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Car Forum / Pontiac / Pontiac Fiero / September 2005car trouble any suggestions?
Heres the thing I have an 85 GT I’ve had a coplete tune up just done and my timing corrected. well every so often when I start my car it’ll start thenidle until it almost dies thenrevs up again (ocasionally it does die) it does the same thing when I put it in gear. Also it does run and gets me to where i need to go but when i first start the can and start driving when i step on the gas it sounds almost like its backfiring but when i drive it for a little bit it gets better, but then the next day its the same thing all over again. does anyone have an idea I would really appreciate it!! Fiero enthusiest b-dog > Heres the thing I have an 85 GT Ive had a coplete tune up just done > and my timing corrected. well every so often when I start my car itll [quoted text clipped - 8 lines] > Fiero enthusiest > b-dog Start off by checking for any stored trouble codes, go to http://www.fiero.nl and click on the image to enter, then click ECM Trouble Codes on the left, that gets you to the page that has all the info you need for that. JazzMan  Signature********************************************************** Please reply to jsavage"at"airmail.net. Curse those darned bulk e-mailers! ********************************************************** "Rats and roaches live by competition under the laws of supply and demand. It is the privilege of human beings to live under the laws of justice and mercy." - Wendell Berry ********************************************************** HC is rather high, CO is rather high, Nx is pretty high. Got a new converter 2 years ago and all were almost zero. Engine runs fine - no missing or stumble. 30 highway, 21 around town, like it has been for the last 15 years or so. Tiny oil plume on start. I'll check the plugs to see if anything is mis-firing or different from cylinder-to-cylinder. What else should be near the top of the inspect-it list? Dave S. > HC is rather high, CO is rather high, Nx is pretty high. > [quoted text clipped - 8 lines] > > Dave S. The converter has little to do with NOx reduction, that's a function of the EGR system. A quick check of that is a visual inspection of the flexible metal tube that runs from the EGR valve on the exhaust crossover pipe over to the bottom of the intake manifold. The tubes are notorious for cracking at the end under the intake. Next, with the engine just started cold and idling, use your fingers to push up on the underside of the EGR valve, you can reach inside the shell and feel a moving part, that's the diaphragm. When you push it up the engine idle should suddenly get very, very bad. Let go and the idle should smooth right out. If nothing happens then the EGR valve is clogged or the pintle is broken off the actuator rod. Next, let the engine warm up. Once it's warm, use your finger to touch the diaphragm again but this time you're not moving it, just feeling it. Rev the engine a few times strongly and you should feel the diaphragm move. If it does not then the solenoid is malfunctioning or there's a problem with vacuum somewhere in the system. JazzMan Signature********************************************************** Please reply to jsavage"at"airmail.net. Curse those darned bulk e-mailers! ********************************************************** "Rats and roaches live by competition under the laws of supply and demand. It is the privilege of human beings to live under the laws of justice and mercy." - Wendell Berry ********************************************************** > HC is rather high, CO is rather high, Nx is pretty high. High HC indicates a misfire. High CO indicates a rich mixture. Misfires cause excess oxygen in the exhaust stream which the oxygen sensor (which only measures oxygen, not fuel or AFR) sees and reports as a lean condition, causing the ecm to richen the mixture. Start by looking for possible misfire causes - plugs, wires, rotor. NOx high indicates advanced timing or hot engine, if everything else were good quick and dirty would be to retard the timing about 4 degrees just for inspection. SignatureRobert W. Hughes (Bob) BackYard Engineering 29:40.237N, 95:28.726W or perhaps 30:55.265N, 95:20.590W Houston, Texas "The city with too much Oxygen" rwhughe@oplink.net OK - I'm looking at more bits of information. The first is that with an ECM snooper I can see that the transitions from Rich to Lean and back are sluggish. The second is the ECM has learned to be slightly lean. The third is that I can see arcing from the EMI arrestors on the plug boots to the head - only on the rear bank. Fourth, all plugs look the same - light tan insulators, light deposits on the hook-shaped electrode. There is no persistant miss. Timing is within spec, but I think the dealership messed up the phase - Is cylinder 1 closest to waterpump, on the oil pressure port side (towards front of car?) ? You'd think the owners manual or factory manual would give a clue... Thanks. Dave S. > > HC is rather high, CO is rather high, Nx is pretty high. > [quoted text clipped - 14 lines] > Houston, Texas "The city with too much Oxygen" > rwhughe@oplink.net > OK - I'm looking at more bits of information. > [quoted text clipped - 14 lines] > waterpump, on the oil pressure port side (towards front of car?) ? You'd think the owners manual > or factory manual would give a clue... If the phase was wrong the engine wouldn't even run. Cylinder one on GM engines is normally the closest one to the water pump end of the engine, in the case of the 60° V6 in the Fiero this is the rear bank, rightmost cylinder. Cylinders are numbered 1-3-5 on the rear bank starting from the