Black smoke

[500ESpain]

The other day, flooring the car in a tunnel I noticed I left a cloud of smoke behind me. Next day, my dad was driving behind me and he said he could see some black smoke coming from the exhaust while doing city driving and nothing when we reached the highway.

Cats (Magnaflow) and oxygen sensor have less than 3000 kms.

Unfortunately I barely drive the car and when I do, it's almost all city driving, definitively not its habitat. Do you think some more highway driving and a good injector cleaner should fix the problem or is there something else I should check? I haven't looked for codes yet, I didn't have time.

Thanks in advance.

[daantjie]

Black smoke is raw fuel being dumped and not being burnt completely. Blue smoke is oil. White smoke is water and/or ATF being burned in combustion chamber. Could be faulty injector dumping fuel.

[500ESpain]

Ok, thanks. I guess there's no way to check the injectors without removing them, right?

[gsxr]

Ok, thanks. I guess there's no way to check the injectors without removing them, right?

There's no way to test without removing them and having the flow checked on a test bench.

Is the engine running smoothly otherwise? Just some black smoke? Do you have a spare LH module you could pop in for testing?

[daantjie]

I am more of an early K Jet guy which uses purely mechanical injectors (starts spraying once the crack over pressure has been reached). I would assume that the 500e has fully electronic injectors, so I am not sure how these would be bench tested, but I am sure the 500e guru's will chime in with a solution On the early K jet cars a common culprit is the cold start injector which fails, and then constantly dumps fuel across all operating conditions.

[500ESpain]

Thanks gsxr and daantjie.

I do have an extra LH module. I'll give it a try.

Do the LH engines have the cold start injector?

[gsxr]

Do the LH engines have the cold start injector?

No: LH-SFI is full electronic sequential injection, there is no additional cold-start injector (that was only used on older CIS/CIS-E mechanical injection systems).

If you happen to have access to a digital scanner, I'd check the LH adaptation, and if you can view live values while driving I'd want to monitor the O2 sensor voltage.

[500ESpain]

Ok, thanks. I'll try that too.

[500ESpain]

Could it also be a faulty coolant temperature sensor? I don't have any related codes but I bought one because the car was overheating. Now it runs cooler with the new viscous fan but, in my opinion, it still has a tendency to run too hot, reaching 100C as soon as you leave the open road.

If I'm not wrong, it's a very easy replacing operation, just unscrewing and screwing the new one. Am I right? Any torque specifications?

[Rouven036]

Yeah it could run rich due to a faulty coolant temp. sensor, but black smoke rich I m not so sure about. Also check hfm LH codes and o2 sensor. Wiring wariness is good?

[500ESpain]

Yes, 02 sensor and harness are new. It's not a constant black situation. So far it has happened under hard acceleration and sometimes while driving in the city with cold engine.

[lowman]

There's no way to test without removing them and having the flow checked on a test bench.

Is the engine running smoothly otherwise? Just some black smoke? Do you have a spare LH module you could pop in for testing?

Of course there is a way of testing without removing the injectors.
How you do that is put a fuel pressure gauge to the system...and checking for fuel pressure drop when doing a injector pulse test.

[500ESpain]

Today I had the chance to take the car out for some testing and the first thing I noticed is that it had to crank for longer before starting. After a little while I started hearing a noise like if someone was tapping the bottom of the car rythmically with a hammer. I thought it was the exhaust hitting the floor but I couldn't really find out where it was coming from. Definitively not from the engine. I removed the rear seat and the fuel pump relay was clearly clicking. Could it be just the relay or the problem is coming from the LH module? Could the smoke (which is actually more white-ish than black now than I've been able to see it myself) be caused by low fuel pressure?

[gsxr]

I removed the rear seat and the fuel pump relay was clearly clicking. Could it be just the relay or the problem is coming from the LH module?

It's not the relay. The LH module is at fault... you can either swap it with another LH module, or repair the module by replacing the electrolytic capacitors inside (search the forum for more info).

Could the smoke (which is actually more white-ish than black now than I've been able to see it myself) be caused by low fuel pressure?

The clicking relay would not cause smoke of any color. White-ish smoke is more likely to be coolant, or possibly oil.

[500ESpain]

Thanks, guys. I have a spare LH module so I'll give it a try and if it doesn't solve the problem I'll take to have the fuel pressure checked.

[500ESpain]

I've replaced the LH module. Relay clicking is gone. A little bit of smoke when accelerating when cold and right after changing the module but no smoke under heavy acceleration with warm engine. Looks like the problem is solved. Knock on wood.