Wierd problem all of a sudden - UPDATE 9/24 September 22, 2010, 09:59:55 PM So I had been driving my 85 XR-7 to work every day for about 3 months now while my 83 was down. I got the 83 going again, and put the 85 back in the garage. Well, I get the 85 back out today, and it has a strange accelleration issue. It only sat about 10 days, and ran fine when I put it away. For starters, it idles perfectly. When it's in park, and you raise the rpms, you can feel an intermittent misfire. This translates to a strange driving experience. It will run ok, unless it strains (like climbing a hill), or you press more than halfway on the gas.I ran the codes and got 21 25 41 77 (note- these are all the same codes it had when all was well).The engine is too hot for me to worm my hand into the schrader valve to connect my fuel pressure tester. I am betting low pressure. What do you guys think the problem will be? Quote Selected
Wierd problem all of a sudden - UPDATE 9/24 Reply #1 – September 22, 2010, 10:12:42 PM I wouldn't rule out gas starting to go bad either , My lawnmower sat for a week this summer and wouldn't start without fresh gas . Quote Selected
Wierd problem all of a sudden - UPDATE 9/24 Reply #2 – September 23, 2010, 08:34:37 AM Gas, fuel filter, fuel pump ?? Quote Selected
Wierd problem all of a sudden - UPDATE 9/24 Reply #3 – September 23, 2010, 09:24:46 AM I think you are on the right track thinking fuel system. I had similar symptoms with my 86 Tbird a couple of years ago. The pump was going bad and it finally required a tow home. Of course once there it started right up. Apparently it was getting hot. Quote Selected
Wierd problem all of a sudden - UPDATE 9/24 Reply #4 – September 23, 2010, 12:43:09 PM its possible if there was trash in your fuel it settled in the injectors and has them and/ or the filter clogged. might need to disconnect and clean sensor connectors. Quote Selected
Wierd problem all of a sudden - UPDATE 9/24 Reply #5 – September 23, 2010, 01:29:52 PM Test the fuel pressure first. If that's fine (but betting it's low) speculate on something else later. If fuel pressure is normal, new filter should be next. Hope this helps. Quote Selected
Wierd problem all of a sudden - UPDATE 9/24 Reply #6 – September 24, 2010, 04:01:02 AM Quote from: ThunderbirdSport302;336389Test the fuel pressure first. If that's fine (but betting it's low) speculate on something else later. If fuel pressure is normal, new filter should be next. Hope this helps.actually , test the fuel pressure while driving per the shop manual.watch the guage deflection (taped to your windshield) in between gears, anything lower than say 18-20psi would have me jumping on a new pump.Last pump I did was running 40 solid psi in the garage and little guage deflection when i manually added trottle.just as soon as you put a load on it though, the fuel delivery problem became very obvious.21 showed up because you took codes from a bone cold motor.25 showed up be not real sure why tests say its a knock sensor.41 showed up due to a lean condition77 showed up because you did not goose test, ignore.seems like the putter is telling your lean.could actually be fuel delivery related so test as i described Quote Selected
Wierd problem all of a sudden - UPDATE 9/24 Reply #7 – September 24, 2010, 11:01:12 AM Welp, I think the fuel pressure is good. It had about 37psi at idle. I put it in drive and held the brake and gas and spooled the turbo up, the pressure climbed to almost 50. I would like to have driven it with the gage attached, but my hose wouldn't reach far enough to close the hood...I raised the idle until I feel the sputter and I saw no fluctuation in the fuel pressure at all.Sooo, either it's an intermittent injector (the only thing in the fuel system in front of the gauge), or it's spark related...?Any further thoughts? PS- I drove it again yesterday, and it seems like it's getting better (maybe). It'd be nice if it was just a batch of bad gas... Quote Selected
Wierd problem all of a sudden - UPDATE 9/24 Reply #8 – September 24, 2010, 02:52:41 PM Bad wire ,plug, had much rain? Quote Selected
Wierd problem all of a sudden - UPDATE 9/24 Reply #9 – September 24, 2010, 05:59:48 PM Quote from: jcassity;33648725 showed up be not real sure why tests say its a knock sensor.The goose test is supposed to produce a knock for the knock sensor to detect. Quote Selected
Wierd problem all of a sudden - UPDATE 9/24 Reply #10 – September 25, 2010, 07:31:11 AM Check your plug wires if your fuel pressure is OK. That could very easily be the issue and is a very easy, cheap fix. On any car I've had, if I was having misfires they were 90% of the time caused by a bad wire. You know what's hell of easy? Changing your fuel filter. Do that while you're changing the wires. It'll cost you less than $100 to do both jobs and you should do both anyways if you haven't done so yet. Quote Selected
Wierd problem all of a sudden - UPDATE 9/24 Reply #11 – September 25, 2010, 09:45:45 AM spray water on the wires at idle at night to hunt down a plug wire jumping arch out of the boot or along the wire path.I hope its not your stator assembly in the distributor.Your looking for blueish white spark. anything less or near orange isnt a good sign. Quote Selected
Wierd problem all of a sudden - UPDATE 9/24 Reply #12 – September 25, 2010, 05:05:18 PM Quote from: jcassity;336625spray water on the wires at idle at night to hunt down a plug wire jumping arch out of the boot or along the wire path.I hope its not your stator assembly in the distributor.Your looking for blueish white spark. anything less or near orange isnt a good sign.Good advice. I am willing to bet it's a spark issue. If the wires are old, which they are on a lot of cars because people never change them for some odd reason, they will not have proper resistance, or no resistance, and your car will misfire.You might not see the plug wire jumping arc. It doesn't hurt to get some new plug wires that are returnable and try them out. Quote Selected
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