Alpine951

My car suddenly started running lean after a wide open throttle run on the highway. been trying to locate a vacuum leak. I have pressure tested the car but can't find an leaks. I was thinking of bring the car to a local shop that I know does do smoke testing. Has anyone been successful going this route in finding a leak?

mtnman82

I bought a 'smokenator' from Speed Force Racing (I think is was SFR) quite a few years ago, which uses a cigarette to generate the smoke. I've used it to find intake leaks in the past. I don't think they sell them anymore, and the problem with it is the cigarette (smoke) doesn't last very long.

I've been trying to find a 'small evaporative emissions leak' on another car, so went ahead and bought a smoke tester off EBay for ~$100. The EBay tester uses mineral oil and hooks up to your car battery and air compressor. It works pretty good, but you have to be careful the wick stays saturated with the mineral oil or you burn the wick up. The local shops all want $150~$200 to do a smoke test so it was worth the $100 investment to me to get one of my own. Next time I do a check on the 951 I will be using this.

Alpine951

I thought those detectors go for way more than that. just bought one off ebay. Place I was going to bring it to has a $105/hour shop rate. buy my own $95 free shipping.

jc in rb

Just went through this a few week ago . Shop i go to found the leak after 2 smoke tests(split throttle body coupler from intercooler .crack was so fine you could hardly see it(length wise )and would only blow open under boost....

dizzyj

I usually pressure test

Alan 91 C2

To identify vacuum leaks, I usually just spray some carb cleaner on the suspect areas. A leak will increase idle speed, immediately. Leaks on the boost side, before the throttle plate, are not as responsive to carb cleaner, with MAF. Create a known leak, and test.

Alpine951

did both pressure tests and spraying starting fluid. no luck.

very frustrating.

Alan 91 C2

I do not think you have a vac leak. There are other reasons for lean operation. Have you looked at the plugs? You can have a bad injector. Or bad ground to the injectors. One thing you can try is a cylinder RPM drop test at idle. Pop the injector connector off one cylinder at a time, and look for equal RPM drop.

Alan 91 C2

when did you last replace the fuel filter?

pcleary1210

I built a smoke machine for $35 or so. $8 air regulator at Harbor Freight, some fittings, some hose, a paint can. Some plans call for a DC dimmer switch but I skipped that, got the right gauge nichrome wire to set it for like 100w of heat dissipation or so. It's enough to burn off the babyoil but not start a fire.

Use Ohm's law to calculate heat dissipation based on resistance and then connect it to your battery. Easy Peasy.

Alpine951

what will looking at the plugs tell me regarding running lean?

I cleaned all the grounds except for the ones under the dash a month ago.

Alpine951

not sure but I want to say 20k miles ago. fuel pressure is 40 # on the rail at idle and 45 when revved (3 bar fpr).

Alan 91 C2

The plugs will show you if the lean condition is for all cylinders, back to gas supply; filter, pump ect. Gas pressure in the driveway, tells very little about gas pressure and flow under load. Have you inspected the gas lines? Got one that is crushed? How about 25 year old rubber lines?

Variation in the plugs color will show you have an injector issue, for the individual cylinder. The injectors do have a final filter/screen in each injector.

Did you spray the carb cleaner around each intake to cyl gasket? I chased a poor idle for some time, before I checked for a leak at the gasket. The gasket had split.

Alpine951

a previous pressure test last month showed a leaking intake gasket. just replaced with all new gaskets. no more leak there.

Tom M'Guinn

I got one of those too and hated it. The cigarette burned out too fast, and left ashes in the intake, and the motor smelled like a smoker for week...