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Old 05-20-2007, 03:00 PM
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check engine light comes on when i let off the gas

i'm having the most difficult time trying to find out what the prob is. i'v looked every where, parts stores, books, internet, and i get close but no cigar! this is my last hope to tell you guys and girls in internet land! i have a 89 fullsize blezer 350 tbi everything under the hood is new including the engine,all senser's cap,roter, wires plugs, etc...tbi unit rebuilt!!!good fuel pressure! the only problem is very rich fuel, exaust will make your eyes water!, when i let off gas pedel, check engine lit comes on, and then off again when i get back on it.code says egr. like i said everything has been replaced! i;m so puzzled,it even did this with the old moter i too!! please can someone help me with this! I love my blazer, here is a pic her!
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Old 05-20-2007, 04:21 PM
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I have a 1992 chevy silverado with a 4.3 V6 I just built. I started driving the truck after the install knowing I`d have to work out the bugs, It had a upper RPM bust and it didn`t idle very good, I drove the truck out of town and it finally threw a code, I checked it and it said "egr failure" I disconnected the egr valve and plugged the vacuum hose, afterwards the truck ran great and has since with the egr disconnected, however, the side effect has been the truck runs rich, you can smell it especially at idle, so I`d say since your symptoms are close to mine it`s the EGR. Check the vacuum connection going to the valve, disconnect it with the truck at idle, it should pull no vacuum since egr isn`t needed at idle, then slightly rev the engine and it should pull vacuum, if it doesn`t then either the line is cracked or it`s not being activated. Most egr valves come with a set of what look to be washers but they are restrictors, they set the amount of exhaust gas the engine gets, and if it`s not in the ball park it throws a code, since mine is disconnected and it gives no exhaust gas and runs rich it seems your valve isn`t working or the passages are stopped up that lead from the valve to the intake plenum. Hope this helps.
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Old 05-20-2007, 05:24 PM
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check engine light

i will try rit now, someone told me i dont have enough backpressure(exaust)???could this have that kind of effect???i have 3 inch exaust pipes with stock headers!
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Old 05-20-2007, 05:28 PM
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check engine light

i checked the vacum, none at idle but increases as i rev it up!
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Old 05-20-2007, 05:41 PM
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check engine light

i.m still at a (?)the egr is new .anymore ideas??
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Old 05-20-2007, 08:29 PM
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Doc here,

Check the Cat, It may be plugged, Check the O2 Sensor, It may be bad or running too cool.

Check your vacuum diagram for a TVS switch between the EGR and The Vacuum source, it may be opening / Closing at the wrong times.

IMPORTANT: Add a ground wire from the COMPUTER case to the Frame / Body, burnish both ends of dirt and paint and use star washers (this cured the identical problem on my DD Vette for Smog testing)

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Old 05-21-2007, 03:26 PM
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check engine light comes on when i let off the gas

there is no cat, o2 senser is new,shoul i put on a cat or can i get rid or the egr alltogether and still run good(not rich)will the computer be rit? help!!!!!!!!
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Old 05-21-2007, 04:13 PM
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Quote:
Originally Posted by country0112000
there is no cat, o2 senser is new,shoul i put on a cat or can i get rid or the egr alltogether and still run good(not rich)will the computer be rit? help!!!!!!!!
Have you tried disconnecting the battery to reset the computer? Maybe you're seeing a legacy code or incorrect reporting of the egr?

I disconnected my egr a couple of years ago on my 90 GM 350 because it wouldn't idle smooth when started - I still get a trouble light when driving and my reader shows the egr - but it runs well enough unplugged without it running rich.
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Old 05-21-2007, 04:23 PM
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Is the EGR freed up ?can you move the pistion in & out by hand? if not its stuck.

Run some extra grounds might be a loose connection.

Or do what I did & rip the ecm out & put a carb on it





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Old 05-21-2007, 04:28 PM
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check engine light comes on when i let off the gas

i reset the computer every time i put a new part on!does the egr need some back pressure to work rit?there is no cat on it. ilike the tbi its dependable.. and i have remote start on it! but if i cant figure out this problem i'll have t stick a intake and carb on it and i dont want to do that!
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Old 05-21-2007, 04:39 PM
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what is the actual code it is throwing the number
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Old 05-21-2007, 04:42 PM
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check engine light comes on when i let off the gas

dont rember the # but its egr
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Old 05-21-2007, 08:59 PM
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Quote:
Originally Posted by country0112000
dont rember the # but its egr
I looked at your list of replaced parts...did you replace or alter the ecm with a chip for performance improvements?

Did you put a larger non-stock camshaft in the engine - or is it a crate motor? Having a camshaft not made to fit within the ECM/Fuel system specs can cause headaches...

I have almost 200k miles on my 90GM 350 4x4 and everyday it starts just like it did when I bought it 8 years ago so I am a fan of keeping the TBI as I've had good luck with mine...don't give up yet!
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Old 05-21-2007, 09:36 PM
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Doc here,

Get a Vacuum pump/gauge.

Connect it up to the EGR with the car running, pump it to about 10 in hg..the valve should rise and the engine miss badly OR stall..If not the EGR is bad..

Spray around the base of the EGR with carb cleaner, if the engine speed picks up, you have a leak, get DOUBLE gaskets and heat resistant RTV and seal both gaskets and the EGR Base to the manifold.these leak all the time.

IF the EGR IS NOT leaking AND is working, you may have it connected wrong, OR have a defective TVS Valve, allowing it to open at the wrong heat range. find out the heat range of the TVS, (by the color on top to the valve) and pump vacuum into the inlet side. Then warm the engine and watch as the vacuum goes away, make a note of what temp it opens the TVS, and compare against the heat range for the valve. If wrong replace the valve..be sure the TVS is fed by NON PORTED vacuum.

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Old 05-22-2007, 03:47 PM
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check engine light comes on when i let off the gas

thank you for all the help!! rambo, it is all stock the only thing different is i have forged flat top pistons, but it done the same thing on yhe old moter!docvett, i tried the carb cleaner, but nothing. vacume is like it should be,egr is opening and closing, (dies down when i open at idle)...i'v always been one to get things figured out, but this one has really got me stumped!!i wish i knew where some of you lived, i'd bring it to you!!!!!!!i know some of you would love to get your hands on it!!!tell you what if you could make the trip, and fix it i'll give you a 1960 chevy truck, no moter or trans... or i have a sb 400 (runs) 157,000 miles on it, i just dont know what else to do!!! i love my truck!!!!!!!!!!
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