# 1991 Pontiac 6000 v6 3.1l running rough



## rusty baker (Feb 13, 2009)

I assume this has fuel injectors. Have you been adding fuel injector cleaner to your gas?


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## Patriot_RAM (Apr 13, 2006)

rusty baker said:


> I assume this has fuel injectors. Have you been adding fuel injector cleaner to your gas?


This car is EFI. Seafoam is supposed to clean the junk out of them. It's cheap enough to try another good cleaner. I'll pick some up today.


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## Rehabber (Dec 29, 2005)

The strongest OTC FI cleaners are Techroline or Gumout with Regane, forget most of the rest of them.


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## nap (Dec 4, 2007)

I would look for either a leaking vacuum line or a leaking EGR valve. Both have parts that operate differently with the engine cold and warmed up. If that has the black plastic vacuum lines, it is possible one has split or the rubber connectors on the ends have simply degraded from age and oil and turned into mush and are leaking.


You can also swing by Autozone and I think Advance Auto (don't know if O'Reillys does it) and have your computer scanned to see if there are any codes present.


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## Rehabber (Dec 29, 2005)

AZ or Oreillys will not be able to scan your car, it is OBD1


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## nap (Dec 4, 2007)

Rehabber said:


> AZ or Oreillys will not be able to scan your car, it is OBD1


well ain't that a bummer. 

OBDI is easy to self scan. It's been long enough I can't remember which 2 terminals to jump to get it to self scan. There should be tons of info on the net about how to do it though.


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## cowboy dan (Apr 11, 2010)

my guess is head gaskets. even if you check the oil and it is not milky, they would still be leaking. the next in line would be the catalytic converter. with blown head gaskets, the cat would be done. the 3.1 is really bad for head gaskets. i could think of others, but one thing at a time


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## Patriot_RAM (Apr 13, 2006)

I only had a few minutes over the weekend to look at it. I did put a bottle of Techron in the tank to see if it cleaned anything out. I'll know in a few days if that makes a difference.

I also checked the resistance on the EGR valve, and everything was perfect there. I think the next thing I'm going to do is check for a leak in the EGR valve. It it had a leak, it would produce issues that sound identical to what I'm seeing. I found something online that said to take it off the car and spray carb cleaner in each of the three holes and see if it comes out the other hole. If it does, it isn't closing all the way and is defective. Sounds like the next cheapest thing to check.

If it was a head gasket, would it use or leak oil? It doesn't have any leaks at all, and the oil stays clean all the way through to oil change time. It also doesn't ever move off the full line.

Thanks for the suggestions! I'll let you know what I find.

David


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## TJ_in_IL (Aug 24, 2009)

I had the same motor in my 91 Beretta. Try cleaning the intake with seafoam (sucking through the brake booster). Also check the IAC and EGR. My EGR would carbon up something awful. I also used to take apart the EGR and clean with carb cleaner, and lube the pintals so they moved smoother. You could have whats called the TCC hanging up. One way to test is to unplug the connector to the TCC. This will prevent the "Overdrive" from actuating, and will cause the car to run at a higher RPM at higher speeds, but when it does not disengage when coasting to a stop, will give you the bucking or almost stall condition. 
I would try cleaning things first, before disconnecting.
Also check out www.beretta.net, and check out the forums there. Since your car has the same powerplant as the early 90's Beretta's, you will find some good info for repair/troubleshooting.

Good Luck!

TJ

After re-reading your post, you may have some injectors going bad. I did a write up a while ago about testing the injectors. The write up can be found here-http://home.comcast.net/~t.pierro/images/Plenum.pdf


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## racebum (Mar 8, 2010)

nap said:


> I would look for either a leaking vacuum line or a leaking EGR valve. Both have parts that operate differently with the engine cold and warmed up. If that has the black plastic vacuum lines, it is possible one has split or the rubber connectors on the ends have simply degraded from age and oil and turned into mush and are leaking.
> 
> 
> You can also swing by Autozone and I think Advance Auto (don't know if O'Reillys does it) and have your computer scanned to see if there are any codes present.


this and a compression test

a down cylinder and bad egr are two of the more common causes once you check things like plugs, injectors etc. make sure to disconnect the distributor or coil when you do a compression test. it's really easy to waste modern coils when the spark has no where to go


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## Patriot_RAM (Apr 13, 2006)

TJ,

I tore things apart after it cooled down this evening. The IAC sensor was nasty, and the pcv valve moved, but was really sticky. The throttle body had a little bit of gunk in the bottom, and a little bit of sticky oil draining out of it back into the air intake tube.

I pulled the plenum and tested the resistance of each injector. They were 23, 37, 16, 13, 15, and 10 with the engine mostly cooled down. I figured with a range of 10 - 13, with low being bad, what's the deal with the high values on the others? Are the high ones good or bad?

I also pulled the EGR and used some carb cleaner to test it for leaks, and it is sealing 100%. 

