1979 635CSi Euro - Henna Revival Project

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tschultz
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Re: 1979 635CSi Euro - Henna Revival Project

Post by tschultz »

So another update.

I found a spare spark plug wire tube and installed that on the valve cover. Now it is looking all there in the engine bay

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I bought a euro speedometer to complete the euro parts. The mileage was very close to what is on this car which was part of the reason I bought it. I think the tachometer without a green stripe is correct for 79 so I didn't buy one if those (although I do like those better).

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I put on the bbs ra wheels. They turned out pretty nice! They also mounted perfectly with my chamfer modification. One negative, I found my 4th tire had a leak and so I have to find another 205/55 to match this set. I'll install center caps soon but want to polish them up a bit. I'll take more photos after I get them on.

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They look even better than the e38 style 5s, in my opinion.

The brakes are starting to work a bit better now though I keep testing them. Now at about 50 miles total. They squeaked for a while and don't seem to any more... maybe a piston freed up.

I have a small misfire but i suspect a weak fuel pump or weak spark and distributor. Need to solve that to really drive it much further away from home.

In the mean time I need to sell my e36 m3/4/5 before continuing much more progress.... I just have too many cars!
http://www.Drive4Corners.com
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'79 635CSi Revival
'80 635CSi
'83 633CSi Callaway Turbo continued as 1988 535is Turbo
SOLD: '81 635CSi/A
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tschultz
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Re: 1979 635CSi Euro - Henna Revival Project

Post by tschultz »

I got the wheels on and they look better than expected which is great! The flat tire was replaced too. However, I am still trying to figure out why the car is misfiring, although seemingly randomly.

I put the distributor at the stock position and know that ignition timing is about right. Sometimes the engine runs great and other times it has this miss like an ignition issue. I replaced my known good icu box and it makes no difference on running condition. I need to see if the coil is simply weak maybe, though I thought I tried that already and it didn't seem to make a difference.

Maybe I need to check the resistance of each spark plug wire and see if one has a variance. I tried pulling each one off and could not identify an individual isolated cylinder problem...

So I'm sitting here thinking the distributor pulse generator is faulty like it was in my 1980. Though it's good enough to keep running and sometimes work... I think that may be the problem. I will say that and spark looked yellow to me (instead of blue) when I pulled a plug wire...

I'm thinking of an ebay 528i distributor to swap in and see if it smooths out the running issue. Any other thoughts?
http://www.Drive4Corners.com
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'79 635CSi Revival
'80 635CSi
'83 633CSi Callaway Turbo continued as 1988 535is Turbo
SOLD: '81 635CSi/A
kronus
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Re: 1979 635CSi Euro - Henna Revival Project

Post by kronus »

Are your injectors known good?
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tschultz
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Re: 1979 635CSi Euro - Henna Revival Project

Post by tschultz »

Yes, new and flow tested!
http://www.Drive4Corners.com
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'79 635CSi Revival
'80 635CSi
'83 633CSi Callaway Turbo continued as 1988 535is Turbo
SOLD: '81 635CSi/A
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Slownrusty
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Re: 1979 635CSi Euro - Henna Revival Project

Post by Slownrusty »

Tom I'm out of ideas. You're heading down the right track with the distributor swap. The AFM, ECU and coil are typically all very reliable components.
Yasin

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tschultz
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Re: 1979 635CSi Euro - Henna Revival Project

Post by tschultz »

Ok update from a few weeks ago. Two main problems I am working through before really continuing further.

#1
Replaced brake master and soft brake lines. Bled and got a good pedal. However on my test drive a few times the pedal went soft and I had to pump a few extra times to get any brakes. Scary and I am not sure how this happens. This was a NOS master. No leaking fluid that I can find. Definitely taking it easy until I figure this out, but I bled all 3 bleeders on the front circuits 2x...

#2
The last test drive, the car was misfiring slightly after heating up to operating temperature. Instead of a slight misfire at low rpm, it increased to higher rpms and more noticeable.

After shutting off the car in the garage, I went to see if the symptoms remained and restart and it wouldn't. I suspected maybe the distributor pulse generator was maybe overheating and starting to misfire a little bit like on my 1980. Since this was one part I hadn't exchanged, I found a replacement 006 unit from a 633CSi. I replaced that and went for a test drive. This felt smoother (maybe placebo?) at first, but unfortunately after about 10 minutes, I noticed a little bit of a misfire and then more and more as I drove it back home.

