Limited acceleration

crawdad-480 · **Joined:** Fri Jan 19, 2007 12:03 pm **Posts:** 47

Greetings,

I was driving my 06 CRD, getting onto the interstate, I stepped on the gas to get up to speed and
the engine wound up to about 2800 rpm, though the engine noise did not seem to correspond. The
jeep lumbered along increasing speed and it seemed the transmission was stuck in 2nd gear. I took
my foot of the gas and went back on it and it shifted and lurched forward. I have been able to
duplicate the problem. Any suggestions. FYI the road was flat. The CRD acted as if a big time
limiter had kicked in.

Thanks,

DarbyWalters · **Posted:** Mon Jul 02, 2007 3:37 pm

Sounds like the "limp" mode. You might want to try pumping the primer at the fuel head (where the fuel filter is) to see if that corrects it. If it does, then you have air leaking in the system...

Cowcatcher · **Posted:** Mon Jul 02, 2007 3:39 pm

Did it throw a code?

Two situations seem to trigger this. The first is a problem detected electronically that puts the truck in the "limp" mode and puts it in 2nd gear. Sometimes this will clear itself but it will almost always turn on your CEL and throw a code.

The second is a mystery and happend to me last week. I don't think it throws a code but the Jeep will hardlu move if not already rolling. it is worse thean "limp" in my opinion and it may be an air in the fuel related issue. In my case the motor sounded terrible, I had RPM's but no power. The solution to this is to park, shut down, wait a minute or so, they re-start. I was ORM at the time and the auto store's code reader was broken so I couldn't check the codes and my guess now is that they will no longer show but if memory serves, others who have experienced this have not gotten a code.

crawdad-480 · **Joined:** Fri Jan 19, 2007 12:03 pm **Posts:** 47

I checked to see if any codes were thrown and one was. Code P1189. I looked this
up on the net and all I could find was

Engine Oil Pressure Switch Circuit

Not knowing if this code may have a different meaning for the liberty, does any one know
if jeep has a different description for the P1189 than what I have above.

Thanks.

JL Rockies · **Posted:** Thu Aug 23, 2007 2:46 am

did you ever find a solution? Mine started acting the same way and I have the same code. Jiffy Lube was involved just before.

CHessMaster · **Posted:** Thu Aug 23, 2007 8:12 pm

If I remember correctly, that's the code that got thrown when my Ambient Air Temp Sensor (on the air filter box) got "disconnected". Might check that.

That would give you a low power condition too......

JL Rockies · **Posted:** Fri Aug 24, 2007 2:49 am

Well, the airbox was removed to install the lift last week. I will check to see if there is anything unplugged. Why would the code point to a oil pressure switch though? Where is this sensor located?

Cowcatcher · **Posted:** Fri Aug 24, 2007 10:21 am

I don't recall anythig plugged into the air box other than the MAF and if that is unplugged it runs better. It also throws a different code.

ATXKJ · **Posted:** Fri Aug 24, 2007 12:13 pm

In the Manual 'Charged air temp sensor' doesn't look like it's in the air box but on top - maybe it bumped?

Ambient air sensor shows to be at the bumper

CHessMaster · **Posted:** Fri Aug 24, 2007 9:59 pm

As your looking at the air filter box while standing the front of the vehicle, it is on the far right side of the box on the top (on the removable lid of the box).

You have to remove the connector to completely remove the top off the airbox.

crawdad-480 · **Joined:** Fri Jan 19, 2007 12:03 pm **Posts:** 47

Greetings,

It turns out I did find the cause of my loss in acceleration. I've been experimenting with the air filter box. There are
two sensors on the air filter box assembly. The MAF sensor, which we all love, and there is a second sensor on the
side of the filter box lid (closest to the engine). I'm not sure if it is temperature or pressure, but my bet would be on
pressure. I had disconnected the sensor and forgot to plug it back in. When it was unplugged, the engine would run
fine, but any type of medium/hard acceleration was a big no no. Once I had plugged the sensor back in, everything was
fine.

Thanks.

SC RIGGR · **Posted:** Mon Sep 02, 2013 1:26 pm

Ditto for symptoms and solution. I had pulled the airbox to get access to idler pulley for an Alt. exchange, and had not firmly seated the sensor. Thanx again to this forum.
Did anyone ever figure out what the p1189 code means? I looked in the tech section and nothing was found.

geordi · **Posted:** Mon Sep 02, 2013 2:32 pm

The sensor on the side of the airbox (which is usually known as "The Mercedes Logo Sensor" for those arriving via search) has no clear usage in the computer that I am aware of. Keith at Green Diesel Engineering may have more information about this, and specific codes that may relate to it.

What I can tell you: The wires on the top of this plug are VERY fragile, and a common problem (without codes, yay!) is for these wires to break internally and cause intermittent losses of power. As discovered, unplugging this sensor also causes power losses and mayhem without codes. The sensor itself is known to Mercedes as a MAP sensor - that is right, it is a pressure sensor, NOT a temperature sensor - and possibly is used by the computer to do actual fuel-map calculations, or maybe a double-check against the actual MAP sensor.

