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Hello, I have a 94 Trans Am all stock started out having a problem with a hesitation upon acceleration and now it has progressed worse. At WOT only get about 2000 RPM's. Has new Opti, plugs, wires, TPS, ICM and moved away from head. Left side exhaust manifold will get glowing red if ran for a period of time. Thanks for any help that can be provided.
 

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Last time my car wouldn't go over 2000rpms I had a clogged Catalytic Converter. Does your car have an accompanying whine while cold and a huge loss of power?

On a more methodological approach:

First things first, what codes do you have? (I see no Datamaster file attached).

Red hot headers mean very lean conditions or extremely poor exhaust flow.
 

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No one can look your DataMaster file over until you attach it to your post.

When exhaust manifolds glow red it's usually from very lean mixtures, or timing problems. Either crank to cam timing, or ignition timing.

Lean mixtures can be caused by clogged fuel injectors that are not spraying enough fuel. Bad fueling strategy by pcm, or o2 sensor not functioning correctly. And many other causes.

Clogged cat, as hrcslam said can do it also.
 

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Discussion Starter #5
No one can look your DataMaster file over until you attach it to your post.

When exhaust manifolds glow red it's usually from very lean mixtures, or timing problems. Either crank to cam timing, or ignition timing.

Lean mixtures can be caused by clogged fuel injectors that are not spraying enough fuel. Bad fueling strategy by pcm, or o2 sensor not functioning correctly. And many other causes.

Clogged cat, as hrcslam said can do it also.
Sorry I quickly found out I didn't know how to post the data file,
 

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Discussion Starter #6
Last time my car wouldn't go over 2000rpms I had a clogged Catalytic Converter. Does your car have an accompanying whine while cold and a huge loss of power?

On a more methodological approach:

First things first, what codes do you have? (I see no Datamaster file attached).

Red hot headers mean very lean conditions or extremely poor exhaust flow.
Thanks for your reply. Sorry couldn't figure out how to post the data file. My car does have a huge power loss don't have a whine. I have DTC codes 34 and 48.
 

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MAP Sensor Signal Voltage Low - DTC 34
MAF Sensor Circuit - DTC 48

Did the issues start before or after all the new parts? Your ICM mount has a bunch of grounds that should attach there. Are any not connected or maybe they are corroded?

A data log would be great to post here.

To attach it, click the "Go Advanced" button. Then on the next page you'll see the paperclip button on the top of the dialog box. Click that and follow the steps through it. (If there is only a "submit Reply" and "Preview Post" button below the dialog box then you are already in "advanced" mode).

A Clogged catalytic converter can cause vacuum (MAP) and air flow (MAF) issues..... But, I'd like to see the datalog to confirm this...
 

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Interesting.. the 48 (no signal from MAS) will put car in 'speed density' mode, but then the 34 will then calculate a dummy MAP using TPS and RPM. The MAP and MAS do not share any direct electrical components. A log would show the O2 voltage, BLM's (if in closed loop), timing and actual MAP values, no MAS if in SD mode. Seems if it's lean enough to glow red at only 2K then an O2 DTC (lean burn) would happen if it's in closed loop. Just guessing.. need the log posted on a shared website..

Here are some diagrams.
http://www.mifbody.com/DTCs/DTC 34.jpg
http://www.mifbody.com/DTCs/DTC 34_2.jpg
http://www.mifbody.com/DTCs/DTC 48.jpg
http://www.mifbody.com/DTCs/DTC 48_2.jpg
 

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both of those problems need to be fixed. map sensor first. that's a critical sensor and you shouldn't expect it to run at all with a failed map and maf sensor, the fact it runs right now is just a fluke, as those control both methods of fuel calculation. backup map mode will not allow high rpm calculations, no wonder you're stuck at 2k rpm. check your engine and ecm grounds first, as having both those sensors fail at the same time is very strange.
 

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If you can post a video of your engine while it's refusing to rev to over 2K that would help.

Looking at your Datalog...

Your MAP and MAF are working according to the log. They read fairly accurately at idle and low RPMs.

When you go to full throttle I see very low AFGS with good MAP pressure, then when you let off the throttle I see very high MAP's with good AFGS.

At 100% TPS and 2000 RPMs you peak at 50 AFGS (gm/s of air flow), in comparison I hit 50 AFGS at 32% TPS and 1600rpms. This points to poor airflow before, inside, or behind the engine.

Further, your (MAP) pressure remaining in the intake after you release the throttle points again to poor flow, this time behind the throttle body.

Your Left hand BLMs are DUMPING fuel into the engine and it's still running lean enough to run red hot.

