84' 3.2 running problems...

[Cubieman]

I have a rough running/missing cylinder(s) situation.
A short rundown of what has happened recently with this car and what parts/tests have been done.

Problem: No start/no crank/nothing!
Solution: Igniton cylinder pawl was broken off, installed new cylinder along with igniton switch. Also installed new DME relay at this time even though old relay was fine.

The car started just fine. I drove down the block and it died, got it to start and got it back to my place and it would not start up again. Now on to the next issue below.

Problem: No start/engine cranks
Solution: replaced both reference and speed sensor, CHT sensor is two wire setup and tested fine, it was NOT replaced. Igniton coil also replaced, although old coil tested OK.

Car now starts and runs but runs VERY rough/missing

Here are the tests I have done following the bentley manual:
Check speed/ref/cht w/ multimeter= OK
Check ICV= OK
Check VAF/IAT = OK
Check Idle switch = OK
Check WOT switch= OK
Check all injectors ohm/12V from connector=OK

Back to basics

All HT leads producing spark= OK
Replaced all spark plugs

Now it gets interesting...
I pulled injector connections w/ engine running. When I pulled the connections it would produce a result (drop a cylinder) EXCEPT on cylinders 2 and 4.
I thought maybe these injectors were not functioning correctly so I pulled the fuel rails and swapped cylinder 2 injector to cylinder 1 and I swapped cylinder 4 injector to cylinder 5.

I thought this would result in a different outcome when I pulled the connections while the engine was running, but it was the same. Cylinders 2 and 4 still did not "react" when connections were pulled from the injectors.
I made sure once again I had spark to the leads and I did.

I am running into a wall and any help would be greatly appreciated. I hope my post isn't too confusing.

[Nick Triesch]

I had a big problem with my injectors. They were sent out and cleaned and tested locally. Passenger side dumped fuel car ran horrible. Replaced injectors with new Bosch units, car runs perfect. Sometimes you just need new injectors.

[Bigtoe32067]

It’s not injectors if he swapped them and the problem remained. I would swap plug wires next and check/ replace dist cap and rotor. If the cap is cross firing internally you may not have any evidence from the outside.
If none of the above works then it’s time for compression test
Good luck
Tony

[Harry998R]

Hi Cubieman,

I can’t help but think that one of the changes you have made has resulted in the problem you now face.

Have you checked the reference sensor gap?

Cheers,
Harry.

[GH85Carrera]

I had weird running issues and checked my reference sensors with a multi meter, and it reported normal readings. After several episodes of struggling to get back home, I just replaced the crank sensors. That was the cure. When just sitting still they always checked out. They had a problem when in use on the car.

My coil was once the issue on a different problem. Those are a real challenge to replace as the Bosch unit the loacal dealer will sell you as a replacement is garbage.

[Cubieman]

Ok, so I did replace the speed and reference sensors previously due to a crank/no start situaton. Could it be that my issues are due to those sensors even though they are new?
I used the BMW sensors, and I did NOT gap the speed sensor as I did not have to mess with the bracket. Both sensors easily came out and went back in

My replaced coil is a bosch unit, still have other coil I can put in

I have spark to all cylinders, I have new spark plugs installed and the fuel injectors should all be ok from my above "test". What gives? So far as I can tell cylinders 2 and 4 are not firing. I used a laser/ir thermometer last night on the header pipes and those 2 cylinders in question are about 100 degrees and all others are 150 degrees thereabouts after the car idles for 20 seconds.

Harry, I can't help but think what you said is true, cause and effect. I didn't have this issue before the new speed/ref. sensors were installed. Again I didnt gap it because I didn't remove the bracket.

Bigtoe: plug wires sound like the next thing, even though they are pretty new. I think I'll do the cap/rotor/wires.

Assuming the cylinders (2&4) are getting fuel and spark what other things might affect them so they don't fire?
Could an incorrectly gapped and/or faulty speed sensor cause these cylinders not to fire? Also, is the reference sensor ONLY used on startup, or is it constantly sending info to Mr. Motronic? Could this be a timing issue? At TDC the rotor points where it should, I did notice inside the cap the rotor made contact with it somehow and there is a small scrape in the cap.

[darrin]

Have you confirmed you don’t have plug wires for #s 2 and 4 reversed?

[RedCoupe]

Before you replace the plug wires check them for proper resistance. Terminal to terminal. If your plug wires have the resistors built into the spark plug terminals, those can fail.

[Cubieman]

I checked last night and all plug wires are in their correct positions according to the manual.
To check plug wire resistance I just need to put a multimeter on both ends? Is this what you are describing?

[Bigtoe32067]

Or just swap them with 5 and 6 and see if the problem moves with the wires to 5 and 6.
If t does it’s the wires if it doesn’t it’s not the wire and I’d do a compression test
Tony

[FrankM_]

My 2 cents :

Why are you 'assuming' that you have spark in an earlier post, you need to check that first !

