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Discussion Starter #1
I need help with my '01 GTP, 88k, no mods. It's running really rough.
This is what's going on: I had put Mobil 1 Extended Performance 15,000 mile synth oil in my engine, and had driven the car for only 5,000 since then as of yesterday. When I'd started up the car yesterday, right away my SES light came on and it started idling really rough. Thinking it could be related to the oil which was already looking dirty, I'd changed the oil with my normal Mobil 1 and started the car back up (the old oil was full, but was looking dirty). It continued to idle rough for a minute or two after that, but then it straightened out and began idling normally like it should. I was relieved and let it run for about 3 minutes before shutting it off, thinking that it would be ok. But... when I started it up again about a half hour later, the rough idle was back, and it hardly had any power at all. It's still idling rough today, and the SES light is still blinking at me.
As I'd said, the Mobil 1 Extended Performance "15,000 mile oil" was only 5,000 miles old and was full when I'd changed it, but the "low" oil life indicator had come on the DIC just a short time before, which seems odd too. I've never abused my car, and had always changed the oil at 3,000k with the exception of when I'd used the extended life oil as I'd said. Anybody got any ideas as to what is happening or what to check? :icon_frow
 

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I need help with my '01 GTP, 88k, no mods. It's running really rough.
This is what's going on: I had put Mobil 1 Extended Performance 15,000 mile synth oil in my engine, and had driven the car for only 5,000 since then as of yesterday. When I'd started up the car yesterday, right away my SES light came on and it started idling really rough. Thinking it could be related to the oil which was already looking dirty, I'd changed the oil with my normal Mobil 1 and started the car back up (the old oil was full, but was looking dirty). It continued to idle rough for a minute or two after that, but then it straightened out and began idling normally like it should. I was relieved and let it run for about 3 minutes before shutting it off, thinking that it would be ok. But... when I started it up again about a half hour later, the rough idle was back, and it hardly had any power at all. It's still idling rough today, and the SES light is still blinking at me.
As I'd said, the Mobil 1 Extended Performance "15,000 mile oil" was only 5,000 miles old and was full when I'd changed it, but the "low" oil life indicator had come on the DIC just a short time before, which seems odd too. I've never abused my car, and had always changed the oil at 3,000k with the exception of when I'd used the extended life oil as I'd said. Anybody got any ideas as to what is happening or what to check? :icon_frow
I seriously doubt it had anything to do with your oil. The problem you're describing sounds like a defective spark plug, plug wire, ignition coil, injector, etc. You need to have some diagnostics done to determine the problem. If you scan it the PCM should have a code in it telling you which cylinder is misfiring, knowing that will narrow your search a lot.
 

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Old oil won't make it run rough but, you might get a tapping valve. Only if you were leaking or burning oil and it went real low would it maybe run rough right before it seized. Also I don't think the computer can tell what type of oil you're using. I believe it just goes by RPMs and length of trips and if the car reaches full warm up temps, short trips hurt more. Mine usually shows less than 10% after 6K. Like fastech said it sounds electrical. I once had a crack in a fairly new sparkplug that made my old car run rough and another time it was a bad wire. Check them first. Good luck
 

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Discussion Starter #4
* UPDATE *
Computer or electrical problems? Seems like when I start it cold it's ok and idles/drives fine, but when I start it after it's been warmed up, it's all jacked up. I'd started it cold last night again, and it ran like a champ. Drove it for about 30 minutes, all was great. Until I got home, turned it off, and decided to restart it to see what it was gonna do, that is. I'd restarted it, and sure enough, it started the heavily labored rough idle again!

Could it be computer or electrical? I'm taking it to Advance to have them scan the codes, might help narrow it down. Anyone ever hear of issues like this?
 

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might be a ing. module kind of hard to tell you what to do yu have to get it on a scanner to see what the pcm doing ihope everything works out for you
 

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Ok, went to Advance last night. The code is "p0203 injector ckt open" (cylinder 3). Does this mean that it's stuck open, meaning a faulty injector? If that's the case, I could replace the injector in that cylinder. What do you think?
 

