Major hesitation at wide open throttle
02-22-2016, 12:27 PM
#62
Chronic Tool Dropper
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I put a rebuilt (by Elektronic Repair c/o Rich Andrade) LH box in it a year or so before Sean bought the car. Part of the summer troubleshooting exercise for the same symptoms last year included returning the box to the rebuilder, where it checked out OK.
The suggestion of "over-fueling" only on the open-loop map (speculation based on symptom description) is a head-scratcher for me. I'm not close enough road-test the LH to see if it's OK. With the relatively limited diagnostics in the pre-'89 car, it gets even tougher.
I put a rebuilt (by Elektronic Repair c/o Rich Andrade) LH box in it a year or so before Sean bought the car. Part of the summer troubleshooting exercise for the same symptoms last year included returning the box to the rebuilder, where it checked out OK.
The suggestion of "over-fueling" only on the open-loop map (speculation based on symptom description) is a head-scratcher for me. I'm not close enough road-test the LH to see if it's OK. With the relatively limited diagnostics in the pre-'89 car, it gets even tougher.
02-22-2016, 02:16 PM
#63
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Yes it now appears we know the cause of the hesitation that was occurring only at full throttle - flooding, essentially. Could this be caused by intermittent Temp sensor connection? Anyway there is a troubleshoot sequence in the WSM for this system, I will ask my shop to go through it, and lend them the manual if they want it. According to the WSM the car is "inoperable" with the Temp sensor unplugged. I may have to get it towed to the shop, which will be the first time I've had an old Porsche towed in the 17 years I've owned one.
02-22-2016, 02:40 PM
#64
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I found another thread stating a problem occurred from the LH not getting correct power from the positive battery terminal. Now, I made this problem a lot worse by playing with those wires and making sure they were tight. They were indeed tight, but they also look pretty bent and nasty on the ends, it would not surprise me if there were an intermittent connection at the positive battery terminal.
02-22-2016, 02:45 PM
#65
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I also noticed my positive battery terminal bolt, the one with all the extra little wires attached, is covered with black grease and so are the ends of the wires. Why? Shouldn't it be clean?
02-22-2016, 02:49 PM
#66
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Yes it now appears we know the cause of the hesitation that was occurring only at full throttle - flooding, essentially. Could this be caused by intermittent Temp sensor connection? Anyway there is a troubleshoot sequence in the WSM for this system, I will ask my shop to go through it, and lend them the manual if they want it. According to the WSM the car is "inoperable" with the Temp sensor unplugged. I may have to get it towed to the shop, which will be the first time I've had an old Porsche towed in the 17 years I've owned one.
02-22-2016, 03:07 PM
#67
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we chased our tails with the computers (the 6 liter devek car) for months.. had them rebuilt.. .WAAY WAY out of spec, said Rich. (10x out of spec) in the end, that wasnt the problem. it was that relay stuck in the wrong socket,, that ninnie!!
anyway, point is, i dont think even a bad set up MAF will be responsible for this dramatic of a problem unless they are really bad!
as far as the temp II, sounds like thats the issue, and just put in a simple resistor between the wires and it will start and run fine to get it to a shop... Or, if that does allow for it to start, just rewired the contacts and put in a new TEMP II sensor. its very easy to install.
anyway, point is, i dont think even a bad set up MAF will be responsible for this dramatic of a problem unless they are really bad!
as far as the temp II, sounds like thats the issue, and just put in a simple resistor between the wires and it will start and run fine to get it to a shop... Or, if that does allow for it to start, just rewired the contacts and put in a new TEMP II sensor. its very easy to install.
02-22-2016, 03:27 PM
#68
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Yes it was the installation of a new Temp II that caused this problem to resurface. I had suspected a bad reading from the old one due to overall rich running and a high cold idle. The car was somewhat better on the new sensor for a short while, until this problem came up again. But now I read John Speake in a another thread saying that the car should run OK with the sensor unplugged or giving no connection, since the LH defaults to a standard setting that does not adjust. So can these symptoms really be from a temp sensor connection gone bad?
02-22-2016, 04:09 PM
#69
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No, I don't think it is temp 2, as was quoted above. Have you tried disconnecting the battery earth strap, unplugging the O2 sensor and then reconnect battery + start up ?
When you do that the LH defaults to mid range of the O2 loop, and often a car with an O2 sensor problem will then run very well.
When you do that the LH defaults to mid range of the O2 loop, and often a car with an O2 sensor problem will then run very well.
02-22-2016, 04:41 PM
#70
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On my '89, my computers were getting insufficient grounds. When the computers found a good ground, the car ran like a top. When the computers couldn't find a good ground, the car would not run and would just shut off. If the ground was present but insufficient, the LH would , for some reason, think that the engine was running lean and dump more fuel. It would continue
02-22-2016, 04:49 PM
#71
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It would continue to add fuel until finally the Engine would not run any longer due to the excessive amount of fuel being delivered. The fix was to kick clean the computer grounds at the back of the V.
02-22-2016, 04:57 PM
#72
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Yes it was the installation of a new Temp II that caused this problem to resurface. I had suspected a bad reading from the old one due to overall rich running and a high cold idle. The car was somewhat better on the new sensor for a short while, until this problem came up again. But now I read John Speake in a another thread saying that the car should run OK with the sensor unplugged or giving no connection, since the LH defaults to a standard setting that does not adjust. So can these symptoms really be from a temp sensor connection gone bad?
02-22-2016, 04:59 PM
#73
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^^^^^^^^^^^^^ OK this is starting to sound like what I need to do. I think it's the LH grounds, because that is exactly the behavior. Dumping more and more fuel until the car will not operate. And this is what it did in the summer. And the shop found baffling voltage/resistance readings at the LH pins, and reported that it had "lost ground control." For some reason they did not know how to deal with this. Cleaning the LH grounds "at the back of the V" is not something they thought of? Can you please describe where these grounds are located? Did you mean to say "kick clean" the grounds (not sure what that would mean).