- the distributor cap / rotor : to be checked / replaced ? You didn't mention that in your 'done list'
- the wiring from the engine bay connector to the injectors. Although the injectors are fired simultaneously, it can be that the wire 'driving' 2 (idem for 4) is damaged somehow. Check for injector open/close 'signal' with scope !
- speed and ref sensor are to be tested with a scope for clean signals (sinus and peak) with at least the right amplitude
- I doubt it is a problem with the ref sensor because the car wouldn't start if it didn't have any ref input, but check anyways with scope

SPD:



REF:


But if you want to do it methodically, follow the official DME test plan :
1. Check all ground connections (on cyl 1 intake, near fuel filter, strap to transmission)
2. Check all wiring plugs (14 pins in the back of eng bay, 6 pins driving the injectors in front, CHT/SPD/REF plugs, throttle, AFM, injector plugs)
3. Check fuel pump running - OK in your case
4. Check DME power - OK in your case
5. Check sensor output : SPD / REF with scope
6. Check coil input signal with scope
7. Check coil (OK), check HT leads, check distributor rotor (1 KOhm), check for spark
8. Check all other sensor inputs to DME (AFM, air temp, CHT, idle switch, WOT switch,...)
9. Check Fuel pressure at rail
10. Check injectors (2 - 3 Ohms resistance)
Check injector driver signal at injector connector with scope.
If unable, voltmeter should show approx 10V

[FrankM_]

For reference, here is what I see on my injector
connector

[cabmandone]

Pull the plug wire off the non firing cylinders, take a spare plug and verify you have spark. Get a noid light and verify you have injector pulse on the non firing cylinders.

[Cubieman]

I had tested with a sparkplug tester that I had spark from all plug wires previously.
Frank, I need to borrow a scope because I want to test these sensors entirely, just need to find one. I should just purchase one, looks like a very essential tool.
I swapped plug wires (old Nology aftermarket deals) and it produced a result.
Here is the result, I don't want to post this but I will. I don't believe I had the plug wires seated on the plugs correctly. Also some of the boots were chewed up likely from incorrectly attaching plug wires and forcing a bad connection.
So at this point when I pull injector leads ALL 6 react and drop the coresponding cylinder.
I have a new cap/rotor/plug wires comming
I sure wanted those Beru wires but it appears the 84' had different length wires so I got Clewetts and 6 wire holders.

The car still idles somewhat badly, but much better than before. I need to adjust and/or clean the throttle linkage because if you pull it to WOT then let it back to idle position sometimes the "arm" hangs up and doesn't press down on the idle switch, just hangs in space above it. Then if you mess with it the "arm" falls and smacks down onto the microswitch.

[cabmandone]

Now that you've got 6 cylinders firing (hey man, it happens) you can start looking at the IACV and cleaning it. Make sure all of your vacuum hoses are in good order. Test fuel pressure and make sure your FPR is doing its job. Then set base idle mixture if necessary but you'll need a Wide band O2 for that job.
A trouble spot for air leak is the intake runner seals as well.

[FrankM_]

Originally Posted by cabmando

Now that you've got 6 cylinders firing (hey man, it happens) you can start looking at the IACV and cleaning it. Make sure all of your vacuum hoses are in good order. Test fuel pressure and make sure your FPR is doing its job. Then set base idle mixture if necessary but you'll need a Wide band O2 for that job.
A trouble spot for air leak is the intake runner seals as well.

Good advice here.
On my '85 rough idle troubleshooting I did find one vacuum tube end cracked and that is enough to leak air in. For good measure I cleaned the ICV and the 2 rubber tubes leading towards it.
I guess the PO must have overfilled it once since there was a lot of oil residue on the walls of the rubber tubes leading up to the ICV.

That fixed most of the problem. Still hunting for better idle, I went overboard and started running down the whole DME test plan, checked every sensor output on the scope.

I bought this analog scope about 10 years back on eBay for $80, but now I would go for something portable and very basic like this (no affiliation) :

https://www.amazon.com/DSO-Shell-Oscilloscope-DSO150-15001K/dp/B076HD5862/ref=sr_1_5?keywords=DSO&qid=1574793706&sr=8-5

It can do much more than my analog scope and it is good enough for the type of signals you can find in our old cars (no need for Canbus logging/decoding,...).

[Cubieman]

I also have oil in the tubes comming to and from the ICV as well. I sprayed carb cleaner through the ICV and stuck it back in. I did use a (homemade) smoke machine and didn't find anything very conclusive as far as vacuum leaks, although I don't know that I had it tapped into the best spot. I do see the rubber piece that connects to a copper tube (by the venturi) is pretty rough and is torn.
While I had the airbox/fuel rails out I did tighten down a number of the intake nuts, some were quite loose!