No power while towing

[k2500suburban]

Hello,
Just got back from vacation in the VA mountains pulling a 7000lb travel trailer and lost 50% of power after engine warmed up. I have the manual boost controller installed running around 10-12 psi boost, no black smoke at all. When engine is cold plenty of power, but when pulling a grade when engine warms up the engine all of a sudden looses power. Temp. never got over 210F engine RPM's were good kicked down into 3 and sometime 2 pulling the big hills and slowed down to 40mph on the interstate. Searched the forum but couldn't find any similar symptoms. Anyone had this problem or ideas what it could be? I was able to maintain speed on the flat land but any grades would slow me way down.

Thanks!
96' K2500 Suburb.

[JohnC]

Any codes?

In the absense of any other information, I would speculate that the ECM is seeing either too much boost or to much intake air temp and is cutting the fuel rate back. Just a WAG, though.

[Robyn]

If your truck is stock other than the manual wastegate control you will see the ECM chop power as soon as it sees boost over what it thinks is ok.
Does the ses light come on? Or possibly it does not work?

If you install a power chip from Kennedy or Heath the issue you are seeing will most likely go way.
The issue is that the original setup was designed to protect the engine from overboost, over fuel and it does do that.

In your case you need a replacement ECM that has the new parameters programed in. Good luck

Robyn

[k2500suburban]

No codes, and stock other than the Heath manual turbo control. What you say about the ECM makes sense because as soon as I would try to power up and build boost the power would just shut off like a switch. Are there any other options than a power chip? Would reducing the spring tension on the waste gate alleviate the problem?

Thanks for the advice!

[Robyn]

That will stop the problem but then you dont get any real advantagefrom the turbo master.

Do a performance exhaust system and the performance ECM and then you can get the power you desire.

If you back the spring down so the boost peaks at no more than 7 psi and then drops to 3-4 you will stop the defuel from happening.
A steady boost of 7-8 will trip a defuel. 10-12 will do it without a doubt.

OH BTW Welcome to TDP :D :D :D

Robyn

[Robyn]

Just a note
When you have the defuel the ses light should come on.
Once that happens a restart will reset the power back to normal

[DennisG01]

Wouldn't a boost fooler work for him? Like the one Kennedy sells? Granted, he won't be using the fooler to up the boost, just trick the computer so it never sees the high boost.

[Shikaroka]

Wouldn't a boost fooler work for him? Like the one Kennedy sells? Granted, he won't be using the fooler to up the boost, just trick the computer so it never sees the high boost.

I've got that combo and it seems to work fine. My boost goes to about 10psi regularly.

[Robyn]

Yes it will
The issue is if a boost fooler is going to be used the truck needs to have a free flowing exahust system to let out the heat and allow the turbo to work better.

A good exhaust system (3-1/2") along with a boost fooler will really wake up that little creature.
For the cost of the fooler I would buy a Heath Maxitorque ECM and then along with the exhaust the sucker will really run.

[DennisG01]

The issue is if a boost fooler is going to be used the truck needs to have a free flowing exahust system to let out the heat and allow the turbo to work better.


True. But if he atleast has an EGT (which is highly recommended if you're playing with the boost), he'll be able to monitor temp's and keep the engine happy until the budget allows for the new ECM.

[Robyn]

That will work.
Its a shame to buy a fooler which once a chip/ECM is purchased will wind up being a waste.

Can you hook the vacuum system back up to working order?
The exhaust should be the first upgrade and will improve performance without causing any headaches.
From this starting point a chip is the best choice but you can use a fooler if you are happy with the power at this point.
Without a free flowing exhaust the addition of more boost is not really a step in the right direction.
Even with the gauges the system cant use the extra boost effectively.

With a kitty corking up the flow along with the small pipe and restrictive muffler there is nothing but heat to be gained.

