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zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO

[Help] 1995 Buick Regal Ignition Problems

My 1995 Buick Regal Custom is driving me and several mechanics in the area nuts. Please bear with me as I explain what the car is doing and steps we have gone through to isolate the problem but so far have not been able to find a fix.

First of all the basic specs:

3800 V6 series L engine
3 speed Automatic with OD model 4T-60
170,000 Miles
Original Owner

This problem and or a series of problems began to occur last spring when the outside temperature warmed up. The car would act like it was missing on one or several cylinders and shudder when shifting into OD. We believe it is 2 problems with one being the Torque Converter in the transmission.

The misfiring of the engine is the other one and the one that I want to find a fix for presently.

When the engine is cold after sitting overnight say 60 degrees this morning in St. Louis it runs like a scared rabbit when you stick your foot into the gas. Shortly after it begins to warm up but before any cooling fan comes on cylinder #6 will begin to miss when the car is under load. With the A/C on it is more noticeable because of the increased load. Yes, we believe we have narrowed it down to cylinder #6.

When the car is just driving down the road at 40 – 70 MPH under normal load it will not miss or it is not noticeable. When you step on the gas or start up a 25 – 30 degree incline the car will miss. This is when the car is up to normal operating temperature.

The components that have been replace or swapped in and out are as follows.

EGR Valve, replaced twice
Fuel Pump and fuel filter replaced
Fuel pressure regulator
Spark plugs
Spark plug wires
Ignition Coils
PCV valve
Fuel Injectors swapped in and out with new ones
PCM Powertrain Control Module swapped in and out with a new one
Electronic Ignition Module, replaced
Replaced the Valve Cover Gaskets while inspecting the Valve Springs
Vacuum @ Idle runs about 19.5 inches
Cylinder compression test all 6 are reading 125 psi

I may have missed a couple of items but we have pretty much tried everything other than replacing the entire engine.

I hope someone has some input on what we may have overlooked and any input will be much appreciated.

Thanks,

Zach


frankpjr

join:2004-03-19
60164-1229

I would get it checked by a good mechanic to check items such as fuel pressure and such as there are many items replaced which has not fixed issue. It would be cheaper overall to have it looked at professionally rather than "installing numerous parts" to try and fix. There was no mention of the mass air flow meter and sometimes that can cause a lean enough condition to cause misfire in a "weaker" cylinder. There was no mention of spark output test, injector flow balance (issue could be in companion cylinder #6 and upsetting balance) You would need block learn numbers and oxygen sensor readings to try to narrow issue to fuel, mechanical or other issue.

There was no mention of a check engine lamp or any codes that may be coming up to lead also in a direction of what is happening. Also a running compression on a fully warmed engine may show a valve that has recessed into the head which can cause misfire.

You might want to ask around for a recommendation of a quality shop which can diagnose your issue as the hardest problems are when it cannot be duplicated, should be easier with it happening just need to find out why. Also a quality shop will have access to help lines such as iATN and Identifix in finding the elusive problem and direction to proceed.

Good luck!


zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO

Hi Frank,

All of the issues that you have so kindly mentioned have been done. Those were some of the ones that I failed to mention in my original post.

As far as a good Mechanic the one that I use is one of the best in the area. As he told me with a 1995 engine it only has the capability of an OBD1 on-board computer output for error codes so he has had to run a lot of additional tests to try to narrow down any problem item. Tests have been run when the engine is hot and cold with someone driving and someone looking at the test readings.

He hasn't totally given up but just needed a break to clear his head!!!

Thanks again for your assistance, it is much appreciated.

Zach


frankpjr

join:2004-03-19
60164-1229
reply to zach3

I am glad you mentioned having a good mechanic. Yes I also have been at a wall at times and just needed to step away to get a new perspective. He might try posting at iATN (he can join if not a member if he has credentials) as you can really get a different view of issues and help from another technician. Yes being OBD 1 really hurts and as such lots of good diagnostic steps have been forgotten with OBD II and the number of codes generated which can lead to a direction.

