Engine/Transmission (1998.5 - 2002) surging, need help

[CEdwards]

Truck has started slowing down, you can feel it defueling. Hit the pedal and it takes off. Doesn't matter what speed, doesn't matter if truck is cold or operating temp. It will slow and then pick up on its own or you can give it a little pedal. It just does this off and on every 10 seconds to 1 minute. Did a little search on here but most posts are about automatics. I read it could be the APPS, bad ground, speed sensor(is there one on a manual?), etc. Can anyone point me in the right direction. Fuel pressure is always good. Does not do it with cruise on. what does this mean? It always had that hardly noticeable fluctuation in rpm with and without cruise on that seems to be pretty normal, but this is different. Changed IAT out and cleaned MAPP last week. ABS light has been on since this problem started, might be coincidence since I just put new ball joints on last weekend.

 

[CEdwards]

Just checked the codes, got p1693. Some kind of companion code that I don't understand. Help anybody.

 

[hcole]

If this is happening on your 2001, it sounds like it is the APPS. I have a 2002 5 speed that I just replaced the APPS on because it was surging like you describe. The reason it doesn't do it on cruise is because the signal for the speed comes fom the ECM and not from the APPS on a manual transmission truck. Get in touch with -- email address removed -- and he'll send you a new one (better than factory) for $160. 00.

 

[blacksheepdiesel]

Some 2001 manual transmission trucks have vacuum cruise. Don't know if the change to electronic cruise came with the 2001. 5 model change to disc brakes or not.

Since yours does not exhibit symptoms with cruise engaged it is most likely the APPS. And Timbo is the man!

Godspeed,
Trent

 

[CEdwards]

I didn't realize it gave codes for pcu and ecu, I was just turning the key off after it said p done. First time to own anything with codes, amatuer mistake. So I also got p0177, water in fuel. I don't think this is related because my water in fuel light never came on when it was cutting out, maybe it was already on there from a long time ago. I couldn't get it to act up last night or this morning, but I think I will go ahead and replace the APPS. hopefully it will smooth my rpms out anyway. I tried to search on here to see how to clear the codes without a scanner. Is this possible? I disconnected the battery before I drove to work and the 1693 code wasn't there but the 0177 was still there. Drove to work and the 1693 was back. By the way does having electronic cruise mean that if the APPS failed you could still drive with the cruise?

 

[hcole]

I don't think so. You have to be traveling at a certain rate of speed (35 mph?) for the cruise to engage.

 

[Bob Cochran]

Mine is an early 2001 with rear brake shoes and has vacuum cruise control. Not sure if it is because a 1 ton or not though.

Oh forgot some codes will go away I think after 4 starts and problem not present. Other codes will have to be removed by a reader. Look for somebody close by with reader or say a Smarty, etc can clear codes for you.

 

[blacksheepdiesel]

I don't think the 1 ton has anything to do with it.

Godspeed,
Trent

 

[Bob Cochran]

I don't think the 1 ton has anything to do with it.



Godspeed,

Trent

I agree but I don't know one way or the other so said so. Sort of a disclaimer!!!!

 

[CEdwards]

where would I find the vacuum actuator if it was vacuum cruise? I assume it would be somewhere near the throttle linkage by the injector pump. I didn't see anything but I need to look closer after I get off work. I guess I need to know what kind I have to help diagnose any problems. Thanks for all the help I have been learning a whole lot about my truck on here.

 

[Bob Cochran]

According to my service manual diesel engines with manual transmissions do not have a speed servo. It says all controlled by ECM having said that I am confused. I know I one time knocked a vacuum line loose and no cruise control. The line went to what I thought was a servo under the left hand battery tray. Bottom line I am now confused and not sure what to tell you. So is it vacuum or electrically controlled I have no clue now. I am sorry no help here on this; probably confusing everybody else along with myself!!!!

 

[blacksheepdiesel]

There are trucks with vacuum cruise and some with electronic cruise. The vacuum cruise will have a 2nd cable hooked to the APPS. The vacuum unit is indeed located under the driver side battery, and yes, the cruise will become inoperable if the vacuum hose is disconnected. A guy can't believe everything he reads, especially when the evidence is contrary.

On a vacuum cruise truck the cruise still uses the APPS to control speed. On an electronic cruise truck the ecm controls the VP44 directly. Therefore, an electronic cruise truck that exhibits symptoms ONLY when the cruise is not engaged points only at the APPS being the culprit. On vacuum cruise trucks a bad APPS will exhibit symptoms with the cruise engaged or disengaged but other items could also act like a bad APPS so more diagnosing is in order.

Hope this clears things up.

Godspeed,
Trent

 

[CEdwards]

Just wanted to follow up on this thread. I changed the apps with one from TIMBO and it seams to be perfectly smooth, no surging. It might be my imagination but the throttle response does seem a lot better. Also, I must have electronic cruise because there are no vacuum lines going anywhere except through the fire wall and I have a 1 ton with rear disc brakes built in the second half of 01. Thanks for all the help and info I really appreciate it. It would be so hard to figure out how everything works without this site and without members like TIMBO who are willing to find a better answer to problems then the people who design these trucks.