Too long to take off

[sawmillman]

Hello All, Just got home from a 4000 mile trip out West. All went well except for 3 times at take off from a complete stop, it took probably 10 to 15 seconds for the old girl to take off from a crawl. That dont sound like much unless you are taking off from a red light with a line of traffic behind you. No other issues. Once we were able to spool up and blast off we went on down the road no problems. No dash lights or codes. It felt like when the fuel filter is clogged, but I just put new filters on before we left, and have replaced them after we got home. Don't appear to be clogged after cutting them open. Any ideas to check? Thanks

[Bob_C]

Do Cats have a throttle position switch?

[sawmillman]

Originally Posted by bob caldwell

Do Cats have a throttle position switch?

Yes Sir it does. After it happened the third time I thought about the throttle position sensor and set my scanguage to monitor it. Of course it didn't happen again to see if the TPS was the cause.

[azpete]

did you replace the fuel filter at the top passenger side of the engine? its mounted just above the frame rail. i have a freightliner xc chassis with a 350 engine.
my coach was doing the same thing. finally stalled on i40 just east of albuquerque.
good sam paid our tow to tumcumcari nm, johns truck service.
small place but very busy.
turns out, we had one injector that had a bad electrical coil, and one partially plugged.
i had the tech, mike, replace all 6 injectors, and the hidden fuel filter. mike also found a bad atmospheric sensor.
in spite of being busy, they jumped right on my coach, and within a day, i was out the door. my wife and animals were allowed to stay in the coach.
mike is a patient man. stepping over the dog every time, and laughing about it.
it was a large bill, but internet research showed it to be fair for what was done.
man, what a difference, hills that i down shifted and crawled up, were now 55 miles per hour climbs.
both johns truck service, and good sam did a great job.

[sawmillman]

Originally Posted by azpete

did you replace the fuel filter at the top passenger side of the engine? its mounted just above the frame rail. i have a freightliner xc chassis with a 350 engine.
my coach was doing the same thing. finally stalled on i40 just east of albuquerque.
good sam paid our tow to tumcumcari nm, johns truck service.
small place but very busy.
turns out, we had one injector that had a bad electrical coil, and one partially plugged.
i had the tech, mike, replace all 6 injectors, and the hidden fuel filter. mike also found a bad atmospheric sensor.
in spite of being busy, they jumped right on my coach, and within a day, i was out the door. my wife and animals were allowed to stay in the coach.
mike is a patient man. stepping over the dog every time, and laughing about it.
it was a large bill, but internet research showed it to be fair for what was done.
man, what a difference, hills that i down shifted and crawled up, were now 55 miles per hour climbs.
both johns truck service, and good sam did a great job.

Yes I changed the filter and the water separater both. Where you getting any codes when this happened to you?

[bdpreece]

Did you happen to check your boost pressure when this happens. Could be a turbo problem, not spinning up or leaking around the rubber boot.

[hex nut]

A few years ago I was driving an '05 C7 powered motorhome. It had the same issues you are describing. Periodic sluggish response from idle. After carefully watching the boost pressure response to acceleration, I determined that I was having sluggish turbo response. I bought a quart of solvent designed to de-solve the carbon deposits that build up in turbo's. Some times these work and some times they don't solve the issues. In my case, it worked and I had no more problems for the remaining time I owned the coach.



Richard


p.s. Coked turbo's are often a result of high exhaust temperatures from an overheated engine. That was the problem in my case.

[sawmillman]

Originally Posted by hex nut

A few years ago I was driving an '05 C7 powered motorhome. It had the same issues you are describing. Periodic sluggish response from idle. After carefully watching the boost pressure response to acceleration, I determined that I was having sluggish turbo response. I bought a quart of solvent designed to de-solve the carbon deposits that build up in turbo's. Some times these work and some times they don't solve the issues. In my case, it worked and I had no more problems for the remaining time I owned the coach.



Richard


p.s. Coked turbo's are often a result of high exhaust temperatures from an overheated engine. That was the problem in my case.

Sounds like worth a try. Do you happen to remember what brand cleaner you used. thanks

[Jon_C]

I would replace the MAP sensor, it measures the turbo boost pressure, if its going bad these are the symptoms it causes.
Ask me how i know ( 2 times, 1 without throwing any codes)

Best of luck.

[hex nut]

I do not remember the brand name, but I do remember that it was relatively expensive. There are a number of brands available on the market. Do a google search on "turbo stiction", you should get a number of hits.


Richard

[Cat]

The TPI could cause this as you know. Another possibility is the atmospheric pressure sensor. The ECM use this to adjust the fuel in relation to the altitude. So as you climb up a mountain and the air density changes so you can't use as mush fuel. If the sensor sticks ( there is a mechanical diagram in it) you will not get a diagnostic code, if the shorts out or there is a broken wire you will get a diagnostic code. But not if the mechanical side of it sticks.
I've seen this sensor cause the low power problems. It is is a cheap replacement cost. I would replace it- it would be one less thing that could cause a intermittent power problem. Safe Travels

[Skip426]

Possible , slow release of the exhaust brake activation air pressure ?

Just thought I'd throw that in to add to the confusion.

[sawmillman]

Originally Posted by Cat

The TPI could cause this as you know. Another possibility is the atmospheric pressure sensor. The ECM use this to adjust the fuel in relation to the altitude. So as you climb up a mountain and the air density changes so you can't use as mush fuel. If the sensor sticks ( there is a mechanical diagram in it) you will not get a diagnostic code, if the shorts out or there is a broken wire you will get a diagnostic code. But not if the mechanical side of it sticks.
I've seen this sensor cause the low power problems. It is is a cheap replacement cost. I would replace it- it would be one less thing that could cause a intermittent power problem. Safe Travels

Cat just thinking here. I will probably just wait till I go out again and monitor the Throttle Position since the scanguage will do that. If the problem was to happen again, and it become constant, and it was the Atmospheric Pressure Sensor, could you drive with it unplugged at sea level?

[Cat]

Originally Posted by sawmillman

Cat just thinking here. I will probably just wait till I go out again and monitor the Throttle Position since the scanguage will do that. If the problem was to happen again, and it become constant, and it was the Atmospheric Pressure Sensor, could you drive with it unplugged at sea level?

Yes you maybe able to see the malfunction on scangauge for the TPI. Normally on a TPI problem. There is one spot in its travel that it loses the signal. So you will have to watch for that spot as you step on the throttle.

Scangage may show the atmospheric sensor readings on it. I'm not familiar with it. If it does---monitor the pressure it is showing it should be very steady since it is measuring barometric pressure. It see if it is accurate--- go to the weather website for your location and see what the weather guys are showing for barometric pressure. The CAT sensor should match it.

Unplugging the atmospheric sensor---- I'm pretty sure if you do that it will default to engine derated horsepower. And get a diagnostic code.
Hope that helps. Safe Travels