Hello, i have an 6.5 diesel Chevy when the engine is cold the engine runs fine. When the engine is warm and pull down the trottle the engine goes in gallop rpm from 600 to 1100 up and down. When i pull the transmission in gear it runs fine. Have replaced the pmd to a remote pmd(new). with no change. Please can you help me. It's an Chevy diesel (no turbo) 1994.

Sounds like TCC brake switch. Normally at a coast you should see about 1000-1100 RPM's, push the brake pedal and motor should idle down to approx 600, let off brake and RPM's come back up, etc. Check wiring at brake pedal switch, grounds, etc. Scan for codes.

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Welcome, BTW. Please fill out signature so that we can all see what your running. Helps when troubleshooting. Go to "User CP" at top of screen and "Edit Signature".

You have a non turbo 6.5L with an electronic injection pump? Rare. Let's see some pics an info on the truck.

It is an Chevy Starcraft g20 6.5 Diesel 1994

Hi, have read the codes, 66 and 32 . The 32 code is an egr problem but have removed the vacuum line from egr with no result engine is still running in gallop (up and down)

I don't see 66 on the list. Anyone able to enlighten us????

Have you checked the brake switch yet?

i had a 94 g20 and it started that and week later new pump

"pulled into gear"

are we talkin' manual or automatic tranny?

Okay. Code 66 is 3-2 shift solenoid. I suspect that when the transmission wants to downshift it is having problems hence your dancing RPM's.

Sometimes a transmission oil change clears up solenoid problems. Otherwise, check wiring at harness and if okay, try replacing the solenoid.

Have checked the brake switch and wires and connectors it's all ok.
Have replaced the I.P. (rebuild) and new injectors but no change, engine still going up and down in rpm. Everyting checked, fuel pump, all wires from I.P. to head connector. I dont know it anymore. Had the van connected to a laptop, no codes, but on statusflag gives an (minimum threshold, and steppermotor inhabation). Could it be the throttle pedal?.

Are you not getting a code 66 anymore? I was looking at some electrical diagrams and seems 3-2 shift solenoid applies to 4L60-E transmission. Do you know which trans is in the van?

Has the EGR problem been fixed?

I think I would go after the codes that you were getting before throwing more big $ parts at it.

Were batteries disconnected for IP replacement??? When were codes scanned for again? Disconnecting batteries will clear codes until problem shows itself again.

About throttle, if you've got the laptop hooked up, you can look at the voltage readings from the APP. Should show 3 different values (Accel ped pos 1, 2 & 3). When problem occurs, see if any of the voltage reading spike or drop out intermittently.

Laptop connected to the Van and codes 66 3-2 shift solenoid and 88 TDC offset error. Throttle pedal looks good got different voltage on 1-2-3 and no spike on it. The transmission is a 4L60 E. When the engine is dancing with his rpm's then a little turn on the steering wheel and the engine runs normal, when no power is ask from the engine, it go's dancing with his rpm's. Only when the engine is cold it runs fine(more resistance) ill think.

Are you saying now that it is doing this at idle when hot or is it still while cruising? Have you checked/cleaned all grounds and battery connections as per FAQ? Also, full results of diagnostic checklist might do some good for this one.

Okay so EGR codes are gone. Trans code still there. And now after new pump TDCO error.

Did you do TIMESET and TDCO learn after installing pump?

Check TDCO on scantool. Should read -0.5 to -1.5 IIRC factory setup. For performance, everyone seems to be going after -1.94 but lets start with the factory specs.

Rpm dancing is only when engine is hot and in park or neutral. When driving the van then no problems. It sounds like fuel solenoid is on - off every time but it isn't. TDC is -2.02 on laptop. The tdc learn function does not working on my new injection pump.

Okay, that is probably your TDCO error. Which scantool are you using?

Please do diagnostic checklist, grounds, batt cables, etc.

What is the location of the fuel solenoid ground wire that is supposed to be on the top of the IP? Location/age of PMD? Age of injectors?

I use gmtd scan tech program from Engh motors. Location of ground is on the fsd cooler kit. PMD is 2 months old and injectors are new from Bosch.

Put the ground wire back on the IP and see what happens. Quick, easy, try that and we'll go from there.

One more thing. According to one of the 'place's expert's, GMCTD, that ground wire NEEDS to be original length or it will cause problems. It is better off left where it was originally.

Ok, thanks ill will try it right now

If the ground wire doesn't do any good, still leave it in its original location and go to the filter harness on the IP. Connects to the optical sensor, has a little black box in the middle of it and then goes to vehicle harness. Disconnect the filter harness and connect the vehicle harness directly to the OS.

