Question on 1999 Riviera Engine issue

Well I have recently bought a 1999 Riviera. I also have a 1997 Riv too.
I've had this 99 for about 6 weeks now, and gone thru it quite a bit.
Replaced spark plugs
Replaced the wires
Replaced the fuel filter twice
Replaced the Fuel Injection Pressure Regulator
Engine Camshaft Position Sensor
Crankshaft Position Sensor
Replaced the fuel pump twice, on 2nd new pump.

Now for the issue I am having....
Runs fine, starts right up.
Mileage is 83,858
I am the 2nd owner of this car.
The problem I am having is everytime I floor the gas pedal , or even only floor it 3/4 of the way down, just enough to engage it into passing gear.
It takes right off like a jet....BUT soon as I take my foot off the gas pedal, the engine shuts down and I coast to a stop. It starts right back up fine.
The engine only shuts down if floored and put into passing mode. If I don't floor it, the engine does not shut down. My mechanic has been trying to figure out this problem for the last 4 weeks now. No engine code errors show up at all. No errors can be found anywhere. He has no idea what it is right now.

Thought I would ask you folks if you've ever seen a issue like this before in your Riviera's ????  
Thanks guys, Mike.....

Mike9874 wrote:

Well I have recently bought a 1999 Riviera. I also have a 1997 Riv too.
I've had this 99 for about 6 weeks now, and gone thru it quite a bit.
Replaced spark plugs
Replaced the wires
Replaced the fuel filter twice
Replaced the Fuel Injection Pressure Regulator
Engine Camshaft Position Sensor
Crankshaft Position Sensor
Replaced the fuel pump twice, on 2nd new pump.

Now for the issue I am having....
Runs fine, starts right up.
Mileage is 83,858
I am the 2nd owner of this car.
The problem I am having is everytime I floor the gas pedal , or even only floor it 3/4 of the way down, just enough to engage it into passing gear.
It takes right off like a jet....BUT soon as I take my foot off the gas pedal, the engine shuts down and I coast to a stop. It starts right back up fine.
The engine only shuts down if floored and put into passing mode. If I don't floor it, the engine does not shut down. My mechanic has been trying to figure out this problem for the last 4 weeks now. No engine code errors show up at all. No errors can be found anywhere. He has no idea what it is right now.

Thought I would ask you folks if you've ever seen a issue like this before in your Riviera's ????  
Thanks guys, Mike.....

Have not seen this one before BUT it sounds like what could happen with wiring problems.  I would check the wiring that would flex if you floored the engine for breaks in the conductor inside the insulation, along with the connectors attached thereto.  My hunch (could be BS) is that as soon as you take your foot off the gas, the engine rocks in its cradle and moves the wiring.  Maybe just a loose connector?  Not sure.   I would think to especially check the wiring at the ignition module and the large connector at the firewall. I would *also* check all the wiring that you/your mechanic disturbed in component replacements (fuel pump, crank/cam sensors, etc.) -- wiggle while running (stay the h-ll away from moving/rotating parts) and see what changes.

...and if it ends up being a broken wire, repair your motor/transmission mounts. The engine should not move all that much; if it does the mounts are wack.

Albertj

Well, since it stalls ONLY when you take your foot off the gas, I would first check the throttle position sensor. If you have a good scan tool, you can watch the voltage as you go from closed to open throttle. It should increase and decrease uniformly in both directions. Secondly, I would look at the fuel trims to see if it is running rich (large negative numbers ). If so, I'd clean or replace the MAF.

Possibly relevant if it's a broken wire - Link

Should be looking for problems here either way.

Thanks guys for all your input, I'll be checking for bad wires and connectors soon.

Well I had a diagnostic tests done at local garage, and the mechanic spent 3 hours testing everything under the sun. Came out with the issue being the Mass Air Flow sensor plus 2 broken motor / transmission mounts.
Got the parts coming Monday, I'll put the MAF sensor in soon as I get it. Then run it for a road test, my mechanic will put in the mounts later this coming week. Had no bad wires or connectors.
Bought a throttle position sensor also. Got that part now. But does not seem to be defective.

Front and rear mounts are broken.

Post a picture when you're up and running and glad to see you're on the right track. I just bought all of my transmission mounts on RockAuto and it made a huge difference.

carguy8888 wrote:

Post a picture when you're up and running and glad to see you're on the right track. I just bought all of my transmission mounts on RockAuto and it made a huge difference.

I've been buying all my parts from Rockauto for years now. I have Two Riviera's  a 1997 and the 1999. Soon as I get everything done on my 99, I'll put the 97 up for sale.  Got a couple of recent pic's....not the greatest quality  LoL

Very nice, I get the picture LOL.