water pump, and 2-4-6 on the front bank starting from the pump. Firing order is 1-2-3-4-5-6 clockwise on the distributor. Normal cause of a sluggish crosscount (rich/lean transitions) is a faulty O2 sensor. Keep in mind that the Fiero ECM is old and slow, so normal crosscounts run around 2-3/second. I've been told that corona discharge is normal around the heat shields at the plug boots, though I've never seen it myself. I would think that actual arcing would indicate faulty plug wires. An intermittent misfire would increase exhaust oxygen and cause the ECM to add more fuel. JazzMan Signature********************************************************** Please reply to jsavage"at"airmail.net. Curse those darned bulk e-mailers! ********************************************************** "Rats and roaches live by competition under the laws of supply and demand. It is the privilege of human beings to live under the laws of justice and mercy." - Wendell Berry ********************************************************** > OK - I'm looking at more bits of information. > > The first is that with an ECM snooper I can see that the transitions > from Rich to Lean and back are sluggish. Bosch sensors tend to be sluggish and asymetrical in response. Try to find an NTK, they seem to work better. > The second is the ECM has learned to be slightly lean. > > The third is that I can see arcing from the EMI arrestors on the > plug boots to the head - only on the rear bank. If you see arcing you have serious misfire, whether you feel it or not. New wires seem like a good idea. A common problem with straight boot wires is cracks in the boot from pulling on them to remove them. This can happen the very first time you try to take them off and they will arc through the cracks. > Fourth, all plugs look the same - light tan insulators, > light deposits on the hook-shaped electrode. [quoted text clipped - 4 lines] > waterpump, on the oil pressure port side (towards front of car?) ? You'd think the owners manual > or factory manual would give a clue... On all American engines at least the #1 cylinder is the one farthest from the flywheel. On a V6 if you look at the block you will see one bank of cylinders is offset from the other one. The bank offset away from the flywheel has the #1 cylinder. GM numbers in crankpin order so 1,35 on one side and 2,4,6 on the other. Ford would number 1,2,3 on one side and 4,5,6 on the other but this isn't a Ford. Actually if you have the original wires, they should have the cylinder numbers on them. > Thanks. > > Dave S. SignatureRobert W. Hughes (Bob) BackYard Engineering 29:40.237N, 95:28.726W or perhaps 30:55.265N, 95:20.590W Houston, Texas "The city with too much Oxygen" rwhughe@oplink.net It's a miracle! Put on a new catalytic converter and CO2 production is cut by 75%! Less than 100 grams/mile. (read again if you are thinking carbon monoxide.) Based on a fuel mass flow calculation I'm now getting almost 80 m.p.g. The previous (fail) readings corresponded to low 20s m.p.g. Sort of like the car actually does. I put in a new O2 sensor (still failed) because the scan tool showed lethargic switching - new sensor, faster switching, looked like HC went up on the graph, but not a real change to any other characteristic. Still, now that it's passed, I'll check the cap and rotor. I'm reminded that one time it was running rough and the dealership found nothing. I figured, after I pulled it off, that the little fuzzy nubs inside the distributor cap should have been metal. Really amazing. Looked like cotton. Not amazing - Dealer service. Anyone have a list of typical responses to sensor drift? I figure that it's still misfiring and will next check (again) to see that spark is going all the right places. Dave S. > > HC is rather high, CO is rather high, Nx is pretty high. > [quoted text clipped - 14 lines] > Houston, Texas "The city with too much Oxygen" > rwhughe@oplink.net CO + CO2 should add up to about 14%. In Texas if it doesn't you fail inspection, indicates dilution of exhaust stream with air and a possible attempt to evade inspection. I switched out my O2 sensor bacause it had slow assymetrical switching. New one switches about 5 times as fast and is symmetrical, but no change in gas mileage. SignatureRobert W. Hughes (Bob) BackYard Engineering 29:40.237N, 95:28.726W or perhaps 30:55.265N, 95:20.590W Houston, Texas "The city with too much Oxygen" rwhughe@oplink.net Missouri's (IM240) clever tykes report grams/mile. I'm not sure what the percentage would come to for my case. What's interesting, if one fails IM240, they inspect for tampering, but if you pass they don't. So you could plug an N2 tank and a CO2 tank with a regulator under the hood (no emissions equip in there) and flood (replace?) the exhaust. As short as the test is it wouldn't take much. I'm sure the actual sensing is on a percentage basis and is extrapolated. The second year I owned the car the O2 sensor fell out. Not the housing the sensor is crimped into, just the sensor core. No light on the dash - just an extra rumble to the exhaust. I hope you're OK after the hurricane. By the way - I spent some time in the Dallas-Fort Worth area. What insane person laid out the highways near Irving? Take an off-ramp in most places and there's an obvious path to get back going the other direction. Not in Irving. Every ramp was a path to another highway. Weird. Thanks for the feedback. Dave. > CO + CO2 should add up to about 14%. In Texas if it doesn't you fail > inspection, indicates dilution of exhaust stream with air and a possible [quoted text clipped - 10 lines] > Houston, Texas "The city with too much Oxygen" > rwhughe@oplink.net |
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