Odd buick 3300 engine issues. high idle, hesitating, etc.

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Odd buick 3300 engine issues. high idle, hesitating, etc.

Post by Tom » Mon Mar 18, 2013 2:42 am

So my wifes car is acting weird. You start it up, sometimes it runs great, idles good and seems perfectly normal.

Other times however it acts like its misfiring, sputtering and idling at about 1200-1300 rpm as indicated by a scan tool.

The IAC valve position climbs higher and higher and topped out at 80 when I was watching it. Car sputters and hesitates when you touch the throttle.

Maf sensor seems to be OK, tps sensor was recently replaced, seems to be working OK. O2 sensor also recently replaced, seems fine. IAC is new too, as well as the ECU, injectors, coil packs, plugs, wires, ect sensor, fuel filter, CCP sensor and possibly other stuff too. All that was replaced around 6 months or less ago.

The misfire can't be traced to one cylinder, seems completely random. Unplugging any injectors or plugs makes the car run significantly different so it seems unlikely to be one cylinder.

Here's my thought process for finding the problem. Tomorrow we're scheduled for a nasty storm, so I probably won't be going far in the snow/ice mix.

So I'm going to test for vacuum leaks. Then pull the IAC and clean the passage, possibly the entire intake depending on how easy it is to pull off.

From there I'll test the IAC using the finger over the plug method/theory I've heard about.

And then maybe clear the codes (tps low, maf low, park safety, o2 rich)
The tps low and maf low is because I unplugged them to test whats going on.

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Re: Odd buick 3300 engine issues. high idle, hesitating, etc

Post by foxmiles » Mon Mar 18, 2013 1:38 pm

A few other thoughts for your snow day tests. I don't know if you've done these or not, but may be worth trying. I think you've covered all the common stuff.
1. MAF - you've replaced this or we're just assuming it's OK? (don't assume) I know you've had it unplugged, but that won't necessarily fix it, just makes it different.
2. Fuel Pressure - (should be a port with a schrader valve), IDK if you can hook to it or not, but it should be 40+psi running. You could pull the vacuum line on the regulator and make sure there's no fuel leaking by. see if it runs different with the vacuum line off.
3. Manifold Pressure - (Vacuum) pull a vacuum line and read the vacuum at idle and blip the throttle. It should be 18+ at idle and drop to almost nothing at wot. it should be steady, not varying much. (it could have a leaky intake gasket, vacuum leaks, etc.)
4. TPS - easy to test it's just a pot. pull it off, hook it to a meter and slowly turn it, make the resistance changes smoothly, doesn't jump around.
5. The Ignition Control Module (under the coil packs) - could cause all kinds of problems. If you have a timing light see if it's firing when it should.
6. Battery voltage - should be 13-14v at 2000rpm. Make sure it's not way off(<12 or >15v).
7. Make sure the throttle is closing completely (could be a floor mat, junk in the throttle body, bad cable or who knows?) it sounds like you're getting more air than you need, probably not clogged passages, but could be sticking IAC or throttle plate.
That's all I've got for now, I'll add more if I think of anything. I'd start with the air leak tests.
Digging with a spoon will accomplish more than leaning on a shovel.

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Re: Odd buick 3300 engine issues. high idle, hesitating, etc

Post by Jarod » Mon Mar 18, 2013 4:28 pm

1: the MAF we're assuming is ok, It seems like reasonable values get sent to the ecu, i'd like to replace it eventually going along with the lets just replace everything theme I've had on this car right now. but the maf is close to $200 and i'm trying not to spend huge amounts of cash on stuff that isn't 100% nessecary right now.
2: thought about fuel pressure, there wasn't anything leaking past when i checked the valve a while ago, but i'll check again.
3: vacuum leaks are high on my list, i'm almost betting with the state of most of the rubber vacuum hoses i've had to replace there is one somewhere completely rotted out and leaking like a sieve.
4: TPS is brand new and i've adjusted it and tested it, seems perfectly fine, may readjust just to be sure, it is within spec atm though.
5: ICM was replaced with a used unit. i'll check that though, I think i've got a timing light, not sure if i've got the wires for it though
6: I've been curious about the alternator for a long time. seems kinda high all the time to me. runs about 14.6v at around 1200rpm, doesnt seem to go up or down much though
7: the pedal seems unrestricted, no floor mats, but i've been wondering id the throttle plate is sticking, either needs some oil or cleaning out. may do that if we get some decent weather, otherwise i'll do that after we've moved.

it runs great, good power and everything, here's the odd thing, if you start it and it idles funny and you let it run for a while to warm up a tad it still idles funny all the time its running if it began with the funny idle, but if you shut it off and start it back up it idles great.

although some days you start it up and it idles good, then you drive it for a while and it starts acting up. cruises nice on the highway though.

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Re: Odd buick 3300 engine issues. high idle, hesitating, etc

Post by Jarod » Tue Feb 11, 2014 5:54 pm


nearly 1 year later, I believe i have found the problem.

I believe the intake gasket is bad. we havent driven the car in about 2 months because of all the brake system issues, but just recently started driving it a little again, and it has been acting up worse.

so I built a vacuum leak tester (I'll be uploading the video on building it soon) and tested the car for leaks. smoke poured out the timing chain cover gasket. which should have no ties to the vacuum system. but that is where the water pump attaches and circulates coolant through the intake manifold... see where this is going now?

I believe the intake manifold gasket has been developing a slow leak. some coolant gets into the intake, which makes it run funny.
I'll be doublechecking this with a compression tester or leakdown tester before I bother pulling the intake and changing gaskets, but I'd say the color and consistency of the coolant lends to a major problem...

don't know how this engine still runs.

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