Kennedy sells the foolers and they are easy to install. Pretty much "Plug and Play" a couple adjustments to get the puter happy and your on the go.

keep in mind that for cruising about 3-5 psi is all you want. Pulling hard should not exceed 10 psi

After 10 psi a charge cooler or a mist injector is almost a must.

If your thermocouple is after the turbo dont exceed 1000F better to stay around 900F

Locating the probe "pre turbo is better and give a better look at the real heat thats building.
My rig has the probe after the turbo in the downpipe. I would not have done this but it was there from Banks. (Not to stay though)

Good luck

Robyn

[rjwest]

" Defuel" is what is occuring Computer tries to open waste gate " can't do it "
So ..set's a Hidden code and reduces fuel to insure boost is lowered..

with the manual wastegate controller you have to reduce spring pressure or add a 'boost fooler' or reprogram the PCM.

Boost fooler works, BUT you are now the Smarts to prevent Overboost,overtemps.

MUST Have gages !!!! Well not really a must,
it's a free country and you are still allowed to destroy your own engine,
as long as you clean up afterward...

For towing in the mountains: The boost fooler With Gages is great ,
I limited my boost to 10 lbs and kept EGT below 900 (post turbo)
Also a TCC lock up switch will really add power in 2nd gear and keep temperatures down
(Engine & tranny )

[Robyn]

The idea of lockup in #2 hole is a good one.
Too bad the factory did not think of it.
Compression braking would be good too.
I have done this with a 700R4 but not tried it on the 4L80.

I always carry a broom and a dustpan behind the seat along with a bag of kitty litter. :D:D Just in case.

Mom always said "Clean up after yourself" we dont have maid service!!

later

Robyn

[k2500suburban]

Wow! This site kicks butt! Thanks for all the advice and wisdom from your experiences. I only recently added the Heath turbo controller and this was the first time towing with it. I didn't think that it would be a problem based on the information given at the time I purchased it, but I know better now. Looks like I have more upgrades to do.

Thanks again!

[Robyn]

If $$$$ are an issue just back off the TM so you only peak at about 7 PSI and drops back to 3-4 PSI.
This will get you out of the defuel situation.

Always loads of help here with a :D

Robyn

[rjwest]

In a devious way the factory did think of 2nd gear tcc llock up,
only a trans overtemp has to occur first, this allows 2nd gear tcc lock up,
lockup in third at lower speed, and allows 4th gear to stay locked until
down shift occurs, also full pressure to the shift clutches

On the 96 and newer, fooling the PMD to sense a high temp is a way to allow above,
But!!!!! full pressure shifts, Need to shift manually and use throttle as a std shift

On 95 and older the tcc can be forced to lock up with out codes , not so 96 up.....
The is a tor-loc that does this and works well on 95 older, has a speed sense to insure
tcc unlocks when stopping, does not work on 96 newer, ( I know from experience,
still have 1 somewhere )

The TCC resister/sw is explained in depth in old posts.

just some info, I did use the Boost fuller method without the manual waste gate..
worked very well, also used the TCC lock up, excellent in the east coast mountains
where 2nd gear hills are common...
was experimenting with a 4-3-4 elect shift switch, worked great, EXCEPT, if you left
sw in 3rd position and restarted truck it would set a code and cause Harsh shifts,
never finished the project with a saftey relay ( sold truck ).
But with the tcc lock up sw and the 4-3-4 sw I could downshft without using the
shift lever....was getting close to a manual controlled auto...

[Slim shady]

I read the whole post and nobody mentioned that the ecm /Pcm will reduce fuel when the coolant temperature goes above 210 degrees. This will not set a code and is done without the driver knowing. Gm states that reduced power will result if the engine coolant temperature goes above 210 degrees, this is done to reduce the chance of overheating the engine when towing. Normal engine power will return when coolant temp goes below 210. RIGHT OUT OF the manual.

Since the first post stated the temp never got above 210 on the gauge this may not apply here but/ it is something that should be taken into consideration. Just a thought.

