Help! Weird Sputtering on 2000; only when warm.
 

Hey guys please help,

This is my first post though I have been reading the forum for a while trying to figure out what's wrong with my wife's bonne. It's a 2000 with about 150k on it.

It runs and drives like a champ until its warm; then it starts sputtering and loosing power. It feels like it is running out of gas and sometimes the tach drops to zero but it still drives (kind of). I changed the fuel filter but it didn't help. It threw a code for a cam sensor and I changed that and it didn't help either. That was the only code and it only came up a couple times.

Also, it seemed to start going bad kind of slowly. At first it would only sputter for a second on the interstate when going over 70. Then it started doing it a slower speeds. Now, as soon it warms up, with the temp gauge right in the middle (doesn't over heat), it does it at any speed when accelerating. No problems starting at all. When the tach drops to 0, you can pull over and restart it and the tach resets.

Nobody around here really wants to work on it so I am kind of stuck. I could have it towed to GM but they want a fortune. Any help you could give would be INCREDIBLY appreciated. I'm not much of a mechanic but with the help of YouTube I have been able to figure out how to do the simple stuff. :) I'm hoping someone has had a similar problem and can help me figure it out. Thanks in advance!

I'd take some carb/intake clearer and spray your vacumme hoses. You might have a leak there. Also this could be a LIM situation. Does your exhaust smell sweet after your car warms up?

Test your coils. I suspect you have a bad one, but only when it's warmed up.

I just youtubed a coil test :) in which you use a little piece of vacuum hose to test the spark. Will that work for this? Also I haven't noticed any sweet smell.

I will look up how to check vacuum lines next and try both of those first.

You guys are fast! Thanks again!

There is a coil test in the tech info section here off the main menu. Just look in testing.

I think it is the middle coil! :) I followed the guide and it read higher on the top terminals than the other two and on the bottom connections it read 0.0. I am going to go grab a new one after lunch and I will let you know how it goes. Thanks again!!!!

Becareful when loosening and tightening the bolts to the coil. They are small and easily broken if not careful. Also be sure to put some dieletric grease on the bottom and top terminals to protect from moisture.

Yep, that one is dead. As mentioned, be careful. The bolts go in to aluminum and strip easy. Just snug.

I had autozone test the coil too and they also determined it was bad. I swapped it out and drove around to it warmed up. It seemed to run a little bit better but when it got hot it started sputtering again. I checked the ohms on the top of the coils again and the middle one was still a little higher (9.x). Could that mean the ICM? I also saw some white smoke when I first started it and kind of thought it smelt kind of sweet; but I really don't know how to tell. I'm not a good judge of the sweetness level. :)

Any ideas on what to try next?

Pull the spark plugs and inspect them. Look for any differences in the tips. All shoudl be clean with a slight gray color.

Ok. They looked alright. One of them had a bit of black gunk but not too bad.

I read somewhere that the cam and crank sensors are on the same circuit. I got the cam error code but could it be the crank sensor instead? Thanks again.

That's a possibility. Does the tach still drop to zero. IIRC the crank sends the signal to the tachometer.

Thanks for your response. That what I was thinking/hoping. I'm going put a crank sensor in and some new plugs. I got my fingers crossed. I let you know how it goes. Thanks again.

I have a similar situation was to blame sensor (ACDelco 213-151 Crank Position Sensor GM Ref # 10456161).
Sometimes jump out code P0336.

Hey guys. I was dead set on get the new crank sensor in tonight but I broke 2 extensions trying to get the harmonic balancer bolt out. That thing is really one there. I admit I did try it with 3/8" drives but thats all I had. Tomorrow I will get some beefier 1/2 extensions and have another go at it. Is there some trick to it? I followed the guide; took off the starter and stuck something in the crank so it wouldn't turn. Put a jack under the extension and used part of my weight bench for a cheater bar. :) Even if I do get it off I'm still not 100% its the crank sensor. I could be in the corner tomorrow, in the fetal position, and crying my eyes out if I can't get this figured out. ;0

You will need a puller with long enough bolts

Yeah, I rented one of those from autozone. They included a bunch of bolts and I think I have the 4" * 1/4" with the fine threads. I just haven't gotten there yet. I have to get the 15/16th bolt off first right? That thing is a nightmare.....

You will need 1/2" extensions and a impact 6 point socket, I forget the size but I have it listed in my write up. https://www.gmforum.com/mechanical-134/harmonic-balancer-replacement-286278/ You will need some PB blaster and I find some heat helps a lot. However, I really don't see a bad crank sensor causing a sputter. That's typically a bad coil(s), bad wires, or bad plugs. If your getting a P0300 code it's random and might be the ICM, if you have a P030x code that's always the same cylinder it's a coil, wire, plug, injector, bad valve spring or possible chipped piston.

