Troubleshooting rough idle 95 PAU

My 95 PA ultra has a rough idle with small but present stumbles randomly.

New:
fuel filter
air filter
spark plug (autolite plat)
plug wires
oil/sc oil
rotated a new coil through without any change

The only thing I can think of now is a vacuum leak, but would that cause a random stumble? Either way, I've done a visual check of everything multiple times and there is nothing obvious. Any places on the L67 that are prone to vacuum leaks, or anything else that could cause my condition?

Have you checked for codes?

Isn't currently throwing any codes. It did once for just a second or two a month or so back when it got bad for no apparent reason. Will the codes be stored in memory? I have a friend that can read them if so.


Also, I'll note that I checked all the plugs and connections last night and all of them looked good, light brown in color.

Some code are stored but most are erasted after a key cycle clean your idle air control that could be the source of rough idle or a miss fire bad plugs or wires there are some ideas

No the codes are not erased after a key cycle... The SES light may go out but the codes are stored in the computers memory... You can actually have Current codes and History Codes with the 94-95 PCM's in these cars...

Currently having the same issue mine is throwing a P0341&42 code, loss cam signal/ cam failure doesn't alway throw a code when it first starts to display symptoms like random missing. Mine threw a code about two months ago and has been getting progressivily worser. But doesn't usually set a code until the engine is warmed up most of the time. The warmer the weather gets the faster it starts to seem to miss. And it always goes away when you restart again until it goes threw another phase of acting up.

I'm now leaning toward a bad Crankshaft Position Sensor. Since I did see the RPM gauge flucuate up and down the other day and the car seemed like it wanted to stall.

BTW how many miles on your PA becuase some things commonly happen around a certian mileage range on 3800's from what I have observed.

140,400 as of yesterday. Cleaned up the MAF but can't get the IAC off without removing the TB and TB gaskets are on backorder, so that will have to wait. I'm going to get the code read and I'm sure that should help with diagnostics, I'll post up again when I have the codes.

It was only bad once a few months ago when it set the code off, since then it has just been very very minor stumbling and rough when idling, and the occasional jump of 100ish RPMs down.

Dang, there was a laundry list in the History. I've never had the codes cleared though, so who knows how far back this goes. I had a traction control issue when I bought the car that I resolved, and when replacing the BPMV, I left the IAT out for an engine cycle or two, but I don't remember it throwing a code.

P0113 IAT Sensor High
P0118 ECT Sensor High
P0132 H02S High Volt
P0341 Camshaft Crank Error
P0502 Vehicle Speed Sensor No Sig
P1571 Traction PW M Link

And these were found too, though I don't remember exactly where, not in the history but not current, don't ask.

P1573 (didn't write down description) google says: "pcm ebtcm data error"
P1650 QDM 2 Error

I can't draw any conclusions from this. Anyone?

The ones starting with 1 would be the history codes. I think they remain in memory as long as they are not cleared and the battery isn't disconnected.

Which if any would be causing my symptoms?

Ziggy, so you're saying
P0341 Camshaft Crank Error
P0502 Vehicle Speed Sensor No Sig
aren't history, but the rest are?

Or just these are history:

P1571 Traction PW M Link
P1573 (didn't write down description) google says: "pcm ebtcm data error"
P1650 QDM 2 Error

P1571 Traction PW M Link
P1573 (didn't write down description) google says: "pcm ebtcm data error"
P1650 QDM 2 Error

These would be your history codes.

Ok. So what do they mean? Every once in a great while (actually, only right after the codes are read for something, first ignition cycle) the traction off light will come on. So What would the other point to? What is ebtcm and qdm 2?

That's pretty much as much as I know about these codes. My book doesn't even list 0571 and 0573, 0650 is listed as "mailfunction indicator lamp, control circuit malfunction"
I guess your current codes are caused by aforementioned sensors which give odd readings once in a while. Which in turn could cause the stumbling.
Maybe someone with more experience with this will chime in.

Currently having the same issue mine is throwing a P0341&42 code, loss cam signal/ cam failure doesn't alway throw a code when it first starts to display symptoms like random missing. Mine threw a code about two months ago and has been getting progressivily worser. But doesn't usually set a code until the engine is warmed up most of the time. The warmer the weather gets the faster it starts to seem to miss. And it always goes away when you restart again until it goes threw another phase of acting up.

I'm now leaning toward a bad Crankshaft Position Sensor. Since I did see the RPM gauge flucuate up and down the other day and the car seemed like it wanted to stall.

BTW how many miles on your PA becuase some things commonly happen around a certian mileage range on 3800's from what I have observed.

This is sounding more and more likely. My car acted up today, it was fluctuating rapidly and wanted to stall, missing really bad, but not consistently. Read the codes again today, and this is what popped up:

P1361 Ignition Control Toggle Error
P1650 QDM 2 Error

And in the real time monitoring datastream Cam/Crank Error showed as "1". The code description seemed to point toward crank position sensor, though it never actually said it.

