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 Why Won't My LT1 Rev?

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toomanytoyz
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DBeaSSt
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Wagon Collector

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PostSubject: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeThu Nov 12, 2009 7:50 am

Okay... so my 1994 DGGM wagon has always been a bit of a dog. Can't quite put my finger on it, but it just doesn't seem as willing to move as my other cars. Since the 4L60E trans was a bit tired, I never thought much of it. Also I always felt like the converter was stalling a little earlier than it should. Since I planned to T56 the car anyhow, I never thought much of it.

Now I have the T56 in the car, it it is much more obvious to me that the car just doesnt' want to build RPMs. It's kind of hard to describe, but with my other T56 car, I can blip the throttle to match revs on downshifts, and it very quickly changes RPM. With this car, It just takes a while for the RPMs to change. The car still feels plenty powerful, but does seem to fall on it's face higher up in the RPM range, say over 3,750 RPM or so.

Car is bone stock, except that it has no cats.

Where should I start? Could the mufflers be restricted? Fuel delivery?

The car probably needs plugs and wires. Perhaps I better get started bringing it up the curve to well being. Does this sound like a tune-up issue? I don't detect any misses. Maybe a slightly rough idle sometimes.

Thanks in advance for any help!
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DBeaSSt
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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeThu Nov 12, 2009 8:12 am

Does the engine feel like it's stumbling? Or just doesn't rev as quickly?

On any car with the miles starting to get up there, I'd always start with the tuneup stuff first. Plugs, wires, maybe an Opti if you're over 100K. PVC, EGR, all that fun stuff.

I did Seafoam in my Roady with around 105K. I did not put any in the fuel tank but used the whole can through the intake. That engine did not run badly at all but there was a VERY noticeable difference afterwards. The engine just felt like it had more pep to it.

It was pretty easy to do. Get the engine warmed up. It's easiest if you can have someone help but keep the RPM's up a bit, around 1,000-1,500 or so. I used the line just behind the TB to slowly pour the Seafoam into the intake stream until the can was empty. The immediately shut off the engine and let sit for 10-15 minutes or longer if you like. Start engine again and let it run until the idle smooths out. Drive it hard or just rev it up a few times to 'blow' all the junk out the exhaust. There was quite a bit of carbon on my garage floor after I was done!

Just my .02. Smile
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stockfornow

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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeThu Nov 12, 2009 8:31 am

I did the Sea Foam thing too a week ago. 1 can in the gas tank, 1/2 can in the oil and the other half down the intake. I used the hose off the brake booster. Let it sit, start it up and watch the smoke.

It started to blow the white smoke out while I was putting it into the intake and I didn't get as much as I thought I would after the start up but it did make an improvement. On my last tank of gas I picked up about 1 mpg (mostly city driving) and should see if I made a better improvement on my highway trip this weekend.

Just as a note, my car ran like crap right after using the Sea Foam. It actually felt like I had a miss when really trying to accelerate. After a half hour of driving the crap out of her, it’s all gone. Car feels stronger now than before. Also, I recommend changing the oil within 100 miles if you put it into the oil crankcase. Mine was very black when changed.

I would suggest trying the Sea Foam before doing a tune up…. (Just my $0.02)
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DBeaSSt
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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeThu Nov 12, 2009 8:40 am

stockfornow wrote:
......
Just as a note, my car ran like crap right after using the Sea Foam. It actually felt like I had a miss when really trying to accelerate. After a half hour of driving the crap out of her, it’s all gone. Car feels stronger now than before. Also, I recommend changing the oil within 100 miles if you put it into the oil crankcase. Mine was very black when changed.

I would suggest trying the Sea Foam before doing a tune up…. (Just my $0.02)

I agree with you. Mine ran rough for a bit too but cleared up after the Seafoam got burned out of the system. I also got a CEL for a month or so afterwards and thought I'd have to replace my O2 sensors but it has since gone away.
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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeThu Nov 12, 2009 8:51 am

Cool... thanks for the quick input!

Mike, it doesnt' feel like it's stumbling, but something's keeping those RPMs from rising. When I blip the throttle with the clutch in (or in neutral), I guess if feels and sounds more like a slight bog than anything. Fuel pressure checks fine under load (I have a "whip" fuel gauge that I can install and veiw while I drive).

