Recent Topics
Needing New Dipstick
by Geauxtiger
06/19/18 05:11 PM
'98 Mercedes E300TD Rotella T5 10W-30 5k miles
by KenO
06/19/18 04:35 PM
Premium guard oil filters
by Jaha24k
06/19/18 04:09 PM
76 super motor oil- synthetic blend 5w-30
by Jaha24k
06/19/18 04:07 PM
Who makes the Mopar 5038041AA filter?
by Quattro Pete
06/19/18 03:55 PM
Ruger Mini-14, yay or nay?
by 28oz
06/19/18 03:51 PM
USPS long long delivery to BlackStone Labs
by Pajero
06/19/18 02:58 PM
House A.c. vent leaking water
by motor_oil_madman
06/19/18 02:55 PM
"synthetic" gear oil and LS additive?
by nthach
06/19/18 01:54 PM
Supertech wix ST8 5514 miles
by jakewells
06/19/18 01:38 PM
Review - Sonax Spray and Seal.
by PimTac
06/19/18 01:36 PM
Lets Get a True Group 4 Sticky going!
by KMJ1992
06/19/18 12:17 PM
Rotella 10W40
by jakewells
06/19/18 10:43 AM
Extend WiFi Range at the Laptop?
by clarkflower
06/19/18 10:40 AM
Silicone containing waxes
by mjoekingz28
06/19/18 09:44 AM
Matrix totaled
by circuitsmith
06/19/18 08:32 AM
Door rust problems
by Dave Sherman
06/19/18 07:51 AM
2016 Honda Civic problems
by dbias
06/19/18 07:39 AM
Royal purple 75-140 in a subaru rear
by 91camarosRS
06/19/18 07:32 AM
OCI. With short trips. Nissan 4 liter
by Gawardawg
06/19/18 06:52 AM
Newest Members
JustaDude, 3horseman, Firedog45, WtsTacoma01, Orion62
65265 Registered Users
Who's Online
107 registered (Audioquest, Audios, 91camarosRS, 2009Edge, ArrestMeRedZ, 14 invisible), 1681 Guests and 36 Spiders online.
Key: Admin, Global Mod, Mod
Forum Stats
65265 Members
67 Forums
285606 Topics
4766428 Posts

Max Online: 3590 @ 01/24/17 08:07 PM
Donate to BITOG
Page 1 of 2 1 2 >
Topic Options
#4458786 - 07/13/17 10:09 PM Diagnostic Help
VetteElite Offline


Registered: 04/20/13
Posts: 115
Loc: -
2008 Saturn Aura
130,000 miles

GM 3.5L High Value V6 - Pushrod w/ VVT
GM 4T45E transmission

I really like this car; looks good, underrated performance, and drives well. At least, it used to... Lately I've been having some issues which I would like to fix the right way without just throwing parts at it. Car doesn't have any codes stored and no CEL. Still drives, but definitely has some problems. If it's a minor fix, I'm definitely willing to keep the car going, but something major and I'll just defer the decision to repair until something actually breaks for real or starts throwing codes.

Symptoms:

1) Hard shifting. 2-3 is the worst, 1-2 and 3-4 can be bad too. This seems to point me to typical GM 4T45e transmission woes. I'm not opposed to eventually putting a reman transmission in the car, but I'm not sure that's actually the problem with the car because of the other symptoms.

2) Occasional hesitation and poor acceleration. Pretty straightforward here, car sometimes doesn't like to get up and go. Other times, press the pedal and it feels like when it was a brand new quick V6 with nothing wrong. I'm thinking this could be MAF or MAP sensor. MAF was cleaned 6 months ago with MAF cleaner.

3) RPM fluctuations. This makes the car really annoying to drive. RPMs like to move around and make the car feel like its lugging and jerking. Even on the highway sometimes the RPMs will move around like the torque converter isn't locked, but then it will "lock up" and RPMs will stay still. Torque converter/transmission problem?

What I know:

Throttle body was cleaned a year ago which fixed a rough idle.

MAF sensor was cleaned 6 months ago with MAF cleaner. It was a long shot attempt to fix some of the symptoms I described without throwing parts at the car.

Engine Vacuum doesn't seem right. Using Torque app I see that my vacuum is around 18 "Hg at idle but drops to around 5 "Hg when driving...and rarely comes back up unless I fully take my foot off the throttle. Normally, I thought the vacuum was supposed to come back up after the initial drop upon acceleration as everything "evens out." This might be a slightly clogged exhaust?

