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Stumbling


mmarinov

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Hi all:

'94 ETC - the last few months, she stumbles/surges at idle and WOT. From past experience seems like a vacuum leak or similar. Of course, the last time I yanked an engine it was a '79 Olds 403.

I do have an SES code - it's for the 'EGR pintle out of position' which I have yet to fix. Does this sound related to performance? Any opinions are appreciated. As far as the SES, is this something I could do easily? These N* engines are a little outside of my comfort zone.

Sidebar - I need to replace the outmost serpentine belt but fail to see how to to remove the bracket directly behind the A/C line and under the motor mount (see pic). Any suggestions?

Finally, the previous owner had the head gasket issues associated with the N* -- I have the repair invoice. It was done at a Caddy stealership in MO in February 2005 @88K. The tech comments say "REPLACED HEAD GASKETS AND INSERTED SLEEVES IN BLOCK". To you, does this sound like the correct timesert repair listed for these cars? Labor was listed at $5K+ and parts were a little over $1200.

Any comments are very much appreciated/thanks!

Mark

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<!--fonto:Arial--><span style="font-family:Arial"><!--/fonto-->2007 DTS Performance - 50K

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As a matter of fact, I <i>am</i> driving 70 MPH in a phone booth.

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You don't have to remove anything to replace the serpentine belt. You use a wrench on the hex nut on the tensioner shown in your picture behind the compressor hose; you can just see the large hex nut. The wrench should stick out to your left, leaning over the pasenger side fender. You push down on the wrench to rotate the tensioner and release tension on the belt, remove it, and put the new one on.

Be sure and make a note of the routing of the serpentine belt before you begin. If you don't have a clue how the new one is routed, you will end up having to find a diagram somewhere before you can complete the job.

The "sleeves in block" apparently are the Timeserts. The total head gasket bill sounds a little high but the parts sound right, assuming that all of the head bolt holes were Timeserted. Other work on the invoice, like changing the water pump, thermostat, and coolant, etc. could account for the rest of the cost. The mileage at 88K is pretty low for this job, but this happens when the coolant goes too long without being changed, and it's not a function of miles. My recommendation is to change green coolant every 1-2 years, and red every 3-4 years, and do NOT push the time limit on the anti-freeze manufacturer's recommendations.

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Yes, I was Jims_97_ETC before I changed cars.

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....

I do have an SES code - it's for the 'EGR pintle out of position' which I have yet to fix. Does this sound related to performance? Any opinions are appreciated. As far as the SES, is this something I could do easily? These N* engines are a little outside of my comfort zone....

If your EGR pintle is out of position at idle, that could easily cause a stumble at low speed. There is not supposed to be EGR action at idle speeds.

Not 100% sure (memory full), but I believe EGR is also inhibited at WOT.

Easy enough to clean the valve. Use a solvent but do not allow the solvent to enter the portion of the valve that contains the coil wire.

Jim

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CHOOSE ONE !

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No need to remove the tensioner. See that square hole in the back side near the bottom center of the pic you posted. That is for the 1/2" square drive lug on a 1/2" drive breaker bar. Insert the lug and use the bar as a handle to move the tensioner. Simplae as that.

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Here is the serpentine belt routing diagram.

Regarding your engineproblems, my cars smyptoms were:

A rough engine condition at part throttle, occasional bucking at light to moderate load, and slight engine stutter when accelerating normally from a stop. I tested almost all of the electrical circuits and found them to be good; the engine acted like it is just not getting enough fuel to run correctly. Very similar to a carbureted engine with low float level, or partially clogged jets.

It turned out that the problem that I had, was the Ignition Control Module failing; syptoms nearly identical to bad injectors ($330 for the replacement module from Rock Auto).

PS

The ICM is the module right under the coil pack.

-George

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Drive'em like you own 'em. - ....................04 DTS............................

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Actually sounds just like my issue with my carbon tracked plug, plugs and wires, could be the culprit. If you have a multimeter check the plugs and make sure the resistance is below 15K ohms I belive is the number. Check the gaps on the plugs, its easier (and almost required) to remove the strut tower brace and coil pack from the engine when you do the plugs/wires.

Try torque braking the engine, with the brake set run the throttle up a little and see what happens, if you notice a stumble, and if its bad enough, it may set a code. If you hace access to a scan tool you can run the misfire graph and that would say if you are having any misfires.