Good luck having it fixed!



ErRoR
Premium
join:2002-10-26
Tullahoma, TN

1 edit
reply to zach3

If your sure it's #6 then it's a possible vacuum leak, injector going bad, bad wire (if your used cheap ones,) bad coil pack (possible even if new) or plug. If the compression is up and it sounds like it is, it has to be a fuel or spark problem when it gets hot. Usually a secondary ignition problem if it acts up hot. Just throwing ideas here since I can't see the car or feel it miss.

Eric

EDIT:
I've seen wiring problems where the harness goes thru the firewall on the passenger side too on those cars. I've worked on many and only seen 2, but it's a possibility?



TheHarvester
Premium
join:2006-08-25
Dana Point, CA
kudos:3
reply to zach3

As far as the misfire goes, I second frankpjr See Profile and have a running compression check done. Also look for a cam lobe that may be going flat.

As far as the transmission shutter goes get a bottle of the A/C Delco limited slip diff additive and pour it in the transmission. We have used it to fix many GM and Ford TCC Shudder issues.
»paceperformance.com/index.asp?Pa···ID=29478
--
mbsastronomy.com


zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO
reply to zach3

Hello All,

I truly want to thank all of you for responding and offering your ideas.

Eric: On the vacuum leak, at idle we are getting 19.5 inches and one of the things that I am going to do tomorrow is to hook up my personal gauge and drive the car to see what the readings are when it actually starts missing. Will report back the results. I have already replaced the wires with good ones and sprayed water on them when it was running and there were no sparks!! My mechanic also changed them out during his testing and found that it did not help. We both changed the Coil pack out I bought a new one and swapped it out down the bank and he had one of his own that he used. He also was able to measure the voltage output and duration with his testing equipment and ruled out the Coils. Same thing with the Injectors he swapped them out with new ones and tested the old ones and they all tested fine. So back to the possible vacuum leak. I will also attempt to spray water on the intake manifold in the area of #6 cylinder and see if that makes any difference while the engine is running.

As for wiring problems on the harness I can see it as a remote possibility but would expect a problem of such to cause problems on all cylinders not just one.

TheHarvester: My mechanic is leaning toward possibly a cracked valve seat that would open up more when the engine begins to warm up. I am not sure how a worn cam lobe would be an intermittent problem unless it is always there but is aggravated by temperature and engine load.

I think I have the transmission problem at bay presently by using a couple of additives.

Me, other comments:This car has many a mile on it but they have all been driven by me and I take care of my vehicles. Oil change every 3K whether they need it or not. Every little noise or ding taken care of as soon as possible. You can still work on the engine without getting dirt or grease all over you hands and clothes. I have always babied my cars starting back in the late 50's going forward. I used to fix everything myself until I finally got so old it hurts to crawl under a car any more. I still will change the plugs and anything that I can work on under the hood etc. But other than that I leave it up to the pros!!!

Thanks Again for all of your inputs and I will keep you posted as to the progress.

Regards,

Zach


zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO
reply to zach3

Ok, today I hooked up my vacuum gauge with a long hose so I could drive the car and watch what happened under different conditions.

First I tested the vacuum at idle:

19.5" @ 900 rpm
21" @ 2000 rpm
21" @ 3000 rpm

Needle steady at all speeds.

Drove the car for about 2 minutes and the needle began to vibrate at a constant engine speed. Also notice the missing in the spark plug when I would step on the gas. Running @ 40 - 50 MPH and attempted to hold speed going up hill with the A/C running the missing was very noticeable and the vacuum dropped down to almost zero.

I actually do not know if zero is an acceptable level under load with the throttle plate partially open.

The vacuum needle was vibrating constantly during all of my driving tests while the car was up to temperature.

Once the test was over with the engine running and the transmission in neutral the vacuum came back up to 19.5" but the needle continued to vibrate constantly.