QDM was longer ago in history, and I don't know what it means, but if it has anything to do with the traction control light, I think it might be unrelated. Like I said, after clearing the codes, the traction off light came on for on engine cycle, but has been fine since.

Anyone have any deeper insight to these codes? Anyone know how difficult it is to change the crank sensor? I was able to see it, but it looks like it might be a pita to change.

the cam sensor is real easy its location is to the left of the water pump but the crank is not hard but it take some time remove pas tire ,remove splash sheild ,with impact remove harmonic balancer,you need a puller to pull harmonic balancer off ,remove plastic cover over sencor kind of take refrance on the position of sencor because there is a GM tool that is to be used to aligne the sencor but it can be done w/out by putting it on slightly lose then slide harmonic balancer on the aligne it to the balance the tighten it up . other idication of crank sencor going bad it when driving on the road the car like hicup the resume no trouble

It does "hiccup" occasionally, but I've only noticed at idle. Could this be the cam sensor as well? Worth changing first because it's easier?

P1361 could be your ICM! P1650 Driver 2-Input Hi Voltage. Quad drivers are mini relays in groups of four (hence the term Quad) that the PCM uses that ground a circuit, like the transmission shift solenoid A and B, Torque Converter Clutch (TCC) Pulse Width Modulated solenoid and Exhaust Gas Recirculation (EGR) solenoids. Monitor the voltage at each terminal for the components above while moving related harness connectors, including PCM harness. If the failure is induced, the voltage will change. This may help locate an intermittent condition. Check for bent pins at PCM and PCM connector terminals. If DTC reoccurs with no apparent connector problem, replace PCM. Remember, the PCM is protected by an internal circuit breaker. PCM replacement is not necessary if the problem is found in the control circuit, or the component.

Where are the PCMs located on these cars? It's pretty dark, but in a quick going over of the engine bay, I was unable to locate it.

The PCM is under the passenger side dash (behind the glove box) You have to remove the lower sound panel and glove box door to gain access. QDM faults can come & go, so like mentioned, erase DTC's to see if they come back & do your homework before replacing.

hmm.... There is a little plastic box that is behind the glove box and is unsecured. Sometimes it will fall behind the glove box and not allow the glove box to close until i take off the box and jam it back in a corner. It's happened twice, and my car has had misfire fits twice. I'll get a picture of the box, but do you think this could be related? I'm sure it's not the PCM, as it's somewhat small and light, but maybe I'm messing with wires or something when I push it back in. I couldn't find where it was supposed to secure to.

Here's what I'm talking about:

http://img713.imageshack.us/img713/1368/img1928da.jpg


Also, what is this? I was thinking security light, but there are two and I don't have a security light, then I thought auto headlights? But thought I saw a photo sensor on the driver side. :confused:
http://img254.imageshack.us/img254/1308/img1930fc.jpg

First pic is either the OLM module or climate control module it should sit vertical under the dash there is area for you to attach it to. Shouldn't cause drivability problems.

Second pic is the sunlight sensor for the automatic headlights and I think the climate control also functions with it.

Part #16192760 should be the TDM or (VATS) module.

I fiddled around in there a bit, didn't notice any lose connections or anything, and the car still runs the same. A buddy of mine talked to a GM mechanic about the problem and I guess he has some print outs for me that i'm going to look over.

HotZ28, you don't seem to think the Cam/Crank sensor is the problem, correct?

code not working with mine website
bellevue acupuncture (http://www.1stchoiceacupuncture.com/)

Well I guess acupuncture does not work on Park Avenues:cwm27:
So codes starting with P1 like P1361 and P1650 aren't history codes at all?:uhoh:

Part #16192760 should be the TDM or (VATS) module.

:sorry: looks like I was way off...

Well I guess acupuncture does not work on Park Avenues:cwm27:
So codes starting with P1 like P1361 and P1650 aren't history codes at all?:uhoh:

They are OBD II codes he has the transition year for OBD I to OBD II. "P" codes are Generic for all car manufacturers with OBD II.

BTW I changed my crank sensor last night. Made it harder than what it should have been. I made taking off the harmonic balancer a nightmare until I figured out that had the puller backwards.:loser:

I need to get a pry bar to hold the fly wheel in order to be able to tightned down the crank bolt all the way but it seems to be holding for now. Will update to let you know if it solved my problem.

I confused them with the AC codes, those with a '1' prefix are history codes :redface:

Good luck with the crank sensor !

I followed the instructions I had printed for me, and it's pointing to my PCM being bad. We'll see if the codes come back or if the roughness goes away; my guess is no.

