see after I play around with the egr... I might have them cleaned and flow checked at least. Thanks for all the advice and input, well worth the $25 to finally see this site in all it's glory!!!
 
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