RE: Changed Computer, now backfires

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RE: Changed Computer, now backfires - 8/3/2006 12:36:19 PM    BStumm Posts: 45 Joined: 7/16/2006 Status: offline So now that I know the difference between the air intake temp sensor and coolant temp sensor.... With the coolant sensor unplugged my backfire problem has gone away. Nothing that concerns me as I expected there may be weird behaviour with the coolant sensor unplugged but now the idle bounces a bit (most noticable in neutral or park) and shifting from rev to forward or forward to reverse often causes truck to die. Anyway, I found a chart that shows what sensors are used in the various modes of open and closed loop operation so I'll review that to see what sensors are suspect (in case its not the O2 sensor) before I buy parts. Here is link to the chart I found, not totally sure what year of dak's its for but I'm sure its similar at least. http://www.v8performance.com/tipsandtricks.htm#openclosed Also, if anyone has any ideas based on this new info I'm all ears. I'd rather troubleshoot a problem and buy the correct part first time than just throw money at it till I stumble on the solution... Call me cheap but yeah LOL. _____________________________ '92 Dak LE Club Cab 5.2L Auto 2wd (in reply to 39dakota4by4) Post #: 16

RE: Changed Computer, now backfires - 8/3/2006 12:57:12 PM    BStumm Posts: 45 Joined: 7/16/2006 Status: offline After reviewing the chart for open loop warmup vs closed loop cruise modes I think the only sensor difference is the O2 isn't in play in open loop. Would it be worth while to reconnect coolant sensor and unhook O2 as a last test or is it now safe to assume O2 is the culprit? _____________________________ '92 Dak LE Club Cab 5.2L Auto 2wd (in reply to BStumm) Post #: 17

RE: Changed Computer, now backfires - 8/3/2006 1:23:16 PM    fishlessman   Posts: 111 Joined: 8/1/2006 Status: offline could it be something simple like a summertime gas mix, i know my 89 wont run right on high octanes in the summer, it needs the cheaper gas in the summer (in reply to BStumm) Post #: 18

Oxygen Sensor? - 8/3/2006 1:35:00 PM    BStumm Posts: 45 Joined: 7/16/2006 Status: offline Ran fine last summer no matter what gas I used and temps got to similar ranges. Since the backfire started I have tried premium gas but normally run the cheap stuff. Wish it were that simple. I should mention I have a hole in my muffler (had it since last winter) that has gradually gotten bigger. I have worried that air is leakin back from there and messin up the readings but it seems unlikely since O2 is in front of catalitic converter and muffler is behind that and hole is on backside of muffler. Seems it would be more likely that the O2 would see weird readings at idle more likely than at cruise as pressure in the backward direction is less at idle. My best guess is that the intermittent computer (PCM) took the O2 sensor out along with it since the truck ran fine one day and next day (after replacing computer) it started backfiring at cruising speed (1600 - 2400 RPMs approx) Also, I've heard horror stories from some people about O2 sensors failing often after replacing the first one or having to get from dealer instead of aftermarket. Not sure if that applies to these trucks, anyone have any experience with aftermarket O2's on these gen1 daks? Anything to avoid or be aware of? _____________________________ '92 Dak LE Club Cab 5.2L Auto 2wd (in reply to fishlessman) Post #: 19

RE: Oxygen Sensor? - 8/4/2006 12:22:47 AM    Americanplayer99   Posts: 38 Joined: 7/26/2006 Status: offline if its running crappy at highway speeds maybe ur cat is clogged up,i kno that will cause it (in reply to BStumm) Post #: 20

RE: Oxygen Sensor? - 8/4/2006 12:31:43 PM    BStumm Posts: 45 Joined: 7/16/2006 Status: offline Considering unplugging the coolant temp sensor eliminates the backfire miss stumble condition at cruise speeds I doubt the cat is the problem. Nearly certain its the O2 sensor, plan to get a new one installed this weekend. _____________________________ '92 Dak LE Club Cab 5.2L Auto 2wd (in reply to Americanplayer99) Post #: 21

