EGR Problems

[A Tilch]

Hi there!!

I have a 98 K1500 with the L56. I have had a severe case of smoking when accelerating from stop. I took it to the dealer and they had no idea what the problem is, even though they were able to reproduce the problem. The said that they think the MAF is bad. When I brought it to their attention that the MAF is used for EGR control and not fueling the thought I was crazy. Well that will be the last time I go there.

I get it home and I put in a new wastegate sol. and the problem is still there. I disconnect the vacuum hose to the EGR. And guess what? Problem gone!!!! But now I have a check engine light.

I have done a lot of research on this page reguarding the EGR system. My question is this. What needs to be done exactly to fool the PCM that the EGR is still connected at is working without replacing the PCM? If not then what needs to be done to upgade to a L65 PCM?


Aaron Tilch

[Turbine Doc]

Aaron,
You may have a bad EGR solenoid there are 2 for EGR 1 for vent & 1 for control look at the schematic on sticker under the hood. I doubt bad MAF. Go to www.***********.com (http://www.***********.com) look in the 6.5 forum for some info I posted there on L56/65 conversion. Do you have access to a code reader if so see what codes you are throwing, I have same set up as you and can do more with some codes to see where to look. Could be bad baro sensor, PCM, gasket, solenoids. Looks like that link isn't going to be displayed; get with Jim Bigley and get my email address and I can send you some more info from my 98 GM manual what to look for.

[ 10-10-2003, 11:33 AM: Message edited by: tbogemirep ]

[DChristie]

Aaron, I recall another post not long ago about egr troubles.

I disconnect the vacuum hose to the EGR. And guess what? Problem gone!!!! But now I have a check engine light.
It's really a bearing problem. wink wink. If you place the egr vacuum line on the egr valve with a ball-bearing in it... visual inspection reveals a stock system, the pcm never see's a leak (disconnected line)hence no SES codes. This should only be used in an "off road"
vehicle as I understand it. I think that was the gist of the earlier post anyway.

[A Tilch]

I have tried the ball bearing thing and then the check engine light came on. I believe that the map sensor that reads the vacuum in the egr valving system is reading a pressure or vacuum from the egr depending on different parameters. GM uses this type of system on their other vehicles that do not have an electronic acuated egr valve. So I do not think that it will work. Unless the check engine light is on for another reason.

Aaron

[triggerman]

It sounds like you more than likely have a P0401 insuficiant EGR flow. Any time you accelerate the egr vacuume should go to zero.If it dosent,you will get what you have. If you tee into your egr vac line with a vac gauge and find you still have vac during acceleration, you will need to change the selinoid that controls the on/off vac to the egr valve.Depending on engine speed through the MAF, you should see 12 to 22 inches of vac opperating the EGR only while holding a steady speed on level ground. If you still have the prob, I'd change the other selinoid and then the baro sensor. Hope this helps