2000 DTS surging poor acceleration

[realestate11]

So I hopped in my 2000 DTS for a run into the city the other day and I was having a hard time accelerating to 70 mph and keeping a steady speed so I pulled off at the next exit 1 mi and it worsened to the point I can barely make 30mph and cant accelerate at all and surges at any speed above idle.

So I stop at a auto parts store thinking hmm when was the last time I replaced the air filter and fuel filter buy both and install air filter in parking lot before I leave. Then I got on the street and nope thats not it! So I then replace the fuel filter and no thats not it either.

Now I am thinking oh right lean air bog must be the fuel pressure regulator so I take out the old one no problem 10 min deal I find that the screen is tore and it has removed before hmm I paid 300 bucks to have it replaced the last time this car had problems nice to know that wasn't done! Normally when the regulator fails it goes rich and wont idle typical the three times I have replaced these in the caddies I have owned. But the regulator was not the problem either and now I have a new regulator fuel filter and air filter.

Ok so now I am getting serious and I run the diagnostic codes I get a couple nagging body issues B1591, B1007 and B0429 none of which I would think would have anything to do with this and then I get the P036 current hmm Oxygen sensor after the converter how could this cause the problem? The problem occurs open or closed loop since it is the same cold or at operating temp. So in desperation I replaced the o2 sensor nope not it either! No more P036 either!

So I run the car in park up to 4000 rpm and it sits there for a bit and it starts bogging remember what a quadra-jet after 1971 sounds like when you put your foot in it thats the sound.

Ok what gives has anybody else had the same issues? Looking for the magic answer here LOL. I am thinking fuel pump but shouldnt that show up on the diagnostic? Low pressure bla bla bla???

I need Help

Thanks in advance

Matt

[Texas Jim]

Maybe a stopped up catalytic converter ??

[realestate11]

Maybe a stopped up catalytic converter ??

I am now leaning towards that I will rev it till it bogs and look at it in the dark tonight! The darn thing has always sounded like rocks rattling around thought it was the heat shield but after putting in a new after cat o2 today I know there is nothing loose down there LOL. One funny thing mileage was fine before this happened and I havent been able to drive it enough to even know now! I did notice that the car had a little loss of power cruising the freeway for a couple days like the A/C compressor was turning on and off (thats what I assumed was going on)

Thanks

Matt

[BodybyFisher]

This in my opinion is a bad CAT. First, it does not have to sound bad to be bad. A CAT can just clog up. BUT, it sounds to me like you have a classic CAT failure, it sounds like a heat shield is loose, right? But you don't find a loose heat shield. Try banging the cat with a rubber mallet, my guess is you will hear rocks clanging. My 91's CAT was so loud, I could not go to drive up windows. But it never clogged. When I removed it, it sounded like an empty can with bolts inside, hollow

My wife had a bad CAT in her 2002 Monte Carlo and it had ZERO power. Jim nailed it in my opinion

You can confirm this before you go to the trouble and expense of replacing it, by buying an exhaust backpressure tester, it screws into the O2 sensor port and will report excessive backpressure from the a clogged CAT. Do a search of the popular tool and parts shops.. Mike

[realestate11]

This in my opinion is a bad CAT. First, it does not have to sound bad to be bad. A CAT can just clog up. BUT, it sounds to me like you have a classic CAT failure, it sounds like a heat shield is loose, right? But you don't find a loose heat shield. Try banging the cat with a rubber mallet, my guess is you will hear rocks clanging. My 91's CAT was so loud, I could not go to drive up windows. But it never clogged. When I removed it, it sounded like an empty can with bolts inside, hollow

My wife had a bad CAT in her 2002 Monte Carlo and it had ZERO power. Jim nailed it in my opinion

You can confirm this before you go to the trouble and expense of replacing it, by buying an exhaust backpressure tester, it screws into the O2 sensor port and will report excessive backpressure from the a clogged CAT. Do a search of the popular tool and parts shops.. Mike

I have had one cat plug sawed it off drove home 1979 chevy 3/4 ton LOL. I have the 1993 STS rattles like hell thought cat once pulled it and wow the cleanest cat I have ever seen after 250 k miles perfect looked like new inside that one was a loose exhaust hanger and heat shield. This bugger boy It has been a lemon since I bought it at 30k miles I tell you this car was built fri at 3pm after a booze break. I am contemplating getting out the plasma cutter and cutting a big hole just before the cat so I can see if it will run bet it does!!! Will this see if it glows thing mean anything????? Hey just curious has anyone that had the headgaskets go to heck have a problem with the cat?

