Surging issues

[Foehammer]

Problem: Explain your problem in concise language---- My truck runs fine at normal speed but occasionally when it is warmed up to operating temp and i have to stop at a light, after i take my foot off the accelerator and after i place my foot on the brake and the rpm's drop down to about 600(idle speed) it will surge quicklly 2 or 3 quick little "vrooms"(rpm 800-900) Throws no codes
Demographics: tell us about your truck and your ambient conditions:Las Cruces NM 89* temp in after noon
- Year: 1994
- Truck model and class (ie: c2500) K1500
- Automatic or Standard Automatic
- Mileage: (indicate miles or km) 186000 mls
- Replaced parts and mods (IP, PMD, chip/PCM, TM, injectors etc)D-Tech PMD bumper mounted on heatsink,CDR
- Model: ‘S’ or ‘F’ engine, NA or Turbo, EGR? "S" engine,Turbo ,Egr(disabled)
- Ambient outside temp: (indicate *C or *F) 89* F
- What fuel are you using? (#1 Diesel, #2 Diesel, Bio, VO, WVO, etc) #2 diesel
- What fuel additives are you using? 8oz PS white 16 oz TC-3W oil/ fillup
- Where are you located? Las Cruces, NM

General maintenance: inspect and evaluate the condition of each. When were they last changed?
- Air filter 4 months
- Fuel filter 4 months
- CDR Valve? 4 months
- Coolant – last flushed/replaced at dont know
- Oil – synthetic/regular, changed at regular oil leaks 1/2 qt/ week constantlly refilling
- Batteries – state of charge, (matched set) replaced at , dont know last replacement
- Battery cables and grounds (removed, cleaned and tightened): 2 months ago
- Glow Plugs - how many miles on them? dont know What type? dont know
- Injectors - last changed at dont know


History: (Describe how the problem first appeared.)
- What were you doing when it happened? slowing down to stop at stop light about 2 weeks ago
- How was the truck running fine before this problem appeared? Runs fine at normal rpms
- Has this problem ever happened before? Not more than 2 weeks ago
- Describe any related factors that might be part of the problem. Has surged in reverse about 3 times before in the past 6 months
- Have you checked for DTC (Diagnostic Trouble Codes)? (Y.N) Y And? only egr codes (31,32,33) and occasional 36 but no codes when it surges


Diagnostics:

1] Starting:
1a] Does the engine start? Y
1b] Does the engine crank over? Y
1c] Are your batteries fully charged? Y
1d] Have you removed, cleaned, and tightened all battery connections? Yes 2 months ago
1e] Does your Wait to Start light come on for a time? no wait to start glow plug light only
1f] Does your glow plug light come on? Y For how long? 10 secs
1g] Do you see smoke from the exhaust while cranking? Y when coldWhat color? whitish

2] Fuel Issues (if not running):
2a] Can you hear your lift pump working? Y
2b] Do you get a steady flow of fuel from the water drain (T-handle) ? Y
2c] Loosen the inlet line from the IP – is fuel coming out (Lift Pump on)? not sure how to do
2d] Loosen an injector line and crank the engine - does fuel come out? _________
2e] Do you hear a vacuum (hiss) when you remove the fuel cap? ___________

3] PMD / IP Issues
3a] Location of PMD (on pump, on intake, remote mounted) D-tech on heatsink in bumper
3b] Condition of Extension harness (if used) Vendor or Homemade? Vendor 4 months old
3c] Condition of grounds / ground wires to IP / PMD. Check Harness. good
3d] PMD Make: Dtech
3e] PMD Age: 3 months

4] Stalling Issues
4a] Do you experience stalling only when hot? ____________
4b] Does it stall under particular circumstances? (ie hit bump, or on accel) ______
4c] Does pouring cool water over the IP seem to help with restarting? _________
4d] Is stalling momentary (engine recovers)? _________
4e] Does SES light come on when engine hiccups? _________
4f] Does cruise control quit working when engine hiccups? ___________
4g] Does re-starting seem to reset engine, restoring cruise and power? _________
4h] Changes to dash lights or instruments during stalling events? ___________

5] Running Issues
5a] On cold start, does upper rad hose get hard before engine warms up? no
5b] Any bubbles or oil film in coolant overflow tank? no
5c] Any white slime on oil surfaces (dipstick, CDR, oil Fill cap)? no
5d] Excessive white smoke from exhaust on cold start? dont think so
5e] Excessive black smoke from exhaust under hard acceleration? a little black smoke when i move from stopped, more black smoke when i punch it

6] Performance Issues
6a] Do you have gauges? no
6b] Maximum boost under load? dont know
6c] Have you added a performance PCM (reflash) or Chip? no
6d] Have you changed exhaust / downpipe / crossover? no

6e] Wastegate – mechanical or vacuum? vacuum

7] Temperature-related Issues:
7a] Single or dual thermostats? single
7b] Have you replaced them lately? Manufacturer of replacements? no

7c] Have you pulled and cleaned Radiator and coolers lately? no

7d] Have you replaced the fan clutch? Manufacturer of replacement? no

7e] (winter) Have you tested your antifreeze? Good to what temp? __________
7f] (winter) Are you using a winter grille cover? ___________

I'm suspicious of my Optical sensor filter harness I took it off to see if code 36 was caused by harness and shortlly after ( within 5 days) it started surging, today i put it back on to see if surging stopped but it still surged and runs rougher

 

[Brooklyn Tow]

Sounds like classic PMD failure...but your FSD is 3 months old.