Diagnostic checklist next. Here is the link, please post all results. http://www.dieselplace.com/forum/showthread.php?t=42248

Have the ground wire replaced to it's original position but no change. The wires (6)from the optical connector goes directly to the main connector.

Post the checklist I linked to next then.

Although I really think TDCO code should get cleared. When you tried to do TDCO learn with ScanTech, was the toggle switch on the adapter cable in its forward-most position (toward the ALDL)? There is a FAQ on their site re: performing TDCO learn.

1. Does the engine Turn over? Yes
1a. Does the engine start? Yes
1b. Do you have a Wait To Start Light & duration lit. No
1c. Ambient Condition (temperature outside) 18 deg. celcius
1d. Engine Cranking speed (if you have an accurate tachometer). Normal
1e. Are you experiencing stalling? No
1f. If Stalling, describe (upon startup only, down the road, hit a bump etc)
1g. If Stalling, do you notice loss of dash or instruments?
-note if experiencing stalling,you must indicate PMD location in #24.
1.1Lift pump test - Opening the bleeder valve gives a lot amount of fuel
2.Service Engine Light - some times on
3.Model year Chevy Starcraft G20 6.5 Diesel 1995
3a. Odometer reading
3b. Miles on major engine components if been replaced (example Injection pump) Engine has 285.000 Km Injection pump(rebuild) and injectors are new
3c. Indicate the model number on the Injection pump. Pump is Stanadyne ds4
4. Have you scanned for engine codes? Yes 66 and 88
5. List exact results on engine codes:3-2 control solenoid and tdc offset error
6.Air Filter condition (visual check) good
7.Fuel filter condition (freshly changed or condition unknown) New
8.Condition of Battery terminal connections (removed, cleaned and tightened OK)
8A.Known condition and age of the batteries. Condition good both the same
8B.Are batteries of differing age or are they a matched set? No
8C.Condition of Major Grounds. (same drill as batt - removed, cleaned, retightened) Checked
9.Upon cold start, does the radiator hose get hard quickly? No
10.Upon cold start, do you have excessive white smoke? No
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) NO
13.During hard acceleration, do you have excessive black smoke? No
14.Do you have any unusual exhaust smoke issues? No
15.Turbo check out - Non turbo
16.Do you have an EGR on the engine? Yes
17.Indicate if you know if it’s a 1500, 2500, 2500HD, 3500, 3500HD. ?
18.Indicate fuel that you are using: Bio-diesel, #2 Diesel, #1Diesel, SVO/WVO, other
18a. If running a VO setup, indicate details of your conversion (homemade, or packaged system)
19.Are you using any fuel additives? If so, please list. No
20.Please indicate geographic region you are in: Netherlands
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. Rebuild injection pump (green tag)
23.Upon unscrewing the fuel cap, do you have a large vacuum formed in the tank? yes, only the engine is not running
24.Location of PMD/FSD? Remote pmd above valve cover near the aircleaner
25.Are ALL glow plugs in proper working order as per this thread? Yes

Try running without the fuel cap. Shouldn't be vaccuum formed in tank. Do you have a diesel specific cap. Gasser cap is no good.

Have removed the fuel cap, and a big psssss was there. It is an original diesel fuel cap.

Cap may have a faulty vent then. Have you tried running without the cap?

Very weird, when i set the idle from 600 to 1000 with the laptop it goes dancing in rpm 1000 to 1500 up and down

Yes, had the engine running yet but it still going up and down without the fuel cap.

Got me stumped then. How's that TDCO code coming?

Yes, the 88-TDC offset is still present, but ill think it has nothing to do with the dancing rpm's. It's very weird that the engine must give a little bit of power by turning the steering wheel or pressing the brake pedal and it runs fine. Then when i loosen the steering wheel the engine runs fine too. But when you press the throttle pedal it comes back, a little turn on the steering wheel and the engine runs normal. But when driving no problems engine have al lot of power and no dancing in rpm when it is in D(drive).
When i pull the connector from the optical sensor it run also fine(less power), no more dancing rpm's.

Hi, 'bird - your OBD1 system usually requires an RFI\EMI filter in the Optic Sensor circuit, oem equipped - you can get a new replacement from Heath Diesel, or maybe locally, there - might try Beta Maskin in Denmark, tell him I referred you

Also, you indicated a Timing Stepper Motor inhibit fault tripped in GMTDScan?

Ok, thanks GMCTD i will look at Beta Maskin for an RFI\EMI filter.

Ask for the Optic Sensor Filter required for OBD1 system

GM # 12553327 electronic noise filter