Thread: 1989 350 w/Holley TBI tuning?

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Just installed a rebuilt stock 350 in my 89 crew cab. New everything, Alt, water pump,Distributor and Holley throttle body. Got it started and rpms are fluctuating from around 1500 down to a stall. The timing was at about 10 degrees ATDC when first checked, I adjusted it up to 0 BTDC(specs on air cleaner) and it's better, but still not right, the book calls for 4 deg BTDC. Has anyone done this setup before, and if so what was the best setting for timing?

Thanks,

Ralph

What it's doing???

I'm still getting an rpm fluctuation at an idle.Not as bad as it was though.

Is the Holley TBI a new part installed after the rebuild? What Holley does not state in their advertisement for the TBI is that you will need modifications to run right. What is your fuel pressure? Let me know if you are still having problems and I can help lead you in the right way to getting it fixed. What book calls for 4 degrees timing? I know that timing should be 0 degrees the computer takes care of the rest. With the rpm surgeing like that one possibility is fuel pressure. What about exhuast , is it stock? Are you getting any codes(check engine light) ,do you know how to pull them and what they mean. Its pretty simple if you dont, let us know.

Yes, it is new and the rebuild was started with the new TBI. I have not tested the fuel press yet, But I have dual tanks and it does it on either tank. The 4 degrees timing is listed in the Haynes Manual. I installed a new exhaust which is stock with a new CAT and new muffler. I hooked up the scanner and the only code I got was #42 EST open or grounded circuit. But this fault was caused by unhooking the Tan/Black wire at the firewall which is required when adjusting the timing. The Holley instructions call for the TPS to be adjusted to .65 volts (at idle)when I scanned it the reading was .72, but this is well within the range required. I have not worked on the truck since Sunday, But I will be able to get back at it tomorrow, and I'm just looking for different things to try.

Trouble code = 42, System= Ignition Control, Indicating= open/short/component failure. You said this has been taking care of correct? Also are ALLLLL of your grounding and power wires reconnected?


I also found on mine I had to actually drive it to get it to drive right so the computer could "learn" the new components.

Ceck with CFM Tech for a fuel pressure fitting and gauge if you need it. Also you do not need to buy a adjustable fuel pressure regulator. From the factory they are made non adjustable so people try to sell you adjustable models for 75 dollars. With a drill and a dremel and 2 hours of your time you can make the stock unit adjustable. Fuel pressure from the factory is Supposed to be 10.5 - 11. PSI (if I remember correctly)if you put a gauge on it it will actually be anywhere from 9 to 12 PSI. You may need to raise the fuel pressure which is not a bad thing. Doesnt mean you will be wasting more gas.




Here are some other places you can get info.
http://www.fullsizechevy.com/forums/...obd-i-ecm-pcm/

Look in the lower left hand corner the print in the yellow.
http://www.cfm-tech.com/GM_tbi_tuning_tips.htm

Great website, lots of usefull info. I do have an exhaust leak at the Y- pipe to manifold connection which may be causing me a lean condition. I'll fix that before going any further on my adjustments. I have a pressure test kit, but Isn't the fuel pressure on these systems controlled by the in tank pump? And just how do you do this mod you are talking about?

Here you go , I had to open up other lap top . Very good reading , check out their ULTIMATE TBI sections.

http://www.thirdgen.org/tbi-afpr

Heres a pic of the pressure gauge I got for mine . You can see it with the adapter. I do have it adjusted at 13 PSI now ,not in the pic. Do you have the stock cam?

Since we are on the subject of 89 TBI's here is another mod you might consider for a improvement in the 89 TBI . LS1 fans on the truck. I think it was well worth it you might consider it in the future.

Good info! I wonder if I can do this with the Holley unit? I have never had a cooling issue, but then again I live in Alaska. By the way I was Born in Houston and lived in NW Houston area about half way to Tomball. I'll give these a try and let you know how it went when I get back to work on Monday.
Thanks for all the help.

Possibly a loose connection on a vacuum line or fitting and maybe a small vacuum leak?????

Originally Posted by Ralph Moore

Good info! I wonder if I can do this with the Holley unit? I have never had a cooling issue, but then again I live in Alaska. By the way I was Born in Houston and lived in NW Houston area about half way to Tomball. I'll give these a try and let you know how it went when I get back to work on Monday.
Thanks for all the help.

Well, if you live in Alaska the cooling fans could be a good thing. You wont have the consistent drag of the stock clutch fan , you could get some better fuel mileage maybe . Also your heater/engine could come to temp faster(helping fuel mileage) since there will be no fans spinning at all UNTIL your engine comes to temp.

I'm all for saving fuel//leaves more money for hot rod parts. The surging was caused by the grey/black wire being disconnected to check the engine timing(EST). once I reconnected it, it ran fine. But it made it awfully hard to check the timing with it bobbing up and down. I drove the truck to work today, ran great, but halfway here I got a check eng light, So I'll have to hook up the scanner again and see what's up.

Update, the check eng light is a code 32-EGR system failure, I clear it and it comes back after about 10 minutes at highway speed. I tried switching the EGR solenoid vacuum line to a ported outlet, but it still came back. Any suggestions?