GregH Posted December 11, 2010 Share Posted December 11, 2010 This bus was brought in with a surging complaint while driving. P0404 present in continuous memory. KOEO and KOER both pass. 3000 miles ago another dealer put an EGR valve in to cure a P0405 and P0471. The current mileage is 84,000. While driving at any throttle position, the EGRDC will cycle from 0% to 100% and back a little faster than once per second. Under heavy throttle, this results in a slight surging sensation. Under moderate throttle, the surge is much more pronounced. VGTDC will also vary about 10% in time with the EGRDC. EGRVP responds as expected - opening and closing fully in response to EGRDC. EBP varies as well, rising above and below EBP_DSD by about 3psi at moderate throttle. No other PIDS seem to be cycling like this. The EGR test passes. The graph is nice and smooth like you would expect from a new EGR valve. The turbo boost test passes, too. Smooth curves and 3psi max boost. I replaced the EBP sensor as a guess. No effect. Anyone have any ideas? Quote Link to comment Share on other sites More sharing options...
mchan68 Posted December 11, 2010 Share Posted December 11, 2010 IAT #2 sensor carboned up, delaying actual input to PCM perhaps? Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted December 11, 2010 Share Posted December 11, 2010 I am thinking out loud here... The last several surging complaints I verified and was able to make recordings for showed the VGT moving in rhythm as you described. These were trucks with badly worn VGT unison ring control slots. I have also seen in recordings EGR valve actuation used to slow the turbocharger under over boost conditions caused by seized unison rings. Performing the IDS boost test will not always pick up unison ring issues and pass a turbo with problems BUT the IDS VVT test WILL always reveal stuck/sticky vanes and wear. P0404 is defined as "Exhaust Gas Recirculation Control Circuit Range/Performance" but I beleive this is based on conditions like sensor inputs and expected values. My thoughts on this type of concern are that it's not necessarily an elctrical issue (sensor or actuator) but a condition causing an air management problem... something is blocked, stuck, gummed up or worn out. I would perform the VVT test before moving on... then start diggin. I hope this makes sense or am I totally off here? Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted December 11, 2010 Share Posted December 11, 2010 You are dead on the money, Keith. I would put all my chips on a turbo crapped out. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted December 11, 2010 Share Posted December 11, 2010 +1. Important to pay close attention to the "shoulders" of the VVT trace... Quote Link to comment Share on other sites More sharing options...
GregH Posted December 11, 2010 Author Share Posted December 11, 2010 In response to Mike - IAT2 could be carboned up. Running down the road, EOT and ECT had cleared 185F and were still rising, with an ambient of 40F, and IAT2 stayed on 104F. It wasn't until EOT and ECT had cleared 200F that IAT2 finally clicked above 104F. It took another 10 miles of steady 65mph before IAT2 cleared 110F. I think IAT2 has got a nice blanket of carbon wrapped around it. For the rest, I haven't run the VVT test yet. Boost test showed significantly higher max boost than other vehicles. Normally I don't see more than 1.5 to 2psi, and this one was 3.04. The EBP and MAP graphs were smooth, but the EBP seemed to stairstep a little more than some other vehicles. I've seen worn unison rings before, but they've always been on turbos that had other problems like being carboned up. I'll run the VVT test next week and see how it looks. Thanks for the help! Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted December 11, 2010 Share Posted December 11, 2010 1.5 to 2psi, and this one was 3.04 3 PSI seems a tickle high tome as well. The information button on the IDS display during the test gives great examples of good and bad results... but I am sure you know that. Quote Link to comment Share on other sites More sharing options...
cbriggs Posted December 13, 2010 Share Posted December 13, 2010 You could also try to take active command of the egr valve, and then the vgt and see which one has effect on the surge. Hotline has had me do that on several occasions (years ago, before all the seized turbos came around) to pinpoint which is cause and which is an effect of the concern. Quote Link to comment Share on other sites More sharing options...
Mikill Posted December 13, 2010 Share Posted December 13, 2010 3 psi on the boost test is too much in my opinion. What is your MGP going down the road? Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted January 7, 2011 Share Posted January 7, 2011 Here is a screenshot of a 07 sicko with a pronounced surge that had a faulty turbo. There aren't too many info pids shown but the vgt versus map tells you everything you need to know. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted January 7, 2011 Share Posted January 7, 2011 Quote Link to comment Share on other sites More sharing options...
GregH Posted January 8, 2011 Author Share Posted January 8, 2011 I removed and stripped the turbo. I couldn't find anything wrong with it. Onion ring was fine, vanes moved smoothly, no corrosion on the center housing. I loaded the shotgun and put in a CHRA, unison ring and VGT solenoid. I also removed and cleaned IAT2 - although it wasn't very cruddy. I did not do the VVT test - the tool was damaged and hadn't been replaced yet. The van was fixed when I was done. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted January 8, 2011 Share Posted January 8, 2011 I am glad to hear it is fixed... With that said, it would have been ideal to have installed the CRH with the old VGT solenoid... road test and evaluate and then if it still surged replace the VGT solenoid... road test and if it still surged clean the IAT-2 sensor and evaluate. This would have nailed down what "did it." Yes, I realize we don't have time to screw around when the flat-rate cloud looms overhead but I personally hate having to do what you did and I have in the past. I always want to know what part was the culprit. I still don't beleive the IAT-2 will cause a turbo surge as MAP and EP are more important and a more direct feedback for the PCM to control the VGT. A sluggish EGR valve or a partially plugged EGR cooler and passage perhaps. In that case I would expect to see the EGR duty cycle trend with the surge for a valve concern but if there is a good restriction or total blockage there won't be any appreciable affect on exhaust back pressure. Unfortunately your recording does not show what the EGR is doing. I have never seen an EGR valve cycle when there is an exhaust back pressure issue caused by the turbo but I have seen EGR valves open to release exhaust pressure to slow the turbo down with high MAP readings (over boost conditions due to stuck unison rings). My experience has been that physical problems with the VGT operation like sticking unison rings, worn unison rings and funky VGT actuators will cause turbo surge. Typically sensor problems are fairly apparent with a good data recording. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted January 9, 2011 Share Posted January 9, 2011 I have a known good vgt solenoid and that was swapped in and it fixed the surge on the truck with the wave form on page 1. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.