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Pontiac 6000, 3.1, 1990 - Engine Runs Rough
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cliving
Novice
Aug 5, 2007, 10:24 PM
Post #1 of 9
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Pontiac 6000, 3.1, 1990 - Engine Runs Rough
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It's basically missing and acts like EGR Valve problems, but I cleaned the EGR and no change. Every now and then it will take off and run great. It acts like water in the fuel, but I have run it enough now that I think it should have cleared. The check engine light is not on. Previous owner supposedly replaced plugs and wires. I'm wondering if the catalytic converter might be plugged. Any help would be appreciated.
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gripadog
Novice
Aug 6, 2007, 5:57 AM
Post #2 of 9
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Re: Pontiac 6000, 3.1, 1990 - Engine Runs Rough
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It could be something as simple as a fuel filter.....I would start with making sure all the new plug wires are completely seated and try a fuel filter....hope that helps
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cliving
Novice
Aug 14, 2007, 10:43 PM
Post #3 of 9
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Re: Pontiac 6000, 3.1, 1990 - Engine Runs Rough
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I didn't check all the plug wires. After I cleaned the EGR valve, I cleaned the throttle body and IAC valve and 02 sensor. That didn't help. Then I replaced the Throttle position sensor and that didn't help and I took it back and traded it in for an IAC valve. That did help. I drove it 3 times and it ran good, but the next day it was missing and running rough again. Since then it's been running good more than bad but it still throws fits. Also, ever since I changed the IAC I am now getting a check engine light where as I wasn't before. It's a code 33 which is MAF - excessive air flow. But that car does not have a MAF sensor. I was doing some research online and got a list of codes and probable causes and this one guy said it's MAP sensor, not MAF; which this car does have. I may change it out next. If that don't work it must be in the ignition sys or catalytic convertor.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 17, 2007, 4:56 AM
Post #4 of 9
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Re: Pontiac 6000, 3.1, 1990 - Engine Runs Rough
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MAP is Manifold Actual Pressure which is vacuum. The manifold vacuum it a good indicator of the load on the engine and the car's computer will adjust things based on that info. If a converter is plugged it will alter the reading the MAP sensor gets and computer makes wrong adjustments. This can be diagnosed with a vacuum gauge put on a T inline to the manifold's actual vacuum.
Car's getting old so make sure all vacuum lines and connections are good. The codes can't tell you that a line is broken but lead you to that diagnosis.
Anytime an engine runs poorly for any reason the converter takes a hit and waiting can kill it and it wasn't the source of the problem,
T
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cliving
Novice
Aug 19, 2007, 8:39 AM
Post #5 of 9
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Re: Pontiac 6000, 3.1, 1990 - Engine Runs Rough
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I went ahead and replaced the MAP Sensor but it didn't seem to help. I returned it to Autozone and they gave me my money back... they're pretty good about it. I'm not sure what to do next. I got to thinking about the cat, and it's probably not the problem... since the problem is intermitent... right? In otherwords it's either plugged or it's not... right? I'm wondering if the cranshaft position sensor could be the problem... aside from that I guess I will start looking at the DIS (distributorless ignition system). But, before I do anything else I believe I will go ahead and pull all the spark plugs, because a friend of mine told me he was using those hot spark plugs and one of them burnt the electrode of the end and gave similiar intermitent symptoms.... Frustrating!!!
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 19, 2007, 10:09 AM
Post #6 of 9
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Re: Pontiac 6000, 3.1, 1990 - Engine Runs Rough
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Plugs sure could make the engine run rough. They are difficult in the 3.1 and you'll see the back three are near impossible without tilting the engine - do that with car in neutral by the way. Plugs should be the exact plugs designed for the car. The days of covering problems with altering plugs kind of ended in the 70s.
A plugged or restricted cat conv is usually smooth about it. Lack of power and could be better when cold and worse when warmed up but smooth about it - that's usually. You can test for exhaust restriction by doing a vacuum test on actual manifold vacuum with a "T" in line. You should see about 18Hg vacuum at idle. Raise idle to a steady 2,000 and it should be about the same and if not that's an indication of exhaust restriction. Doesn't say what though. Vacuuum reading will spike up to like 21Hg or so when you quick raise the idle up and let go.
Converter can be diagnosed as a restriction by loosening exhaust parts before it for a test and if all is well it gets blamed. Trouble is it probably got killed and was not the source of the trouble and could just do it again.
Just some ideas I'm spitting out to pin this down. Check for vacuum leaks by spraying carb cleaner at suspect spots and idle should not change and if it does somethings leaking there. Watch out on hot parts and don't soak it as it can flash.
Another thing to root out secondary ign parts (plug wires coils etc.,) is using salt water sprayed on them and look for arcing. It shouldn't. Easy on hot stuff. Best with cool engine and with some darkness for that.
Just some ideas,
T
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cliving
Novice
Aug 19, 2007, 9:02 PM
Post #7 of 9
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Re: Pontiac 6000, 3.1, 1990 - Engine Runs Rough
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Well, I pulled the plugs and may have found the problem. Two of the plugs on the firewall side (hard side) had double the gap they're suppose to have. Also a connector on one of the plug wires stayed on the plug when I pulled the wire off; don't know if it was already broke or if I did it when I pulled the wire off. Also, one of the plugs was not tight. Anyway, I cleaned and regapped the plugs and put them in, fixed the wire, and the car ran great, and the check engine light is not even on now.....unbelievable!!! However, after the way it was acting before... intermitent problem... I'm not yet convinced it's fixed. As previously stated one of the reasons I didn't mess with the plugs is because they were just replaced not long ago... also I did pull one of them and it looked fine... also because I didn't think plugs and wire would give intermitent problems like that... and oh yeah, what about that check engine light? I guess what they say in the book is correct... don't assume anything and make sure all the basic stuff (plugs and wires, fuel filter, etc.) is ok before getting too deep in all that other stuff. Just thought I'd let you guys know, hoping the info helps you. 
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cliving
Novice
Aug 20, 2007, 11:50 PM
Post #8 of 9
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Re: Pontiac 6000, 3.1, 1990 - Engine Runs Rough
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Well... I spoke to soon. As good as it was running yesterday, today it started acting up again, and it's once again sporatic. It's not missing near as bad as it was originally though and the check engine light hasn't came back on. I went ahead and replaced all the plugs and wires tonight, but to no avail. I may try removing and testing the igintion module next... I don't know.
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cliving
Novice
Sep 9, 2007, 12:01 PM
Post #9 of 9
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Re: Pontiac 6000, 3.1, 1990 - Engine Runs Rough
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Well, I'm still working on it (I was on vaction for awhile). Thought I had it fixed a couple times, but it's just that intermittent thing. Runs good and then it don't... no pattern.
I have been through all the sensors. Also tested fuel pressure. I had the ignition module checked at Autozone and it checked ok. I bought 1 new coil and tried it in each of the 3 coil positions, but that didn't help. I was about to pull the intake plenum an start checking the injectors, but decided to pull plug wires while it was running BAD, and low an behold 2 cylinders do not have spark and they are mates 2-5 coming out of the same coil. It just so happens that was the last position I tried the new coil and it's still in place (new coil for those two cylinders). I trying to find out if the crankshaft positon sensor would affect only 2 cylinders, as is the case with mine. I looked for loose or burnt wires and all look ok. I'm going to check and see if autozone can test the ECM (computer). What else can it be????
Chuck
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