denny411 Posted February 4, 2004 Share Posted February 4, 2004 I`ve been working on a 93 pontiac lemans that has me baffled. It is sputtering through the exhaust, and sounds like it is missing on one cylinder. So far I have replaced the cap,rotor,plugs,wires,fuel filter,fuel pump and pickup screen.(basic normal tune up parts) I`m getting a lean O2 reading on the diagnostic,(hence the new fuel pump) but no other codes have shown up. I`m also getting a backfire through the intake under acceleration. it does sound very much like it is running out of fuel, but it has better than 1/2 a tank. I have checked compression, and all cylinders are within specs (159-175psi) I have even put air pressure to each cylinder,and turned the engine over by hand until the valves closed to be sure that I had no burnt valves. Any thoughts? Quote Link to comment Share on other sites More sharing options...
Z-TARD Posted February 4, 2004 Share Posted February 4, 2004 Bad injectors maybe? Quote Link to comment Share on other sites More sharing options...
denny411 Posted February 4, 2004 Author Share Posted February 4, 2004 I checked the resistance of the injector, and got 2.0 ohms. The manual calls for at least 1.2 ohms. Thanks for the input. Quote Link to comment Share on other sites More sharing options...
dmyntti Posted February 4, 2004 Share Posted February 4, 2004 It still could be a bad injector. The injector could be clogged or mechanically jammed and the ohm reading would still be right. If you can get ahold of one you can use an injector pulser and a pressure guage on the and watch the pressure drop from each injector seperately. Maybe you can rent one of these pulsers. I have one you could borrow if you can't find one locally (I'm about two hours away form you) Good luck Quote Link to comment Share on other sites More sharing options...
datsunlover Posted February 4, 2004 Share Posted February 4, 2004 Hmm... maybe the MAP sensor? I've heard of a lot of GM's with similar problems caused by faulty map sensors... Quote Link to comment Share on other sites More sharing options...
David K Posted February 5, 2004 Share Posted February 5, 2004 Denny, i have a 94 Pontiac Transport, and guess what, im having that same exact problem!!! http://hybridz.org/phpBB2/viewtopic.php?t=30855 Quote Link to comment Share on other sites More sharing options...
denny411 Posted February 5, 2004 Author Share Posted February 5, 2004 I`m going to check the map sensor and egr valve tonight. I do have a spare throttle body on the shelf. I might swap the injectors to see what happens. Quote Link to comment Share on other sites More sharing options...
denny411 Posted February 5, 2004 Author Share Posted February 5, 2004 I didn`t have time to do the checks that I planned, but I did put a vacume gauge on it. I have 15 to 16 inHg with a very very slight fluctuation between the two. vacume is a little toward the low side but still within specs. The slight needle fluctuation suggests a fuel problem. The engine has a positive pressure egr valve on it that is difficult to diagnose for a vacume leak. A minor leak at the egr could also result in the low floating needle. Quote Link to comment Share on other sites More sharing options...
Guest twinturbo240z Posted February 5, 2004 Share Posted February 5, 2004 I've had the same exact problem on my Dodge Ram 150 van. Turned out to be the 02 sensor that was bad. Hope that helps. Quote Link to comment Share on other sites More sharing options...
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