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What would troubleshooting the LH entail? I'm assuming the ISV output is a pulse, maybe a square wave? If so, can we look at it via an O-scope? It looks like pins 10 and 23 on the LH2 connector are relate, one tagged a Close, the other as Open....
What would troubleshooting the LH entail? I'm assuming the ISV output is a pulse, maybe a square wave? If so, can we look at it via an O-scope? It looks like pins 10 and 23 on the LH2 connector are relate, one tagged a Close, the other as Open....
Maybe this is what I need to do as well. Is there some analysis done to determine what needs to be fixed, or does this just mean send it in and get "the works?" In either case, what does this cost?
What would troubleshooting the LH entail? I'm assuming the ISV output is a pulse, maybe a square wave? If so, can we look at it via an O-scope? It looks like pins 10 and 23 on the LH2 connector are relate, one tagged a Close, the other as Open....
Contacted last night from Rich at ERI. THE LH IS WORKING PERFECTLY! Back to hunting down vacuum leaks. Someone in the club here has a smoke machine to trace down if it IS a vacuum leak.
Since there is interest in the 1985 - 1986 Porsche 928 Idle Speed Regulator and how the 25 pin Bosch LH fuel injection module controls it, I prepared a PDF document that provides details on the theory of operation and oscilloscope photographs of the waveforms. I will also make a post at the 928 Owners Club ( www.928oc.org ) tech forum on the subject.
Did a smoke test this evening. Found 4 leaks. Evap hose on the "control valve" (944-110-429-00) on the crossbar clamps were not tight, the other end of one of those evap hoses was loose at the vacuum valve (928-110-429-08) down along the fender well, the brake booster vacuum source fitting for all the smaller vacuum lines is cracked and leaking, and what I think might be the throttle shaft down low under the pipe organs. Corrected the loose clamps, JB welded the brake booster fitting. ECU's are not back from Rich's so won't be able to confirm any improvement in idle until then. Have videos but too large to upload.
Guys, As Mike indicated previously the LH and EZ computers are FINE, so the LH is NOT the cause... Since this will be my DD, I went ahead and had Rich inspect and repair any questionable solder joints, replace aging capacitors, etc, on BOTH computers so they'll last another 30 years. Well worth the $$ IMHO... Thanks again Rich!
Mike and I ran the smoker again yesterday to double check the results. The brake booster's plastic vacuum piece no longer leaks after the JB Weld repair (Don't flame us... I'll be getting a new one from Roger if they're not NLA) - for now it's O.K. One of the organ pipe sleeves was leaking (they are a bitch to get right), so we loosened the clamps, re-positioned the sleeve, tightened the clamps and it sealed - so that's O.K. The leaking hose on the passenger side fender (runs from the valve on the cross-member to the charcoal canister valve) is a dual dimension rubber hose - we rigged a replacement hose and used better clamps - so that's O.K. (again, I'll order a new hose from Roger if it's not NLA). Re-tightened both clamps at the cross-member and they sealed up - so both are O.K. The only, quite literal "smoking gun" is coming from the throttle body plate rod packing gland...
HINT: When running the smoker, turn off EVERYTHING in the shop so no air is moving and it's as QUIET as possible... This way you see the smoke, and HEAR the air and the smoke oil bubbling through the TB rod's tensioner spring... BINGO! It's best to view the TB rod from the front of the engine, looking under the intake runners. That's the last one to correct and of course the hardest to get at... Is it possible to remove the TB from the rear without removing all of the intake runners? I know we'll need to remove the "T" and get the airbox & MAF out of the way... Also, is there a DIY tutorial on how to repair / replace the TB plate rod?
I gotta say, that damn smoke machine is awesome! We've checked all of these connections, including the TB rod, more than once old school with brake cleaner, starting fluid, etc, while idling with negative results - not even a blip on the radar. Hook up a smoke machine and find 4 or 5 vacuum leaks, from major to minor, in 60 seconds.
Joel and Mike, replacing throttle body bearings is not TOO bad a job.
Getting the throttle body out without removing any of the bolt on intake runners is doable, to my understanding. T-pipe definitely has to come out.
As for the throttle body, match mark the throttle blade, remove the screws with a GOOD Phillips head screwdriver and FIRM pressure into the screw. Be super careful on this. Screws are brass, and I have not found anybody who has replacements. (Though I do have a spare throttle body, just in case.) Shaft pulls right out. Getting the bearings out...
I put the throttle body in my toaster oven and baked it to 400 degrees for 10 minutes. Then failed with various puller attachments. All this did was destroy the bearings, leaving the outer shells. I ended up threading a 5/8-11 NC tap into the shell. It was what I grabbed in relative desperation. I am sure another sized metric tap would have worked fine. My intent was to thread the tap in until it bottomed out, then it would push the bearing shell out of the throttle body. What actually happened was the bearing shell started turning once the tap really bit in. Either way, it worked.
After cleaning the throttle body, it went back into the toaster oven at 400 degrees for 10 minutes. I retrieved the new bearings from the freezer where they had been cooling for hours. Quickly, throttle body out of the oven, tap the bearings in place, let all cool. Work good, last long time.
The new bearings are better than OEM. OEM only had a seal on the outer edge. Roger supplies S4 flappy bearings for installation on throttle bodies. These bearings have seals on both sides.
Bearings are INA, part # HK10122RS. They were only $13.75 two years ago. Get them and a new throttle body mounting O-ring, 999 701 436 40, and be good for another 20 years.
Tools of war.
Results of using tools of war.
Bearing bore is not blind per se, but stepped. Meaning you can't tap the bearing out from the other side.
Other side of throttle body bearing bore.
New bearing tapped into arm side of throttle body shaft side of throttle body.
New bearing tapped into the other side.
Drop of green Loctite 290 on each throttle blade screw. Don't want them to come out...
Great Pictures, Seth. ECU's come back today. Will know if we have to go down the throttle bearing route.
Well it's been a long trip down this rabbit hole and main cause has turned out to be the cheap $25 ISV I got on eBay. There were several vacuum leaks which were addressed and the idle was brought down to 1200 RPM after connecting the ECU's. I decided to put a Bosch ISV I had in my parts bin in (the original that came with the car was jammed). Before I did that I compared the flow through both ISV's. The cheap one had no restriction in flow either open or closed by blowing through it compared to the Bosch which had a good restriction closed. I ran across a post from Roger that he has proven aftermarket units for around $85. The engine is now running at 775 RPM and very steady. I even disabled the idle circuit on the jumper terminals ('85-'86 only) on the front of the engine and set the curb idle a little higher because it was a low as 600 rpm. I know this old Bosch that I had in my parts bin seems smooth mechanically and only time will tell if it will hold up. I will drive it this week and see if it fails. Joel will take over from there.
03-08-2019, 11:37 AM
