Quick question

Thanks Rick. I do have a pressure gauge in the house so I'll get that little thing out to use. I can put that in easy view no problem so I can see it and the scanner at the same time.

Now, I was frantically watching about 7 things at once on my scanner before so I didn't pay attention to specific things, if you will, now i will narrow it down. Thanks for helping me organize myself - I have a lot going on besides the car so I'm trying to remember everything .

I should be able to get to more investigating tomorrow after work, when the car is nice and warmed up again. I'll report back then.

I just read through the thread, and didn't see if you've ruled out the plugs, wires, and coil packs by replacement or testing. It doesn't sound like it would cause a current drain, but failing ignition components have been known to cause some odd problems.

Yes AA, you're right. I haven't ruled those out yet BUT...as of August, the plugs and wires are brand new. That doesn't mean they're not bad though, of course. I'll throw on my other set of coils just in case sometime.

I scanned the car all the way to work and back today and my idling problem never showed up, even when I tried to coax it into happening, but I DID notice that about half the time while I was idling my battery volts would from from 14.8 down to 13.2. Not all the time, but I did notice it. I'll be scanning again tomorrow to work and back...

While idling my battery voltage will fluctuate from a low of 13.4 to 14.1 max.
Actually even while cruising I never get above 14.2 volts.

Hmmmm ok. Noted.

Doesn't look like I can get much farther with this until I observe more closely what's happening on the scanner while my car goes insane. It just stinks that it's unpredictable.

Is your scanner able to log data to analyze later on? If so, you can upload your scan and we can take a look.

Yes but I don't know if it'll do it for the '95. Not MY scanner, I mean. I'll read up on it. I know you can record like 30 seconds of data for OBDII but I might only be able to do a snapshot for the OBD1.5.

EDIT: Looks like I can only snapshot on this model. No timed recording. I may just take a video of the scanner screen when the problem happens next, just to make things easier on anyone who're helping me with this problem.

Well, I never have a camera to take a video of the scanner while the car is running, BUT, I tried REALLY hard this timeto find a correlation between the battery power and when my idle drops, and it seems they're doing it at the same time. Not one before the other like I mentioned previously. I've caught it doing this twice. The idle will drop and while that's happening the battery power drops to 12 or 11.8 sometimes. At this time, it does NOT appear my fuel trims are affected at all when my idle goes all wonky.

Just as a refresher, this only happens below 35 MPH or at idle, and when I'm coasting, letting go of the gas real fast, or sometimes just sitting there.

I would guess that the alternator stops working at the very low RPMs, which is why they dip together. I know that's a setting on the later PCMs.

Do you think the IAC is the cause of the rapid idle drop in the first place.?
I'm assuming your not getting any codes or an SES light, unless I missed something.

The IAC is opertaing correctly according to my scanner, even when my idle is messing around. SOMETIMES this activity triggers my Fuel Trim Sensor Lean code, but not always. That's the only code I've been getting for months.

Due to my work schedule, I have yet to check my fuel pressure and IAC cleanliness. SHOULD be able to tomorrow.

Check the operation and cleanliness of EGR pintle also. If you haven't already.
Although my experience with bad / sticking EGR's would be when coming down from highway speed on an off ramp, for instance, and as your slowing to stop or merge the SES light comes on and engine starts to run like crap and / or stall.
But dirty and sticky EGR's can provide different symptoms than what I just mentioned.
On a Blazer I had, I would have to remove the EGR at least once per year to clean it and clear the code. Haven't had that problem with the Riv yet but they have the same type EGR's.

I did clean the EGR recently,gave it a new gasket, and the valve was loose for sure. And according to the scanner, it opens and closes with the throttle or speed or however it operates. Either way, it's consistent according to the scanner. Would the PCM say it's working right even if the valve itself is sticking?

I still wonder if this doesnt have something to do with the alternator. I have another thread where I'm discussing a grinding noise that I've narrowed down to the alternator or it's tensioner pulley. Someone mentioned the alternator regulator going bad as well as the bearings.

I suppose if the alternator bearings were real bad, the alternator could put enough of a drag on the engine.
But I would think it would have to be real bad, very noisy and cause possible belt slippage before resistance from a bad alternator would do what your experiencing.
But if the voltage regulator is going bad, or is bad, you won't have all the noise and resistance to rotation, just a drop in voltage or fluctuations in voltage.

I checked my alternator output voltage, seems good. 14.8 at idle. But I found another problem - bad water pump. The pulley is wobbling so bad it's not funny. I wonder what I'm doing this weekend . While I was messing with somethings, my scanner was showing 159 on my LTFT under warm idle in Park. Seems a little strange that the engine would have to add so much fuel for just idling. Does that make sense? I don't know too much about the computer aspect ofcars yet - not as much as i want to anyway.

I know I haven't posted here in a while, but I also haven't been able to do much with the car lately except drive it. You all know how things come up relentlessly...

Anyway, just because I had the time to screw around, on my way to and from work today I had the scanner running on the car. I was watching mainly my fuel trim. Yesterday my Lean code came back and lit up the engine light like it occasionally does, but i didn't have my scanner handy. This morning, I turned the car on and the light was still on, and my LTFT fuel trim was 'pegged' all the way lean, at 159. It was like that for about 3 miles then my fuel trim dropped back to normal at 128-130 and the light went off. It then behaved normally until I got back home this afternoon. I parked in the driveway and just let the car idle and watched t fuel trim carefully. Sure enough, my idle started going haywire all on its own.

