Rod Underwood

[QUOTE=Dennis Wilson]Rod,

The resistors are on the panel in front of the left fender well. Two wires on the coil (15 post) will run to the resistors. Make sure those connections are cleaned of corrosion.

Also, have you cleaned the 14 pin connections by the jump post?


The resistors are on the panel in front of the left fender well. Two wires on the coil (15 post) will run to the resistors. Make sure those connections are cleaned of corrosion.
[QUOTE=Dennis Wilson]

Sorry about the 15 question, I found it and it has 6.9 - 7.0 volts.

Cleaned the resistors, they were really nasty, but appeared to have good contact when I removed them, but they're nice and clean and Corrosion X'd now.

The 14 pin connector, clean and Corrosion X'd.

I started it and (more info) if I force it to rev, it will try to backfire, and then come out of it.

I'm going to give it up for the night, have a happy 4th.

Rod

hacker-pschorr

Yup - same with my 81 before & after the blower.

It is much better now (99% perfect) problem is I was chaning so much on the car in such a short amount of time & the average temp is much higher than the last time it started like yours.

I'm having a hard time remembering when mine "cleared up" - or what I did just before. I'm pretty sure when I found the #3 intake runner leaking & fixed it, this issue got 99% better - it was causing such a massive air leak, my car was running way lean upon startup since the cold start loop was not prepared to compensate for such a huge leak. You already did the brake cleaner trick so I doubt this is an issue.

The barn door unit does have a temp sensor in it - that could be bad??

I was chatting with Jim Page @ Page Auto (ok, I'm there 3-4 days a week on average) He told me a story a while ago (just came to mind) about a 928 that came in over 20 years ago, almost new. It had a major cold start issue (I'm guessing like yours) and it ran either rich / lean (cannot remember) once warm. He was actually told by the dealer (closest one at the time was 2 hours away) the factory "fix" for this issue was to wire in a resister to the temp sensor tricking the computer to run richer (it was too lean, now I remember). I'll try to jog his memory on Thursday about this. Hell, go buy a low resistance potentionometer (spelling? Hey, its late). Turn it up a few notches - see if anything changes. Cannot hurt anything.

John Speake

I am not too familiar with the US models, but this sounds like an L-Jet system with barn door airflow sensor - right ?

I have the Bosch booklet on the L-Jet system. From what is described, it sounds like the cold start parts of the system are OK (thermo time switch, etc) but that until the water temp starts to rise the engine is clearly running very weak.

Is this correct Rod ? Is the time taken for it to resume normal running dependant on engine water temp and to some degree on ambient temp ?

I can scan parts of the L-Jet book for you - it is a very clear description of the system.

I assume you have checked the water temp sensor ? That would appear to be the main factor in warm up phase. This thread is so long I didn't notice is this is something you have already checked...

Rod Underwood

John, everyone,

The car will start immediately - every time, then stumble immediately, it will then slowly come up to speed and seem to be fine. If I wait about a minute, it will begin to bog down, if I force it to rev, it will backfire lightly -briefly sound like it is firing on 4 cylinders or so, and then come up to speed. It will bog down at this point under any load - backing out of the garage. It will go through this routine two or three times - bog down, clear itself and come back up to speed and then it will be fine. This takes three to four minutes.

It will clear itself sooner if I repeatedly rev it up to 2-2,500 rpm or so. But this is a bit obtrusive in parking lots. It does this warm or cold, initially it only seemed to do it at cold start, but lately, I've noticed it also repeats the ritual at warm start as well.

Here's what I've done so far, not in any particular order:

US 82 - 5 speed

1. Replace the O2 sensor - Bosch 11027 one wire from NAPA
2. checked for vacuum leaks, replaced the vacuum lines
(I've drenched the engine, with a fire extinguisher handy, on three different occasions, when running with carb cleaner, and detect no change in engine speed)
3. Replace the Plenum-runner boots
4. replaced the AAV (and removed it from the system)
5. Removed the vacuum limiter
6. replaced the high and low throttle switches, low currently unplugged
7. replaced the entire mass air flow unit
8. removed EEC valve from the system
9. removed the A/C idle solenoid valve from the system
10.(unplugged the vacuum lines to the two rear pressure regulators, this helped, but I plugged them back in, based on comments regarding long-term implications from Hacker- it went back to previous behavior)
11. replaced the TSZ switch unit
12. Swapped out the cold start injector
13. Swapped out the thermo-time switch
14. New temp II switch
15. New plugs, plug wires.
16. Distributor cap and rotor look brand new on the inside
17. Reset the timing, it was off a bit.
18. Cleaned, scrupuously, the front two, under engine, rear grounds (Corroxion X'd them as well). Haven't cleaned the two under dash grounds - I'll do that today, probably
19. Coil No. 15 connector has 6.9-7.0 volts
20. Cleaned the two ignition resistors (Corrosion X as well)
21. Cleaned the 14pin connector at the front jump point
22. Replaced a weak battery
23. Disconnected air pump
24. Checked the "green wire", mine's not green, from the distributor to the onnection near the jump post, it seems perfect.
25. Checked fuel pressure - 29 psi when running (2 bars) and goes to 32 when I shut it off, will hold for about 30 minutes and then drop slowly to "0". I noticed the fuel pressure will rise to about 32 psi when the engine is dragging down, so it doesn't "seem" to be a low fuel pressure problem, just the opposite during these events
26. New fuel pump and filter
27. I've Corrosion X'd the entire fuse panel and checked the fuses, rotated all of them, and found no bad ones.
28. (I didn't do it, but I believe the brain was swapped before I bought it, with no effect, but I can't be positive about this)
29. Can find no vacuum leaks in the A/C system under the dash - when I had it out.
30. New air filter
31. Checked vacuum advance and retard on distributor, seems close to specs from WSM
32. (Replaced ash tray that a PO had removed to install a radar detector, but that had no effect either)


If I can find out what's wrong, I'm going to go back and reinstall some of the items that I've removed, but for the moment this is about where I am. I may have missed something, but fire away.

