96 3.8 MAP Sensor question

[tempfixit]

96 Lesabra 3.8 engine (Sisters car and she lives about 650 miles from me so this is over the phone type deal)

Getting code P0108 MAP Sensor High voltage output. She had code cleared and within 2 miles check engine light came back on. This was done at a parts store in larger town about 80 miles away.

Week ago the car would vibrate while driving at times (like driving over washboards on a gravel road but not the issue) She took to the local mechanic which is from the old school era and he said it was running on 5 clyinders and replaced something but doesn't know what (trying to find out part). I am thinking it was a injector. Today she called and said it was doing the same thing again, and also told me that at times when she steps on the accelerater at any speed it boggs and vibrates then she let's up and accelrates again and it fine. Could a bad MAP Sensor cause this?????
If I understand right from doing a search on code P0108 and MAP Sensor that the high ouput could mean a rich fuel/air mixture but could it cause the vibrating issue???? but if the map sensors is bad the pcm goes back to preset values if I am correct.

I am going to have her try to get it scanned for codes again if possible to see if any new codes are present since this vibrating problem occured again today. Don't know if the mechanic had the battery disconnected or not to clear codes when working on it.

Any advice greatly appreciated.

[maxwedge]

On this car the map is connected directly to to the intake, under it is the pcv valve, there are several seals involved, loss of vacuum would would cause a high voltage signal, it could be bad, the engine could have a vacuum leak, the seals could be missing from something being worked on prior. No quick answer here, this needs to be looked at by someone familiar with the causes of the condition, if it has serious misfire issues this can set the code. Check this link. http://service.gm.com/gmspo/mode6/pd...c38K_H__yE.pdf

[tempfixit]

Originally Posted by maxwedge

On this car the map is connected directly to to the intake, under it is the pcv valve, there are several seals involved, loss of vacuum would would cause a high voltage signal, it could be bad, the engine could have a vacuum leak, the seals could be missing from something being worked on prior. No quick answer here, this needs to be looked at by someone familiar with the causes of the condition, if it has serious misfire issues this can set the code. Check this link. http://service.gm.com/gmspo/mode6/pd...c38K_H__yE.pdf

Thanks for reply maxwedge. Sister did call saying that mechanic changed one of the coils. Being that this vibrating is intermittent could a camshaft sensor or crankshaft sensor be a problem? She is still trying to find a place close by that can scan for codes again. Thanks again for advice.

[maxwedge]

Not usually, for the condition you descibe, reading the codes really is not the issue, somone who knows what they are doing must look into this .

[tempfixit]

Update:

She took the car to another place in town that has a scope machine. They could not find anything wrong when it was hooked to the machine so they checked the plug wires and found a bad wire so they put a new set off spark plug wires on and that fixed the vibration that was described. Checked the codes and it came up again with MAP sensor code. At first they put a new MAF sensor on that did not fix the problem instead of the MAP sensor like code said.

With the engine light still being on my sister got the MAP sensor herself. I mentioned to her that since she was replacing the MAP sensor she may as well change the PCV also, so she got that also. I did send her a email with the thread on changing PCV but she failed to read it thoroughly and ended breaking the piece on the plenium that holds the PCV in place. OK she made a mistake so she took it back to the garage and had them get a new plenium and install it. Well they did the work and engine light was off like it should be BUT after work was done she started the car at the shop to take it home and it filled the garage with raw gas fumes and gas was coming out of the tailpipe, drove it 1 block and said the car had a slight miss so she took it back immediately. They then said that a vehicle with this many miles (140,000) anything could go wrong including the injectors but the engine was running fine for a week or better before she broke the plenium. Garage claimed that they did nothing wrong when doing the plenium switch which I believe they damaged some injectors when changing it. They changed a injector on believe cylinder # 5 and said everthing was fine. SHe again drove the vehicle and said it still missed so they said it had to be another injector. Replaced another injector and garage took it for a drive got about 1 mile out of town and lost the oil pressure and took out the bearings. (I should add that when she bought the car approximately year and a half ago the intake gasket was replaed because of leaking coolant into oil.) Now they are claming that the coolant going into the oil at that time is what took out the bearing even though the car has been driven for this length of time and over 5000 miles.