Does your cruise control function normaly?

Who's ext. cable are you running?

 

[buddy]

Where are you leaking oil? If you open the oil fill when truck is idling hot is there a lot of blowby vapor flying out? I see you replaced your CDR. If you are getting a lot of oil in the intake that can cause surging when oil hits the cylinders.

Maybe also the EGR, it was disabled, but did you block it off or just plug the vacuum line?

Did you remove the line from the EGR solenoid to the vacuum sensor on the drivers side firewall? That would give you the DTC 33, and might affect PCMs use of the wastegate solenoid too. If you didnt remove that line then you have a vacuum leak somewhere which will affect turbo operation giving you lots of black smoke when you punch it.

Need to get yourself a chip for the PCM out of an "F" engine, works much better. I have one you might be able to borrow if thinking about buying an aftermarket.

Are you putting some oil in the fuel?

 

[Foehammer]

brooklyn -Cruise control functions normally and pmdcable

buddy-im leaking oil from the oil cooler lines at block or near,when i open my oil fill i have blowby vapor kind of looks like a steamy cup of coffee, i changed my cdr because i had a light coating of oil in the intake not a lot just a little

egr is just plugged in the vac line for now, i know this is not the preffered method but I am on tight budjet and was going to block off when i change all my injectors and glows when i can afford i was also going to clean optical senaor at same time to avoid removing upper intake and replacing gaskets more than once

I have not removed the vac line from vac sensor and i think i have a leak at my wastegate actuator because the previous owner had put what looks like caulk or jb weld on an area of it, when i can afford i will get a heath "f" chip and turbo master. i need a boost gauge first tho.

if you have a spare chip i would greatly appreciate borrowing it and would even be interested in buying it from you if you would consider selling it.

i am putting about 12-16 oz of tc-3w 2 stroke in the fuel with about 8 oz of powerservice white in each tank. i think my code 36 is coming from a dirty optical sensor or cloudy fuel, dirty tank or possibly even the optical sensor harness as i believe it is the original and when i took it off recentlly i noticed my truck seemed to run smoother so i m pretty sure i at least need a new one of those.

in regards to my surging at idle i read a post today about surging at idle caused by coolant temperature sensor but im not completely familiar with all the landscape of my engine yet(6.5 noobie) if any one has photos they could post or know of links to other posts that describe/show how to change/identify CTS i would be very grateful. i have also considered the lift puimp might be failing correct me if im wrong but the lift pump for a '93 is not only compatible but a stronger lift pump and should get one of those if i need a new LP.

brooklyn thanks for the response any help is greatly appreciated

And buddy again thank you for all your help when ever i post you always have good advice and thorough explanations

 

[Brooklyn Tow]

Correct on the 93 LP

 

[buddy]

The CTS is another possibility. It is the sensor sticking up out of the thermostat housing on the passenger side, very accessable.

If the CTS fails or the wire to it breaks, the harness is loose it would provide a reading of high resistance which means cold temps, and it can kick into high idle.

Try unplugging it and see what the engine RPM is at idle.

 

[Foehammer]

Ok when i unplug the CTS it goes into high idle(850 rpm) and that is with my engine still warm. What should i be looking for and what is this telling me.
also when I inspected the plug I noticed rust in one of the terminals and the insulation was cracked anyone no where I can get a pig tail for this?

 

[NVW]

Ok when i unplug the CTS it goes into high idle(850 rpm) and that is with my engine still warm. What should i be looking for and what is this telling me.
also when I inspected the plug I noticed rust in one of the terminals and the insulation was cracked anyone no where I can get a pig tail for this?

Unplugging the ECT puts it into cold start advance so that's working.

Try slowly revving the engine up to 2000 rpm and hold, then slowly back to an idle. It should be controlled and smooth.

Leo

Edit: The rusty terminal could interrupt the circuit causing the high idle you experienced disconnecting the ECT sender, that or a break in the wire.

 

[buddy]

With bad connection or a cooked wire, both can contribute to high resistance readings to the PCM which will interpret it as cold.

By unplugging it you showed that the normal PCM reaction to losing continuity is to jump up to 850 rpms, which is in line with the surging you have seen.

If you have a digital multimeter and can measure resistance in the sensor itself, at 60 degrees or about cold in the morning it shoud read around 4000 ohms, give or take like 500. And when warmed up to about 185 degrees it should be 200-400 ohms.

If you want to take a continuity reading from the sensor harness back to the PCM harness I can describe how to test that.

 

[Foehammer]

thanks buddy i will try to get a multimeter to do that test soon, ill let you know when i do so that you describe the test to me
sorry guys that i have not gotten back recently my mom has been in the hospital getting a pace maker installed