I had an ignition mod. go bad after it got hot. Car kept stalling. It's the silver box that the three coils sit on and is easy to change too. Just makes sure you get the coils back in the correct spot!

Well I can rule out the crank shaft sensor and the spark plugs. :( I really thought it was the crank sensor but I should of listened. It was heartbreaking because the crank pulley was quite a pain. I could only find 3" bolts in town and it took forever. Anyway, I am going to get the cat. converter checked tomorrow and I think I will take the ICM in as well for testing. I know if I stick with it I will get there eventually.....

Remember, sputter is a weak spark. Inspect the spark plugs again. I had a cracked plug once, it looked like a small scratch.

DId you check your fuel pressure at the rail?

No I haven't checked the fuel pressure yet. How do I do that? Is there a guide for that one?

You will need a pressure test. https://www.gmforum.com/trouble-shooting-test-procedures-141/fuel-pressure-test-284304/

Also you may want to check you battery cables and engine grounds. You're engine grounds are going to be a wire bolted dierctly to the engine and going directly to the body of the car. I forget does the a 00+ bonnes have a voltmeter on the dash?

Yeah. It does have a voltmeter in the dash. It always runs a little high. Does that mean anything? Also I forgot to reset everything after I installed the crank sensor. I just did it and I am letting heat up again now. I was hoping maybe that would make a difference.

What's a little high you should be running between 11.5 and 13.5 volts

The middle of the gauge is 14 and it is a little above that so I'm guessing 15. It has been a little high since I changed out the alternator about a year ago. Also, I just let it heat up again and now it won't even start when hot. Whatever it is, it is getting progressively worse. I don't have a pressure gauge but I think I can rent one from Autozone; or maybe I'll just make one. I'm starting to think its the fuel pump going bad. That would make sense right? What do you think?

I'm going back to the LIM.

You need to check for spark when it's not starting.

How do I test that?

I checked the fuel pressure and it seems fine. I'm also getting spark when its hot. My neighbor seems to think its the o2 sensor. Would that throw a code? Its the one of the back of the engine behind everything; kind of close to the back spark plugs? Oh I checked the vacuum like and it seems ok too. Any more ideas? I am about to pull my hair out! I didn't think this would be this hard. :(

I don't see the O2 sensor causing a sputter. Weak spark causes a sputter. And 9 times out of 10 that's bad coils. Do you have stock coils in this car or a after market?

You're right! I just checked it again when it was hot and I am not getting a spark. Before I was getting a spark but maybe it wasn't quite warm or something. I checked all the coils and replaced one. I think they are ok. Maybe I should check them again? Two are aftermarket and I think one is still original. If its not the coils then whats left, the ICM?

If it's still causing problems when hot, then you haven't found the bad coil. I've seen several work fine cold, then fail hot. And that's what it sounds like is happening with you. Did you say you changed one coil already? If so, use that coil you took off and swap a different coil and see if it corrects the problem.

Because you have now determined you don't have spark you can forget everything else and concentrate on the ignition system. Your options are, bad coil, bad ICM, there are other things but they tend to be all the time, not just when hot.

May not be a bad idea to remove all the coils, lift up the ICM, and clean everything up. A little corrosion can cause a lot of problems.

I sure would like to hear the out come of this problem! The internet is saturated with it on GM cars. My 95 olds has been down for a month, very simular to yours!

I would like to know if there is a way to test and see if a quad driver is shuting down (computer protection)at a point where engine temp is reached, and some action called for by the computer , trips a shutdown , causing a stumble or no start condition.

I dont like throwing parts at it either.

Hope you find it.

Hey guys,

I'm really glad I got a reply because it reminded me that I needed to let everyone know that I did get it fixed. Danthurs was right on.

It was the icm. Apparently, when the engine got hot the icm would spaz out. I didn't want to spend all the money on a new one since the car is getting pretty old. So I went to the junk yard and got a icm off of a grad prix; came with coils and all. I swapped the whole unit out and it has been running like a champ ever since. Also, I think there is a leak in the lower intake manifold but I'm not sure I'm going to mess with it since we are probably going to trade it in.

Anyway, thanks again for everyones' help!!!!

Thats good to hear!!!!!!!!!!!!!!!!!!!

I had my ICM tested a o'riles auto parts and it was good might try that again but heat it up with a hair dryer first. Also have another one from junk yard that I have on there now, but no change.

Bummer. I would let the car heat up and check for spark. That would let you know if it is ignition related or otherwise. Hope that helps; worked for me. Good luck!