Bad Idle on my 6.5, Please Help

[Harqobispal]

Hello all,
I have a 1996 6.5l Chev TD. It was running poorly about 1 year ago(it was stalling and dying all the time). I bought and installed the heath PMD/FSD kit. At the same time i installed a new lift pump and regrounded everything. I also removed the TURBO POWER cowl. The truck ran perfectly for a year.
Now i have a new prob. It is pretty much exactly like this post.

http://www.dieseltowingresource.com/showthread.php?t=2552&highlight=missing

After the truck gets warmed up it start bucking, missing, shuddering , shaking.
If you speed the engine up above 1000 rpm runs smooth as silk. I have had it surge only 2 times when it was doing this missing, bucking thing. The first time it was very scary, was coming up to a red light and i could tell as the truck was slowing down it was doing the bucking/missing thing. Then just as the truck slowed to a stop it revved and surged forward. THen when back to missing. I replaced the main fuel filter 2 times. also ran more than one tank of fuel through it. It has been doing this for about 6 months off and on.
Does anyone here have any ideas why my truck would be doing this?

 

[Acesneights1]

Any codes ?
Any smoke ?
A seroiusly gacked up EGR can cause a rough idle but I don't think it would be bucking. You replaced the lift pump but what about the OPS ? Is the lift pump pump good presuure ?

 

[chrisk1500]

How many miles on that IP?

 

[JMJNet]

My suggestion is to DO the diagnostic checklist. It is located on the sticky under "Technical Library" in the 2nd post.

That way, you can do it in a more thorough manner to eliminate the easy stuff and we are not guessing.

 

[Harqobispal]

Sorry for the late reply, been busy. I checked everything over again when it was doing it the other day. It is very annoying because sometimes it will idle perfectly and other times it is horrible(bucking shaking) you can also hear it miss when you are outside and near the exhaust. Again typically it only does this when warmed up and when below roughly 1000 rpm.
I have replaced the lift pump, i also checked it again and the flow seems normal. I have not replaced the OPS (is that the oil pressure switch?) No Codes, and no smoke. Engine really shakes when it is missing bad though.
There is roughly 169,000 miles on this Injection Pump if it is the original. I dont see anything to indicate it is not original. Thank you to all you guys that replied. The Checklist is below. Could it be bad injectors or something?

Diagnostic Checklist
0. Describe in detail the problem you are having. Please be as descriptive as possible.- The truck misses bucks and shakes at idle. It is typically when the truck is warm. It will not do it when the truck is revved up above roughly 1000 rpm. It has been doing this for about 4 months. It will also sometimes surge. The surges have happened twice. It has a new fuel filter and lift pump. Also has Heath PMD relocator
1. Does the engine crank, or 'turn over'? - Yes
1a. Does the engine start and run? - Yes
1a1. If the engine does not start - Crack injector line: do you have fuel? Yes/No – N/A
1b. Do you have a Wait To Start Light & the amount of time (seconds) lit. Yes – time is normal
1c. Ambient Condition (temperature outside indicate F or C) _____ ° 30F
1d. Engine Cranking speed (if you have an accurate tachometer).
1e. Are you experiencing stalling? – No- However sometimes it feels like it will when it is at idle bucking , missing and shaking.
1f. If Stalling, describe (upon startup only, down the road, hit a bump etc) – Does not stall
1g. If Stalling, do you notice loss of dash or instruments? –N/a
-note if experiencing stalling,you must indicate PMD location in #24. PMD is relocated to skid plate