I immediately replaced the coil to see if the one in the car was weak. At first start, things seemed smoother again. But after a short check, the same problems showed up.

So here is the summary of parts related to spark to explore what else could be problematic:
-I have new correct spark plugs.
-Inspected but OLD plug wires.
-Replacement good Distributor (same performance as old dist.)
-NEW distributor cap (minor improvement in misfire, but not significant)
-NEW replacement coil (same performance as old coil)
-Original ICU Box
-ECU is a replacement and appears to work well. It doesn't control spark, just injector pulse
-NEW fuel pump, fuel filter, fuel lines, fuel tank, injectors...
-E12 throttle adjustment followed and reset with idle screw and linkage stop. TB cleaned
-AFM exchanged with 1980 635 and no change in rough running. Suspect AFM OK ad wiper track does not give any jerky running
-Combo relay exchanged with spares. No difference in rough running. Thought maybe ECU fuel circuit was faulty if relay want clicking on and off
-

Regarding the ICU box, it seemed to me these are either working or not, but maybe it gets weak as is overheats? Maybe I can check this since I have a known good one in the other car. If the problem occurs, swap the ICU and see if on a warm car it makes any difference?

I guess the combo relay could have similar problem as it heats up. Will have to check that, just like the ICU box. Speaking of, some good detail on the combo relay

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Regarding the spark plug wires, I have a tough time believing they are causing a problem. But maybe as they heat up a few have higher resistance and weaker spark?


Any other ideas? ](*,) I am running out of explanations on either problem above :cry:
Last edited by tschultz on Mon May 20, 2024 9:57 pm, edited 1 time in total.
http://www.Drive4Corners.com
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'79 635CSi Revival
'80 635CSi
'83 633CSi Callaway Turbo continued as 1988 535is Turbo
SOLD: '81 635CSi/A
Cogeniac
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Re: 1979 635CSi Euro - Henna Revival Project

Post by Cogeniac »

Here's an out of left field suggestion... Check your voltage regulator module. IIRC this is a plug-in unit inthe alternator. I had a friend with an E9 CSL that had similar symptoms. He was pulling his hair out over it for months.. I put the distributor pulse on a scope and when she started misfiring all hell broke loose on that signal. I casually went over to the alt and disconnected the field wire and Poof! Misfire and electrical chaos stopped. He hightailed it tothe dealer and replaced the regulator module and the problem was gone. Bastard never really did thank me for that..
Scott Andrews
Petaluma, CA
1980 Euro 635, "Rocinante", the Truth.
1972 3.0 CS
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Cogeniac
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Re: 1979 635CSi Euro - Henna Revival Project

Post by Cogeniac »

I was looking over your posts from above. The dyno curve is exactly what I would expect from an M90. The power seems down a bit. Should be up around 208 hp, but from my driving experience, the torque on that engine starts at 1500 and stays flat for the entire RPM range... One of the all time best engines I have driven...
Scott Andrews
Petaluma, CA
1980 Euro 635, "Rocinante", the Truth.
1972 3.0 CS
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tschultz
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Re: 1979 635CSi Euro - Henna Revival Project

Post by tschultz »

Another update.
Thanks for the idea Scott, I was about to check that next if the below attempts didn't work. Luckily, it doesn't seem like the voltage regulator is a problem.

I think I have the car running well finally! It seemed like my distributor may have been faulty with the pulse sender since it shut off one day after pulling in the garage. I will still have to try testing it but in the mean time, I obtained an 015 distributor from a 633. This had a better (not discolored) pulse sender. But I put that in the car and I saw an improvement in running characteristic. I'm not sure that the 008 unit was bad, but i decided to keep troubleshooting with the one that was working and I can still swap in the original at a later date. The advance curves may be slightly different. I established that baseline knowing that the distributor was not weak, purchased from an e12 guy.
I was still having a little stutter and misfire after running for a bit however, so I decided I needed to do more investigation and get back to basics a little bit:

I kept the new coil in place just to rule that out as a possible contributor. Last week, I tested with the ICU from my 1980 but found the same symptoms so I confident that part is working as intended and put the original back in the car. I had a hard time believing the spark plugs were causing issues after disassembling them and fitting them into the valve cover channel.

I decided to see if I could put some carb cleaner in the ports for the vacuum advance and retard ports on the throttle body in case they were a little dirty. So, I did that and forced some air through both to make sure they were not clogged at all and not giving me proper advance or retard function... It seemed like the vacuum retard port may have been partly clogged, though it is such a small hole it is tough to tell for sure.

