Thread: Engine surging, hesitating (It's Fixed !!!)

About a month ago, I replaced my LIM gaskets (with aluminum ones), new UIM (Dorman) new gaskets, pcv, etc. (Thanks for all your help on my doing this) After this, my car ran really strong for the first couple of weeks, and then I noticed hesitation when pulling hills. On the flat, it ran well. At the suggestion of some others, I replaced my plugs and wires (both AC Delco). This made no difference. Others said maybe it was the MAF and I should unplug it and see if it ran any better. When I tried this, my car ran much better, and in fact, I drove it for a couple of days this way. So, I just purchased a brand new MAF and after installing it, took it out for a drive. Still runs like crap. Just tonight, I tried unplugging my O2 sensor on the manifold to see if there was any difference. It seems to run better. (Does it run open loop this way???) Any harm to my engine???
I also tried spraying all the possible vacuum leak areas (manifold, hoses, etc.) with carb cleaner but there was no change in the idle speed. Idles great, smooth and if I goose the throttle, it revs up fine with no hesitation.

Thru all this, I have had no codes, other than when I had the MAF unplugged. I have a code reader but do not have a scanner.
I know I should probably find someone to scan it, but I don't know anyone in my area to do this.

Sorry if this is long, but I needed to explain what I have done.

Anyone have any further ideas on what I can try.
I really appreciate any help you can give me.

Oxygen Sensors Overview

read that bottom part. describes it a lot i think. i am going to replace mine because i have less performance and bad throttle response.

just replaced mine tonight and it seems to have a little bit better throttle response, will post back more info on gas mileage improvements after work tomorrow.

That sounds spot on to being a bad O2 sensor. You run fine in closed loop with the MAF unplugged. Pop in new O2 sensors and go.

do the o2 sensors pop any codes when they fail?

Update?

Originally Posted by e6600

do the o2 sensors pop any codes when they fail?

depends how bad it is.

I finally decided to spend the money to have the "stealership" do a scan on my car tomorrow. They are also going to check the catalytic convertor. I really hope it IS the cat since they would then have to replace it under the extended warranty on the cat for my car. ( 10 years, 120,000 miles)
I will post back with the results of what they find.

Originally Posted by BDEGhost

I finally decided to spend the money to have the "stealership" do a scan on my car tomorrow. They are also going to check the catalytic convertor. I really hope it IS the cat since they would then have to replace it under the extended warranty on the cat for my car. ( 10 years, 120,000 miles)
I will post back with the results of what they find.

If you didnt just post this, I would have. Be willing to bet that the cat is starting to plug. My car was so bad it wouldnt go over 20mph.

Good Luck.

Took my car into the dealer today, and they test drove it first and immediately said that the cat was clogged. No testing... Luckily they had a cat w/downpipe in stock and ripped off the old one, put the new one on and my car was fixed. I drove it and I will tell you that this thing now runs like a bat out of H*LL. I really don't remember it having this much power since I owned it but maybe the cat was slowly clogging for a long while and I just got used to the lack of performance.
The best thing was that my total cost for this was $0.00 (nothing, nada, nix !!!) They replaced the cat under the extended warranty on the cat but at first they tried to tell me that the warranty was only 8 years/80,000 miles. I told them to look again and check Service Bulletin #05551. They did and agreed that I was right. No argument.
So, if any of you have a 2001 or 2002 GP under 120,000 miles, and your cat is bad, you are entitled to get it replaced for free. It doesn't matter if you are the original owner or not. Additionally, if you have already paid someone to replace the cat within the mileage allowance, you can fill out a form to get reimbursed for the cost of the cat plus labor. You can find the entire forms on line at:
http://ww2.justanswer.com/uploads/GM...er_impalas.pdf

There are also other GM cars covered under this warranty. Read the documents for specifics.

All in all, I feel really lucky to have this taken care of for free. I was anticipating getting screwed by the dealer some way or another, but it didn't happen.

Thanks for listening.

Thanks for the follow up. I took advantage of the free new cat too. Glad it fixed your issue.