October 23, 20169 yr The 1-3 results are pushing the ok barrier. It may be indicating a head/gasket problem, valves, rings, scored cyls just on that side. Ide redo the test for good luck. Listen through the oil fill cap or pcv line for air. Check the radiator for bubbles as well, the air is going somewhere. Im pretty vauge on this test as Ive only done it once. Compression numbers look decent enough for me. The engine runs good, uses minimal oil, and consumes no coolant right? Plugs were nice color... At 200k the more you test the more you'll find. I still wonder if the issues causing the failure have been resolved. You have a good cat on there now and we have not seen 950 rpm idle since the origional test. What would happen if you were to take the emissions test again?
October 23, 20169 yr Author I replaced the headgaskets 2 years ago, just before the emissions test I had to do to register it. Fel pro gaskets, except OEM intake gaskets. It uses minimal oil. No coolant issues. Not been over normal temp ever since then. Yeah, it's getting down to can't find anything else wrong. I put the exhaust - cats and O2 - that it passed with 2 years ago back on for the retest. I wanted to do everything I could to hopefully get it passed without having to go back again. You can't get a waiver if you do your own repairs, so I'd be stuck paying for everything. I'm going to put the plugs back in, and run it in the dark to check for arcs. I retested a couple of the cylinders twice in the original compression test, and got essentially identical readings. Update - no arcs on wires or plugs. Tomorrow, I'll put my o scope on the O2 sensor.
October 23, 20169 yr Just out of curiosity, did you sharpen and regap the plugs before reinstalling them ?
October 23, 20169 yr Author 2 were gapped in spec, 2 were a bit out wide, so I fixed them. They are new from the reseal, not worn.
October 30, 20169 yr Author After a bit of delay, I had a chance to hook up my oscilloscope to the O2 sensor. These were taken after warmed up. 2 seconds per division Horiz, 0.5V per division Vert. Checked that the exhaust system is grounded well beforehand. The first one has the short flat line [far left] showing the zero V reference position.
October 30, 20169 yr The voltage varations look too small. It barely ever makes it to the rich side of 0.45 volts.(if I`m reading voltage correctly). You should see up to .8 -.9 volts on upward swings. Any lower and the catylast will not stay hot enough to be fully active. How does the waveform compare w/the one from your other emission passing car? How does the O2 sensor voltage/waveform react to propane enrichment? To a sudden vacuum leak? To blipping the throttle? Here are some typical waveforms http://www.autolabscopediagnostics.com/sensors2.html Might just be a bad sensor.
November 1, 20169 yr Author Above is a trace from my 87 Above is a trace from my 93 I also let air in via the feed to the HVAC controls storage tank. The effect was that the trace drops to the low level, following the curves similar to the drops in the normal traces above. After a bit, the trace would begin to move up again, looking like the ECU started compensating.Similar happened in reverse when I injected propane. For that, I added a T into where the feed hose picks off for the IAC valve. Capped when not using. Dialing the propane on / off would do what you would expect. Propane makes the trace go high, then after a bit, the ECU starts to compensate. Turning off, trace drops to the low level.I considered putting a new O2 sensor in the 93 - until I noticed that I will have to remove the heat shields to get a wrench on it. Also, adding that this O2 sensor [and exhaust] passed the test 2 years ago,and has not been on the car since. Although, the test 2 years ago didn't have the idle test.... But then there is the similarity of the 2 cars. Note - the 87 happened to level off by the time I took the picture. I revved it for a bit, and it began cycling again. The 87 is the "reference" car, it had its final test a few years ago.
November 10, 20169 yr Author Well, I finally ran out of ideas for other things to check, and had time, so I went to get it retested this morning. It passed! Even better, they confirmed that this was the last time! Thank you to everyone who shared ideas, etc.
November 11, 20169 yr Could we see the results? Its not important now but for fun, since this thread is a mile long anyways.
November 11, 20169 yr Chances are very high that the first test results were bogus. In general 4 cylinder engines rarely fail the test and these old sube's are almost always a sure pass.
November 13, 20169 yr Test from today - FAIL: Cruise Hydrocarbons = 102ppm Limit = 220ppm CO = .78% Limit = 1.2% RPM = 2441 Idle Hydrocarbons = 577ppm Limit = 220ppm CO = .54% Limit = 1.2% RPM = 923 Cruise HC 44ppm CO .03 RPM 2519 Idle HC 178ppm CO 0.0 RPM 744 Passed! Well something sure changed. Good chance that functionality of the CAT played a roll here since readings across the board are lower. I also need to note the idle was at spec in the final test, since that was the biggest red flag to me. Something went wrong there in the first test for sure. Nicely done DaveT
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now