PontiacBonnevilleClub.com

I love my 98 bonnie Se, she used to fly down the road as smooth as silk. Recently I've been having troubles. First I was getting p0300,303,306. That was easy to fix put in New wires and a new coil pack. I've poured over the forums and have seen many posts on how to clean the maf how to test it and so on. My problem is its only getting 11.75-11.6 volts. I'm currently pulling apart the wire harness being careful not to damage anything else. I think the wires go back to the pcm, but I'm going to remove the three connected to the maf plug, and replace them. I've checked and cleaned all the engine compartment grounds. The maf is good, should the voltage be the same as the battery. If I change the wires should that fix the problem. The car keeps having voltage drops and erratic rpms. The voltage comes back up if it doesn't die first. I just can't figure out why is doing this it only started doing this when the coil pack went bad. The icm is good as well. The grounds are all clean and tight. The alternator is working fine. I'm at a loss I was hoping someone that had had this problem in the past and was able to fix it can help me out, any advice anyone had is greatly appreciated. Sorry my first post is so long winded.i forgot to add I fixed and replaced vacuum lines.

I recently bookmarked the next link for myself to peruse.
You may find it helpful, too with the insights into troubleshooting voltage drops.
http://en-us.fluke.com/community/fluke- ... oting.html


There are 2 ground buses beneath the carpet near the kick panels, 1 on each side.
They can develop corrosion and wreak all sorts of havoc.
I'd try cleaning those up first.
This thread has pictures of the buses viewtopic.php?f=19&t=30286
The driver's side bus terminates at 2 ring terminals near the parking brake and the pass. side one with only a single ring terminal on the nearby frame .

Thank you for helping me I cleaned the body grounds by the driver side door but I didn't see the buss. Pictures really help, after reading the info on ground issues and the slight difference in voltage drops causing problems, one of my next questions was could a voltage drop of .25 volts really be a problem, great links Thank you so much. I'm really tired today I've been swapping out parts of four different vehicles for the last couple weeks and I think I'm going to relax today and start fresh tomorrow. Thanks for your help and time.

You're quite welcome.
The forum has been a tremendous resource for me, too since members have shared their Bonneville wisdom quite freely.

Like you, I have a few Bonnies that I've been working on and sometimes you just need a break.

I may be wrong, but I doubt that a .25-.40 voltage loss affects the MAF sensor.
It's possible that the MAF is bad.
A bad MAF will cause code P0102. Erratic RPMs and stalling are MAF failure symptoms.

Like most things, there are other possibilities, too.

A simple but very important test, is to hook up a vacuum gauge, bring the engine to 2000 RPMs and see if the vacuum reading holds steady or if it drops.
At idle , expect around 20 psi. Slightly lower at 2K.
If it slowly drops, your catalytic converter has gone bad from the misfires dumping gas into the exhaust.
This creates a blockage in the exhaust that causes all sorts of problems.

I'd also check the fuel pressure to make sure a failing fuel pump isn't the cause of the MAF code.
Expect fuel pressures to be mid 40's or so.
The pressure should jump by 8-10 psi when you pull the vacuum hose off the fuel pressure regulator.

If you replace the MAF, I'd strongly recommend Hitachi brand. They are the original equipment sensors (which get labeled ACDelco and then the price doubles).
Most here will tell you that the OE Mafs are far superior to aftermarket ones.
Rockauto has the Hitachi MAF for under $75 and using the discount code (Pontiac Bonneville Club Vendor's forum RA post) that may be your total cost with shipping.
http://www.rockauto.com/en/moreinfo.php ... 91&jsn=401

If cost is a major issue, some have opted for used OE, pulled from junked cars.

Thanks again, this forum is probably one of the most useful to me then anything else the Internet can offer. My hats off to the designer.
Well like always I couldn't stay away for a day, last night I went out to check a few more wires but when I took off the engine cover my flashlight shined down into the valve cover and out of the coner of my eye my worst nightmare cane true and I saw antifreeze. So I'm another victim of intake gaskets failing. I never seen any white smoke and the fluid levels really. I'm just hoping I only have to treat it down to the top of the heads. I'm going to use the Dorman brand from what I've read here in the forums they seen to be the best fix. They cost a little more than the others but when weighed against chasing generic cel codes around for days. I would pay twice as much.
I'm still going to finish cleaning all the ground points in the cabin, no point in stopping now.
I was afraid that this p0102 code was really be caused by the intake but until last night I had no visual sign to verify it. I would post pictures but I don't see a way to add attachments not the best at using computer.

The intake gaskets failing is just a matter of when, rather than if.
Catching the failure early is great.
It means that your engine should remain sound.

You'll save yourself future troubles if you do the LIM gaskets now, too.
It's not the worst job in the world to do but it is time consuming.
This write up is one of the very best guides http://www.pontiacbonnevilleclub.com/fo ... c3591.html
It was the one which gave me the confidence to tackle the job.

I used FelPro LIM gaskets and the Dorman UIM for my 98 SE.
ACDelco gaskets are preferred by some.

Yeah, I'm glad I saw it just a little bit of antifreeze in the heads . It seems to be really minor right now I checked my oil and have no visible signs of it being had gasket. Thank God. This means I can put it off for a while. I only drive it a couple times a week and not farther than a mile total. This gives me time to finish chasing wires. Finished with the engine compartment, get a really load humm from the fuel pump. I figure that's a good indication that is either going out or in need of new wires. I've had a loud whistle coming from transmission not sure if it's the torque converter, or the trans pump. One of the reasons I was putting of the intake gaskets. Thinking that I should get a real thread going on it and see if I can get a better handle