Excessive Smoke

[BillCarry]

Just got home from a ten day trip in our motor home. About half way through began to belch exhaust smoke when heavy throttle was used at speed (like when going up a fairly steep grade). I have a boost gauge and EGT gauge and both indicated normal (6-8 lbs of boost and max of about 1100 degrees or less EGT) when the smoking would occur. As time went on the situation got worse.

Got home today and checked DTC (counting panel light flashes). Have a code 35, injector pulse width error - response time short. Also showed a code 78, waste gate solenoid fault, but I think this was left over from a problem I was having a few weeks ago with low or no boost which I was able to correct by snugging all vacuum and electrical connections and giving the solenoid a shot of WD-40 (per advice of John Kennedy).

Would appreciate any thoughts by those more expert about such matters before I place myself at the mercy of the local Chevy dealer.

Motor home, which I have owned since new in 1994, now has 248000 miles on it. The engine is a skirted block AMG new engine with about 70,000 miles. The injector pump was new with the engine which was installed by Peninsular.

[Robyn]

This may sound simple....buttttttttttt....check the air filter and related pipes.

[BillCarry]

Will check out the air filter, etc. One other symptom is hunting which occurs during very light throttle decels at highway speed.

[DmaxMaverick]

"Hunting" (or unusual up/down shifting) occurs when there is less than expected power at a specific throttle position.

[Robyn]

When was the PMD last replaced ???

Normally the PMD just fails PLOP DONE... but I have seen pulse width error messages in conjunction with a failing PMD


If you have a good spare or a new spare it would not hurt to swap them and give it a go.

If that corrects the gremlin then mark the old one as GET YA HOME MAYBE unit.

[More Power]

...I have a boost gauge and EGT gauge and both indicated normal (6-8 lbs of boost and max of about 1100 degrees or less EGT) when the smoking would occur....

Doesn't seem typical. I would expect boost pressure to drop and EGT to rise when more black smoke is seen.

[BillCarry]

I checked the intake system and replaced the intake filter. Plugged in a standby PMD. Neither had any effect on the smoking issue. Anybody got any other ideas or suggestions?

[Robyn]

This is beginning to sound like an injection pump issue.

Possibly the fuel solenoid is getting HINKY (The actual fuel control valve...not the shut off)

Have you tried some fuel treatment?

Even a couple quarts of tranny fluid will clean things well.

[JohnC]

It's a long shot, but I seem to recall someone who had a similar problem and it was cured by changing the fuel filter. Don't recall the specifics, and I know it sounds counter-intuitive; probably related to injection pressure, atomization, and/or timing. Or, it could be my oldtimers disease...

[DmaxMaverick]

It's a long shot, but I seem to recall someone who had a similar problem and it was cured by changing the fuel filter. Don't recall the specifics, and I know it sounds counter-intuitive; probably related to injection pressure, atomization, and/or timing. Or, it could be my oldtimers disease...

I wouldn't call it a long shot. Most common issues are cured by simple routine maintenance items, such as filters, hoses, seals, and even the fuel filler cap. Always check off the pennies and nickels before throwing down the dollars.