The other sheet I had but was missing the last page so I couldn't finish the test was the 1350 and it said it was Trac related. I noted that when the codes are cleared the Trac light comes on for ONLY ONE ignition cycle and all systems work properly. I almost want to ignore the code because it does not seem to be related, but I don't know. Opinions?

Also, since I seem to need to replace my PCM, what cars can I steal PCMs from? I'm assuming I'll need an H-body with the L67 supercharged, correct? Year ranges?

1995 Buick Park Avenue Ultra

Also, since I seem to need to replace my PCM, what cars can I steal PCMs from? I'm assuming I'll need an H-body with the L67 supercharged, correct? Year ranges? #16183247 LeSabre '94-95 Elec Cont Module (ECM); (6-231, 3.8L)
Application:
1994-95 3.8 V6 SFI “L” L27
1995 3.8 V6 SFI “K” L36
1994-95 3.8 V6 SFI supercharged “1” L67
1994-95 truck 3.8 V6 SFI “L” L27

MEMCAL IDs:

“L”: BMYU, …
“1”: …
“K”: …
EPROM type: 27C512

Buicklesabre custom(1994 - 1995)
buicklesabre limited(1994 - 1995)
buickpark avenue(1994 - 1995)
buickpark avenue ultra(1994 - 1995)
buickriviera1995
chevroletlumina apv(1994 - 1995)
oldsmobile88 royale(1994 - 1995)
oldsmobile88 royale ls(1994 - 1995)
oldsmobile88 royale lss1995
oldsmobile98 regency1994
oldsmobile98 regency elite(1994 - 1995)
oldsmobilesilhouette(1994 - 1995)
pontiacbonneville se(1994 - 1995)
pontiacbonneville sse(1994 - 1995)
pontiactrans sport(1994 - 1995)

So you're saying the tune is the same for the supercharged L67 and the N/A L36? And is ECM and PCM the same? Just want to make sure, I expected to have to find one out of a supercharged car.

Edit:Hmm, this looks like it might be less painless than I was expecting. I did a quick check of eBay and found a new one. This appears to be correct.

http://cgi.ebay.com/ebaymotors/16183247-PCM-94-95-PARK-AVENUE-LESABRE-98-88_W0QQcmdZViewItemQQhashZitem3efd24f933QQitemZ270 535031091QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAcces sories#ht_901wt_958

I just find it hard to believe the L36 runs the same tune as the L67. Or is there something else controlling fuel trims and the like somewhere else?

The bone yard I got the BPMV from had several LeSabres and Bonnevilles and a 98 or two. I'm looking for R or S in the 10th of the vin, correct?

So you're saying the tune is the same for the supercharged L67 and the N/A L36? And is ECM and PCM the same? Just want to make sure, I expected to have to find one out of a supercharged car.

Edit:Hmm, this looks like it might be less painless than I was expecting. I did a quick check of eBay and found a new one. This appears to be correct.

http://cgi.ebay.com/ebaymotors/16183247-PCM-94-95-PARK-AVENUE-LESABRE-98-88_W0QQcmdZViewItemQQhashZitem3efd24f933QQitemZ270 535031091QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAcces sories#ht_901wt_958

I just find it hard to believe the L36 runs the same tune as the L67. Or is there something else controlling fuel trims and the like somewhere else?The PCM's are the same, but the operating parameters "tune" are in the Eprom which you will remove from the existing PCM & install in the replacement.

The Eprom then is the chip that fills the void shown in this picture?

http://info.rockauto.com/getimage/getimage.php?imagekey=321698&imageurl=http%3A//info.rockauto.com/SMP/EM3247_FULL.jpg

Yes. The eprom goes in there.

Thanks guys!

R and S in the 10th of the vin corresponds to 94 and 95, correct?

Schlotzky, have you been able to check the IAC valve yet?
Because I had to replace mine (94 PAU), it was the cause of a hard start / no start condition. Turns out the thing was full of soot!

Now the car starts right up as it should, plus the idle has improved significantly as well.

Finally got hold of a throttle body gasket, so I was going to take care of that sometime this week. I need to do the same for my Camaro.

Let's go back and review your first post.
My 95 PA ultra has a rough idle with small but present stumbles randomly.

New:
fuel filter
air filter
spark plug (autolite plat)
plug wires
oil/sc oil
rotated a new coil through without any change

The only thing I can think of now is a vacuum leak, but would that cause a random stumble? Either way, I've done a visual check of everything multiple times and there is nothing obvious. Any places on the L67 that are prone to vacuum leaks, or anything else that could cause my condition?Now, in our most recent post, we were simply responding to your questions concerning the PCM; however, not agreeing with that as being the source of your problem. So let's go back to the basics and clear all DTC's and see what (if any) come back. Once that is done, proceed with a fuel pressure test. (I see no mention of FP test anywhere in this thread). Post the results of both.