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It probably means one of your clips is loose. If that's the case however, it would happen spiratically. If it is an injector it would happen when it's cold more than when it's hot. The code doesn't really match the time it happens. I just responded to a guy who has this problem, but at inverse times. Check your clips anyway. Go get yourself some top end cleaner, remove your intake from the TB, start the car. Hose the engine down until it stalls, let it sit for 10 minutes, start it back up and let it run until the smoking stops.
 

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P0203 Diagnosis

Ok, went to Advance last night. The code is "p0203 injector ckt open" (cylinder 3). Does this mean that it's stuck open, meaning a faulty injector? If that's the case, I could replace the injector in that cylinder. What do you think?
This means you need to do more testing. This code relates to an electrical failure, not a mechanical failure, so a stuck or dirty injector isn't your problem. Open means infinite resistance like an unplugged injector, poor electrical contact, broken wire, or faulty PCM. You'll need an ohmmeter and either a 'noid' light, test light or P194 bulb. If you measure the resistance of the #3 injector it should measure the same as all the other injectors, if it has higher resistance it's bad. The test lights are used to connect across the connector to the injector to see if the PCM is actually 'pulsing' this injector while the engine is running.:)
 

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Thanks for the info. I just checked the #3 cylinder injector, and it seems a little loose, actually. It rotates slightly, and the other injectors don't hardly move at all. There is also a little coolant puddling around the injector (and the other ones, so I will need to replace my LIM at some point real soon too). I'm going to clean the area around the injector and then take it out, replace the O-ring, and make sure it's tight in the clip. How do I test it with the ohmmeter?
 

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Thanks for the info. I just checked the #3 cylinder injector, and it seems a little loose, actually. It rotates slightly, and the other injectors don't hardly move at all. There is also a little coolant puddling around the injector (and the other ones, so I will need to replace my LIM at some point real soon too). I'm going to clean the area around the injector and then take it out, replace the O-ring, and make sure it's tight in the clip. How do I test it with the ohmmeter?
Depends on the type of ohmmeter for the scale setting. Select the ohms x1 or ohms x10 scale and then 'sync' the meter by touching it's two leads together (meter should zero out). Look at the injector where the connector attaches. There you'll find 2 terminals. Connect your black meter lead to one terminal and the red meter lead to the other terminal. I'm not sure about the resistance they should read because they vary but all of your injectors should have fairly close readings, probably with 10-15% of each other. All the injectors will move if you twist them hard enough, they're just stuck. Use oil or grease to lube up the O-rings when you put it back together - no silicones.:)

If the injector tests good your probably not getting a pulse from the PCM. Could be wiring, connectors, PCM, etc.
 

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The ohm meter I had just broke when I turned the dial, I'm gonna buy a cheap one and test it like you said. Is there anything special I'd need to do to change the injector, if it turns out to be that? If you know how to test the PCM specifially, please let me know. If it is the PCM, that'll be perfect excuse to get the Digital Horsepower PCM, and also a smaller than stock pulley and a Ubend delete.
 

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Sure, to test the PCM and wiring to the injector, insert either a 'noid light', test light, or P194 bulb across the terminals in the injector connector (the one that goes to the PCM) while it's unplugged. Start the car and see if the light pulses. If it does the PCM and wiring are OK. If it doesn't blink it has a defective PCM or broken wire.

Nothing special really needed to replace the injectors but you might consider replacing the other injector o-rings while you have the rail off. Sometimes they tear when coming apart (especially when they are stuck like yours are). Also grease them up when you put it back together to allow the o-ring to seat in easily. It might help to spray penetrating oil around those stuck injector o-rings to allow easier disassembly, you'll have to pry the fuel rail upward to get the rail and injectors loose.
 

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About that warm engine miss-fire...... Did you pull the vacuum hose off the regulator to check for a leaky regulator??(a warm engine restart miss-fire is a classic symptom of a bad regulator)
One thing people need to know about these "code readers" commonly used by do-it-yourselfers and auto parts stores is that they aren't always accurate in reading the codes or the people doing this process aren't interpreting the info correctly. I see this a lot at my shop.
Reason I'm even suggestiong this is it's extremely uncommon to have an injector problem on a 3800. This may be a missfire code and not necessarly an injector problem. I want to know where that coolant came from. If coolant is seeping into a cylinder(this occurs much faster when the engine is warm and the cooling system is under pressure) this condition needs to fixed ASAP before more severe problems happen also.
If I were you, I would hook up a good scanner and be sure of the problem and fix that coolant problem.

