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Car Forum / Pontiac / Pontiac Fiero / February 2006limp home mode
86 2m4 woke up last monday and it started running very bad, acting like timing problem.running very rich! had a guy holding the plug wire with insulated wire pullers and he was getting shocked through the to body. They misted the plug side and said that it was sparking all over the place through the ignition wires. the wires test good. The thing reports on a Snapon tester as being in limp home mode. The ignition wires are a few months old, the plugs are new, distributor new, I am going after a new coil and noise resistor. HELP!!! maybe you should check codes and see why it is in limphome before spending a pot full of money.  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 The only codes I have so far pointed to coolant fan switch failing to respond to the request, which does explain the overheating I was getting. , so I got a new coolant fan switch, and at 20 yrs old i went ahead and got a new coolant sensor. It was in looking at the codes that we found out it was in limp home mode. It idles real rough and stalls a lot until we take off the map sensor then at least it will run but again very rich, we were not getting a fauliure notice on the map sensor. The distributor was not bad, but the thing runs better with the newer design so I am keeping it. >maybe you should check codes and see why it is in limphome before >spending a pot full of money. One item that won't show up on a scan is a faulty EGR valve and that can cause very poor running. If that turns out to be the case, don't even bother with a generic aftermarket unit, get a GM one. > 86 2m4 woke up last monday and it started running very bad, acting > like timing problem.running very rich! had a guy holding the plug wire [quoted text clipped - 7 lines] > > HELP!!! egr tested out good. the block mounted fan switch is bad and i got hte worng one, should have it this weekend. coil did not help at all. all the cabling was toned out and appears fine. next test will be when fan switch comes in and new ignition wires are put on. i think what i thoght was a noise filter is really a tach capacitor or something, at least that is what it looks like on the drawings. >One item that won't show up on a scan is a faulty EGR valve and that can > cause very poor running. If that turns out to be the case, don't even [quoted text clipped - 11 lines] >> >> HELP!!! Still nothing good ro report. all the sensors that had reported bad are replaced, Fan switch is in place, we removed the tach noise filter (fiugred out what it was called and that gm does not make one any more) The thing is still missing and cross firing on the other sensors. we can not get it out of limp home mode. do i need to have the computer reset to clear this state in this model? had a master mechanic come by with some of his hardware and he looked good and long at the computer and did not see any reason for it to be in limp home mode. all the sensor seem to registering good now. the only way to get even partial reliablitiy is to remove the connections to the map sensor. >egr tested out good. the block mounted fan switch is bad and i got hte >worng one, should have it this weekend. coil did not help at all. all [quoted text clipped - 18 lines] >>> >>> HELP!!! Assume you've checked the timing and closed off the egr tube into the manifold - If the failure you have is a sudden one, it is likely to have a single cause. If it is still arcing out of the plug wires it can only be due to resistance to arcing in the atmosphere the plug sees. I'd guess either timing or an air leak. If it was plug wires or plugs, the onset would be slower and vary depending on engine load. I doubt the computer has enough brains to stay in limp-mode. The tach capacitor is likely to be good and any feed-through is real electrical noise. I had a coil fail and the tach needle bounced everywhere. Thought it was the filter until I did the midnight engine run and saw the coil glowing blue. Dave S. > Still nothing good ro report. all the sensors that had reported bad > are replaced, Fan switch is in place, we removed the tach noise filter [quoted text clipped - 31 lines] > >>> > >>> HELP!!! Okay tonight tried again. Limp home mode is still on the computer. We tried to start it and it ran but is so rich it will not run unless it is at 2k or above, will not idle. we are showing no codes in the computer other than limp home mode. i thinking my thottle body at 140k miles may need a rebuild but do you really think this is the problem i check all the connections to other sensor and still nothing. is limp home mode making it run this way, and if so how we get it cleared? >86 2m4 woke up last monday and it started running very bad, acting >like timing problem.running very rich! had a guy holding the plug wire [quoted text clipped - 7 lines] > >HELP!!! Disconnect the battery for a few minutes - this will reset the computer. Then if it goes into limp mode again you still have a problem > Okay tonight tried again. Limp home mode is still on the computer. We > tried to start it and it ran but is so rich it will not run unless it [quoted text clipped - 15 lines] >> >>HELP!!! battery was unpluggd for hours., maybe even a day or more. any more ideas i really need a car, this is i my dialy driver for what 17 years, and I miss it!! >Disconnect the battery for a few minutes - this will reset the computer. > Then if it goes into limp mode again you still have a problem [quoted text clipped - 18 lines] >>> >>>HELP!!! Well it is running again. the elctrical problems came from a to loose fitting ratiator cap which i still have to get. i bought it at the dealer so no I need a better sorce. the rest was caused by the less than 1 yr old egr valve. i will also be getting a gm egr valve. thanks for all the tips. I for one would be interested to learn why a loose radiator cap would cause an electrical problem. Be aware that the Stant catalogs list the incorrect cap for a Fiero - you want a NON-VENTED cap > Well it is running again. the elctrical problems came from a to loose > fitting ratiator cap which i still have to get. i bought it at the > dealer so no I need a better sorce. the rest was caused by the less > than 1 yr old egr valve. i will also be getting a gm egr valve. > > thanks for all the tips. |
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