I've got a lot more parts to update and install on this 99 Riv. Too long a list right now to brother writing about. But when I'm done should be running really fine. I've had my 97 for about 9 years now. Always wanted a 99 model, but could not find one close enough to my area with low mileage, that I liked.
This 99 needs the proper maintenance done which has not been done for a long time it seems. I've got lots of time to get everything done. No hurry.

Mike9874 wrote:

Well I had a diagnostic tests done at local garage, and the mechanic spent 3 hours testing everything under the sun. Came out with the issue being the Mass Air Flow sensor plus 2 broken motor / transmission mounts.
Got the parts coming Monday, I'll put the MAF sensor in soon as I get it. Then run it for a road test, my mechanic will put in the mounts later this coming week. Had no bad wires or connectors.
Bought a throttle position sensor also. Got that part now. But does not seem to be defective.

Front and rear mounts are broken.  

On these 3800 engines, this vintage, I've heard of aftermarket/replacement throttle position sensors dying, but not the OE ones.

My MAF finally quit around 360K miles/22 years of use - it did not fail outright, just gave bad readings. I had to use a scan tool and look at driving logs to figure out what the heck was wrong.

Motor mounts OTOH don't last all that long on this car. They last longer if you don't mash the loud pedal too hard from a dead stop. I've wondered for some time if the 2000 and later mounts for the Lucerne could be fitted.

I've got another question, for any of you guys that might know.
I bought a spare gas tank for this 99 Riv. One in it now was pretty rusted out around the top ring.
The Retainer Ring had to be screwed into top of the tank, because the clips that hold down the Retainer Ring were rusted off.

So I bought a used tank off a 2000 Buick Lesabre , 18.5 gallons. Suppose to be an exact fit for this 99 Riv. The only thing that seems to be a little different is the vents on top. The Riv only has 2 top vents.
This tank has 3 top vents. Would this make any difference, I wouldn't think it would, but I see most of the other tanks only have 2 top vents.

I can't imagine why that would make any real difference, but I also would probably ask one or another of the older gearhead mechanics at the dealership about that.

Albertj

Update on my 99 Riv stalling issue.
I put a new Mass Air flow Sensor on, and then gave it a test drive, I could not make it stall out anymore. Also had better acceleration too. So that was definitely one of my problems. Engine seemed to run a lot better.
Now for the bad part...LoL

I had also bought a Throttle Position Sensor about 2 weeks ago from rockauto, never put it on thou.
Even thou after installing the MFT sensor, I thought putting on the brand new TPS would be a good idea. One on there was 21 years old. Soooo I installed the new TPS, then took the 99 Riv out for another test drive. It ran very badly, stalled out 3 times under fast acceleration, engine sputtered going up hills, etc...
So I took off the New TPS sensor, and put the old one back on, ran a little better, but still was not running well. I am guessing that when installing a TPS sensor, their is a correct way to install it or maybe something has to be reset ???
I tried disconnecting the negative battery post for 5 mins. This seemed to help more too.
You guys got any ideas what I did wrong installing the new TPS sensor? I still got the older one on and afraid I messed something up.
Both these two sensors also use the 5 star security type screws too. The MAF & TPS

Almost forgot, I got a appointment later today with my mechanic to replace my two broken motor mounts. front and rear ones.

There is some adjustment to it. It runs on a 0-5 volt signal. At idle/closed throttle, it should be something like .4-.6 volts. At WOT, it should be above 4 volts. You can monitor the signal with a good scan tool, or by probing the connector with a meter. There are 3 wires, ground, 5 volt reference signal, and sensor value.

LARRY70GS wrote:

There is some adjustment to it.  It runs on a 0-5 volt signal.  At idle/closed throttle, it should be something like .4-.6 volts.  At WOT, it should be above 4 volts.  You can monitor the signal with a good scan tool, or by probing the connector with a meter.  There are 3 wires, ground, 5 volt reference signal, and sensor value.

The other thing about the TPS is it has to be installed such that the pawl in the sensor engages properly with the lever in the throttle body.  Or else it gives BS readings. I am not sure how you install that thing properly with the TB on the car, but I assume it can be done. I've only removed/installed them with the TB off, and it's easy to engage the lever with the pawl that way. You can fit the sensor and twist it into place, or hold the throttle partway open and put the sensor on the TB and put the screws in finger tight, then let the throttle arm go and tighten the mounting screws.

BTW on other sites I have read posts from people that have replaced the TB sensor, in general they say that you really need to get a Hitachi TB sensor if you are replacing it because the cheapest replacements do not last long at all. When  I replaced mine I shopped around for a genuine Hitachi and managed to find one being sold as surplus.  Works fine. I only replaced mine because I was completely overhauling a junkyard TB - I am overhauling my original one now and have no plan to replace the TPS.

