Did some performance mods, now she won't idle...
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5.0 and 5.7 Discussion, Did some performance mods, now she won't idle... in Cadillac Engine Technical Discussion; I've got a '95 Fleetwood Brougham...LT1... So I've done some performance modifications to the car since I bought it. I ...
  1. #1
    cadillackid1959 is offline Cadillac Owners Member
    Automobile(s): 1959 Coupe Deville, 1995 Fleetwood Brougham
    Join Date
    Apr 2007
    Posts
    14

    Did some performance mods, now she won't idle...

    I've got a '95 Fleetwood Brougham...LT1...
    So I've done some performance modifications to the car since I bought it. I got the car with 108,000 miles on it, and I just turned 224,000 on the odometer. Still running like a top except for a bad idle and wanting to stall at stop lights. I saw a similar post go up today, but thought I should start a new thread because of the modifications I've done. Here's the modifications:

    Flowmaster dual chamber mufflers in place of the factory mufflers
    resonator mufflers deleted
    Mallory ignition coil
    K&N Cold Air intake (the Impala SS piece)
    Trick Flow air intake elbow
    Granatelli mass air flow sensor
    Comp Cams Pro Magnum 1.6 ratio self aligning roller rockers
    Comp Cams pushrods (stock length)
    throttle body coolant bypass
    Hypertech 160 degree thermostat
    Autometer A pillar gauges (oil, temp, volts) - all electric gauges-
    I still retain the factory temp sensor also in conjunction with the gauges

    Recently installed:
    Optispark cap and rotor
    water pump
    spark plug wires
    throttle position sensor
    the roller rockers
    the pushrods
    the coolant bypass
    the 160 degree stat
    K&N recharge kit for the air filter

    So the problem is, if you sit at a stop light, the idle drops way off after sitting still for 10 seconds, and the car tries to stall. The check engine light also comes on sometimes, and last night I had the pass key fault light on as well...never seen that one before. It only started doing this yesterday after I cleaned and recharged the air filter. A friend of mine at the dealership told me that I should take my mass airflow sensor off and clean it with some carb cleaner, because more likely than not, it was coated with K&N air filter oil. I did this, and it didn't fix the problem. The last time I drove the car (about an hour ago), the cooling fans were on when I pulled into my driveway and put it in park, and they stayed on...the Autometer gauge was only reading 155 degrees. I'm ruling out the fuel filter, because I change my fuel filter with every other oil change (overkill, I know, but it never goes bad that way either), and the car did get a new fuel pump about 75,000 miles ago. Could this be a bad temp sensor? Or have I finally reached the point where I need to reprogram the PCM to deal with the modifications? Any help would be greatly appreciated....Thanks in advance!

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  3. #2
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
    Automobile(s): 94 Fleetwood Brougham
    Join Date
    Aug 2004
    Location
    Rockford, IL
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    47
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    Re: Did some performance mods, now she won't idle...

    Well with the mods, by all means you need it tuned, after my experience tuning the LT1, ALL LT1's NEED to be tuned! You will see much more improvements in power and drivability.

    If you CTS (Coolant Temp Sensor) has failed, (you did reconnect it after the Opti swap?), you definately CAN see problems like you describe. Also, has anyone tried to tune it? It almost sounds like there is a corrupt flash going on. Both fans on sounds like limp home mode (in other words protect it as much as you can). But it will run poorly, so that sorta rules that out.

    Try this. Before you start for the day, use a DVM and measure across the CTS, and then measure across the IAT. It should be almost identical in reading. A dataloger is handy here.

    Any codes? That really should be the first question. Are you missing a pulse on the Opti? It will do some strange things.

    If it was me? Toss the Granitelli MAF. Not worth a dime, the honestly cause more problems than they could possibly solve, especially on the LT1. You need the MAF screen in there. That WILL cause idle issues. If you sprayed the MAF (I do not recommend harsh chemicals on them!), did you do it hot? Like engine on recently? That could damage it. Either way, try these steps.

    1. Disconnect battery for a few min and reconnect and try again.
    2. Disconnect the MAF and try it, it should improve if the MAF is the issue.
    3. If you can't measure the CTS (down on the left side of the Opti/WP), disconnect it and short it with a paper clip. Once warmed up, see if it is better. Or put in a resistor, say (see this link http://www.megamanual.com/v22manual/mwire.htm) 3400 ohms for a cold start and switch to a 200-300 ohms once up to operating temps. This will isolate the temp sensor.
    4. Get it tuned, you will REALLY wake up the car. Ask Caddycruiser how his runs... There are some good tuners out there. Don't hesitate to talk to them, find out what they can do. Remember, tuning isn't gonna fix a poorly running engine, but it will do wonders for mods that are done and you aren't seeing the power come out of them.

    Things like larger throttle bodies, descreened MAF's or descreening the factory MAF or "IAT Mod" are not good mods, some are rather expensive and never do very much if anything for the cars performance. Some have their place, but rarely....

    I can say for sure, your combo should do pretty well, but without tuning you need some things done to get the full power out of it. Doing some datalogging and further tuning really will dial it in.