I believe that when the plenium was replaced they damaged some injectors causing gas to wash the clyinder walls and go into the oil pan breaking down the oil which took out the bearings.

The garage denies any wrong doing in performing this plenium change and says my sister is responsible for cost of engine and installing.

Is there a way to determine what caused the loss of oil pressure and causing the bearings to fail??

All opinions are welcome.

[BNaylor]

Why was the plenum replaced assuming you are referring to the Upper Intake Manifold Plenum? Normally you can replace the plastic retainer that fits over the PCV valve and that holds the MAP sensor separately without replacing the plenum.

Hard to tell by your post but were the lower intake manifold gaskets ever replaced?

[tempfixit]

Originally Posted by BNaylor

Why was the plenum replaced assuming you are referring to the Upper Intake Manifold Plenum? Normally you can replace the plastic retainer that fits over the PCV valve and that holds the MAP sensor separately without replacing the plenum.

Hard to tell by your post but were the lower intake manifold gaskets ever replaced?

Sorry I wasn't clear with my post.

Yes the Upper Intake Manifold Plenum was replaced because of broken piece that holds PCV valve and MAP sensor. I did not see a picture of what was broken, either the housing where the PCV valve sets in or the plastic retainer that fits over the PCV valve and holds the MAP sensor. Like I stated in update post, I believe they damaged some injectors when removing fuel rail and injectors to remove plenum.

Yes the Lower intake manifold gasket was replaced when she bought the car about year and a half ago because of coolant leak. She has driven the car since this gasket was replaced without any problem with oil pressure until this work was done.

I believe that damaged injectors allowed excessive gas to wash clyinder walls and mix with the oil causing it to thin out and break down thus greatly reducing the oils abiltity to reduce the metal to metal friction that is its purpose.

My question is: How can a person determine if the bearings failed because of gas in the oil or coolant in the oil??

Thanks for advice.

[BNaylor]

To answer your question the best way is to get a sufficient sample of the engine oil and send it off to an oil analysis lab.

Do the latest mechanics know the LIM gaskets were replaced? Depending on long she drove it before the coolant in the oil was detected it is quite possible to have the bearing damage occur back then. First thing the coolant does is affect the camshaft bearings and then the connecting rod and crankshaft bearings. Plus residual amounts of coolant and water may remain until the engine crankcase is properly flushed out.

On removing the fuel injector rails really not that much to it. With fuel injectors left intact on the rail you pull up on the rail and it just pops off with no fuel spillage. Even if the top fuel injector o-ring seals were bad and fuel leaked out the fuel seepage or intrusion back into the lower intake manifold injector port would be very minimal or none at all. See pic below.

The situation doesn't sound good and proving the latest UIM work caused the problem will be hard to prove.

[Hapynzap]

Wow I am sorry to hear about your sister's car. This sounds like the classic mechanic seeing a woman coming and running up the bill. She may have had better luck at a dealer service center.

Is there any water in the oil now? The new Upper Intake Manifold may have been installed improperly.

[tempfixit]

Thanks guys for input. Just talked to her by phone and she has not been needing to add coolant at all. The mechanic that did the New Upper Intake Plenum installation is the same one that did the Lower Intake work before. She checked the records and found that she has driven the car for 31,000 miles since the Lower Intake work was done, so it makes me believe that the coolant issue was not the culpurt for the bearing failure. Like you state BNaylor it is going to be hard to prove anything, so I quess she will have to bite the bullet and install used engine and hope for the best.

Thanks again for all input.

[Jrs3800]

First things first...

How long was the car driven with a Miss? If it was driven a while with a miss the PCM will see the extra added oxygen in the exhaust stream and its correction is to add more fuel to the mix.. In some cases this can be a really bad thing..

How many miles did the car have on it? Was the upper intake replaced due to an upper intake failure?

Generally these engine are pretty rock solid, the flaw of these engines is in the lower intake gaskets and the upper intake design..

My 2nd 3800 II suffered an intake failure..... Later down the road, it spun the #4 rod bearing... When i tore the engine apart I found the rod bearings to be pitted to different degrees...