Here's what I observed: My RPMs would rise like they always do (up and down and up and down) and AFTER the RPMs rose and fell, the fuel trim would become lean and back to normal, lean and back to normal again. That makes perfect sense...the idle goes up, car needs more fuel. Ok, so what i concluded in my own mind was that this is JUST an idle problem, and not a fuel problem. Make sense?

My mechanic is insisting on a vacuum leak still at this point, but I have no money right now to pay him to go over the car with a fine-tooth comb at the moment, so I'm still doing what I can on my own. As you may or may not remember back in the pasts posts in this thread, the only vacuum leak I found was the EGR valve gasket, which has been replaced. Doesn't mean it's not something else, but I'll have to take the time to go over the engine my self sometime, and time I don't typically have when it's convenient to check the car out.

So, in the meantime, if anyone has any new suggestions at this point, I'm all ears! I guess i should mention my EGR and IAC appear to be operating normally too. If anyone needs to know anything else just ask. I'm going to be scanning the next few days on the way to and from work anyway.

Thanks everyone!

You've got to be looking at a vacuum leak, EGR or MAF sensor issue, IMO. The only way to find out for sure is to have someone with a good scanner and tailpipe probe monitor the entire car for a while. I wish I had more knowledge of your scanner and scanning the S1 engines, I would be more help.

Have you put a vacuum gauge on the car?

Agree, it still smells like a vacuum leak to me.

Quote :

Here's what I observed: My RPMs would rise like they always do (up and down and up and down) and AFTER the RPMs rose and fell, the fuel trim would become lean and back to normal, lean and back to normal again. That makes perfect sense...the idle goes up, car needs more fuel. Ok, so what i concluded in my own mind was that this is JUST an idle problem, and not a fuel problem. Make sense?

I wouldn't come to that conclusion, because fueling is not based on RPMs, it's based on engine load and air intake. There are times when the engine uses more fuel at 2kRPM (in boost) than it does at 3k RPM, depending on the situation, gear, etc.

I suspect the changing RPM and LTFT values could both be symptoms of the same problem, whatever it is, but I would not think one is directly related to the other.

Although it seems this problem can wait, I wouldn't drive the car in this condition for very long. There's probably some knocking happening in the engine at this point. Running on a lean condition with a supercharger is even worse than running 87 octane, imo.

what happened to the old fashioned vacum leak testers? you know the hand held ones that you plug into a vac line with gauge,and then pump ,and watch the gauge for loss of vacum?? do those types work on our car?

I do have a vac/boost gauge on the car, and it read too low of vacuum (15-17 in gear at operating temp). i fixed the EGR vacuum leak and it went up to 19 in the same situation. For whatever reason, now it's gotten lower so something is leaking, unless my actual gauge connections are bad now. However, months ago, I detached the gauge so I could eliminate it as a problem and my problem still came up, so the gauge is good and not the cause of the leak.

I guess you're right...it'll have to go to a pro soon.

As far as driving it lean, this is a VERY intermittent problem and only comes up every couple weeks for a few miles. I'll just have to get some cash saved up for my mechanic to look at it correctly. He's very experienced and found the solution to an electrical problem in my sister's Reatta that no one else had a clue about. Anyway, I do also agree it's a vacuum leak now, all things considered, included what you all just told me.

Actually I forgot to mention that as my RPMs go up when my idle goes nuts, my vacuum actually increases (goes from like 16 to 20, for example) while my RPMs rise too. Like this - RPM rise, vacuum increase, RPM drop, vacuum decrease. Hope that means something. I know it's SUPPOSED to do that, seeing as the throttle body isn't openining any, but if the problem IS a vacuum leak, would the vacuum gauge really respond so well or in that way?

You've probably already mentioned it somewhere, but where is your vacuum gauge hooked up to on the engine.
The fact that your vacuum is increasing right along with your rising idle RPM is curious. Have you hooked a separate vacuum gauge to your MAP sensor and see how that is reacting during these events. This can be a very helpful measurement.
Have you had the time to spray some solvents, such as MAF cleaner or something similar at all the usual points to see if you get an RPM change anywhere, possibly indicating the source of a leak.
Never mind about about the MAP Sensor as it seems the 95 does not have one.

I have the gauge hooked up to the fuel pressure regulator vacuum line. Like i said, I reinstalled the original line and took out the gauge line to eliminate that as a possible failure point a month or two ago. At the same time, as you mentioned, I sprayed throttle body cleaner in every gap I could think that could contain vacuum. The only one I found was the EGR valve gasket, and i fixed that.

I didn't know the '95's had a MAP sensor...I thought that was just the Series II engine. Do you know where it's located? I do, however, remember seeing on my scanner a diagnostic for "MAP 'something'..."

Let me try and look it up for you.
In the mean time, maybe someone with a 95 can explain.
I'll look at a couple of other sources i have for Tech Data on previous year Riv's.

What is the actual code you were getting (Lean Code)??

I'm still looking for the actual picture and location of your MAP (Manifold Absolute Pressure) sensor.

If someone with a 95 could help out, please.!!!!

I'm still looking.

There is no MAP sensor on the series one.

It might be something to try, but try removing your vacuum gauge, I'm not sure how you installed yours, but often the plastic tube that comes with the units is not the greatest. I had a strange vacuum leak that was also doing odd things to the fueling(the boost/vac gauge hooks right in with the FPR vac line). The crap plastic tube had a slight split in it, and when under boost it would open, then back to vac it would be a large vac leak for a few seconds until it sucked itself closed.

Not sure it its at all related, but its something to rule out.

and FYI, my engine runs vac of around -25 in-hg