Thanks everybody

[BodybyFisher]

You know, I am sorry, I thought you were talking about the 93... You are talking about the 2000.. As I noted, GM got a bad bunch of CATs around that time. This is the tool I would buy to test it

<a href="http://www.autobarn.net/xxxw-ta-33600.html" target="_blank">http://www.autobarn.net/xxxw-ta-33600.html</a>

Also, here is my off topic Monte Carlo thread regarding NO POWER and what I went through to figure out what it was. It was covered under warranty. I believe that EMISSIONS COMPONENTS are covered a long time by GM, like 80,000 miles, I am not sure how long however it might be 5 years, not sure though. While this was a Monte Carlo, I thought that it could be helpful for others on this board as GM received a batch of bad CATS in the early 00's. By the way, my name was Scotty back then.

<a href="http://caddyinfo.ipbhost.com/index.php?showtopic=4391" target="_blank">http://caddyinfo.ipbhost.com/index.php?showtopic=4391</a>

[realestate11]

You know, I am sorry, I thought you were talking about the 93... You are talking about the 2000.. As I noted, GM got a bad bunch of CATs around that time. This is the tool I would buy to test it

<a href="http://www.autobarn.net/xxxw-ta-33600.html" target="_blank">http://www.autobarn.net/xxxw-ta-33600.html</a>

Also, here is my off topic Monte Carlo thread regarding NO POWER and what I went through to figure out what it was. It was covered under warranty. I believe that EMISSIONS COMPONENTS are covered a long time by GM, like 80,000 miles, I am not sure how long however it might be 5 years, not sure though. While this was a Monte Carlo, I thought that it could be helpful for others on this board as GM received a batch of bad CATS in the early 00's. By the way, my name was Scotty back then.

<a href="http://caddyinfo.ipbhost.com/index.php?showtopic=4391" target="_blank">http://caddyinfo.ipbhost.com/index.php?showtopic=4391</a>

I have plenty of pressure gauges around here and started life as a machinist (have three lathes and 2 mills in the garage) So I will just measure the thread on the o2 sensor I threw out and make an adapter cool 15 psi Ha! Remember the Scotty postings I have been lurking long before I was a member! I hope this is it I am frustrated at best!!! Oh yea should have mentioned it the 2000 has 180k miles!

Thanks

Matt

[BodybyFisher]

I was very frustrated to, that I do all of that diagnostic testing and finally had to admit I was stumped and sent it to the dealer. I gave up, you are still sticking with it.. I think this will be your problem.

Read this I found it at this link >> <a href="http://www.aa1car.com/library/converter.htm" target="_blank">http://www.aa1car.com/library/converter.htm</a>

Driveability symptoms such as a drop in fuel economy, lack of high speed power, rough idle or stalling are classic symptoms of excessive backpressure due to a plugged converter. Checking exhaust backpressure and/or intake vacuum will tell you if there's a blockage (more on this subject in a minute).

EXHAUST BACKPRESSURE CHECKS

To diagnose a plugged catalytic converter, you can check intake vacuum or exhaust backpressure. To check intake vacuum, connect a vacuum gauge to a vacuum port on the intake manifold. Start the engine and note the vacuum reading at idle. Then increase engine speed to about 2,500 rpm and hold steady. Normal vacuum at idle for most engines should be 18 to 22 inches Hg. When the engine speed is increased there should be a momentary drop in vacuum before it returns to within a couple of inches of the idle reading. If the vacuum reading is lower than normal and/or continues to drop as the engine runs, it probably indicates a buildup of backpressure in the exhaust. Remember, though, that intake vacuum can also be affected by retarded ignition timing and valve timing. What's more, some engines are much more sensitive to small changes in intake vacuum than others, so checking backpressure rather than intake vacuum may give you a better indication of what's going on.

Checking backpressure requires connecting a pressure gauge to the exhaust system. Use a gauge that reads up to 8 to 10 psi and is calibrated in 1/2 inch increments. Or, use a metric pressure gauge calibrated in kilo-Pascals (kPa). One psi equals 6.895 kPa.