1h. Check turbo inlet and air filter for obstructions. Cone filters have lost disk and stopped air to turbo. – No Obstructions
1i. In a no-hot start, pour a bottle of room-temp water on the injection pump. Does it start now? yes/no – n/a
1.1 Lift pump test - describe results – When water bleed valve is cracked a good supply of fuel comes out and engine does not die even if you rev it.
2. Service Engine Light while running?- on/off/intermittent - no
2a. Service Engine light does glow during start/cranking/bulb check: Yes/No - Yes
3. Model year 1996
3a. Odometer reading (indicate if in miles or km) 169,139 Miles
3b. Miles on major engine components if been replaced (example Injection pump) Don’t know IP, lift pump and PMD are only 1 year old. All filters are only 2 months old.
3c. Indicate the model number on the Injection pump (starts DS4 or DB2......) DS4
4. Have you scanned for engine codes? (varies by pre/post 96) yes/no Yes, there were none.
5. List exact results on engine codes:
6. Air Filter condition (visual check) Clean
7. Fuel filter condition (freshly changed/condition unknown/mileage since changed) Clean
8. Condition of Battery terminal connections (removed, cleaned and tightened) Clean and tight
8a. Known condition and age of the batteries. 1 year old, good condition
8b. Are batteries of differing age or are they a matched set? Matched set
8c. Condition of Major Grounds. (same drill as batt - removed, cleaned, retightened) All of these grounds were cleaned and re-grounded 1 year ago when new PMD was installed.
9. Upon cold start, does the radiator hose get hard quickly? Yes/no N/A
10. Upon cold start, do you have excessive white smoke? Yes/no Only initially it does not seem excessive
11. Do you have excessive cranking time before the engine starts? No
12. Have you used the block heater, and does this effect engine starting?(only try for starting problems) N/A
13. During hard acceleration, do you have excessive black smoke? Yes/no - No
14. Do you have any unusual exhaust smoke issues?- No
15. Turbo check out - pass/fail - Turbo seems to be working
16. Do you have an EGR on the engine? (An F or an S engine code 8th VIN digit) -NO
17. Indicate if you know if it’s a 1500, 2500, 2500HD, 3500, 3500HD. - It is a 1996 K2500
18. Indicate fuel that you are using: Bio-diesel, #2 Diesel, #1Diesel, SVO/WVO, other - Normal Diesel
18a. If running a VO (Veggie Oil fuel) setup, indicate details of your conversion (homemade, or packaged system) N/A
19. Are you using any fuel additives? If so, please list. – occasional seafoam
20. Please indicate geographic region you are in: (example: Texas or Canada) – Minnesota, USA
21. Do you have any service history available that might pertain to the problem you are having? - No
22. Please indicate any modifications to the vehicle that might help us diagnose better. - Cartridge air filter has been removed and K&N cone filter has been installed
23. Upon unscrewing the fuel cap, do you have a large vacuum formed in the tank? yes/no – No not really
24. Location of PMD/FSD? On the pump/remoted over intake/remoted out of engine bay (please specify placement specifically) – PMD/FSD is located on Skid plate below engine.
24a. If remote mounted, describe wiring harness (homemade or purchased from a vendor?)- Purchased Heath Remote PMD kit.
24b. Indicate the location and condition of the FSD/IP grounding wire. - I would assume it is part of the heath harness.
25. Are ALL glow plugs in proper working order as per this thread? -Yes they all work.

 

[Harqobispal]

Looking for Help on missing and bad idle

I am just following up on this. My 6.5L is still suffering from this problem. It seems to be getting worse. It is now missing at freeway speeds. Not alot but you can feel when it misses. Still no codes, have not been stranded yet. Yesterday at a stop light i thought i was going to be though. Engine was missing, bucking, lurching really bad. If you hold the RPM above 1000 runs normally. It is very annoying.
Does anyone know what could cause this?

Thank you all for this forumn as well. I have read alot of your posts. I just wish one would address my problem, so i could fix it.

Thank You.

 

[Acesneights1]

Sounds like alot of miles on the IP. These IPs don't really like ultra low sulfur fuel. Since you have already dealt with Bill Heath I would give him a call. He can tell you how to do the IP test. If it fails I would do injectors too. IIRC you have to bring it up slowly to 2000 rpms(engine at operating temp) try to hold it there then slowly bring it back down. If it won't hold at 2000 or drops off when you come back down IP is shot but double check that procedure with Bill unless someone else wants to chime in on it. You can also check with your local stealer to see if the pump was ever done under warranty and at what mileage. They can run the vin.