On the VW TDI side, unplugging the MAF sensor does put the car into a "default" fuel map, however the computer doesn't actually do this until after the first time you have tried to accelerate into second gear. Until that point, the car is sluggish (you don't notice this at idle / parking lot speeds) almost as if it is in limp mode. On the CRD, unplugging the MAF instantly puts the computer into the 'default' fuel map and throws the code. This second sensor has no equivalent on the TDI that I am aware of, however, the behavior of the CRD when it is unplugged is very similar to the TDI when the MAF is unplugged.

If we can better understand the usage of this sensor, perhaps GDE can eliminate the effects if / when it gets unplugged... Or at least link it to a code.

papaindigo · **Posted:** Mon Sep 02, 2013 2:49 pm

Keith can correct me if I get this wrong doing it at least in part from memory. My Parts notes say that's the IAP (inlet air pressure) sensor 5101120AB (pressure sensor on side of airbox). Exactly what it does relative to the engine's computer system I don't have a clue either but IIRC the GDE tune turns this sensor off although I'll admit I've not unplugged mine to see what if anything happens.

KD6ICZ · **Posted:** Sun Sep 08, 2013 2:51 pm

Cowcatcher wrote:

The second is a mystery and happend to me last week. I don't think it throws a code but the Jeep will hardlu move if not already rolling. it is worse thean "limp" in my opinion and it may be an air in the fuel related issue. In my case the motor sounded terrible, I had RPM's but no power. The solution to this is to park, shut down, wait a minute or so, they re-start. I was ORM at the time and the auto store's code reader was broken so I couldn't check the codes and my guess now is that they will no longer show but if memory serves, others who have experienced this have not gotten a code.

This exactly what happened to me today about 30 minutes ago! Drove down to my coffee shop (10 miles or so on freeway) and everything was great! Went to leave and getting on the freeway the engine started shaking and had no power. Finally got up the ramp and when the TC locked it didn't have enough power to maintain speed. Turned off OD and drove it home in third gear. A little smoke came out on the on ramp when I floored it but none I could see after that.

When I exited the freeway it almost wanted to stall. I stayed on it and made it to the signal where I turn into my apartments. It stalled. I restarted it and it stalled again. Restarted and slightly pressed on the throttle and put it into gear. Then it took off like a bat out of hell like nothing was wrong!

WTH??? No CEL. I haven't checked codes. I am on my third full tank of B20. Would that have anything to do with it?

UPDATE: I tried to read DTC's with my VCDS and "I think" it said no codes in Mode 3. So I was going to drive it around the block hooked up to graph some numbers (throttle position, rail pressure, water temp) and then I lost communication with everything except engine RPM and load %. So I shut everything down and restarted, now I have a CEL and cannot communicate with the ECU with either VCDS ODB II or GDE scanner. Is my issue a electronic issue?

UPDATE 2: I disconnected the battery for a couple of minutes and reconnected. I was able to communicate with the ECU. Only codes were the U0121's. Cleared them and CEL went out. Drove around the block (including freeway) all is back to running normal...
Weird...

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DOC4444 · **Posted:** Sun Sep 08, 2013 7:04 pm

Biodiesel is a powerful solvent (even B20). There is a strong likelihood that it freed up some sludge that plugged your fuel filter. If your rig has over 100K miles and has not at least occasionally been run on bio along the way, you need to replace your filter because of being blocked. If you want to keep running bio, buy a case of filters. It will eventually clear out.

DOC

KD6ICZ · **Posted:** Sun Sep 08, 2013 8:13 pm

DOC4444 wrote:

Biodiesel is a powerful solvent (even B20). There is a strong likelihood that it freed up some sludge that plugged your fuel filter. If your rig has over 100K miles and has not at least occasionally been run on bio along the way, you need to replace your filter because of being blocked. If you want to keep running bio, buy a case of filters. It will eventually clear out.

DOC

I currently have 65k miles and the current filter has 13k miles. I thinking at this point it was the ECU that screwed up. The second I completely turned it off and back on it started running normal. But I will keep an eye on the filter. I was told by a biodiesel "expert" (Neil Young's son) that B20 is not enough bio to clean the fuel system. It has to be pure biodiesel. I have a new filter that I could put on just to make sure.

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naturist · **Posted:** Mon Sep 09, 2013 8:30 am

I, too, doubt the solvent-unleashing-crud theory. Partly because B20 is not that powerful, and partly because the main effect would the the clogging of the fuel filter, which would not likely be reversible. That is, it would not come and go.

I do hope the OP gets it sorted out. Intermittent lack of power not only sucks, but can be dangerous. Nothing like pulling out onto a crowded highway and finding you got no go, as your ears catch fire because the driver of the semi coming up behind you curses you and your descendants.

Limited acceleration

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