    Other reading on the CTS....
    http://www.wellsmfgcorp.com/pdf/Counterpoint2_2.pdf



    Quote Originally Posted by cadillackid1959 View Post
    I've got a '95 Fleetwood Brougham...LT1...
    So I've done some performance modifications to the car since I bought it. I got the car with 108,000 miles on it, and I just turned 224,000 on the odometer. Still running like a top except for a bad idle and wanting to stall at stop lights. I saw a similar post go up today, but thought I should start a new thread because of the modifications I've done. Here's the modifications:

    Flowmaster dual chamber mufflers in place of the factory mufflers
    resonator mufflers deleted
    Mallory ignition coil
    K&N Cold Air intake (the Impala SS piece)
    Trick Flow air intake elbow
    Granatelli mass air flow sensor
    Comp Cams Pro Magnum 1.6 ratio self aligning roller rockers
    Comp Cams pushrods (stock length)
    throttle body coolant bypass
    Hypertech 160 degree thermostat
    Autometer A pillar gauges (oil, temp, volts) - all electric gauges-
    I still retain the factory temp sensor also in conjunction with the gauges

    Recently installed:
    Optispark cap and rotor
    water pump
    spark plug wires
    throttle position sensor
    the roller rockers
    the pushrods
    the coolant bypass
    the 160 degree stat
    K&N recharge kit for the air filter

    So the problem is, if you sit at a stop light, the idle drops way off after sitting still for 10 seconds, and the car tries to stall. The check engine light also comes on sometimes, and last night I had the pass key fault light on as well...never seen that one before. It only started doing this yesterday after I cleaned and recharged the air filter. A friend of mine at the dealership told me that I should take my mass airflow sensor off and clean it with some carb cleaner, because more likely than not, it was coated with K&N air filter oil. I did this, and it didn't fix the problem. The last time I drove the car (about an hour ago), the cooling fans were on when I pulled into my driveway and put it in park, and they stayed on...the Autometer gauge was only reading 155 degrees. I'm ruling out the fuel filter, because I change my fuel filter with every other oil change (overkill, I know, but it never goes bad that way either), and the car did get a new fuel pump about 75,000 miles ago. Could this be a bad temp sensor? Or have I finally reached the point where I need to reprogram the PCM to deal with the modifications? Any help would be greatly appreciated....Thanks in advance!

  4. #3
    cadillackid1959 is offline Cadillac Owners Member
    Automobile(s): 1959 Coupe Deville, 1995 Fleetwood Brougham
    Join Date
    Apr 2007
    Posts
    14

    Re: Did some performance mods, now she won't idle...

    NODIH: Thanks for the input! I posted that up this morning before going to sleep...I'm a third shifter (musician)...
    Anyway, here's what we found out. After I went to bed, my father took the car over to Advance Auto Parts and they connected it to an OBD1 code reader. No codes. Then they opened the hood and found the one thing I hadn't even thought of...a bad vacuum hose off of the throttle body. They replaced it and Bingo! It ran like a top again. This doesn't really explain the cooling fan issue to me however. I just ran the car from Fond du Lac,Wi to Green Bay and back, and no cooling fan issues at all...the temp never got about 165.
    Thanks for the advice on the Granatelli. I put it on there a couple years ago when I bought the car, not knowing if would actually make a difference or not, and I haven't had any problems with it now in 115,000 miles, so I've just left it on...it was cold when I cleaned it too...I had figured that it probably wouldn't like it very much if I sprayed it down while hot, thanks for the advice on that too...
    Now, if I could bug you just for a few more moments, I have a couple more questions...

    1. Who should I talk to about tuning the PCM? I'm a relatively young guy (32), and you'd think that someone in my age group would have a grip on car computer fundamentals and resources, but the newest car I've done tricks to so far is 1959 ( I've got a '59 Coupe Deville with a dual quad 390, a '30 Ford Model A with a full race '59 390 mill, and am currently working on a '50 Mercury that's getting a '61 Caddy 390 for power), so I'm pretty far out of the loop when it comes to computer tuning, but I do know my way around the engine compartment...just used to seeing older ones...

    2. I'm thinking about putting some aluminum heads on this thing from a Camaro/Firebird/Trans Am along with some headers...Any thing that will make this difficult? I had a broken exhaust manifold bolt that turned into an exhaust leak from hell (bolt broke off on its own while the car was idling...craziest thing I've seen)...I've drilled out and rethreaded the bolt hole, replaced the manifold gasket and it's still leaking, so i've always been one to "fix things faster", and I've been told that the aluminum heads are a nice upgrade. Any thoughts?

    3. I've been contemplating putting a pretty lopey cam in the car (just for fun and to scare the import tuner crowd ...) At that point, would it help to go with a larger throttle body?

    Anyway, thank you very much for all of your thoughts and ideas!

  5. #4
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
    Automobile(s): 94 Fleetwood Brougham
    Join Date
    Aug 2004
    Location
    Rockford, IL
    Age
    47
    Posts
    7,490

    Re: Did some performance mods, now she won't idle...

    Glad you found it! AC will do fans on for sure.