Sounds like I need to get back to the basics and make sure everything is in good shape. Thanks for the tip on the Seafoam. Are there different flavors for oil, gas, and intake, or is it all from the same can?
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DBeaSSt
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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeThu Nov 12, 2009 9:30 am

I think it's all the same can. I don't remember seeing different ones anyway. A pretty inexpensive way to start though. Smile
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stockfornow

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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeThu Nov 12, 2009 9:42 am

DBeaSSt wrote:
I think it's all the same can. I don't remember seeing different ones anyway. A pretty inexpensive way to start though. Smile

All the same can and definitely the inexpensive way to start. Wink
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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeThu Nov 12, 2009 1:56 pm

I would never ever put seafoam in the crankcase. From what I've read, it contains stuff which will do bad things to your oil and bearings.

EDIT - Seafoam ingredients:
Isopropyl Alcohol (rubbing alcohol), pale oil, and naptha.

GM TEC ingredients:
2-BUTOXYETHANOL, naptha, 4-METHYL-2-PENTANOL, 9-OCTADECENDIC ACID.

One other link to perhaps a better product: [You must be registered and logged in to see this link.]

Kevin, check your TPS too. If it's giving a false low reading, the PCM will be holding the engine back. Try swapping TPSs or throttle bodies between the cars and see if anything changes.
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toomanytoyz

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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeThu Nov 12, 2009 5:07 pm

Maybe your valvesprings are getting tired? Mine start to Float around 4200 or so in the Marshmallow... Wink
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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeThu Nov 12, 2009 7:07 pm

With the T56 and gears, it should rev like a mofo. Once mine gets over 3000, it absolutely takes off. The exhaust note is sublime...
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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeThu Nov 12, 2009 8:52 pm

i wouldn't seafoam anything,. the crap coming out of the combustion chambers can just as easily be removed by driving the car with a container of water hooked to the egr hose,.for a day or 2,.
ever wonder what "blowing" the crap out of the motor does to the catalytic converters?
o2 sensors etc?
better to run the motor hard,.
the seafoam in the crankcase is guaranteed to plug up the oil pickup screen,.

JMHO
Kev i,m with billy on this,. the tps for throttle response,. a dirty maf for rpm issues etc,.ASSuming you have free flowing intake and exhaust etc,.

Nick
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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeMon Nov 23, 2009 3:13 pm

Well, I put plugs and wires on it. Helped quite a bit. I did notice the throttle body is filthy, and the MAF ain't too clean, either. I'll work on it some more. At 150,000 miles, I'm thinking it's about time for an Opti, too... but I'm too cheap to buy one.

At least it'll rev-match downshifts now when I blip the throttle. That's a big improvement.

Here's a picture of the wires and plug install. LT1 wires FTMFL! What a PITA. Wheel off, under the car, over the car, balancing on the exhaust manifold with my right toe... I'm getting too old for this ish!

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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeMon Nov 23, 2009 4:20 pm

Looks like your car is either swallowing you up, or it tasted you and is spitting you back out.
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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeMon Nov 23, 2009 4:32 pm

You put your right arm in
You take your right arm out
You put your right arm in
and you shake it all about.......
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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeMon Nov 23, 2009 10:12 pm

Bewber wrote:
Looks like your car is either swallowing you up, or it tasted you and is spitting you back out.

I got ejected in the form of spit-up several times...

Krzdimond wrote:
You put your right arm in
You take your right arm out
You put your right arm in
and you shake it all about.......

...because it was caught somewhere between the exhaust manifold, air conditioner compressor, power steering pump, alternator, said wires, hoses, etc. for said components, accessory bracket, overflow tank, fuse accessory block, receiver dryer...

Seriously... did GM even consider putting something on the driver's side of these freakin' cars? Bastards. No my hand is all bruised up and I'm all pissed and stuff. At least the car runs better now, though! Very Happy
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PostSubject: Re: Why Won't My LT1 Rev?   Why Won't My LT1 Rev? Icon_minitimeSat Nov 28, 2009 1:20 pm

Yeah its really interesting and great from you. You are becoming popular man.

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