RE: Oxygen Sensor? - 10/23/2006 4:30:40 PM    BStumm Posts: 45 Joined: 7/16/2006 Status: offline OK so I let this repair slide for a while... Was still driving the truck some but not alot as I was using a diff vehicle for work. So I got a new O2 (bosch OE style from autozone) and installed it yesterday. Didn't drive the truck yesterday as I was possitive this would fix the problem. Decided to drive truck to work today and sure nough, damn thing is STILL backfiring. It was pretty cold this morning so took a while for warm enough to use the o2 and it was running fine then but once warm and o2 came into play bang bang bang... It does it at about 1600 to 2400 rpm's in any gear and at any speed at approx those RPM's while maintaining speed or at VERY SLIGHT accell or decell... A previous test of unplugging the coolant temp sensor (history above) resulted in the backfire problem going away so I KNOW it has something to do with open vs closed loop and highly probable is the o2 sensor. Guess now I suspect wiring of o2 circuit, how to test? Any other ideas that might cause this? One other thing, I have a pretty bad hole in my muffler. Could this mess up the o2 reading? Seems the o2 is a LONG way from the muffler. o2 is at the Y pipe ahead of the cat converter and muffler is way at back of truck bed. I've been holding off on getting a new muffler until the backfire is resolved as I dont wanna blow out a brand new muffler with this problem but maybe the muffler IS the problem??? Any other ideas? _____________________________ '92 Dak LE Club Cab 5.2L Auto 2wd (in reply to BStumm) Post #: 22

RE: Oxygen Sensor? - 10/23/2006 10:32:09 PM    BOOMER_87 Posts: 177 Joined: 10/8/2006 Status: offline had the very same thing happen to me check your positive battery cable for breaks etc and also the small wire from the starter it sounds like you have a short (in reply to BStumm) Post #: 23

RE: Oxygen Sensor? - 10/24/2006 1:23:36 PM    dodgedakotacrazy   Posts: 178 Joined: 10/9/2006 Status: offline check the timing..sounds like a timing problem the computer controls the timing. (in reply to BOOMER_87) Post #: 24

RE: Oxygen Sensor? - 12/6/2006 1:57:34 PM    ssrdo   Posts: 19 Joined: 12/5/2005 Status: offline Have you found out what your problem is yet? I have the same problem and cant find it (in reply to dodgedakotacrazy) Post #: 25

RE: Oxygen Sensor? - 12/6/2006 2:35:03 PM    BStumm Posts: 45 Joined: 7/16/2006 Status: offline Unfortunately no. I have not looked into the positive battery cable as suggested above and should do that. I'm also tempted to buy a new coolant temp sensor as with that unplugged the backfire goes away. I had done some simple testing of the temp sensor before but who knows... But that part is only like $12. I also need to investigate the wiring to the O2 sensor. As mentioned before, replacing the O2 sensor did not fix the problem. _____________________________ '92 Dak LE Club Cab 5.2L Auto 2wd (in reply to ssrdo) Post #: 26

RE: Oxygen Sensor? - 12/7/2006 4:37:58 PM    ScatDak Posts: 11 Joined: 11/30/2006 From: Merced California. Status: offline To me it sounds like maybe the fuel sync is off a little bit. That could explain the backfiring, You might want to take it to a dealership and have them set the fuel sync. Have them check the fuel sync and reset it as necessary. < Message edited by ScatDak -- 12/7/2006 4:38:59 PM > (in reply to ssrdo) Post #: 27

RE: Oxygen Sensor? - 12/8/2006 1:48:31 AM    rapaxis   Posts: 12 Joined: 11/25/2006 Status: offline Have you checked your MAP sensor yet. I had a truck once that did this and I eventually tracked it down to a MAP sensor going bad. _____________________________ Rapaxis (in reply to ssrdo) Post #: 28

RE: Oxygen Sensor? - 1/10/2007 2:05:37 AM    lesimon   Posts: 171 Joined: 7/29/2006 Status: offline O2 sensor or fuel pump my 92' Dakota 318 backfired with the same symptoms u r having sounds like a fuel problem to me not the computer (in reply to Americanplayer99) Post #: 29

RE: Oxygen Sensor? - 1/10/2007 2:56:31 AM    BOOMER_87 Posts: 177 Joined: 10/8/2006 Status: offline depends on if you have 2 o2 sensors < Message edited by BOOMER_87 -- 1/10/2007 3:02:37 AM > (in reply to Americanplayer99) Post #: 30

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