Diagnosing D-Jet Problem...solution & update, All of a sudden...loss of power... |
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Diagnosing D-Jet Problem...solution & update, All of a sudden...loss of power... |
MikeInMunich |
Jul 6 2018, 08:13 AM
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#1
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Member Group: Members Posts: 392 Joined: 19-November 13 From: Munich, Germany Member No.: 16,674 Region Association: None |
Greetings once again from Munich gentlemen! (IMG:style_emoticons/default/bye1.gif)
It started with a thought and no wood to knock on, seriously! (IMG:style_emoticons/default/mad.gif) I was driving around Munich about 6 weeks ago and thought to myself, this car is running perfectly and needs nothing. What could go wrong? Then literally, less than a few minutes after that, it started. A light hesitation in the lower RPM range. Seemed like the car was choking a bit, or missing on once cylinder. I was at a D-Jet workshop last year with Dr. D-Jet. See https://oldtimer.tips/de/ Volker is a great guy and knows as much about this system as anybody. He tested the vacuum on my MPS last year and informed me that it was "borderline". So that was the main culprit. I took it out, sent it to him and this year it was indeed worse and thus the main culprit. Volker disassembled it and replaced the copper diaphram. Now it's tight like new. Some may be surprised that this is possible and / or where he got a new diaphram from. He had them manufactured or perhaps, I'm not sure, manufactured them himself. PM me if you want / need one and I'll send you his email address. So, with my restored MPS I hooked it up and, low and behold, the problem was quite the same, only about 10x worse! (IMG:style_emoticons/default/hissyfit.gif) Now, with the car immobile and Volker hundreds of km away, I'm practically on my own, with his and your advice, to try to track down the real problem. Volker thinks that because the MPS was operating sub-optimally previous to my purchase of the car that the mechanic or the P.O. had compensated elsewhere to get the car to run properly and that now that the MPS is sending a different signal to the CPU, things are off. More info: Just before the problem started my milage was really bad The CPU is the correct one for my MPS and working according to specs. Volker tested it. Engine has about 5,000 miles on it. Was rebuilt and running GREAT. Fuel pressure was set at 29 psi only about a year ago. I reckon it could have hardly changed on its own since then. (IMG:style_emoticons/default/idea.gif) The engine was originally a 1,7 but is now 2liters with a “proper FI performance Webcam” (as stated by the mech ic who rebuilt the engine) No adjustments were made to the FI to get it to run properly. It was running excellentwith a virtually perfect idle when warm and just slightly rough for the first 3 Miles or so. TPS plate and air temp sensor are new. What do y'all reckon could be the culprit? What should I be testing? I'm taking it to a place to tell them what to test, including: Fuel Pressure Plugs Compression CO value TPS setting Timing & dwell search for Vacuum leaks grounds Valve adjustment Fuel filter Relais Injectors... What else should I have them look for? Thanks for your input! With best regards from what was just ranked The Most Livable City in the World by Monocle Magazine, Mike in Munich |
Dr-DJet |
Jul 10 2018, 03:53 PM
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#2
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Dr-DJet Group: Members Posts: 14 Joined: 21-May 16 From: around Frankfort, Germany Member No.: 20,021 Region Association: Germany |
Hi,
Mike did not mention to you and to me that he does not have the original engine installed. He had his 1.7 engine bore increased to 2.0l and changed cam to unknwon spec. (IMG:style_emoticons/default/WTF.gif) It is of course not possible that any open loop control ECU and MPS will notice that. Even a closed loop injection system would have trouble with that. His previous MPS lost vacuum and thus saw far too low vacuum enriching A/F mixture artificially. When it is back to factory spec what happens? Of course mixture is far too lean for an engine that has 25% more air volume and a total different volumetric efficiency and fuel need. Both are hard coded into each ECU and each MPS. I do not understand how Mike could forget to mention this fact (IMG:style_emoticons/default/confused24.gif) . If he is lucky he now has an engine similar to an original 2.0l engine. Then he could use components from that engine. But without knowing engine mechanics and his specific cam changes in detail, that is impossible to say. My weeks of support for this trouble case is over. I learned of the total engine changes today. I am surprised what speculations have built up here in 914world why a factory spec MPS should not fit a normal engine. Bosch has supplied 10s of thousands of MPS as spares (and 100s of thousands originally). How would Bosch workshops have survived if they would have had to retune each spare MPS in field? (IMG:style_emoticons/default/headbang.gif) Do not create such fairy tales. Bosch Classic delivers repairs of MPS to their spec until today for many car models with Mercedes-Benz still being the largest user of D-Jetronic MPS. So please do not base wrong speculations on such a case where someone tries to fit original components on a total different and unknown engine. Sorry guys, I normally do not write here, but this was just too much fairy tale on false ground. See you on oldtimer.tips if you like. Best regards, Dr-DJet |
