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i have a rough idle on my v-6 95' 4.3 vortec. i noticed it after i put in stp fuel injector cleaner in the gas tank. could i have chemically burned something or is it coincidence? also could it be from my k&n intake/gibson exhaust that the engine is taking in more air than fuel burning? there is a sweet octane gas smell too. not the regular exhaust smell i usually smell. could it be an air sensor problem on my intake. OH YEA AND IT TAKES LIKE 4 SECONDS FOR MY ENGINE TO START TOO. A LONG START AND A ROUGH IDLE MEANS WHAT?? please help!
 

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Resident Mechanic
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check the seal around the intake in ALL spots, also make sure your airflow sensor is plugged up thats can casue the exact problem ur havin
 

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Since you say it happened after...

you used the STP fluid, I'm guessing you have freed up and loosened carbon buildup. It may have partially clogged or blocked the EGR system. I serioulsy doubt that anything has been harmed. The smell is the STP burning off. To really clean out the carbon buildup will require more than STP in your gas. Get a good top end cleaner and run it through your main vacuum hose in the the top end. I recommend Sea Foam Carbon Cleaner or GM Top End Cleaner.
 

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Re: Since you say it happened after...

blueskyjack said:
you used the STP fluid, I'm guessing you have freed up and loosened carbon buildup. It may have partially clogged or blocked the EGR system. I serioulsy doubt that anything has been harmed. The smell is the STP burning off. To really clean out the carbon buildup will require more than STP in your gas. Get a good top end cleaner and run it through your main vacuum hose in the the top end. I recommend Sea Foam Carbon Cleaner or GM Top End Cleaner.
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I'm with that!!!:thumbup:
 

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The Primered Panther
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That's a good idea, try that fist but if that doesn't work poor some Marvel Mystery Oil in your tank. It's supposed to clean out all of you sensors including O2 sensors in your exhaust.
 

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Rough Idel

I have rough idel as well. 95 s-10 4x4 "W" Vin CPI V-6 Vortec. I recently put new plugs, (A/C Delco, New cap, new rotor,new wires) and I changed the oil to a syn blend, and still I'm getting a code: which = "Rapid Misfire" Can anyone explain why this is still happening? Not to mentioned in the morning when I crank up I'm getting this deposit coming out of the tail pipe. I recently had a new cat put on. A universal one but that should not be causing that to happen.

Also, How many miles should I be getting between changing my front disc pads? I have roughly 4k and now they are squealing like a lill "B_ _ _ _" Any help would be greatly apprieciated and recommendation on pads.

Thanks in advance!
 

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The Primered Panther
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Where did you get the plugs and wires from? I would guess that it's running a little rich and that is probablly why your getting the stuff coming out of your tailpipe, that might make it misfire to.
I usually get more miles than that on my brake pads, your sure there's not just a rock between the pad and the rotor right? If it is the pads then i would get a good set with a lifetime warrenty, they last a long time.
 

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I got the plugs,wire (Sparkforce), Ignition rot, Distributor all from Discount Auto Parts.

The brakes I got from PepBoys. I got a step up from the 16.99 one's I paid 39.99 or something like that. What I didn't do was to turn the rotors prior to installing the new disc. Perhaps that put or took some useful life out of them. It's also the primary vehical and get a lot of use. And it's a lot of stop and go traffic. But I still think that I should of gotten more use out of them.
 

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The Primered Panther
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yeah you should've gotten more than 3,000 miles out of em unless your just really hard on the brakes. If your rotors weren't really bad when you changed them it shouldn't be the problem.
 

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yeah the rotor were fine.
On another note my gas mileage sucks big time. I'm only getting about 14.5 miles to a gallon. Any advice
 

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When you say you're getting a code...

please be specific. What number code? I am not familar with a code named "rapid misfire". If your plugs, cap, rotor and wires are all ok then I can give you the two most likely causes. Number 1) Rough idle is usually caused by carbon buildup on the EGR pintle that keeps it from closing. It can be pulled and cleaned. Number 2) Cause of poor mileage, rough idle is that the CPI unit is leaking at the regulator. It will usually trigger codes 32/EGR and 45/Rich.