A backpressure gauge can be connected to the exhaust system one of several ways: by removing the oxygen sensor and connecting the gauge to the hole in the exhaust manifold; by removing the air check valve in the air pump or pulse air system and connecting the gauge here; or by drilling a small hole into the head pipe just ahead of the converter to attach the gauge (never drill a hole into the converter itself!). One drawback of drilling a hole is that the hole will have to be plugged by a self-tapping screw, plug or welded shut after you've taken your measurements. Also, drilling is not recommended if the head pipe has a double-wall construction.

Once you've made your connection, start the engine and note the backpressure reading. Depending on the application, the amount of backpressure that's considered "normal" will vary. On some vehicles, backpressure should read near zero at idle, and should not exceed 1.25 psi at 2,500 rpm. Others can handle 0.5 to 1.25 psi at idle, but should have more than 4 psi during a snap acceleration test.

If you find a relatively high backpressure reading (say 8 to 10 or more psi), there's obviously an exhaust restriction that will require further diagnosis. Don't jump to conclusions and assume the converter is plugged because it might be a collapsed pipe or muffler.

One way to rule out the pipes and muffler is to visually inspect the exhaust system for damaged components. Another way is to drill a small hole in the pipe aft of the converter and check backpressure here. If the reading is lower (or is less than about 1 psi), the rest of the system is OK and the converter is what's causing the restriction. Or, disconnect the exhaust pipe aft of the converter. No change in backpressure would indicate a blockage at or ahead of the converter. If backpressure drops back to normal, the problem is not the converter but a collapsed pipe or muffler.

If you suspect the converter is plugged, you can disconnect and remove it. Then hold a shop light by one end of the converter and look in the other end. If you can't see the light shining through the honeycomb, the converter is plugged and needs to be replaced.

You can also recheck backpressure readings with the converter removed. If readings are at or near zero, you've found the problem. But if backpressure is still high, there's an obstruction in the head pipe or manifold. Sometimes a collapsed inner tube inside a double-wall head pipe will create an obstruction that acts just like a plugged converter. Another cause can be a heat riser valve on an older V6 or V8 exhaust manifold stuck in the closed position.

CAUSES OF CATALYST FOULING

To clean the exhaust, the catalyst inside the converter must be exposed to the hot exhaust gases. Lead, phosphorous and silicone can contaminate the catalyst and prevent it from working its magic. Lead used to be the most common contaminant, but is no more since it was eliminated from gasoline. Phosphorus is still a threat, and comes from motor oil. So if an engine is burning oil because of worn valve guides or rings, phosphorus will shorten the life of the converter. Blue smoke in the exhaust and an emissions failure are pretty good clues that the converter has been fouled with phosphorus.

The new "SJ" rated motor oils contain less phosphorus than earlier SH rated oils. The difference isn't much (about 20% less compared to SH oils), but over time the lower level of phosphorus reduces contamination to extend the life of the converter.

Silicone can find its way into the exhaust if the engine develops an internal coolant leak through a crack in a combustion chamber or a head gasket. Silicone will ruin the oxygen sensor as well as the catalytic converter, so chances are if the converter has been fouled the O2 sensor will also need to be replaced. White smoke in the exhaust is a clue that there's an internal coolant leak.

CAUSES OF CATALYTIC CONVERTER PLUGGING

Prolonged overheating or short term severe overheating are the leading causes of catalytic converter plugging. The underlying cause here is often fouled or misfiring spark plugs, or a burned exhaust valve that leaks compression and allows unburned fuel to pass through the combustion chamber into the exhaust.

The average light off temperature at which the catalytic converter begins to function ranges from 400 to 600 degrees F. The normal operating temperature can range up to 1,200 to 1,600 degrees F. But as the amount of pollutants in the exhaust go up, so does the converter's operating temperature. If the temperature gets up around 2,000 degrees F or higher, several things happen. The aluminum oxide honeycomb begins to degrade and weaken. The platinum and palladium coating on the honeycomb also starts to melt and sink into the ceramic substrate reducing its effect on the exhaust. This accelerates the aging process and causes the converter to lose efficiency.

If the overheating condition persists for a long period of time, or if the temperature soars high enough, the honeycomb itself may breakdown and melt forming a partial or complete obstruction and causing a sharp rise in backpressure. A complete blockage will cause the engine to stall shortly after starting, and will not allow exhaust to exit the engine.