Good luck, Jake L.
 

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Thanks for your help guys, I've got a multimeter instead of an ohm meter now, and it's got so many settings that I don't know which one to use. It doesn't have the settings that the ohm meter had.
I'm gonna get a noid light, test light, or P194 bulb today to test the PCM and wiring.
I didn't pull the vacuum hose to check for a leaky regulator yet, I'll find out how to do that and then do it. I had a different Advance scan it last night (while it was misfiring I drove it over there, short drive), and it's got 2 codes now, misfire in cylinder 3 and the injector code I'd gotten before. I really appreciate your expertise, I'll let ya know what I find out...
 

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Thanks for your help guys, I've got a multimeter instead of an ohm meter now, and it's got so many settings that I don't know which one to use. It doesn't have the settings that the ohm meter had.
I'm gonna get a noid light, test light, or P194 bulb today to test the PCM and wiring.
I didn't pull the vacuum hose to check for a leaky regulator yet, I'll find out how to do that and then do it. I had a different Advance scan it last night (while it was misfiring I drove it over there, short drive), and it's got 2 codes now, misfire in cylinder 3 and the injector code I'd gotten before. I really appreciate your expertise, I'll let ya know what I find out...
The new code for #3 cyl misfire backs up the P0203 code. It will continue to set #3 cyl codes as long as a problem is present. Refer to previous post for multimeter setting (ohms x1 or ohm x10). The P194 bulb will be the cheapest and easiest to find "test light".
 

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Discussion Starter #16
The lowest ohms setting on my multimeter was 20, which would not read anything but 1 on the meter. So I changed it to the lowest volts setting, and cylinder 3 read from 8.4 to 8.5 in pulses. The number 5 cylinder (which is fine) read the exact same thing. I assume that this means that the proper pulsing is getting to the injector, and that the injector itself may indeed be the issue. Is there anything specific online that I could reference with instructions on taking off the fuel rails so I can replace the injector? I'm ordering it today, should be in a couple of days.
 

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Before you go and buy an injector, make sure yours is actually bad. It does sound like the "pulse" time signal from the pcm is the same as other cylinders. But that still doesn't completely lable the injector. Normally we would watch for a fuel pressure drop as we activate each injector separately(this is called a fuel pressure drop test). The bad one or ones would be much less that the good ones(they are supose to be within 1.5 lbs-factory specs- of each other).
Pretty sure you don't have the equiptment for this test, so do the noise test instead! This would be a long skinny screw driver(we use a stethascope). Touch(firmly) a part of that number 3 injector and put your ear against the handle of the screw driver and listen for it's ticking with engine running. Then listen to other cylinders(touching them at the same spots) to see how they sound. The bad injector will barely be audible(or not at all) compared to the good ones. If this test isolates an injector---------go shopping.
As far as R&R, unhook the fuelines from fuel rails, remove whatever vacuum lines and wiring that may interfer with fuel rail removal, then there are 4 spots along fuel rail right at manifold that have a bracket which is bolted to the manifold(4, 6mm nuts). Then simply remove. I usually get some sort of small pry/bar under each injector and pry them up a bit until they break loose from intake and then the whole assy can be lifted up for service.
Before reassy, clean al the holes for injectors and lube them with some sort of light grease or brake silicone for easier injector reinstall. Make sure the o rings on the bottom of injectors look good(no cracks or tears) before reassy.

Good luck, Jake L.
 

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Discussion Starter #18
I have completed the repair, and it was my injector which was partially broken. Upon pulling it out, I'd noticed that the plastic base just beneath the o-ring was partially cracked off which must have caused a leak. It runs great now, no problems at all.

Thank you all very much for your help, it had only cost me a total of about $63 to fix this. If I'd have taken to a shop, it would've been a whole lot more!
 
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