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Discussion Starter · #1 · (Edited by Moderator)
I have a 2002 Chevy s10. This is the LS 2.2L and my 5th S10 but my first 4cyl. I am having issues but it gets alot worse when I turn the ac on. It bogs and stumbles and doesn't accelerate like it should. I just bought this truck so I was going through the normal tune up stuff. Spark plugs, wires, coils and all that. I have great spark. So I ran codes and had O2 code pop up so I changed that and the code is gone. Then I got a 0718 code for flex fuel sensor. So I changed that and the code is gone. But no change. So then I found a way to check the flow of the catylic converter and it showed blockage. So I took it off and beat the guts out of it and put it back up. Truck runs a little better but still the same problems. I changed the fuel filter just incase it was a little clogged (it was) but still no improvement. I'm lost so I started tracking vacuum and found several lines cracked and leaking. So I replaced them with new vacuum hose. But nothing changes. So I found this vacuum line coming off of the intake that someone has capped. (see pics) when I take the cap off it completely changes the truck but doesn't fix the problem. So I think this might be my issue. I'm not getting any codes now. Can anyone shed some light on this please. I'm lost. Thanks in advance.
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My 2002 doesnt have that vacuum port at all.
 

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Discussion Starter · #3 ·
Just checked fuel pressure and it has around 40-42 psi while running. Which is what the manual says it should be. I wonder if it's the computer.
 

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Discussion Starter · #4 ·
It comes and goes and seems to run pretty good with the ac off. When I turn it on it runs horrible.
 

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The three small vacuum hoses should be secondary air injection, EVAP, and the vacuum reservoir/ HVAC controller.
 

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A 2002 should be a flex fuel vehicle. If it is, pressure should be around 60 psi. The non-flex vehicles run about 42 psi.
 

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I just fixed that vacuum issue on my 2000 2.2L Xtreme. Since your 2002 has AC, are you able to control the airflow between the windshield defrost, vent, and floor? If the HVAC controls do not function properly, that port is the vacuum source for the reservoir which also controls the HVAC blend doors in the cab. The inside diameter of the vacuum hose is 7/32" and you'll need a length of 30" between the throttle body and reservoir. If you do a search on "2.2L vacuum lines" you'll be rewarded with a boatload of good information related to resolving most of your HVAC vacuum issues.

Good luck!
 

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Upon re-reading your initial post, when you say "it runs rough when AC is on", can you describe what you mean? Does the motor run smoothly but abruptly changes, such as misfires or misses, when you turn on the AC? Or when you turn on the AC, now the whole vehicle shakes/shudders a bit more? If the second description is truer, then your issue may be tied to the AC compressor and clutch rather the engine. The AC clutch and compressor will strain the motor when engaged. Lastly, how would you describe your AC performance? Depending on the condition of the AC clutch and compressor, you could be experiences problems because of them rather than your motor.
 

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Discussion Starter · #11 ·
Upon re-reading your initial post, when you say "it runs rough when AC is on", can you describe what you mean? Does the motor run smoothly but abruptly changes, such as misfires or misses, when you turn on the AC? Or when you turn on the AC, now the whole vehicle shakes/shudders a bit more? If the second description is truer, then your issue may be tied to the AC compressor and clutch rather the engine. The AC clutch and compressor will strain the motor when engaged. Lastly, how would you describe your AC performance? Depending on the condition of the AC clutch and compressor, you could be experiences problems because of them rather than your motor.
What's weird is without the ac off it runs rough but when I turn it on it gets real rough. But to comes and goes. The ac doesn't change with the switch to defrost or the floor. It comes out of all. So I was thinking that's what the vacuum was. But I can't find where it goes though. I have Google vacuums for this model and haven't had any luck on diagrams or images. Also checked YouTube.
 

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Discussion Starter · #12 ·
So today I replaced the Intake Air Temperature sensor and it ran great for about 30 mins. I thought I had it fixed. But after about 25 miles it went right back to the same crap. I am so lost. I'm beginning to think it's the computer.
 

