Began running poorly all of a sudden!

[ExEspirit]

Need some help so we don't replace unnecessary components. 91 Elan.
I have taken the time to review the entire thread about "suddenly began running like crap", posted by tweetdriver63 including responses. Have also reviewed the info about the CAS and new updated Hall sensor.

Will include all diagnosis to this point. Compression OK. High tension wires and coils OK and supplies spark to all 4 cylinders OK. Spark plugs OK. Began with a simple test by listening for rpm change removing one plug wire at a time at spark plug. No rpm change on cyl number 1 or number 3. RPM does change on Cyl number 2 and 4. Again good spark at all 4.
Next step checked for RPM change by removing injector connectors at injector one at a time checking for rpm drop.
Has no RPM change at cylinder 1 and 3 and does change on cylinder 2 and 4.
With engine running, using a "noid light, have injector pulse at cylinder 1,2 and 4. No pulse at cylinder 3.
A quick check with a 12v test lamp shows B+ or battery voltage on both terminals of the injector harness at cylinder number 3.
This tells me we have a possible ECM concern with the lack of injector pulse at cylinder 3. Along with a possible injector problem at cylinder number 1.

Since I have no trouble codes being stored in the ECM, I am leaning toward ECM and Injectors.
The check engine light has only appeared briefly over the recent past and no codes have been stored that will lead me in a direction.

My question would be this:
Since the CAS and Hall Effect system plays a part in the injectors syncronization, should we go forward with the "Hall" updates and or CAS , before any further ECM and Injector pulse checks?

I want to attempt to avoid any future concern with the CAS and Hall Effect since this is obviously an area of concern on this vehicle.

I did find the mention of a possible poor connection both at the injectors and at the harness near the bulkhead under the coolant bottle, however with 12v. on both wires at injector number 3 and no pulse, this tells me the integrity of the wiring to the ECM should be OK.....With the exception of any possible short to voltage on those 2 wires.

I will be looking at Injector cleaning or replacement, along with any possible reasons for intrusion of charcoal somehow bypassing the fuel filter which may have restricted the number 1 injector. Re: charcoal cannister as mentions in another thread on the Forum.

Thank You very much in advance for any help on this topic.

[bobbrown]

Firstly it may be an idea to down load the manuals that is assuming you do not already have them as the engine management one does have some fault finding flow diagrams .
The fuel injector system and ignition is a two drive system, so on the injectors the same drive drives two of the injectors e.g. 1 and 3 and 2 and 4 simultaneously and the ignition is wasted spark so 1 and 4 and 2 and 3 fire together. So if you had a fault on the ECM then it would affect two cylinders not just one. There have been issues with the coil packs as well as the cas and hall effect sensor as others will no doubt point out and it is important to remember the ECM will try to hold the rpm at idle even if you remove a plug lead so you have to listen for a change in note as you remove the lead or listen for the crack as the spark jumps the gap you created when removing the lead.
The fact you are getting a good spark and the lead removal only made changes on 2 and 4 would lead me to not suspect the coil as that drives 1 and 4 and 2 and 3 so 2 and 4 are on opposite sides of the coil
As for injectors that seems to get a little more complex as you say a "noid light" check shows number 3 faulty and removing the leads effects 2 and 4 which does not seem to ring true, I tend to go for the old screw driver to the ear trick and listen to the injectors pulse as the fire.
Engine light and codes are only generated if a fault is detected on a point that is measured or monitored so if there is a faulty spark plug or a faulty injector I would not expect to see a fault code as there is nothing in the ECM to detect the fault.

[tweetdriver63]

As you said you've read both my threads (running like crap, and the more recent one involving the canister), I won't re-hash. I'll just say your problem sounds 100% identical to mine when it all started. I'll be watching this thread closely.

Have you tried swapping around the injectors, putting a known good injector in the #3 spot? Maybe swap out the injector in #3 for the #2 or #4 injector and see if the bad cylinder changes. The mechanic did that on mine to see if anything changed, in order to confirm injector fault vs circuit. It appeared to be a bad injector, but ultimately he found that the #1/#3 injector circuit wouldn't support operation of 2 injectors (Connect only the #1 or the #3 and it worked. Connect both and neither worked). That led to replacing the ECM. Of course, my car has become the automotive equivalent of a patient of Dr House.

[ExEspirit]

Great info already.
I don't have the vehicle beside me at the moment, however I will take a listen with a stethescope on Monday, and determine if we have the ticking at each injector.
Engine does come off idle and revs fine although with a misfire.

Learning that the injector driver handles 1 and 3 and another ECM driver handles the 2 and 4 injectors, we'll check for the "noid light" pulse with the wires removed from all injectors...just in case that number 1 injector is shorted. I checked for a pulse with the engine running disconnecting one injector at a time.

So then, would it be advisable to go ahead and do the CAS/hall effect update even if not directly related to my concern at this moment?

Wiring schematics for ECM and Injector wiring would be a great help.

Could you possibly direct me to the service manual download?

Thank you again.

PS. Have not removed or swaped any injectors as yet. I am in early stages of diagnosis at this point.

[tweetdriver63]

You'll see a link on the menu bar at the top of the page, just below the LEC banner. Click there and follow the instructions. That will get you a password to download the manuals. As an alternative, you can also find them with google.

Where are you located? I'm pretty sure the closed-loop engine management manual is on here. Google "Lotus Elan M100 closed loop engine management manual" or the like, and you should be able to find it.

The manual does describe how to test all the sensors, etc.

My car appears to have had at least two separate issues. One was the ECM, which may have been caused by the power surge I had last year. The ECM might also have been damaged due to injector problems. The other issue was the blockage of the fuel filter, and the fouling of the injectors, apparently caused by the charcoal canister. I don't know if one problem caused or contributed to the other, or if they just came to a head at about the same time by coincidence. I'm praying there aren't going to be anymore issues when the mechanic gets the new canister and injectors fitted Monday. God only knows how much the bill for diagnosis and repair already is.

[ExEspirit]

Thank You.

We are in Las Vegas, NV.

Will update with findings.

[tweetdriver63]

Since I don't know cause-and-effect with all the things that have been found needing attention on my car, I'll try to keep you updated, as you may want to check them out on yours as well. The latest is the fuel pressure regulator, which was found to be bad after the new canister and injectors were installed.

[tweetdriver63]

The latest on my car is that it is sometimes bucking at around 2700ish RPM on light acceleration when the engine isn't warmed up to operating temp, and according to the mechanic, on some test drives, it had a serious hesitation on accelerating from a stop. It is serious enough that they don't want to let the car go because they're afraid I might get T-boned pulling across traffic. They said if it did it then, I wouldn't be able to get out of the way. They also say it is still running a little lean.

This morning they did a little test of the MAP sensor. What they did was disconnect the battery, disconnect the MAP sensor, reconnect the battery, and do a test drive. The result was that the hesitation and bucking were both gone. Of course, with the MAP sensor disconnected, you don't get good running at higher power settings. They are currently going after replacing the MAP sensor, and I've got my fingers crossed.