I decided to check the vacuum advance and retard functions manually and found that the retard function wasn't operating properly. It didn't turn the reluctor wheel. when i sucked on the hose, even really hard! After checking, I had a vacuum connector that was plugged with black carbon! So that wasn't helping anything. Once I got that replaced, I made sure manually that the vacuum functions were turning the rotor inside the distributor. Obviously it turned as it should once the clog was gone.

I had pulled out my timing light already and thought I should check total advance. With everything disconnected, I got the timing set at about 36-37 degrees total all in advance. I find this easier than trying to strobe the ball at a specific rpm. My timing mark is on the alternator mounting bracket and a matching paint mark on the harmonic balancer. So it is easy to rev it and watched the advance. I adjust the light to about 36 degrees and then try and get the mark to line up as I rev it past 3000-3500 rpm.

Knowing that was about right, I was puzzled to find the idle hunting a little bit and not being smooth as i'd expect from what I am used to in my 1980 635csi. So, I pulled out the idle air screw on the throttle body and cleaned the nose of the screw. It had some carbon but wasn't bad. I also decided to see if while running the TPS would change the idle sound (if I turned it one way or the other). No change either way... So I pulled off the TPS and did a continuity test. The idle circuit and WOT were not consistently contacting when I tested with my multimeter. So, I grabbed a spare from my e28 parts stash and luckily the TPS functions the same with the same pinout, even if slightly different shape/size. I put that one knowing one as good and hoping it would make a difference .I had one bad TPS and one good in my spares, but I haven't really heard of them going bad otherwise... maybe the contacts were just dirty and a cleaning will fix the original back to functional. Not sure it made much of a difference, but maybe. I was sort of doing multiple things quickly here.
In testing this, I found a little slack in the throttle and double checked the e12 throttle FAQ. I noticed I could adjust it slightly and found that upon restart this helped a little bit. The slack is on the pedal side instead of the TB side but matches the picture on the e12 website. It felt like this adjustment was a pretty big one, but maybe just because the TPS was working to tell the ECU when the engine should be in idle.

So upon test drive, everything is running better! I am not sure what one thing solved it, but it seems to be a combination of all the fixes. I may or may not have had a misfire, or I may have simply had improper timing of the engine being compounded or masked by the bad TPS and lack of vacuum advance and incorrect ignition timing.

The car is now idling nicely around 950-1000rpm when warm and I am not feeling this misfire when driving. It wasn't lean surging, definitely a misfire, but I bet it woudl do that if the ignition timing was too advance while cruising since the vacuum hose was plugged. I drove around about 6-10 miles and the car was feeling the same level of smoothness as when I left. More importantly, there isn't a surge or half stutter when coming off idle and trying to rev.

A NOS master turned out to be faulty and I have a random soft pedal that pumps up. I have another new master cylinder coming to swap in this week. But the car seems to be drivable now and I can see how it handles and continue with other little fixes.

More updates soon.
http://www.Drive4Corners.com
Image
'79 635CSi Revival
'80 635CSi
'83 633CSi Callaway Turbo continued as 1988 535is Turbo
SOLD: '81 635CSi/A
Cogeniac
Posts: 86
Joined: Mon Nov 27, 2023 4:25 am
Location: Petaluma,CA
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Re: 1979 635CSi Euro - Henna Revival Project

Post by Cogeniac »

Your combo relay diagrams had me a bit confused until I realized you had colored the AFM switch signal blue, That is what holds the contacts onthat side of the relay closed after the engine starts (held there by the AFM vane closing the AFM switch.
Scott Andrews
Petaluma, CA
1980 Euro 635, "Rocinante", the Truth.
1972 3.0 CS
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Cogeniac
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Re: 1979 635CSi Euro - Henna Revival Project

Post by Cogeniac »

Your misfire is at speed, right? That pretty much rules out a vaccum leak, since that would be more pronounced at lower RPM, I think. What plugs are you running? Could be they are too cold. I use WR9LS Silburs (bought several NOS stashes on eBay). My experience is that the TPS switch does very little. The engine is seldom operating at WOT, and whatever effect the switch has at idle or WOT, it seems minor.

Many years ago I gave up on the Bosch ignition box, and retro-fitted an MSD unit. Solved all of my idle misfire issues. Never did experience any high RPM misfires.
Scott Andrews
Petaluma, CA
1980 Euro 635, "Rocinante", the Truth.
1972 3.0 CS
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