 

[Bullseye240]

I would double check all my fuel lines between the tank and IP. Any slight leak will cause the IP to draw air and cause a miss. Mytruck had a miss under slight load and occasionally while running down the highway. It would also stall and surged once. It would run ok at a high idle (900-1100 rpm). I replaced my lift pump with an FRB5 and installed a spin on prefilter between the new pump and the tank. When I removed the original lift pump I noticed the fitting on the IP side of the lift pump was lose enough I didn't need a wrench to remove it. Since I installed the FRB5 my truck has run flawlessly. It even runs quieter and idles smooth as silk. Keep in mind this truck has 236000 miles on it and as far as I know it has the original IP. I would try this before replacing an expensive IP. Just my .02 worth.

 

[JiFaire]

I'm with Bullseye on this one... always do the cheap stuff first. Besides, if you DO end up installing a new IP, then you have this nice, air-free fuel to feed it with

Remove and clean EVERY ground... then check all of your fuel lines from tank to IP... you can pressurize your fuel lines from the tank side to see if a leak develops somewhere. Aces is right that your mileage is getting up there, but if you have been running some lubricant with your fuel, your IP shouldn't be worn out, yet.

Jim

 

[Missy Good Wench]

When the engine is idleing and "Missing" is there any excessive smoke from the tail pipe.
A bad injector can fail to work properly at idle due to lower pumping pressures.

If the beast runs ok when cold, try this. Dump 2 quarts of 30wt oil in the fuel tank. Mix it with a little diesel so it will pour in easily and mix well.

Run the rig and see if the issue is better or goes away.

If the problem abates then your IP is probably needing help.

The electronics are constantly minitoring things and if any anomalies present then the ECM changes settings trying to compensate for the issue. (Surging)

One bad injector can make the thing run horrible at idle but there will be smoke if its a missfire.
Now if its a bad pumping chamber/plunger in the IP then the injector may not even POP causing a miss.

Keep us posted

MGW

 

[mfgguru]

I would double check all my fuel lines between the tank and IP. Any slight leak will cause the IP to draw air and cause a miss. Mytruck had a miss under slight load and occasionally while running down the highway. It would also stall and surged once. It would run ok at a high idle (900-1100 rpm). I replaced my lift pump with an FRB5 and installed a spin on prefilter between the new pump and the tank. When I removed the original lift pump I noticed the fitting on the IP side of the lift pump was lose enough I didn't need a wrench to remove it. Since I installed the FRB5 my truck has run flawlessly. It even runs quieter and idles smooth as silk. Keep in mind this truck has 236000 miles on it and as far as I know it has the original IP. I would try this before replacing an expensive IP. Just my .02 worth.

I would tend to think that if it was sucking air, it would get worse as the engine demands more fuel and sucks harder on the fuel line. Could be a plugged tank sock, but that usually causes higher RPM stumbling and even stalling. That was my experience. I'm with MGW on this one. Sounds like mechanical problems ie. IP or Injectors. I hope not for your sake H.:smile5:

 

[Turbine Doc]

There is a diagnostic test to help rule out IP, whenever you get get erratic speed control one has to suspect the IP armature, as well as just plain ole tired IP so 1st test in addition to checking gnds & other connections for cleanliness, is to run in cruise control, that removes the APP (Accellerator Pedal Positioner) from the loop and speed control is then with PCM governing, if still erratic your APP isn't cause of erratic rpm, if running with cruise clears it up then APP wiper/contacts may be dirty, many have CAREFULLY opened APP and cleaned the contacts and restored operation.

Bill H also recently shared with me a trick that has identified for them many a bad IP, run truck to full warmed up 20-30 minutes of driving if possible, put truck in Park, rev engine to idle to 2000 rpm slowly and then for 3 count at 2000rpm then slowly retard back to idle, is if hiccups during run up/down like a gasser with bad ignition timing get your wallet out you are due and IP in near future.