I could shut the engine down for less than 5 minutes and restart it and the vacuum would go to 19.5" with a steady needle.

Defiantly Temperature Sensitive!

I then went to an engine rebuild shop that comes highly recommended and spoke with the owner. He suggested spraying the Intake Manifold with Ether rather than the water trick. He said that if the vacuum leak is on the outside the engine will rev up. Sounded like a great idea so I had a can of Ether and tried his suggestion.

Pulled a blank. He then told me to have the Shop that works on the car to do a Leak Down Test on cylinder #6 while the engine is hot not cold. I have that scheduled for next week. He told me we were looking for a crack between the Intake & Exhaust valve, a small leak in the head gasket, or still a leak in the intake manifold where the Ether could not get to.

By the way the engine repair shop was recommended by one of the fellows at O'Reilly's that I deal with on my parts. Turns out that fellow that owns the engine shop also does the repair work for the Mechanic that I use. He did not know that until we had a long conversation and the shop was mentioned. He also said the he only recommends that shop along with one other one in a different area of town.

Sounds like I at least am working with the right people.

I will keep everyone posted on my progress.

Zach



ErRoR
Premium
join:2002-10-26
Tullahoma, TN

1 edit
reply to zach3

Just a thought here, but a cam lobe going flat shouldn't cause it to run great cold and miss hot. It's something getting hot and breaking down. Cracked valve seat should show up on a compression test when the engine is hot if it's had enough to cause a miss. I have seen the injector rails get clogged with rust and debris causing this to happen too...just a thought. I know it will set a check engine light, but unplug the mass air and see if it still runs. If so drive it and see how it acts. Sometimes they will run unplugged. Just and idea. Post back.

Eric

EDIT:
Please don't spray the intake with ether. If any gets on the coils or an plug wire, you might burn your car down. Use carb cleaner with the hose on it around the intake and see if the idle picks up. Be VERY careful when doing this tho! Go around the top plenum lower intake and see if anything happens.


zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO

1 edit

Eric,

I used "Ether", whoops, but was well aware of what I was doing. Had a fire extinguisher handy just in case along with a garden hose. Anyway nothing happened do to the design of the manifold the test was inclusive. You can only reach the outside of the intakes and not the inside areas.

I will make sure to have them check the injector fuel rails for debris if he has not already done so but when I looked at them this afternoon it didn't look like they had been touched.

I will unplug the Mass Air Sensor and see what happens. Exactly what should I be looking for??? I would expect that the MA would cause all cylinders to act up not just one???

Thanks Again for your input.

Zach

I also wanted to add that this afternoon after I came back home after the test drive, with the engine at idle and the vacuum meter vibrating at 19.5", I pulled the hose off of the meter and put it up to my ear and listened for any noise. I could hear a tick, tick, tick, like a valve opening and closing. The sound would change in frequency when I increased or decreased the engine RPM but the amplitude or sound level remained constant.

I will try this again in the morning when the engine is cold and the vibrations are not present and see if I hear anything.



ErRoR
Premium
join:2002-10-26
Tullahoma, TN

2 edits

said by zach3:

Eric,

I will unplug the Mass Air Sensor and see what happens. Exactly what should I be looking for??? I would expect that the MA would cause all cylinders to act up not just one???

Thanks Again for your input.

I've seen bad MAF meters cause missing and bucking under loads. It may or may not run unplugged, but some will and it's worth a try. The ticking you hear may be the injectors? your vacuum will drop off the more throttle you give it and pick up as you let off. That's how the fuel pressure regulator increases fuel pressure when u accelerate. If the vacuum gauge happened to build steady vacuum then you'd be looking at a plugged up cat converter, but that don't seem to be your case, but something to keep in mind for the future for diagnostic purpose. A leak down test on the cylinders will tell you a lot too. Good luck with it.

Eric

EDIT:
It wouldn't hurt to wiggle the wiring harness around where the injectors plug in and the main harness that goes thru the firewall on the passenger side of the car. Just something else to try.

