poof from exhaust pipe

[mel kessler]

I have a 1988 911 3.2 engine it has seemed to have a miss when first started . it gets better after running but sounds as to have a valve sticking or anyway while running it make poofs out of the exhaust pipe. i checked the compression back several years and it was 170 to 175 on each cylinder. do i have a valve sticking, or a bad plug wire, or injector? valves have not been adjusted in several years ,thanks for anyones advice!-----Mel

[tharbert]

Welcome to the forum Mel!

You ask some great questions and given more info, some here may be able to point you in the right direction. As you really haven't provided enough info to give you the answers you are looking for, maybe I can suggest a course of action?

You said you did a compression test a few years ago. Doing another one now will help you see if your compression numbers have changed. A severe drop in compression will tell you which cylinder has problems.

Good luck and post some pictures of you car.

Be sure to use the search function of this site. It will yield most all the informatoin you need.

Tom

[mthomas58]

Intake leaks are common and produce the symptoms you describe. One way to check for leaks by spraying some starter fluid or carb cleaner around each intake port looking for any change in idle which will confirm a leak. If you find a leak, retorque your intake barrel nuts (notorious for coming loose) first. This might help but usually the intake will need to be pulled and the gaskets replaced.

More info here:

Intake Gasket Replacement Project with pics

[kidrock]

Mel,

you state that a compression check hasn't been done in several years, as well as a valve adjustment hasn't been done in several years.

Either of these will go a long way in telling you the current condition of your motor.

Anyways, as a rough guide, are the following:

Puff of smoke at start up: Usually caused by water condensation in the case, which is common for our cars as long as it is a short and infrequent puff. Long puffs or a puff at every start-up probably indicates a more serious problem.

Long puff of white smoke during hard acceleration is usually indicative of a rich running condition due to unburnt fuel...adjusting the fuel mixture may cure this problem.

Long puff of blue smoke during hard acceleration is usually indicative of a problem within the piston rings and/or cylinder walls, necessitating some type of machining or motor work.

Long puff of blue smoke when immediately letting off the gas pedal after hard acceleration is usually indicative of bad valve guides, which is common on the 3.2 motor...necessitating work on the cylinder heads.

I'm not an expert, but this is a rough guide which I've read in previous threads here. As previously stated, a search will produce many answers on this subject.

Good luck, welcome to the site and we're all looking forward to pix of your car.

[Por_sha911]

You have been given good info above. Please let me add a few thoughts. A needed valve adjustment would definitely cause problems but you usually hear the louder that usual clicking of loose valves. The need for a valve adjustment is based on miles and not time. How many miles since a valve adjustment? How often do you change your oil?
A leak-down test will tell you a lot about the condition of each cylinder.
Also, be careful about spraying a lot of starter fluid on a hot motor. We want to diagnose (not BBQ). I am overly cautious but I think it is wise to have a fire extinguisher around for that 1 in a million chance.

[stlrj]

If you think it's a bad ignition wire, spray some water on it while the engine idles.

[mel kessler]

I retorqued the intake bolts, some did move a little .I also sprayed the starting fluid but could tell no difference. The compression has seemed to have dropped 10 to 15 lbs per cylinder(all of them). No loud valve sounds but if you hold the gas down about 3000 r.p.m.s every once and a while you heard a poof or two from the exhaust. The car don't run bad or idle bad. I 'am going to replace the rotor ,wires,and cap. I don't see this helping but they are old. I have owned the car about 7 years and have ran it maybe 3,000 miles mainly to car shows.I still feel this is a valve problem.----Thanks Mel

[Por_sha911]

Did you look up the miles since the last valve adjustment?

[Zeke]

When a Carrera cools, some fuel may crystallize on the injector. I read this here and I guess it takes more than a day. When my car sits for 2 weeks, it runs on 5 until the injector (whichever one it is) gets hot and then the car runs smooth. It takes 2-3 miles.

Just another thought.

[kidrock]

I'd do a valve adjustment, then run a can of Sea Foam or Techron through a full tank of gas.

[mel kessler]

I put new plugs ,rotor, and cap on then ran a can of sea foam through, car is running even better and idle is great! Thanks for all your help.----------------Mel

[kidrock]

great to hear, Mel. You should consider a valve adjustment soon. I've done 2 in the 18 months I've owned her...it really isn't Rocket Science.

You didn't forget the pix, did you????