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93 Blazer CPI Rough Idle...

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Old 03-31-2005, 10:22 PM   #1
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93 Blazer CPI Rough Idle...

Looking for a little help here.... I have a 93 S-10 Blazer with the CPI engine.

Last year I had the fuel pump go out so it was replaced along with the fuel filter.
In October it died again and was towed the dealer, distributor was found to be bad and replaced.

November it developed a rough idle, would almost stall and surge as well as occasionally stall... Very disturbing when you are trying to turn into a parking spot and have it die...

So I did a tune up (new plugs, wires, air filter and coil). Ran some fuel injector cleaner through it.. no improvement.
Took it to the dealer, they said the CPI was bad (it had been replaced 4 years ago). Instead of paying 800 to the dealer , I ordered the CPI and nut kit from Rock auto and a new manifold gasket. No change.

Next, checked the EGR, moved free, no carbon.. cleaned it anyway.
Replaced MAP sensor
Replaced IAC and cleaned passage
Ran Sea Foam through engine
No change..

Thought maybe I got a bad CPI, so returned it and got another... still no change...
I have checked all the vacum hoses and all are attached...

Off Idle it runs great, mileage seems good, no miss or stutter except at idle....
Any one have any ideas... I really do not want to go back to the dealer, but I don't want to keep going off in the blind....

I've read a bunch of threads on here that arer similar... and have tried most of what I have seen.... but it seems no one ever post if the problem was resolved and what the solution was...
Old 03-31-2005, 11:13 PM   #2
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Re: 93 Blazer CPI Rough Idle...

Quote: Originally Posted by John Wiz
Looking for a little help here.... I have a 93 S-10 Blazer with the CPI engine.

Last year I had the fuel pump go out so it was replaced along with the fuel filter.
In October it died again and was towed the dealer, distributor was found to be bad and replaced.

November it developed a rough idle, would almost stall and surge as well as occasionally stall... Very disturbing when you are trying to turn into a parking spot and have it die...

So I did a tune up (new plugs, wires, air filter and coil). Ran some fuel injector cleaner through it.. no improvement.
Took it to the dealer, they said the CPI was bad (it had been replaced 4 years ago). Instead of paying 800 to the dealer , I ordered the CPI and nut kit from Rock auto and a new manifold gasket. No change.

Next, checked the EGR, moved free, no carbon.. cleaned it anyway.
Replaced MAP sensor
Replaced IAC and cleaned passage
Ran Sea Foam through engine
No change..

Thought maybe I got a bad CPI, so returned it and got another... still no change...
I have checked all the vacum hoses and all are attached...

Off Idle it runs great, mileage seems good, no miss or stutter except at idle....
Any one have any ideas... I really do not want to go back to the dealer, but I don't want to keep going off in the blind....

I've read a bunch of threads on here that arer similar... and have tried most of what I have seen.... but it seems no one ever post if the problem was resolved and what the solution was...
Wow, that's the exact same problem my father in law is having with his 93' w/CPI. I posted a thread,"CPI Injection Issues", and we're having the same bad luck with our diagnosis. Today I cleaned IAC port & cleaned and reseated the IAC. After that the idle went back to normal for a very short time (20-30 minutes)any then started surging and dying again after the test drive. It also has a lot of spark knock. Does your's have spark knock too? I'll keep you posted on our progress and vice/versa.

Last edited by tardis454; 03-31-2005 at 11:23 PM.
Old 03-31-2005, 11:22 PM   #3
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Re: 93 Blazer CPI Rough Idle...

Nope, no spark Knock... as it was running fine after the dealer replaced the distributor, I have kind of ruled that one out... (might be a mistake though.....)
Old 03-31-2005, 11:28 PM   #4
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Re: 93 Blazer CPI Rough Idle...

Quote:

Last year I had the fuel pump go out so it was replaced along with the fuel filter.
In October it died again and was towed the dealer, distributor was found to be bad and replaced.

Did it have spark knock before it died?
Old 03-31-2005, 11:38 PM   #5
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Re: 93 Blazer CPI Rough Idle...

Quote: Originally Posted by tardis454

Did it have spark knock before it died?
Nope, I was having a bit of a high speed miss.... had actually picked up the stuff to do a tune up... and it died on the side of the road... just went flat at about 60 MPH... had it towed and was told that the distributer shaft went (it was wobbling,) .. Ran fine after that.. for about 3 weeks until the rough idle started...
Old 04-01-2005, 12:51 AM   #6
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Re: 93 Blazer CPI Rough Idle...

check the fuel pressure at idle
Old 04-08-2005, 08:43 PM   #7
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Re: 93 Blazer CPI Rough Idle...

