Washed The Engine Bay and Now It Won't Run

[sptcoupe]

This is the engine bay of my 1986 X/19, with the 1500 FI engine with the Bosch L-Jetronic. Because the FI system is the same as used on our spiders, I'm hoping someone can help this old carb guy.

So I washed the engine bay with the usual degreaser, hosed it down, and it wouldn't start after that (it was running perfectly before). Used compressed air to blow off the Allison ignition and AFM and generally dry the engine. Let it sit between tries to start it, and after about an hour and 5 tries, had a colossal backfire (like a hi-powered rifle shot), which I think was through the exhaust, but couldn't tell because I was in the car. Tried it again, and after a few more backfires (not nearly as bad and in the intake manifold), it started. Now it idles perfectly and starts normally, but it won't come off idle.

By that I mean that if you give it gas, it revs for about 1 second or less, than goes back to idle. If I hold the accelerator down, it will continue to surge like that, but never higher than 2000 rpms, and I get backfires in the intake manifold. So it kind of vrooms, then idle speed, then vrooms, then idle speed, all the while with frequent backfires in the intake and the air filter. I took the air filter off and the AFM door moves freely, so it seems the computer is cutting the fuel supply after initial tip in when trying to accelerate.

When I washed it down, I had the air filter covered and the ignition covered in plastic, and I dried everything and used air to blow everything out before I tried to start it the first time.

Tonight after sitting for 5 hours, I blew out and WD-40'd every connector I could see. Took the top off the AFM and did that as well. No change whatsoever.

While I had the top off the AFM, I noticed that no matter what I did with the throttle, the AFM armature would not move, except very briefly (maybe 3mm or so) as the motor would surge briefly on tip in . If I keep the throttle open by using the linkage, and moved the AFM armature, it would rev higher before returning to idle. So it seems the AFM isn't opening/advancing when I open the throttle? Could that colossal backfire I had have damaged the AFM?

I also discovered a charcoal canister tucked up against the rear firewall with an unplugged vacuum port, but plenty of vacuum. What should that port be attached to, and should I leave it open or plug it or hook it to some other vacuum port?

[vandor]

Maybe the AFM door has some anti-backfire valve that is not open? Take the intake hose off and look at the AFM flap.
Also possibly a large vacuum leak between the AFM and the intake?
Not likely, but if the TPS goes bad and the ECU always receives the idle signal, then the ECU will cut fuel at 1500 rpm.

[So Cal Mark]

I agree, check the flap in the AFM and also the intake boot. The backfire may have blown the hose off of the AFM

[RoyBatty]

Is it possible that the backfire has forcibly wedged the AFM into a stuck position?

[RRoller123]

Regarding the charcoal canister, I have no idea if it is functionally the same on an X1/9 as Spider, but it is likely so. This is the Spider schematic of vacuum hoses, etc for the canister.

[sptcoupe]

The AFM flap moves freely, but I don't know if it is actually working correctly. I'll check for leaks again tonight.

I found a schematic of the X's charcoal canister, and in fact the tube is meant to be opened to the air - at least from the schematic. Anybody else have other ideas on it?

[bradartigue]

Did you look at the flap or just see that it was turning by observing the top? Some flaps have a door in them that blows open (and breaks off occasionally) in the middle of the door. The car will idle and do little or nothing else, usually idles high.

Not sure about the WD-40 on everything, that sounds worse than engine degreaser. Did you pull the plugs and look at them?

[sptcoupe]

Tried it again today, and it started and idles beautifully, but had the same issue. Took the AFM off and inspected and cleaned it with crab cleaner, and cleaned the pins as best I could in the AFM and the plug. I could see nothing wrong at all with it, and compared it to a 124 unit I have and also saw no difference in appearance or function. But when I put it back on, it wouldn't (and won't) start at all! I have triple checked for leaks and have none - either before I cleaned it or after.

[RRoller123]

This new problem points to the connector that ties the AFM to the ECU.

[sptcoupe]

Just an update, as Andy (ToplessExpat) and I finally got back to the car last night. Good news, it is running perfectly again.

So the short version of the diagnosis and fix was that both the AFM plug and TPS plug had initially gotten wet when I washed the engine. I dried both of these and from what I could see, the ECU was dry at that time. After I used air on it the first time to dry it out, it finally started and idled fine, but then it wouldn't rev beyond about 2000 rpms and it backfired. As I tried later to troubleshoot it, I used air on it again, and it got worse - wouldn't start at all. So what happened was that the second time I used the air, it forced water that was in the TPS harness and the AFM harness right into the ECU. Last night, when we popped the ECU plug, it was soaked! Dried it all out, and presto - all issues solved.

Along the way we replaced the original AFM (which was badly worn) with a NOS unit, and re-calibrated the TPS using Brad Artigue's guide. Runs very nicely now. I also have a NOS ECU ready if for some reason the original begins to act weird as a result of its soaking - but so far, so good.

Many thanks for all the help from you guys and Andy (and Brad formhis manual). We celebrated with a bottle of real Chianti wine, good Italian cheese, olives and prosciutto, left the mess in the garage for today, and called it a night.