By the way, John, I know this is the fourth of July and it is especially nice of you to offer to help someone from one of the former colonies. That shows real character.

Thanks
Rod

Rod Underwood

Where should I wire it in? In which circuit? I'm game

Rod

Dennis Wilson

Rod,

When it backfires is it through the intake or exhaust? Exhaust means too much, unburnt or late firing. Through the intake means it is too lean due to settings or an air leak. Also, backfiring through the intake can blow out seals, hoses or blow vacuum lines off the intake. You may want to check for leaks one more time and pay close attention to areas the spray can't reach, like the bottom of the rubber connectors between the spider and upper plenum.

Dennis

Rod Underwood

I can make it pop "very lightly" through the intake, not the exhaust. I really drenched each runner, each upper connector - top and bottom, all of the vacuum connections - had carb cleaner running off of almost everything. I can't image that I could have missed a leak, but of course, something is still wrong. The entire engine was filled with carb cleaner. Luckly no fire!!!

I quick kick of the accellerator will cause the light pop, but a slow rev up won't.

It seems so time related. Wouldn't a vacuum leak create a more constant problem? I'm obviously missing something, but I've been through it so many times, I can't imagine what it is. Of course the fact that I've been through it so many times suggests that I may be making the same mistake over and over.

I'm going to advance the timing a bit - 12 degrees, let it cool and see what happens. It seems that the pop may have started when I corrected the timing to 8-10 degrees.

Rod

Dennis Wilson

Rod,

A cold engine needs more fuel and air to run properly. If too much air or not enough fuel, you get a poor cold start condition and possible backfiring. I chased a vacuum leak on my 80 924 (RIP) before I removed the intake and discovered a blown gasket at the bottom. Of course, that was an area I couldn't spray.

If everything else is correct, you might try increasing the A/F mixture.

Dennis

Rod Underwood

How do I do that? I can change the idle speed with the large "bypass" or "control" screw on the front of the throttle body, but I don't immediately see any other adjustments.

I have really soaked the bottom of the runners, but I may have to remove them and regasket the whole thing is I can't find anything else.

Rod

hacker-pschorr

I will not be able to talk to Jim until tomorrow - based on what I remember, he added the resistor to the temp switch on the coolant bridge (the one sticking straight up - the other just feeds the temp gauge).

There are spade connectors on everything so wiring something in without changing the factory connections shouldn't be very hard.

Rod Underwood

The Temp II I assume.

Thanks Have a great 4th!!!
Rod

Dennis Wilson

Rod,

The adjustment instructions are on page 24-24 but I would try the resistor first. Do you have an A/F meter that you can tie into the O2 sensor line?

Dennis

Rod Underwood

Drilled out the plug and turned it clockwise to make a richer mixture. It was almost entirely closed when I drilled it out, but I went the rest of the way - about 1/8 turn. I have to let it cool a bit, it started right up and didn't hesitate, but I hesitate to think that did it. I'll wait a while and check it. No Air/Fuel meter. @##$@!@~!$

Okay, that "seemed" to help, at least on start up, not a definitive solution yet, but a definite maybe. One test isn't really enought, I've been down that road before, only to have my hopes dashed!. I was at least able to back out of the garage without any hassle. It did try to stutter, at the 1/8mile point of my drive, the same old spot, but I "think" a significant improvement. Maybe we're on the right track. Now with Hacker's resistor fooling the brain and keeping it a bit richer a bit longer might do the trick.

Further driving. After start up, warm/hot, it still goes through exactly three cycles of running fine, dragging down, and then rebounding. After the third cycle, it seems to be done and away we go. Cooler start-up seems better.

Stopped and look at my local Radio Shack for Potentiometers. A cheap item, but what range would I look at? and they have "three" leads, one in and one out, and.....? Is the third a ground?

Rod

John Speake

Hi Rod,
If you are fooling temp sensor 2 then you would need a pot of 1000ohms ("1k"). IIf you have a meter, set it to about 400ohms between the wiper and one of the pins. Note which way you need to turn the pot to incrrease resistance (richen mixture) so you can play later.

You can then ignore the other pin.

Wire the pot in series with the lead to temp 2. I have done this before on L-Jet motors.

I can scan the pages of the L-Jet manual I have...

Rod Underwood

[QUOTE=John Speake]Hi Rod,
If you are fooling temp sensor 2 then you would need a pot of 1000ohms ("1k"). IIf you have a meter, set it to about 400ohms between the wiper and one of the pins. Note which way you need to turn the pot to incrrease resistance (richen mixture) so you can play later.

You can then ignore the other pin.

Wire the pot in series with the lead to temp 2. I have done this before on L-Jet motors.

I can scan the pages of the L-Jet manual I have...[/QUOTE

Well, it's in there and now I need to try it over and over with different settings. I tried 400 ohms and it was better, but not fixed, I tried 1000 ohms and I "think" it was worse, so now I'm just fiddling with it. ;-)

The temp II sensor for the 82, for a cold start, -10C, 14F should have 7-12k-ohms and 20,C68F should have 2-3k -ohms. Shouldn't I be shooting for these values, to make sure I get a rich mixture?

Thanks a lot for your help.

I may run wires to the temp II sensor lead (put it in the orange wire, not the brown, I assumed the brown was ground) and keep the potentiometer in the car so I can change it while I'm driving to see what helps when it starts to sputter. How quickly should the engine respond to a change in the resistance?

Rod