Next, you should proceed with what padriver mentioned, by checking the function (and cleaning) of the IAC. Once these steps have been completed & results posted, we can proceed to the next step. HotZ28, you don't seem to think the Cam/Crank sensor is the problem, correct?With "a rough idle & small but present stumbles randomly" anything is possible, that is why we take 'baby steps' diagnosing the problem!

Well I took off the throttle body to get access to the IAC and doing everything right including soaking the bolts in PB blaster, I stripped the heck out of one of the screws and was unable to remove the IAC. I cleaned it pretty well from inside the throttle body though, probably as good as it could get anyway, and there is no change in the idle. Who's idea was it to use aluminum phillips-head screws with thread-lock on something that gets really hot?

Anyway, I can replace it if need be, but there is no way I'm getting it out without destroying it, and I figured the 60 dollars could be better spent.

Fuel pressure test will be next, I will update when completed.

Thank you, you all have just told me what I need to do to fix my car. It hiccups, on occassion and the "crank shaft position" sensor is indicated by the code reader. My tachometer occassionally zeros out and does not work after a hiccup, until I shut the car off, then restart. Very infrequent, but if it is getting worse, then it needs fixed.
Sounds like too much work for me, I'll give it to a mechanic.

Hopefully I'll rent or otherwise complete the FP test this week, but I'd like to add some possible useful data.

The car today was "hiccuping" not just on idle. It would do so through the RPMs up into the 2500-3k range. Not consistently, but plenty noticeable stumbling. This lasted only about a minute, and things returned to normal.
The car also takes more time to start up sometimes. I will have to hold the key in start for up to a full 1-2 seconds. Usually it will start like the Camaro; almost with the flick of the wrist.

FP test to come asap.

Sorry; been really busy with finals.

I was reading 32-34PSI at idle, and when I stomped on the brake and went almost WOT in reverse, it was reading about 42PSI.

I kept the car running, and as I was leaving, it threw another P1361 (Ignition Ctrl Toggle Error) and the P1650 QDM 2 Error was there as well, but I backed out and went back into current codes and the QDM was gone.

If it helps at all, I'm getting about 16-17 mpg regardless of driving style and city/highway mix. I've had as much as 85% highway and got 17.3mpg. 100% city is about 16.4mpg.

Ok the fuel pressure is actually ok, A little low but not bad yet..... 32 at idle can happen under vacuum.. seeing it go right to 42 Psi when you blip the throttle is good as well..

The code 1361 is a dead ringer for a 94-95 3800 PCM failure... But before you try that, have the Ignition Control Module tested and make sure its not failing.. What is supposed to happen is the PCM is supposed to take over Timing control after 400 Rpms, with a code 1361 this is not happening and you are running in Module Mode Timing, this is a dead set 10* of advance iirc..

I'd say either bad ICM or Possible Bad PCM...

Any tips on how to test the ICM? And where exactly it is/what it looks like? Maybe be worth it to just replace it with a unit from a wrecker? Possibly with the PCM as well.. the place I go to seems to be dirt cheap when it comes to non-essential parts.

Advance Auto Parts or Autozone should be able to test it... Most of the time it will take a series of repeat tests to heat the module up to see if it hit a failure.... The test will sometimes say its good when its not always the case..

The ICM lives under the coils, remove the 3 coils and you'll see the ICM... You will have to remove the wire harness from it..

The PCM is a good failure point on these cars... If you can get an ICM and PCM cheap enough I would pick up both... Its good to have a spare of these 2 items especially when you get up in age and miles with these 3800's..

My money is still on the PCM tho.. Just remember I can't promise this, so I could be wrong........ But thats where my money is...

Ah, THAT ICM. lol. Yeah, all the cars at the yards I go to don't have engines. PCM should be easy enough to get a hold of, but I will see if I can get the icm tested.

I've got a 96 Camaro with the 3800 Series II. Do these cars use the same ICM? That'd be an easy free swap to check if so.

According to Rock Auto parts catalog, they two cars use the same ICM. I'll see if I can swap them out and report back.

The car is running similarly with the icm from my other car, but I'm going to keep it in for a while and see if the SES light comes on again. The PCM is the best place to jump next?

The car is running similarly with the icm from my other car, but I'm going to keep it in for a while and see if the SES light comes on again. The PCM is the best place to jump next?

Thats where I would be looking next..

Thanks for all the help. I'll follow up when I have some new info.

Changed out the pcm with one from a bonneville. When I took mine out, I was surprised to see that the car already had a GM Re-manufactured PCM. It hasn't thrown a code since the ICM swap, nor has it run super rough as it did when it threw codes, but it's still not idling smooth and while I haven't measured the gas mileage since the swaps, it seems to be similar based on mileage vs gas needle. (15-16 mixed)

The only thing I can think of for gas mileage that I haven't done is the o2 sensors, but I can't imagine that would cause the rough idle.