-----

Any thoughts on what may be causing these problems? I don't have a ton of time right now to be troubleshooting and fixing things, but I would like to know what is going on so I can get around to fixing it if possible. Like I mentioned, car still drives and doesn't have a CEL, so I'm not panicked about any of these symptoms yet. I'm moderately handy, can do routine repairs and even some moderately complex ones if you give me a good set of detailed instructions. If it's transmission, I'll be taking it to a transmission shop though.

Top
#4458800 - 07/13/17 10:22 PM Re: Diagnostic Help [Re: VetteElite]
Merkava_4 Offline


Registered: 01/30/07
Posts: 17501
Loc: Clovis, CA
If no CEL, then each of the different sensors need to be hooked to a scope to examine wave forms; especially the MAP and MAF sensors.

Top
#4458802 - 07/13/17 10:27 PM Re: Diagnostic Help [Re: VetteElite]
VetteElite Offline


Registered: 04/20/13
Posts: 115
Loc: -
That's what is frustrating. Car definitely does not run like it should, yet it isn't throwing any codes.

Top
#4458821 - 07/13/17 10:40 PM Re: Diagnostic Help [Re: VetteElite]
Merkava_4 Offline


Registered: 01/30/07
Posts: 17501
Loc: Clovis, CA
The offending sensor(s) are working fine most of the time to keep the computer satisfied, but then act up enough to cause drivability problems. Happens all the time to different cars. You either hook them up to a scope or wait for them to get bad enough to throw a code.

Top
#4458831 - 07/13/17 10:53 PM Re: Diagnostic Help [Re: VetteElite]
zrxkawboy Offline


Registered: 11/30/04
Posts: 1761
Loc: SD
I would take a look at the TPS.
_________________________
"Think of all the Ford owners who will someday want an automobile." John Dodge


Top
#4458843 - 07/13/17 11:04 PM Re: Diagnostic Help [Re: VetteElite]
Thax Offline


Registered: 11/07/10
Posts: 786
Loc: VA
From what you are describing , possible cause could be the throttle body assembly. The throttle position sensor is integrated in this unit. I would perform a capacitor discharge on the battery. Then perform a throttle body relearn procedure. Unfortunately I think this is going to require a fully bi-directional scanner with scope function to properly diag.
_________________________
97 Grand Prix GTP
11 Jetta 2.5 SE
ASE P2 Parts Specialist
AIA Import Part Specialist
KIA certified Senior Technician, Hybrid certified.

Top
#4458884 - 07/14/17 12:44 AM Re: Diagnostic Help [Re: VetteElite]
Linctex Offline


Registered: 12/31/16
Posts: 6148
Loc: Waco, TX
Originally Posted By: VetteElite


Symptoms:
1) Hard shifting. 2-3 is the worst, 1-2 and 3-4 can be bad too.
2) Other times, press the pedal and it feels like when it was a brand new quick V6 with nothing wrong.
3) RPM fluctuations.


1) Pressure control solenoid? That's what it sounds like

2) & 3) - you've got a bad ground somewhere. Add some bonding straps and see if the problem goes away. These new computerized cars love having good grounds.
_________________________
"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."

Top
#4458949 - 07/14/17 05:18 AM Re: Diagnostic Help [Re: VetteElite]
Trav Offline


Registered: 11/20/06
Posts: 18848
Loc: MA, Mittelfranken.de
Originally Posted By: VetteElite

Engine Vacuum doesn't seem right. Using Torque app I see that my vacuum is around 18 "Hg at idle but drops to around 5 "Hg when driving...and rarely comes back up unless I fully take my foot off the throttle. Normally, I thought the vacuum was supposed to come back up after the initial drop upon acceleration as everything "evens out." This might be a slightly clogged exhaust?
Any thoughts on what may be causing these problems?


Transmission shifting issues are routinely misdiagnosed due to engine performance issues, engine doesnt run right the transmission doesn't run/shift right either its really that simple. It looks you might be dealing with a partially clogged cat, that will cause all you describe without throwing a code until it gets so bad it causes a misfire and flashing CEL.
Hook up a mechanical vacuum gauge to the engine, to insure proper readings, if its indicating a bad cat its time to go a bit further down that road.

http://www.aa1car.com/library/converter.htm
_________________________
ASE L1, Master. Deutsch Meisterbrief.