Have you also had hard starting problems? Strong odor from exhaust? Strong odor of fuel in the intake manifold? Have you changed your fuel filter? Have you checked your fuel pressure?
 

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The Primered Panther
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It could also be a vacuum leak or your oxygen sensors, it could be a lot of things.
 

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The code number wasn't on the equipment that was used at the shop, It specifically said Rapid Misfire. Now the reason it ended up in the shop was because when trying to leave for lunch one afternoon it would not start. I sprayed some starter fluid into the thorttle body and it started but then stalled. Spent the money to have it towed and they ended up checking the pressure and replacing two relays.
 

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I haven't pulled or cleaned my EGR. I did spray a whole can of cleaner into the throttle body though at least a month ago. I'll check all of my line tonight

How many miles are you getting between brake jobs?
 

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What type of gas mileage is everyone getting out there? I have a 95 S-10 4x4

How would I know if my CPI is leaking too?
 

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The Primered Panther
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it might be any of your oxygen sensors. well i don't know how many miles i get on my brakes cause i've only changed them once since i had it and i've had it for almost 2 years, and i drive it a lot, of course I'm harder on the gas than I am the brakes.
 

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Ok.

Has your SES light come on? If it has, read the codes and give us the numbers.

The easiest low tech way to see if the CPI is leaking is to remove the plastic vortec cover on top of the manifold, remove the Manifold tuning device. Using a strong flashlight look inside the manifold towards the passenger side in the center area. You should be able to see the CPI unit. Look around the passenger side of the unit where all the nylon fuel tubes with poppets are connected. Look for a clean, gas washed area or small puddle of gas. If you see either one it's leaking. If there is a very strong fuel odor it may just be starting to leak. Some CPI owners have also reported small cracks in the plastic fuel tubes on the driver's side of the unit.

here are more high tech checks
You must change the fuel filter first to eliminate it as the problem. Be certain to install it in the proper flow direction. Also check the fuel pump fuse located at the bottom left of your fuse panel. You’ll need an assistant to do most of the following checks.

CPI regulator check
Connect the fuel pressure gauge to the Schrader valve. Start the engine. Fuel pressure should be 58-64psi. Once the engine is at normal operating temp, open the throttle quickly. Fuel pressure should quickly approach 64psi. If the pressure was ok at idle but doesn’t increase to near 64psi under quick throttle applications is an indication that the CPI regulator is faulty.

Turn the ignition on, don’t start. Listen for the fuel pump to run for 2 seconds. The pressure should be between 58-64psi after the pump starts up. After 2 seconds when the pump stops the pressure may vary by several pounds, then it should hold steady. If the pressure doesn’t hold steady, wait 10 seconds and repeat the test, but pinch the flexible fuel return line and see if pressure holds. There are flexible hoses located down the firewall at the end of the metal tubes feeding into and out of the manifold. If pressure still doesn’t hold, it’s the CPI unit regulator at fault. If the pressure holds with the line pinched, the CPI regulator is ok. Check for a partially disconnected fuel dampener (pulsator) or faulty fuel pump. I don’t know where the pulsator is located, I’m guessing it is part of the pump assembly.

Fuel pump check
To check the fuel pump on an OBD1 S-Series you’ll need a long wire with an inline 10amp fuse to run from the positive battery terminal to the G terminal (fuel pump) of the ALDL connection. The G terminal is the bottom left one. Many vehicles also have a connector under the hood. Mine is located near the distributor. With ignition off connect the wire to run the pump. With the pump running, see if the pressure is within the 58-64psi range. If the pressure is higher, check for restricted fuel lines. If the pressure is low pinch the return fuel line, pressure should increase above 64psi, don’t exceed 75psi. If it doesn’t increase it points toward faulty fuel pump (since you already confirmed the CPI regulator is ok), partially disconnected fuel pulsator, or partially restricted pump strainer. You should have a good idea if there is a problem with the pump now.
 

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Thanks for the input. I had the fuel pump replaced about a year ago.

I'm concerned about those disc pads though, it's like I'm changing pads every two to three months or so.
 

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The SES light has been on. Once when it was very cold outside in the morning it stayed off, that was until about 3 miles down the road.
 
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