First I'd try opening up the exhaust, before the cat, and see how that helps. If it does, replace cat. Try removing #15 in this diagram from the exhaust manifolds and running the engine. It will be loud as hell and you should NOT run it like this for a long period of time. Disconnect them, start engine, rev to see if it improves to more than 2K easily, then bring back to idle and turn off engine.



If there is no difference, then I'd pull the left hand fuel injector rails and see if any are not firing.
 

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Discussion Starter #13
If you can post a video of your engine while it's refusing to rev to over 2K that would help.

Looking at your Datalog...

Your MAP and MAF are working according to the log. They read fairly accurately at idle and low RPMs.

When you go to full throttle I see very low AFGS with good MAP pressure, then when you let off the throttle I see very high MAP's with good AFGS.

At 100% TPS and 2000 RPMs you peak at 50 AFGS (gm/s of air flow), in comparison I hit 50 AFGS at 32% TPS and 1600rpms. This points to poor airflow before, inside, or behind the engine.

Further, your (MAP) pressure remaining in the intake after you release the throttle points again to poor flow, this time behind the throttle body.

Your Left hand BLMs are DUMPING fuel into the engine and it's still running lean enough to run red hot.

First I'd try opening up the exhaust, before the cat, and see how that helps. If it does, replace cat. Try removing #15 in this diagram from the exhaust manifolds and running the engine. It will be loud as hell and you should NOT run it like this for a long period of time. Disconnect them, start engine, rev to see if it improves to more than 2K easily, then bring back to idle and turn off engine.



If there is no difference, then I'd pull the left hand fuel injector rails and see if any are not firing.
Okay I unhooked the two number 15 pipes from the exhaust and at WOT the the RPM's are back!!!! So you think plugged converter?
 

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Okay I unhooked the two number 15 pipes from the exhaust and at WOT the the RPM's are back!!!! So you think plugged converter?
Yup. Replace cat. If funds are tight, go get a 3" pipe from the parts store and cut off the cat and put the pipe in it's place until you can get it to the exhaust shop. Throw in a high flow aftermarket one, not much to gain for performance, but the are A LOT cheaper. I paid $70 for my high flow (when I had one) installed.

After you remove the restriction in the exhaust, data log again and check you BLM's. If they are still dumping fuel in the left bank we need to figure that out next....
 

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Discussion Starter #15
Yup. Replace cat. If funds are tight, go get a 3" pipe from the parts store and cut off the cat and put the pipe in it's place until you can get it to the exhaust shop. Throw in a high flow aftermarket one, not much to gain for performance, but the are A LOT cheaper. I paid $70 for my high flow (when I had one) installed.

After you remove the restriction in the exhaust, data log again and check you BLM's. If they are still dumping fuel in the left bank we need to figure that out next....
What about just gutting the converter short term?
 

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You could do that too. That stuff is tough, especially whens it's clogged up. Good luck and let us know how it goes.

If you decide to pull the Y pipe to do this, make sure you soak the manifold bolts for a few days before you loosen them and take it easy. They are very likely to be seized on and just break off when you try to remove them and they are not easily replaced.

I thought the same thing. I ended up just taking a saws all and cutting the cat off, then putting a tube in it's place. A couple 3" exhaust band clamps make this easy. It also makes installation of a new aftermarket cat easy too. No welding needed, just band clamp it in.

Like these....


 

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Okay yes that looks easier than a gut job I will try that. Thanks again for your help this is as close as I have been to solving this issue!!!!
 

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:LS1LT1flag:No Problem
 

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:LS1LT1flag:No Problem
Got the new pipe installed today had a few too many Coors Lights while I was installing so didn't get to take it out on the road but it sounds really good. Now hit the pedal no hesitation and will hit 5k RPM with no problem. I will take it out tomorrow and let you guys know how she runs. I would like to do another data log and have you look it over also if you will please. Thanks so much for your help and also telling me about the band clamps those are awesome!!!!
 

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Got the new pipe installed today had a few too many Coors Lights while I was installing so didn't get to take it out on the road but it sounds really good. Now hit the pedal no hesitation and will hit 5k RPM with no problem. I will take it out tomorrow and let you guys know how she runs. I would like to do another data log and have you look it over also if you will please. Thanks so much for your help and also telling me about the band clamps those are awesome!!!!
No problem that's what we are all here for, enjoy your night. Beer sounds like a great idea! :cheers:

Post it up when you get a chance. You'll want to take it on a good long drive to let the BLM's readjust properly. But, do keep an eye on those BLM's to make sure they are coming down to normal.

Yeah, those band clamps are the best exhaust invention ever.
 
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