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Discussion Starter · #13 ·
Upon re-reading your initial post, when you say "it runs rough when AC is on", can you describe what you mean? Does the motor run smoothly but abruptly changes, such as misfires or misses, when you turn on the AC? Or when you turn on the AC, now the whole vehicle shakes/shudders a bit more? If the second description is truer, then your issue may be tied to the AC compressor and clutch rather the engine. The AC clutch and compressor will strain the motor when engaged. Lastly, how would you describe your AC performance? Depending on the condition of the AC clutch and compressor, you could be experiences problems because of them rather than your motor.
About the compressor and clutch. It seems to work as it should. It's not the coldest in the world but it works. I live in South FL so ac is crucial. But it just seems like whatever is malfunctioning is altering the timing or something along those lines.
 

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Discussion Starter · #14 ·
Today I also pulled the plugs to have a look. And they were burned white so it's running very lean. But I have 42 psi of fuel pressure. So I don't know. Possibly injectors? But would injectors come and go. Because sometimes it runs pretty good.
 

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Have you tried disconnecting the battery for 30 minutes or so to reset the computer?
 

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As already stated, proper fuel system pressure for the flex fuel 2002 2.2L’s is ~60psi. While troubleshooting my 2002 2.2L, that is what I saw driving around with a fuel pressure gauge cable tied to my left windshield wiper arm. I suggest you focus on that. The 2.2L engines are weak, and the AC compressor running is going to negatively affect the engine even if there are no problems.

P.S. The problem is almost never the PCM.
 

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I would never say never...however, since it is an easy thing to do...just disconnect battery for at least 10 seconds. That action should clear whatever errors may be resident in the PCM memory.

Next, the fact that your blend doors are not redirecting air flow correctly indicates you can likely correct this issue by running a vacuum hose from the top of the throttle body to the vacuum reservoir. Also, your will have to find and insert a splitter so vacuum goes to the reservoir along with another tube embedded in the main harness. On my 2000, that main harness is located on and enters the driver's side firewall.

Fuel pressure as well as issues with AC are all possible gremlins. Fact that your newly replaced spark plugs indicate a lean fuel mixture points toward fuel adjustment. On these PCM controlled vehicles, there are multiple sensors which play a role in fuel adjustment/mixture. I am not sufficiently familiar with this model's sensors but these motors could include: throttle position sensors, O-2 sensors, coolant temperature sensor, etc. I know remove and replace approach can get costly quickly so try and find troubleshooting steps online to assist you with testing.
 

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The engine should not run any different with the AC on. The idle should increase slightly, but that's it.
 

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Manbearpig, I agree but what is causing the rough idle?

Here's an old picture (taken many years ago by Rhotpursuit) that shows what the vacuum reservoir looks like and where on the fender to find it. The reservoir is hidden but visible in this photo because the ABS module has been removed. In the center of the image, next to the black split wire bundle is a back flow valve and T which splits off into two branches--one to the reservoir and the other to the plastic tube for the HVAC controls. The plastic tube is embedded in the main wire harness and provides the vacuum necessary to control HVAC actuators and doors.
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What are the LTFTR and STFTR warmed up at idle? Live data is important to eliminate pure guess work. Injectors could be clogged so LTRTR will be constant around 20 in stead of normal varying from +10 to -10. Techron Injector Cleaner works well. You can see the before and after by the change in fuel trims (it may take some miles driving.) If you take the vacuum hose off the fuel pressure regulator while running, what does the fuel pressure go up to? Does the FPR hold vacuum? The vacuum line to the HVAC would make it lean, but is small enough it would not be an issue off idle. Usually it is only noticed because the vents don't change. I think the default is to the legs. Sticky Carboned up EGR could be erratic and run lean, or burned out EGR gasket (if yours has EGR). Remove clean and inspect. What is compression? Manifold vacuum?.Low compression could be why you thought the cat was bad. Gas cap seal? Get a live data scanner for ~$40. You've already thrown in an o2 sensor, trashed your cat (eventually you will get a P0420 for your effort) and an air temp sensor without fixing your problem.
 
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