1999, 6.5 L Diesel. rough idle, hard shifting.

hello. I own a 1999 gmc sierra 3/4 ton 6.5 L Diesel.
if I don't plug in my block heater, even at 10 celius (50 fahrenheit).
when I start it up, truck runs rough. but idles smooth when i go put it in gear but when I drive off with it, it seems like hard shifts, gives fuel, than no fuel.

i'ts like stop and go till the engine warms up and smooth out. and at highway speeds it seems to shift in and out of over drive all the time. after awhile it loses over drive. and have to park it. and re-start it. put computer on it got a 1870 fault code. (transmission slippage)

it seems like I got a engine and transmission problem here. I was hoping someone ran into this problem before and can tell me what's causing this to happen.

thanks.

Kevin

I don't know if diesels have a Mass Air Flow Sensor (MAF) or not but if you have a K&N or other oiled air filter, your problem may be that filter contaminating the MAF sensor. GM has TSB on that.

Do you have one of these oiled filters?? Get rid of it.


Info - Automatic Transmission Shift, Engine Driveability Concerns or Service Engine Soon (SES) Light On as a Result of the Use of an Excessively/Over-Oiled Aftermarket, Reusable Air Filter #04-07-30-013A - (Jan 25, 2005)

2005 and Prior GM Cars and Light Duty Trucks

2005 and Prior Saturn Models

2003-2005 HUMMER H2

This bulletin is being revised to add additional model years and to clarify warranty coverage. Please discard Corporate Bulletin Number 04-07-30-013 (Section 07 -- Transmission/Transaxle).

DO THIS:

First, Inspect the vehicle for a reusable aftermarket excessively over- oiled air filter.

DON'T DO THIS:

DO NOT repair MAF sensors under warranty if concerns result from the use of an excessively/over-oiled aftermarket, reusable air filter.

The use of an excessively/over-oiled aftermarket, reusable air filter may result in:

• Service Engine Soon (SES) Light On
• Transmission shift concerns, slipping and damaged clutch(es) or band(s)
• Engine driveability concerns, poor acceleration from a stop, limited engine RPM range

The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF) sensor causing contamination of the sensor. As a result, the Grams per Second (GPS) signal from the MAF may be low and any or all of the concerns listed above may occur.

When servicing a vehicle with any of these concerns, be sure to check for the presence of an aftermarket reusable, excessively/over-oiled air filter. The MAF, GPS reading should be compared to a like vehicle with an OEM air box and filter under the same driving conditions to verify the concern.

The use of an aftermarket reusable air filter DOES NOT void the vehicle's warranty.

If an aftermarket reusable air filter is used, technicians should inspect the MAF sensor element and the air induction hose for contamination of oil prior to making warranty repairs.

Transmission or engine driveability concerns (related to the MAF sensor being contaminated with oil) that are the result of the use of an aftermarket reusable, excessively/over-oiled air filter are not considered to be warrantable repair items.

If the engine runs OK after it warms up, then the problem could be with the glo plugs. Either the glo plug module is not signaling to heat up or a couple of glo plugs are failing.

If the transmission uses engine/pump vacumn to shift, the engine running bad could affect how it shifts. If it is electric assist, then you have two seperate problems.

I can't see the MAF sensor fixing/cleaning itself after the engine warms up. It should continue to give problems until it is fixed.

the air filter I have on it, is the regular one from the dealer. no aftermarket.

and when I turn the key. it seems like i hear weard noises coming from my guess would be a glow plug module. so Maybe i'ts on his way out.

and I believe the transmission is electric assist

1870 fault code (transmission slippage). and on a highway it will always shift in and out of over drive. till i lose the overdrive. and have to re-start the vehicle.