    1. I have been tuning my LT1 and a few others for a couple years now, so I can help there. Officially trying to get a tuning business started actually (can do pretty much any GM V8 and a lot of V6's from 85-07). Shoot me an email, n0dih@att.net.

    2. Iron heads out flow the 92-96 aluminum heads from GM. So stick with the irons unless you are going to something better. Honestly if you are wanting to go with heads, talk to Dwayne about his on ImpalaSSforum.com, he has the Advance Induction heads and it up your way. I am just down in Rockford, used to live in Darien, WI. Not too awful far. Dwayne can be sorta rough around the edges, so don't let him ruffle your feathers. He does a lot of people.... exhaust bolts are messy, they leak air into the O2 sensors and screws fueling way up. Watch leaks there, and GM really screwed us on exhaust manifold bolts....

    3. When I ran my combo by Comp Cams (stock, including my factory 3.42 gears) they came up with a fairly healthy cam. Like a CC502 or CC503 (forget which now). I think it was the CC502. http://videos.streetfire.net/video/9...lt-_116738.htm Still might do it... Got almost a quarter million miles now, so that is my reservation....

    Holdbacks? Converter, stock one is gonna keep you held back. S10 converter works well, most people hit a wall in performance till the coverter gets replaced. Stock one is a tight one. People have been in the 13's on stock cams, it is a lame one, but honestly, there is a lot in the car with it still. I would do (in order) gears and posi, exhaust (2.5" with Dynomax 17749's http://www.pontiacstreetperformance....p/exhaust.html, then cam, converter, headers. And PCM tune it along the way, as for most you will need to anyway to make it run right.

    PCM tuning? Well, if you know how to properly tune and jet/spring a carbonator, distributor, etc, you can tune a PCM, tools are different (laptop and tuning problems and interface cables), but the concept is the same. Just 100x more variables! Heck, get started in it if you are serious into tuning (I am!!)

    Quote Originally Posted by cadillackid1959 View Post
    NODIH: Thanks for the input! I posted that up this morning before going to sleep...I'm a third shifter (musician)...
    Anyway, here's what we found out. After I went to bed, my father took the car over to Advance Auto Parts and they connected it to an OBD1 code reader. No codes. Then they opened the hood and found the one thing I hadn't even thought of...a bad vacuum hose off of the throttle body. They replaced it and Bingo! It ran like a top again. This doesn't really explain the cooling fan issue to me however. I just ran the car from Fond du Lac,Wi to Green Bay and back, and no cooling fan issues at all...the temp never got about 165.
    Thanks for the advice on the Granatelli. I put it on there a couple years ago when I bought the car, not knowing if would actually make a difference or not, and I haven't had any problems with it now in 115,000 miles, so I've just left it on...it was cold when I cleaned it too...I had figured that it probably wouldn't like it very much if I sprayed it down while hot, thanks for the advice on that too...
    Now, if I could bug you just for a few more moments, I have a couple more questions...

    1. Who should I talk to about tuning the PCM? I'm a relatively young guy (32), and you'd think that someone in my age group would have a grip on car computer fundamentals and resources, but the newest car I've done tricks to so far is 1959 ( I've got a '59 Coupe Deville with a dual quad 390, a '30 Ford Model A with a full race '59 390 mill, and am currently working on a '50 Mercury that's getting a '61 Caddy 390 for power), so I'm pretty far out of the loop when it comes to computer tuning, but I do know my way around the engine compartment...just used to seeing older ones...

    2. I'm thinking about putting some aluminum heads on this thing from a Camaro/Firebird/Trans Am along with some headers...Any thing that will make this difficult? I had a broken exhaust manifold bolt that turned into an exhaust leak from hell (bolt broke off on its own while the car was idling...craziest thing I've seen)...I've drilled out and rethreaded the bolt hole, replaced the manifold gasket and it's still leaking, so i've always been one to "fix things faster", and I've been told that the aluminum heads are a nice upgrade. Any thoughts?

    3. I've been contemplating putting a pretty lopey cam in the car (just for fun and to scare the import tuner crowd ...) At that point, would it help to go with a larger throttle body?

    Anyway, thank you very much for all of your thoughts and ideas!

  6. #5
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
    Automobile(s): 94 Fleetwood Brougham
    Join Date
    Aug 2004
    Location
    Rockford, IL
    Age
    47
    Posts
    7,490

    Re: Did some performance mods, now she won't idle...

    I just love to nail it and leave 2 black streaks..... With my 3.08's and posi in (temp axle till I get my 3.42's or maybe spring for 3.90's) I still still burn the tires off very well....

    Quote Originally Posted by cadillackid1959 View Post
    ....
    3. I've been contemplating putting a pretty lopey cam in the car (just for fun and to scare the import tuner crowd ...) At that point, would it help to go with a larger throttle body?

    Anyway, thank you very much for all of your thoughts and ideas!

  7. #6
    cadillackid1959 is offline Cadillac Owners Member
    Automobile(s): 1959 Coupe Deville, 1995 Fleetwood Brougham
    Join Date
    Apr 2007
    Posts
    14

    Re: Did some performance mods, now she won't idle...

    Cool! Thanks for the info man...I'm sending you an email right now....

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