The Green's Machines

1998 Deville - high mileage, keeps on going, custom cat-back exhaust

2003 Seville - stock low mileage goodness!

2004 Grand Prix GTP CompG - Smaller supercharger pulley, Ported Exhaust Manifolds, Dyno tune, etc

1998 Firebird Formula - 408 LQ9 Stroker motor swap and all sorts of go fast stuff

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Thanks! I'm used to attaching the socket to a bolt to move the tensioner - this one just wasn't obvious to me.

Thanks for your tip on the coolant changing - I'll have to do that since it comes up frequently on this board.

Mark

....

I do have an SES code - it's for the 'EGR pintle out of position' which I have yet to fix. Does this sound related to performance? Any opinions are appreciated. As far as the SES, is this something I could do easily? These N* engines are a little outside of my comfort zone....

If your EGR pintle is out of position at idle, that could easily cause a stumble at low speed. There is not supposed to be EGR action at idle speeds.

Not 100% sure (memory full), but I believe EGR is also inhibited at WOT.

Easy enough to clean the valve. Use a solvent but do not allow the solvent to enter the portion of the valve that contains the coil wire.

Thanks, JimD - not to go n00b on you but where is the EGR located? I need to get a shop manual - I know someone posted links here recently.

Thanks!

Mark

<!--fonto:Arial--><span style="font-family:Arial"><!--/fonto-->2007 DTS Performance - 50K

<!--fontc--></span><!--/fontc-->

As a matter of fact, I <i>am</i> driving 70 MPH in a phone booth.

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As JimD said, a stuck open EGR valve will make the engine is very unstable at low RPM. I am pretty sure EGR is disabled during WOTs, so it would not make difference. You may have separate problems. Start with fixing EGR valve.

The saddest thing in life is wasted talent

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Here is the serpentine belt routing diagram.

Regarding your engineproblems, my cars smyptoms were:

A rough engine condition at part throttle, occasional bucking at light to moderate load, and slight engine stutter when accelerating normally from a stop. I tested almost all of the electrical circuits and found them to be good; the engine acted like it is just not getting enough fuel to run correctly. Very similar to a carbureted engine with low float level, or partially clogged jets.

It turned out that the problem that I had, was the Ignition Control Module failing; syptoms nearly identical to bad injectors ($330 for the replacement module from Rock Auto).

PS

The ICM is the module right under the coil pack.

-George

George:

Thanks so much for the diagram - that's going in the car file!

MM

<!--fonto:Arial--><span style="font-family:Arial"><!--/fonto-->2007 DTS Performance - 50K

<!--fontc--></span><!--/fontc-->

As a matter of fact, I <i>am</i> driving 70 MPH in a phone booth.

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Actually sounds just like my issue with my carbon tracked plug, plugs and wires, could be the culprit. If you have a multimeter check the plugs and make sure the resistance is below 15K ohms I belive is the number. Check the gaps on the plugs, its easier (and almost required) to remove the strut tower brace and coil pack from the engine when you do the plugs/wires.

Try torque braking the engine, with the brake set run the throttle up a little and see what happens, if you notice a stumble, and if its bad enough, it may set a code. If you hace access to a scan tool you can run the misfire graph and that would say if you are having any misfires.

EGreen - I changed out the wires and plugs today (they were both OE, shame on me!) with new Delco wires/plugs. I was able to replace the plugs without removing the coil pack or the strut tower brace but I'm with you, it would have been easier access-wise.

Anyway, I turned it over after the job was done and that made A HUGE DIFFERENCE! She runs smooth as silk at both idle and WOT. Prior to the replacement WOT was only getting me to 5,500 or so but now she flies up to 6,500 with a great redline shift. Thanks to all who gave their 2 cents with my questions.

Next week it's EGR cleaning time. :D

<!--fonto:Arial--><span style="font-family:Arial"><!--/fonto-->2007 DTS Performance - 50K

<!--fontc--></span><!--/fontc-->

As a matter of fact, I <i>am</i> driving 70 MPH in a phone booth.

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Glad its all sorted out.

The Green's Machines

1998 Deville - high mileage, keeps on going, custom cat-back exhaust

2003 Seville - stock low mileage goodness!

2004 Grand Prix GTP CompG - Smaller supercharger pulley, Ported Exhaust Manifolds, Dyno tune, etc

1998 Firebird Formula - 408 LQ9 Stroker motor swap and all sorts of go fast stuff

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