Top
#4458953 - 07/14/17 05:30 AM Re: Diagnostic Help [Re: VetteElite]
Donald Offline


Registered: 03/21/04
Posts: 20450
Loc: Upstate NY
Easy to diagnose the problem. It's a Saturn.
_________________________
2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)


Top
#4458992 - 07/14/17 06:45 AM Re: Diagnostic Help [Re: VetteElite]
kc8adu Offline


Registered: 08/02/05
Posts: 894
Loc: dayton oh
sounds more like a clogged cat to me.
disconnect the pipe in front of it and look at the vacuum again.with a real vacuum gauge.
do a before and after.
if the map is lying to the pcm same result.transmission is being programmed to shift with the data the pcm sees.
if engine is down on power and the shift is being performed for the power it is supposed to have under said condition it will seem harsh.

Top
#4458999 - 07/14/17 06:50 AM Re: Diagnostic Help [Re: Donald]
kc8adu Offline


Registered: 08/02/05
Posts: 894
Loc: dayton oh
not even close.if that was sarcasm you are wrong.
its a saturn in name only.
Originally Posted By: Donald
Easy to diagnose the problem. It's a Saturn.

Top
#4459019 - 07/14/17 07:13 AM Re: Diagnostic Help [Re: Trav]
The_Eric Offline


Registered: 03/31/10
Posts: 5354
Loc: Iowa
Originally Posted By: Trav
Originally Posted By: VetteElite

Engine Vacuum doesn't seem right. Using Torque app I see that my vacuum is around 18 "Hg at idle but drops to around 5 "Hg when driving...and rarely comes back up unless I fully take my foot off the throttle. Normally, I thought the vacuum was supposed to come back up after the initial drop upon acceleration as everything "evens out." This might be a slightly clogged exhaust?
Any thoughts on what may be causing these problems?


Transmission shifting issues are routinely misdiagnosed due to engine performance issues, engine doesnt run right the transmission doesn't run/shift right either its really that simple. It looks you might be dealing with a partially clogged cat, that will cause all you describe without throwing a code until it gets so bad it causes a misfire and flashing CEL.
Hook up a mechanical vacuum gauge to the engine, to insure proper readings, if its indicating a bad cat its time to go a bit further down that road.

http://www.aa1car.com/library/converter.htm


Agree on possible bad converter. A good sign is your MAP readings at part throttle that aren't coming back up.
_________________________
2005 Lincoln Aviator 4.6 DOHC
2000 Honda Accord 2.3
2001 Hyundai Elantra 2.0
1979 Ford F-150 351M

Top
#4459068 - 07/14/17 08:27 AM Re: Diagnostic Help [Re: VetteElite]
VetteElite Offline


Registered: 04/20/13
Posts: 115
Loc: -
I appreciate everyone's responses, except Donald; why would you even post in my thread? This car was widely praised and respected - even winning north american car of the year - precisely because it wasn't the typical [censored] GM had been spewing out.

Sounds like most everyone agrees with my gut that it's an engine problem, not a transmission problem. I actually don't have a mechanical vacuum gauge, so this sounds like a good excuse to go get one. That could at least help us figure out if its the cat vs a sensor.

I'll keep bad ground in the back of my head too. Car is driven on salted roads all winter and, while it's not badly rusted, there is some corrosion in the engine bay area.

Top
#4459096 - 07/14/17 09:09 AM Re: Diagnostic Help [Re: VetteElite]
mightymousetech Offline


Registered: 04/03/17
Posts: 1444
Loc: Ontario, Canada
Could also be VVT related. Stuck solenoids?
_________________________
Mighty Mouse Tech
Acura Tech
2010 Civic Si Castrol 0W40, Redline MTL
2013 BMW 135i M Sport Edition Castrol 0W40, Redline MTL

Top
#4459107 - 07/14/17 09:24 AM Re: Diagnostic Help [Re: VetteElite]
SHOZ Offline


Registered: 06/28/03
Posts: 5744
Loc: Illinois
Or the vapor emission valves stuck open?

Does it have an Idle Air Control valve?
_________________________
2008 Hyundai Accent 1.6L 5 sp manual hatchback
2010 Hyundai Genesis Coupe Track 2L Turbo 6sp manual

Top
Page 1 of 2 1 2 >