EDIT2:
There's a TSB for your problem,but it's for a clogged fuel rail/injector. I would make sure you take that rail off and clean it out really good.

zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO

Good Morning Eric,

Well I just came back from running the tests that I can.

First of all the Ticking noise is not present when the engine is cold. I seems to begin just as my temperature gauge lifts off of the peg about 2 - 3 minutes of 30 MPH driving. That is also when the vacuum needle begins to vibrate. Also I was mistaken in my last post the frequency of the Ticking sound remains constant even when I vary the engine RPM. I find this interesting and I do not understand exactly why!!

I disconnected the MAF and thought we were on to something but as the engine warmed up and the vacuum gauge begin to vibrate I could get the cylinder to miss during acceleration.

Saint Louis is rather cool this morning with 63 degrees and rain at present so the tests may change when it gets hot. 85 plus degrees is where the problem becomes most noticeable.

Later on today I will wiggle the wiring harness and take another look at all of the electrical connections and see what I find. I will need to wait until Monday to get an answer on the fuel rail/injector TSB and see if my Mechanic is aware of this and actually cleaned these out or not.

Thanks for the new ideas.

Zach



ErRoR
Premium
join:2002-10-26
Tullahoma, TN

No problem! I just hope you get it figured out as these problems can beat you to death...lol

Good luck!

Eric


zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO

Eric,

Something has me really confused this morning.

The Ticking holding a constant frequency as I very the engine RPM's.

I for the life of me cannot think of one thing on a drive train that does not very in frequency, that one can hear with the human ear, with engine RPM's, can you????

Zach



ErRoR
Premium
join:2002-10-26
Tullahoma, TN

2 edits

said by zach3:

Eric,

The Ticking holding a constant frequency as I very the engine RPM's.

I for the life of me cannot think of one thing on a drive train that does not very in frequency, that one can hear with the human ear, with engine RPM's, can you????

Zach
By frequency you mean a high pitch hum? anyway you can record it and post the wave file?

Edit:
I would really like to hear it, but from what you say it almost sounds like a bearing worn in the transmission, but hard to say without hearing it.
4T60-E's are good transmissions, but with that many miles on it, it's bound to be worn some.

zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO

Eric,

No the frequency is not like a high pitched hum. The best guess I can make is about 20 HZ. I do not think it is coming from any thing like a bearing or even the transmission. It sounds like a flapper valve opening or closing?? Hard plastic not steel.

Possibly I did not make my self as clear as I should have. The noise comes from the end of the vacuum hose that I pulled from the gauge and placed near my ear to see if I could hear something. That is the Tick, Tick that I am hearing. I wish I had a way to record it but I do not. The sound is not exactly a tick but it isn't a thud either somewhere between!! Attempting to describe something like this is like trying to teach Helen Keller to speak or read.

The other thing that I noticed was the vibration and noise happen like someone turned on a switch. Like a temperature sensor is coming on when the temperature of the engine reaches a certain point. This also does not necessarily correspond to the temperature gauge in my cars dashboard.

Zach



ErRoR
Premium
join:2002-10-26
Tullahoma, TN

1 edit
reply to zach3

downloadtest-tones.zip 37,216 bytes
I agree...very hard to figure out. As far as the freq, pick a sound that's in the ball park.

Eidt:
Where is the sound coming from to the best of your knowledge? There's a balance shaft and bearing that runs under the intake?

zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO

Eric,

I could not pick a sound from the test frequencies that you sent that matches what I am hearing. I hear a sound that happens say about 20 times a second. That is the frequency that I am taking about. WOW this is really hard to explain!!

The sound is coming from the inside of the vacuum hose. If you cover the hose with your thumb or put it back on the gauge you can no longer hear the sound.

If you stand outside the car with the hood up you can not hear the sound.

Placing your ear close to the running engine you cannot hear the sound.