Bartlett 914 |
Jul 10 2018, 05:06 PM
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#3
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Advanced Member Group: Members Posts: 2,216 Joined: 30-August 05 From: South Elgin IL Member No.: 4,707 Region Association: Upper MidWest |
Hi, Mike did not mention to you and to me that he does not have the original engine installed. He had his 1.7 engine bore increased to 2.0l and changed cam to unknwon spec. (IMG:style_emoticons/default/WTF.gif) It is of course not possible that any open loop control ECU and MPS will notice that. Even a closed loop injection system would have trouble with that. His previous MPS lost vacuum and thus saw far too low vacuum enriching A/F mixture artificially. When it is back to factory spec what happens? Of course mixture is far too lean for an engine that has 25% more air volume and a total different volumetric efficiency and fuel need. Both are hard coded into each ECU and each MPS. I do not understand how Mike could forget to mention this fact (IMG:style_emoticons/default/confused24.gif) . If he is lucky he now has an engine similar to an original 2.0l engine. Then he could use components from that engine. But without knowing engine mechanics and his specific cam changes in detail, that is impossible to say. My weeks of support for this trouble case is over. I learned of the total engine changes today. I am surprised what speculations have built up here in 914world why a factory spec MPS should not fit a normal engine. Bosch has supplied 10s of thousands of MPS as spares (and 100s of thousands originally). How would Bosch workshops have survived if they would have had to retune each spare MPS in field? (IMG:style_emoticons/default/headbang.gif) Do not create such fairy tales. Bosch Classic delivers repairs of MPS to their spec until today for many car models with Mercedes-Benz still being the largest user of D-Jetronic MPS. So please do not base wrong speculations on such a case where someone tries to fit original components on a total different and unknown engine. Sorry guys, I normally do not write here, but this was just too much fairy tale on false ground. See you on oldtimer.tips if you like. Best regards, Dr-DJet Dr=Djet It seems you took this personally. I was not an attack on you or your ability. When I stated that the MPS made it worse, that was a statement from a troubleshooting stand point. It in fact turned out to be the case. |
Dr-DJet |
Jul 11 2018, 02:26 AM
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#4
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Dr-DJet Group: Members Posts: 14 Joined: 21-May 16 From: around Frankfort, Germany Member No.: 20,021 Region Association: Germany |
Dr=Djet It seems you took this personally. I was not an attack on you or your ability. When I stated that the MPS made it worse, that was a statement from a troubleshooting stand point. It in fact turned out to be the case. Hi, yes I take it personally if I read so much bullshit in a case where someone completely changes his engine from 1.7 to 2.0l and everyone expects this to run well and doubts my trouble-shooting, Bosch factory specs etc. And also the statement that the 2nd MPS makes the car run better is not correct. Mike got a second MAP sensor from me which was very richly adjusted (not by me and on the upper tolerance side). Just to help if there would be something odd with his own one. But also that one makes him drive just 800m as Mike wrote me yesterday evening. What does that tell us. Car runs with cold start valve and cold fuel enrichment then problems start. What a surprise! My last statement in this case: A modified engine from 1.7 to 2.0 l will NEVER run well with 1.7 components. No matter how you tune or detune a MPS. |
MikeInMunich |
Jul 11 2018, 05:22 AM
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#5
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Member Group: Members Posts: 392 Joined: 19-November 13 From: Munich, Germany Member No.: 16,674 Region Association: None |
Dr=Djet It seems you took this personally. I was not an attack on you or your ability. When I stated that the MPS made it worse, that was a statement from a troubleshooting stand point. It in fact turned out to be the case. Hi, yes I take it personally if I read so much bullshit in a case where someone completely changes his engine from 1.7 to 2.0l and everyone expects this to run well and doubts my trouble-shooting, Bosch factory specs etc. Why would you think that everyone doubts your trouble shooting, Bosch specs or that everyone expects a 2.0 to run well with an MPS calibrated to spec for 1.7 liter engine?? (IMG:style_emoticons/default/confused24.gif) You’re jumping to illogical conclusions and getting defensive-aggressive unnecessarily. There’s certainly no reason at all to take anything written here personally. |
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