Just took a look at my 98 FSM. They have connector end views, so I looked at the TPS. It is a 3 wire connector. looking at the open end of the connector, retaining clip up, the wires are labelled left to right, C-B-A, C being a Grey wire (Reference Voltage Feed 5 volts), B being a Dark Blue wire (Throttle Position Sensor Signal), and A being a Black Wire (Sensor Return). If you turn the ignition on, engine not running, you should be able to back probe the connector to see the sensor value with the throttle closed, then slowly open the throttle to wide open and watch the voltage increase uniformly. Should be something like .60 volts to 4.5 volts.

Just a quick update on the old TPS sensor. Its running A LOT better now. Really didn't do much besides pulling the neg battery post off to try and reset everything. The new one I bought is made by ACDelco so its a oem factory part. 99% of the engine parts I've bought are ACDelco .

As far as buying a Hitachi TB sensor for my 1999 Buick ....don't think I will or EVER buy a Hitachi part. I suppose I could change my mind....maybe.

Its running a lot better now, even with the old TPS installed. Have one tiny issue, when going up a hill, say doing 35 or 40mph, the engine might stutter just a little, giving it more gas at that time, will smooth the engine out. This does not happen very often, and I can't make it do it.
Thinking about putting a new EGR on, also maybe replacing the OS2 sensor. Overall thou its running pretty well. Eventually I will get it running even better. :-)

I've done a little more research on these "Genuine Hitachi TPS" sensors ....what a joke. These are the cheapest sensors you can buy, they go for 25 to 28 bucks on Ebay, brand new. Any other brand costs more. I would recommend ACDelco myself, or any other brand that rockauto sells. They do NOT carry the Hitachi brand.

I hate to break this to you , but there are sensors that came stock made by hitachi.  Namely the MAF.  I replaced mine a few years back.  I'm certain that it was the original one on the car.  The markings and numbers on it matched the Hitachi one I bought exactly.  So the OEM MAF on my car was a Hitachi. I was told by a mechanic I trust, to either buy the AC Delco, or the Hitachi, no other manufacturer.

LARRY70GS wrote:

I hate to break this to you , but there are sensors that came stock made by hitachi.  Namely the MAF.  I replaced mine a few years back.  I'm certain that it was the original one on the car.  The markings and numbers on it matched the Hitachi one I bought exactly.  So the OEM MAF on my car was a Hitachi.  I was told by a mechanic I trust, to either buy the AC Delco, or the Hitachi, no other manufacturer.

Ok I understand that Larry.
I bought the ACDelco one for my MAF , the Hitachi one listed on Rockauto was the cheapest sensor for a MAF, also has only a 1 year warranty.
The ACDelco one cost a lot more, but comes with a Two Year Warranty.  

Now that being said, most all if not all of the ACDelco parts are made in China.

For the TPS sensor, I bought was also ACDelco part, again made in China. There is no Hitachi one listed on Rockauto. On Ebay its 26 bucks. Cheapest part you can buy for a TPS .....

When I have a choice on which brand I want to buy for my 1999 Riviera, 99% of the time I will choose ACDelco.  They useally have the longest warranty, BUT not always. I buy most of my parts from Rockauto.  

My point is, that Hitachi parts seem to be the cheapest part you can buy for your Riviera Larry, and the shortest warranty offered.

I went on the advice of a mechanic about the MAF.  Normally I would buy the AC Delco, but he told me the Hitachi was just as good.  And As you said, cheaper.  Didn't look at the warranty.  When I unboxed the Hitachi, it was exactly the same part, same markings, exactly.  My conclusion, Hitachi made the part for GM.  Still good after 2 years, so I guess I am ahead of the game.

The AC Delco parts are usually the most expensive, but not always. Years ago, I bought some AC 41-101 Iridium plugs for the Riv. When I unboxed them, it had an AC part number on them, and also, the NGK part number (ITR4A15) and NGK stamped into the metal shell. The AC's were actually 2.00/plug cheaper.

LARRY70GS wrote:

I went on the advice of a mechanic about the MAF.  Normally I would buy the AC Delco, but he told me the Hitachi was just as good.  And As you said, cheaper.  Didn't look at the warranty.  When I unboxed the Hitachi, it was exactly the same part, same markings, exactly.  My conclusion, Hitachi made the part for GM.  Still good after 2 years, so I guess I am ahead of the game.

Yes, if after two years its working fine, then your all set. Most likely last a lot longer too.

In my case I replaced my own MAF myself, took me 5 mins to remove and install new one. Very easy job. Made my 99 Riv run a lot better Larry, This one part has made the biggest difference in performance so far. Still got a tiny little bug left.

On my 1997 Riv, all the sensors are original ...I've never replaced any of them, dam car runs great too.
Got over 209,000 miles on it now.