I went ahead and purchased a new PCV valve and AIC valve and will put those in tomorrow. Oh, and a new PCV hose to replace the one I broke pulling the valve out. 

Anyhow, with what I found, there is certainly a few things that could be going wrong. My only question at this point is the injector resistance range being so large. I'm confident in the Fluke meter -- What do you think?

Thanks for the help!

David


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## racebum (Mar 8, 2010)

google what resistance should be for your car. it's obd1 which is somewhat universal in that 10-15ohm range. 37 seems excessively high but do check the specs. what's the most odd to me is the spread you have going on. 

http://fuelinjectorconnection.com/shop/

can clean and flow your injectors. actually if you call and ask the question you'll probably get an answer. this is the single best injector site i know of online.


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## Patriot_RAM (Apr 13, 2006)

I decided not to mess with it. I called the guy at the injector place and ordered a set. This weekend I'll install those, the new PCV valve and hose, and the IAC valve. I'm going to throw a new fuel filter on it for the sake of the new injectors at the same time. 

I'll let you guys know how it turns out.

Thanks!

David


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## TJ_in_IL (Aug 24, 2009)

Please report back, as I am curious.
I have never seen values that high on injectors. 
Glad to see there was still some good use for the write up.

TJ


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## Patriot_RAM (Apr 13, 2006)

TJ_in_IL said:


> Please report back, as I am curious.
> I have never seen values that high on injectors.
> Glad to see there was still some good use for the write up.
> 
> TJ


Well, I put the injectors and new sensors in this morning and started it up. It started rough at first as expected, but then started running smooth as a top about 15 seconds later. The injector instructions say to run it for fifteen minutes at an idle when you first start it, so I began that process. After a minute and a quarter, something in the motor started knocking and clunking and tapping pretty loudly. argh....

I'm not a mechanic (but I'm very mechanically inclined and have more common sense than most people I meet) , so I have no idea what the problem is, but the injector install was pretty straightforward. I'm not sure what I missed. I don't think any dirt or anything got in the top of the motor. I was very careful, but there was potential for some to get in when I removed the rails since some of the injectors came off with the rail even though the clips were off.

Am I correct in the assumption that if some gunk dropped in there it may be toast? Or do you guys think it could be something else?

Thanks for the help,

David


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## racebum (Mar 8, 2010)

very doubtful junk was dropped in. in a situation like this i would start with basics and work up, that means

1. compression test 
2. check the timing belt/chain to make sure nothing skipped a tooth
3. check ignition timing
4. remove valve covers and inspect for broken valve springs
5. test egr 
6. check fuel pressure


i have a feeling something in here won't jive

leaking spark plug wires can also do this. if it's dark out when you hear it knocking look to see if any energy is visible between wires. i've seen oil coated wires actually arcing off on the block before. 

the compression test is the single most important test to start with. also unhook your distributor and or disable the coil{s} in some way. compression tests with live distributors can fry coils since the energy has no where to go


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## pur3vil (Oct 9, 2010)

Sounds similar to mine, I've got a 91 3.1 3sp as well. My car itself has a dead cylinder in it that's never affected drivibility, I know weird eh, #3 cylinder is stupid low on comp. My car started an idle hunt today which prompted me to do a few quick online checks and therefore I am here.

Few things I would check, CTS or coolant temp sensor, O2 sensor may be going bad, both of these will sometimes trip a code, but not all the time. And both of these are diretly related to the temp of the engine, when they are clod they do a completely different job then when the engine is at operating temps. These are also the things I need to check regarding my issue of idle hunt turned into SES light and good idle. It could be a vacuum leak, however be reminded it could also be a vacuum leak, I would check all the hoses and also do a spray test around the intake where it mates to the heads, use starting fluid, and spray the mating surface as close as you can get it WITH the engine running. If there is a vacuum leak there the engine will pull in the starting fluid and will generally stall.

Depending on loudness and the type of knock / rattle it could be a dead lifter. They can get extremly loud, and by running that much seafoam through the crankcase could have inadvertanly turned things worse by breaking something up that didn't need to be broken up, as stupid as this may sound it could be the case, I've seen more engines break from running a degunkifiying substance through it then they've helped usually becuase they remove all the crap that the engine is USE to having, will leave you with looser tolerances in bearings which creates a drop in oil pressure which can result in a spun rod bearing, and could be the cause of this knock... If the car itself SOUNDS like it is running ohkay.. it's probably just a dead lifter. Valve springs don't usually break. If the car started to run rougher, like it's missign another cylinder then I would check for a spring broke but not before then. 

My .02 now I have to figger out what broke on mine so I can fix this stupid idle hunt.

Update on mine, Code 44
?Prolly the EGR valve that looks like it's leaking something feirce and blwoing soot all over my throttle body ..






Jacob
91 6000-LE 3.1 3sp 160k
92 Astro 4.3 CFI 4sp 400k
97 Grand Prix GT 3.8 4sp 156k
03 Sebring LX 2.4 4sp 98k ( the one that doesn't run, needs head, damn timing belt )


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