[Robyn]

Interesting bit about the coolant temp defuel. My dually will run to 220F on a hot day before the fan comes on and I have never felt a loss of power. ????????

This thread is bringing to light all sorts of interesting tid bits.

Robyn

[rjwest]

I had very good results with a 180 deg full flow thermostat (2)

Was willing to except less MPG ( if any ) for driveability.

The TCC lock made a big difference in Engine temperature ( along with a through
cleaning of the radiator,condenser,oil cooler,trans cooler)

There was one thing which I never figured out, some days the engine had lot's of
power, other days felt a little week. Never any codes, and really could not find
any parameters in the PCM that seemed abnormal, Kind of like it just did'nt 'feel
well' that day. weird.

Than , somedays, wow, lot's of power, but these were days with VERY low humidity
and temps in the 30-40 deg range...

The 6.5 REALLY needs an intercooler....

Note: Most of my driving was with a 3000 lb plus truck camper. LOT's of drag..

[Slim shady]

Came across that tidbit of info while reading the manual given out at the GM tech school on the ds4 pump. The sensor inputs are described and it shows what inputs affect the ds4 pump. This is not the case for the DB-2 pumps just the little electric guy.

The defueling doesn't happen all at once just in increments according to how far above 210 up to 240. The lose of up to 25 percent of engine power can result from this engine protection.

SERVICE BULLETIN number 47-63-03 dated Sept 1994, filed in section 6E Engine Fuel and Emission. Just for the non believers.

[Slim shady]

I had very good results with a 180 deg full flow thermostat (2)

Was willing to except less MPG ( if any ) for driveability.

The TCC lock made a big difference in Engine temperature ( along with a through
cleaning of the radiator,condenser,oil cooler,trans cooler)

There was one thing which I never figured out, some days the engine had lot's of
power, other days felt a little week. Never any codes, and really could not find
any parameters in the PCM that seemed abnormal, Kind of like it just did'nt 'feel
well' that day. weird.

Than , somedays, wow, lot's of power, but these were days with VERY low humidity
and temps in the 30-40 deg range...

The 6.5 REALLY needs an intercooler....

Note: Most of my driving was with a 3000 lb plus truck camper. LOT's of drag..

I have used large opening 180 thermo that I bought at the performance store. They worked well in the dual stat setup. never ever ran above 185, ever. went to 195 dual large opening in the winter and never went back to the 180 so far. Mileage went up slightly oil stayed cleaner longer. My little beast likes to run warm. Of course the intercooler does help intake temps a great deal.

So far the hottest it has ever been is 200 and that is with a scanner hooked up so I could see what the computer is seeing. I don't tow a lot so the 195 stats are good for me.

The thermo stats are also not legal for street use, at least that is what the package says. I can't figure out why they wouldn't be legal but heck, let em check for them and then I can explain. A few days on the feds would be ok. LOL

[Robyn]

Interesting

Now then a ???????? can there be an internal fault in the PCM programing that would cause a defuel under fairly normal circumstances.

My 94 Burb has never been a powerhouse during hot weather. I have a 180 Stat in it since the rebuild.
I have checked all sorts of things and once the outside temp gets up into the high 80's on up the thing is a slug.
Now this is normal to a point due to the light dry air but my dually is not affected nerly so much.
Could be the IP is also on the edge of the envelope too, but it starts and runs fine even when hot, just a tad doggy???

Just a thought to muse.

Possibly also the stock exhaust system is to the point that it is producing too much back pressure and in conjuction with the Hot weather sets in motion a cascade effect that results in the power loss.


:confused::confused:

Robyn

[Slim shady]

Interesting thought but! I couldn't say. I do know my little oil burner runs good even in hot weather, 90 plus: but it does run much nicer in the 80 and below temps. The intercooler did make a big difference in the way the truck ran period. It was one of the best mods I have done.

I regularly saw 200 degree intake air temps on hot days under boost at around 8 psi. Now the highest i have had so far is 110 under 10 to 13 psi boost. Big difference!