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Problems with TBI - help me please...

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v8fan_russia

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Hi.
I've just purchased a winter daily driver - 1991 Chevy Blazer K5.
It has a TBI SBC 350 with 4l60. Non catalitic, if it does matter.
The engine was not working properly - VERY high idle and stalls when i put the car in gear
frown.gif

The IAC was cracked, replaced with new one(according to Haynes manual). Also replaced spark plugs and wires. Cap and rotor are in good condition.
The engine idles good now, but still stalls in gear
frown.gif

Checked ignition timing - it was kind a off, so - i've set it to 0* (according to the label under the hood), with EST disconnected.
No effect. Still stalls in gear.
BUT - if i'll disconnect EST - it will NOT stall in gear and idles perfectly.
But without EST the perfomance is very low...
What happened to the engine ? What should i replace to make the car run good ?
Will ECM from my 1992 ex-TBI Caprice 9C1 work on this car (i've converted the Caprice to carb this summer) ?
Thanks a lot
 
Hey! Welcome to the forum!

Does the engine still idle high? Or is it fairly low? Stock TBI should be idling at about 650 rpm at an idle. If it is idling lower, you may need to bump the idle speed up a bit, then re-set your TPS.

Also, try setting your timing to about 5 degrees, the stock timing curve in the ECM's programming is pretty conservative.
 
The engine idles now at 700-750 in neutral, but i cat make it lower (or higher) with the screw on the left side of the throttle body.
I've tried to raise the idle up - even up to 1200rpm.Even with such a high idle engine stalls with EST connected and works without EST...
Damn, i can understand HOW quadrajets works on both of my Chevy Caprices and i can rebuild them anytime, but i can't fix TBI :(

WBR,
Nick from showy Russia :)
 
Did you reset the idle though (on the ecu) when you adjusted it on the TB?
Your manual should tell you how to set 'base idle'. I can't remember the procedure off hand but a search will find it on here.
Where abouts in Russia are you?
 
Found this
heres how you can adjust idle tho if everything looks good..Take a paper clip and jump the ALDL in the 'A' and 'B' pins.

Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.

Start engine. You are now going to adjust "minimum air". There is a Torx screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.

Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).

If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait 5 minutes. This will clear the ECM of all trouble codes. Re-connect the battery and drive the car for 20 minutes to allow the ECM to relearn your driving style.

It was part of this thread:
http://coloradok5.com/forums/showthread.php?t=152399&highlight=tbi+base+idle
__________________
 
Yes i did.
First of all, i've disconnected the batt.
Then i've seated the valve of IAC.
After that i've reconnected the batt. , shorted the self-diagnostics terminal of the ALDL and turned the ignition on.
After 1 minute (for allowing to IAC to seat in TB completly) i've removed the connector from IAC and started the engine.
After that i've adjusted the base idle with the screw in the left part of the throttle body, shut the engine off and removed the paper-clip from ALDL.
Reconnected the IAC and started the car...
Fine idle in N, no idle in gear :(

I'm from Izhevsk - it's the city, where AK-47 and other "Kalashnikov" machine guns are made ;)
 
Have you checked vacuum hoses for leaks? Strange that it works with the est disco'd.
Maybe DYeager may chime in when he sees this.
Spent a short time in St. Petersburgh a couple of years back. Your language is hard to learn!!:D
 
Yep. No leaks. Checked the hoses, intake mainfold and throttle body gaskets, vac. booster.
Vacuum gauge reads 11" of mainfold vacuum at idle, steady.
It is very strange to me too that it won't work with EST :(

St. Petersburg is beautiful city, but it's weather is horrible all over the year ;) As for language - yeah, russian is one of the most hard languages (too many exceptions and so on), except deutch, maybe :) But i must say, that english is not so easy too ;)
 
Just a thought...have you checked the fuel filter? I dont know if that has anything to do with it...but it could. I wish I could be of more help because I have a tbi too, but have never had this problem.
-Harrison
 
Well, its either going to be fuel or spark, obvoiusly...

Did you check the fuel pressure while you put the transmission into drive? Maybe a bad fuel pump or oil pressure switch could be keeping it from running. Doubtful though, since it works with EST disconnected.

I would check the voltage at the MAP sensor to make sure you are getting voltages that are roughly within specifications.

With that said, I would suspect a faulty ignition control module (in the back of the distributor). There is a sequence to test them, but I forget. Possibly a bad computer, but those are pretty rare.

Try to eliminate different areas to narrow the problem down. I know it can get tedious, but it is worth it. I enjoy working on the TBI more than I like carbs. Go figure...
 
I was just gonna mention, check out the EST troubleshooting charts on chevythunder.com, but CB77GMC beat me to it, lol
 
87BrnRsd said:
Have you replaced the map sensor?
-Harrison
Click to expand...
No i have not, since i don't have a spare one...
If it's a matter of faulty MAP, HEI module and so on - than i'll convert this engine to carb...
I have a spare quadrajet, HEI and edelbrock-2104 ;)

Oh, BTW - happy Thanksgiving to everyone :)
 
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