Im picking up alot of spark knock on my engine, I run a data logger, and it counts the knocks. It will get very very very high at times... I never felt my idle was as it should be, but commonly wrote that off with the mods I did to it. I think my shitty Advance Auto spider died again... This will be the third replacment of their defective spiders, along with the countless defective heater cores, sensors, and other random moving parts. I dont think their parts are made to work for months at a time, kinda some sorta drive it one day a year parts or they might break from excessive use. Any who, I have no idea where the knock is comming from... I also have no idea with my spark advance runs so high... and jumps so much... I dont kno why that whole god damn system is even on my blazer... I hate it, i really dont see the need to advance and retard timing based on the judgment of a shitty quality sensor that senses noise in about the noisiest place ever. Damn shits just stupid.
Old 04-08-2005, 09:29 PM   #8
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Re: 93 Blazer CPI Rough Idle...

has anyone changed the dist. cap and rotor they are very prone to carbon tracking?
Old 04-09-2005, 11:00 AM   #9
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Re: 93 Blazer CPI Rough Idle...

The distributor , cap and rotor are new AC/Delco parts... done just 4 months ago... but I did try a new Cap and rotor, no difference...

It seems to get a bit worse when it warms up... I'm about ready to park it i'm so fed up with it...... I have never had so much trouble repairing a car...
Old 04-09-2005, 05:42 PM   #10
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Re: 93 Blazer CPI Rough Idle...

]try Cleaning The Egr
Old 04-09-2005, 07:33 PM   #11
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Re: 93 Blazer CPI Rough Idle...

Quote:
I'm about ready to park it i'm so fed up with it
Im with you, I just tore out my third CPI spider and have it sittin down in my basement cuz I cant afford another one right now... Shit, its as much if not more than the paint I need for the entire vehicle, and powder coat for the wheels. I had someone pulse the injectors while I had the intake off and I watched the squirt, they look fine and shoot a nice clean mist of gas... however there is a shit load of gas in the lower intake... just puddles of it and the such. Nothing is leaking while im watchin the spray... the "nut kit:" which is also the dumbest name for a fuel and return line... looks ok, no cracks, no leaking that I can see when gas is goin through it... but still gas in the intake... I feel fairly confident that replacing both of these will fix my shit... but thats like, ummm 450 cheapest... and Id probably want the aftermarket regulator to put on the new spider so this stops happening, so it will probably be more like 575. And thats just insane !!! For a vehicle that hasnt run up to par since day one... with every internal in the motor lookin great and every test showing good signs... its just bullshit... basically I have a more than perfect motor... running like ass because of an overabundance of electronic bullshit that just malfunctions ALL THE TIME.
Old 04-10-2005, 11:04 PM   #12
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Re: 93 Blazer CPI Rough Idle...

I can relate....

Looks like I have found it, even though the distributor was just installed by the dealer and the timing was good...

I checked the timing today and it was advanced.. so I set it back to 0 and it seems to be fine.... I had it out for a bit and then the wife had it... no surge, no stumble, no stall...

What bugs me the most is that the dealer had checked it and had diagnosed it as the CPI... could have saved myself $300 and countless headaches if I checked it myself first.. lesson learned on that one...

But in all the years working on cars, I have never seen timing advanced cause idle problems like that....
Old 09-06-2007, 10:37 PM   #13
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Re: 93 Blazer CPI Rough Idle...

95 chev 4.3 L Cpi. Starting problems. Replaced the fuel pump same problem.
Just pulled the upper plenum. left side of spider was washed, right side
very dirty and also i think there was oil in the right side also. Should i replace the whole works or just the fuel pressure regulator. Does anyone have any
ideas. Thanks!
Old 01-01-2008, 07:57 PM   #14
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Re: 93 Blazer CPI Rough Idle...

sorry to bring this back from the dead... but my 93 blazer is having the same issues...

hard starting (pumping gas sometimes will crank it)
rough idle
spit and spudder wot (only in spots)


new parts include a distributor, wires, cap, and injector

new parts on the way include regulator and nut kit

any other clues as to what it could be? tps sensor? iac? egr?
Old 03-06-2008, 11:17 PM   #15
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Re: 93 Blazer CPI Rough Idle...

Wow, i just rebuilt my motor and i'm having the same problems. It starts to idle rough after it heats up. I can hear it missing every now and then. I guess i need to check the timing... I heard that you have to cut a wire at the computer, check the timing set it. And then splice the wire back. Is that true?
Old 03-06-2008, 11:32 PM   #16
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Re: 93 Blazer CPI Rough Idle...

Egr.
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