It only comes from the hose. It comes from deep inside the workings of the vacuum system somewhere.

That is the best I can explain it presently.

Sorry,

Zach



ErRoR
Premium
join:2002-10-26
Tullahoma, TN

OK, where does the vacuum hose go?



TheHarvester
Premium
join:2006-08-25
Dana Point, CA
kudos:3
reply to zach3

said by zach3:

TheHarvester:I am not sure how a worn cam lobe would be an intermittent problem unless it is always there but is aggravated by temperature and engine load.

Regards,

Zach
Just throwing possibilities out there regardless of how remote the chances are. I have seen many things that made no sense what so ever. It is possible though. The valve wouldn't be opening all the way and When the engine is cold it runs rich. As it warms up the the computer starts to lean the mixture out until it gets into fuel control and is running quite lean. When an engine is running lean it doesn't take much to cause a misfire.

On that ticking noise, Is it possible it is some sort of pulse width modulated vacuum switch?
--
mbsastronomy.com

zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO
reply to ErRoR

Click for full size
The clear hose feeding off of the temporary tee is the one that I have hooked to the gauge and it is sitting in the car. The device that it is fed from is the manifold with the other end going to valve like device that most likely turns a vacuum on and off to the larger line next to the tee. The larger line appears to go to a manifold with 4 or 5 lines in it headed back along the frame rail on the driver's side of the car. Most likely to the gas tank????

zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO

1 edit
reply to TheHarvester

Harvester,

I understand about throwing out all of the possibilities!! Thanks.

I think you are on to something with the pulse width modulated vacuum switch. See my previous post.

The large line could have a leak in it that nobody had found yet but there are still many questions to be answered.

Thank Again,

Zach



TheHarvester
Premium
join:2006-08-25
Dana Point, CA
kudos:3

1 edit

1 recommendation

That is a modulated vacuum switch for the Evap. You don't want to read the vacuum from that hose.
Try the hose going to the fuel pressure regulator, PCV valve or brake booster.
--
mbsastronomy.com


zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO

So that is the answer to the clicking sound and why it doesn't vary in rate/frequency.

Ok, I will move the connection to another spot.

Thanks,

Zach



TheHarvester
Premium
join:2006-08-25
Dana Point, CA
kudos:3

And the cause of the vacuum gauge bouncing.

I don't think that engine has a PCV valve hose. I think the best place may be the fuel pressure regulator.
--
mbsastronomy.com


zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO

PCV valve doesn't have a hose and is on the front end of the engine. The Fuel Pressure Regulator is the object right in front of the blue connector in the picture and I will hook it up there.

Will post back about the bouncing needle and any noise that I can hear in a little while.

Thanks,

Zacj



ErRoR
Premium
join:2002-10-26
Tullahoma, TN

1 edit
reply to zach3

TheHarvester, I wasn't trying to say you were wrong by any means, as I've seen some pretty strange things also that made no since what's so ever...lol.

As stated, the fuel pressure regulator or booster would be a more consistent vacuum reading rather than the EVAP purge valve.

Eric

zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO

Hi Eric,

I hooked the vacuum gauge between the manifold and the fuel pressure regulator and the problem of the vibrating needle and the clicking sound went away!! Thank you very much!!

Now back to the missing problem! Will need to wait until Monday on that one. I have an appointment with my Mechanic and will discuss the fuel rails etc. with him then.

Thanks,

Zach



ErRoR
Premium
join:2002-10-26
Tullahoma, TN

Good luck! I sure hope you can get this solved. The world of auto repair is so fun eh....lol

Good luck once again with it

Eric


zach3
Zach
Premium
join:2000-05-04
Saint Louis, MO

Good Morning,

Eric, you mentioned this in an earlier post:

EDIT2:
There's a TSB for your problem,but it's for a clogged fuel rail/injector. I would make sure you take that rail off and clean it out really good.


Do you have a source on this TSB that I can download??

Thanks,

Zach