Some degree of restriction inside the converter honeycomb can also be caused by accumulated deposits: phosphorus from oil burning and/or carbon from oil burning, a rich fuel mixture or frequent short trip driving where the converter rarely reaches light-off temperature). Physical damage to the honeycomb as a result of road hazards or severe jolts may cause the relatively brittle ceramic honeycomb to break or crumble inside the converter shell. A rattling noise when you shake or thump the converter would tell you there's loose debris inside. A undamaged monolith converter should make no noise

[Texas Jim]

Several years ago, I took a driving vacation from Texas up to Montana, back down theu Yellowstone then back to Texas.

Was driving my 1984 Fleetwood with about 120,000 on it. In the middle of Montana, with no town for MILES, (in the mountains of course) the cat stopped up.

Thru trail and error, I figured out that if I JUST BARELY gave it gas, it would run. The more gas you gave it, the LESS power it had. You could floor it and it would completely STOP and eventually almost die.

Going downhill, I could get it up to 60 or 70. By the time you topped the next hill, you would be over on the shoulder going MAYBE 20. Then speed up down the next hill and fo it again.

FINALLY made it into a town and to a muffler shop. Don't remember EXACTLY the price, but it was WAY out of line. Like 4 or 5 hundred dollars and this was in the early 90's. Hated to spend THAT MUCH when out of town and if anything happened later, there would be no warranty without driving back to Montana.

Went and got a motel, then found a Wal Mart. Bought a cheap hacksaw and a BIG screwdriver. Sawed about an inch and a half slit in the pipe just in front of the converter. Used the big screwdriver to pry and bend the pipe to make a hole where exhaust gas could escape.

Drove it the rest of the vacation with no trouble. (Just a little loud) When I got back home to Texas, took it to a local shop and had it replaced AND had him weld up the hole in the pipe.

The muffler guy laughed at my way of solving the problem when a long way from home but as I think Clint Eastwood said... "A mans got to do what a mans got to do."

[Logan]

In park. You can only rev a Northstar so far. There is a RPM limiter. The PCM will cut the fuel off.

[realestate11]

Well we will see what today brings. Yesterday evening I checked for battery shorts low voltage while it was exhibiting the problem 14.4 within a couple tenths of a volt the whole time Not It.

Matt

[realestate11]

Ding Ding Ding we have a winner one totally plugged converter!!! Can we say melt down! The converters front half was all crumbly bits the second half yikes one big melted mass. I took out the old TE72 Hilti hammer drill with a 23 inch long 2 3/8 diamiter bit and in 5 seconds no more melted rock!!! Vacuumed the whole thing out and I now have a car that drives great again. Now for the hard part I will have to search for a cat at a good price! The cat and resonator? appear to be one piece so inexpensive cat $200 and weld or GM $660 and change out the parts.

Thanks for all the great input

Matt

[BodybyFisher]

Ding Ding Ding we have a winner one totally plugged converter!!! Can we say melt down! The converters front half was all crumbly bits the second half yikes one big melted mass. I took out the old TE72 Hilti hammer drill with a 23 inch long 2 3/8 diamiter bit and in 5 seconds no more melted rock!!! Vacuumed the whole thing out and I now have a car that drives great again. Now for the hard part I will have to search for a cat at a good price! The cat and resonator? appear to be one piece so inexpensive cat $200 and weld or GM $660 and change out the parts.

Thanks for all the great input

Matt

Thanks for letting us know what it was. I can't help with what CAT to use, cost is a consideration here. Its important to get a CAT that will be as efficient as the OEM unit as your emissions system will balk at it. I think we had a member who replaced with an aftermarket CAT only to get O2 sensor codes, you might do a search.

Check www.rockauto.com and www.gmotors.com for prices. Mike

PS, good fast diagnosis Texas Jim

[lothos]

Check www.rockauto.com and www.gmotors.com for prices. Mike

I'll agree with RockAuto, I've been buying parts from them. They've got great prices and fast shipping along with helpful customer service. I had an exchange with them for a defective part and they shipped it out free the day I called. That was my first order with them, and I've done two more since.

I also like the classic car magnets you get with the order, I've been putting them on my toolbox

There's also a 5% off discount code you can use, click the link in my signature below this.

[realestate11]

Ok an update makes me wonder about getting a new cat my car after 240 miles with the gutted cat gets 22.3 mpg before 18.4 mpg even when I bought it with 30k miles what a different car wow! So I get the p0420 no kiding nothing ther computer! What mileage does a healthy 2000 dts get with a good cat?

Thanks

matt

P.S.

I am a realtor so this is slow stop go and then long distance commute 40 plus miles