I can't say that this is the Mechanics fault, nor can I say that it isn't.. But I will say if I have to work on a 3800 II that has had an Intake or lower intake gasket failure the first words out of my mouth will be " I can't promise nor gaurantee the engine or work I perform on this engine as it may fail down the road due to the recent failure... "

Its a sad thing, But I have no trust at all in a 3800 that has ruptured an upper intake or the lower gaskets.. I have seen a battery of these engines fail after a gasket or upper intake failure...

Best of Luck on the motor you use as the replacement, and best of luck to your sister..

[BNaylor]

Originally Posted by tempfixit

Thanks guys for input. Just talked to her by phone and she has not been needing to add coolant at all. The mechanic that did the New Upper Intake Plenum installation is the same one that did the Lower Intake work before. She checked the records and found that she has driven the car for 31,000 miles since the Lower Intake work was done, so it makes me believe that the coolant issue was not the culpurt for the bearing failure. Like you state BNaylor it is going to be hard to prove anything, so I quess she will have to bite the bullet and install used engine and hope for the best.

Thanks again for all input.

The question I have which may or not help as to the veracity of the mechanic is why the UIM was replaced for the broken plastic MAP sensor bracket. Was the UIM part damaged or was it just the bracket?

The other issue or question is what brand LIM gaskets were used when they were replaced. Did the mechanic use the old style plastic framed or the new GM aluminum framed or an aftermarket brand. I'm not a fan of any GM/Delco OE gaskets and use the Felpro brand only.

Based on the P0108 DTC I would not be surprised to see the LIM gaskets bad again. In other words a second failure. That DTC can set when the front bank LIM port gasket goes bad at cylinder #1. The coolant and/or high heat from the pressurized cooling system comes right up the crankcase ventilation port from the LIM via the UIM and damages the MAP sensor. I worked on one not too long ago with a very similar issue.

[tempfixit]

Originally Posted by BNaylor

The question I have which may or not help as to the veracity of the mechanic is why the UIM was replaced for the broken plastic MAP sensor bracket. Was the UIM part damaged or was it just the bracket?

The other issue or question is what brand LIM gaskets were used when they were replaced. Did the mechanic use the old style plastic framed or the new GM aluminum framed or an aftermarket brand. I'm not a fan of any GM/Delco OE gaskets and use the Felpro brand only.

Based on the P0108 DTC I would not be surprised to see the LIM gaskets bad again. In other words a second failure. That DTC can set when the front bank LIM port gasket goes bad at cylinder #1. The coolant and/or high heat from the pressurized cooling system comes right up the crankcase ventilation port from the LIM via the UIM and damages the MAP sensor. I worked on one not too long ago with a very similar issue.

To my knowledge the UIM part was damaged but I have not seen it or a picture of it.

I do not know which LIM gasket was used but I am assuming it was a aftermarket set.

I asked about any coolant leak occuring but she said she did not have to add any coolant since the repair.

The car was driven maybe 150 miles with a miss, then the coil was changed ran fine for couple of days and starting missing again for couple days until plug wires were replaced.

The New UIM was from Napa.

Do you know the part number for the FELPRO LIM gasket?? She is going to have them replace the LIM and install the New UIM before installing the used engine. Any other things that should be checked before installing used engine?

Thanks for all input and advice

PS: She is going to have the mechanic at the construction company look at the bearings on the bad engine to see what caused the bearing failure. I may also suggest removing LIM to see if the gasket had again failed.

[BNaylor]

Originally Posted by tempfixit

Do you know the part number for the FELPRO LIM gasket?? She is going to have them replace the LIM and install the New UIM before installing the used engine. Any other things that should be checked before installing used engine?

You're welcome and good luck!

Latest FelPro LIM Gasket Kit for SII 3800 Engine. Part number MS95809-1.





This how it will look with the port and end seal gaskets properly installed using the FelPro brand as an example. Along with the bead of hi-temp RTV silicone sealant at the 4 corners where the port gaskets and end seal gaskets meet. These end seals are the pinned which is the most common.

[upacreek]

HI,
I am the sister with the 96 Buick problems. First of all I do appreciate all of the input. My question now is, will driving the car with the broken plentum so that the map sensor was not secure hurt the car or any sensors?