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Old 08-17-2012, 02:19 PM   #1
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misses once warm

Alright so my 90 fox runs like poop on any day that it's over 80 outside . So far I've replaced the tps, maf (sn95) , whatever the sensor us that mounts on the back drivers side. I've also cleaned the egr and iac as well as the throttle body itself. The car runs great save for a little bit of an idle hang until it's warmed up then it misses a bit at any throttle input. Almost like it can't see the TPS input. When this happens and I go to wot the car will appear to lean out and during this time the cel will come on for a second or two then go out once I'm out of wot . At night when cooler the car runs perfect. It has recently thrown codes 33 41 and 91, but now the 41 I'd gone since I re grounded the o2 sensor wire on the sensor side. At the pcm side it is grounded fine. Any thoughts to why this could be? Also timing is at 13 degrees and I'm running 92 octane
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Old 08-17-2012, 02:37 PM   #2
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Check coil
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Old 08-17-2012, 02:51 PM   #3
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Also a thought may be is your exhaust may be touching some fuel lines or the exhaust is breathing on a aftermarket external fuel pump... I've had cars run like crap until the exhaust was re routed. But check your coil first as stated above..
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Old 08-17-2012, 08:13 PM   #4
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I had the same problem with my 94 GT. it turned out to be the coil. So along with the others, I think it is a coil.
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Old 08-18-2012, 12:45 AM   #5
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Re: misses once warm

Oh and to add to it when it rains the car does the same thing but a million times worse... Like it can't sense the tps... And it dies when I stop... Did it on the way home tonight... Only ran decent at wot
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Old 08-18-2012, 12:53 AM   #6
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Re: misses once warm

I'll go along with the coil or a small crack in the distributor cap.
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Old 08-18-2012, 01:23 AM   #7
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Re: misses once warm

Trojan even with the rain? And the cap rotor and wires are all brand new. But I'll snag a coil tomorrow and see what it does
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Old 08-18-2012, 01:42 AM   #8
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Re: misses once warm

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Trojan even with the rain? And the cap rotor and wires are all brand new. But I'll snag a coil tomorrow and see what it does
Yes, they can do that even in the rain. Once a coil starts downhill it steadily and sometimes quickly gets worse.


That it gets so much worse in the rain is what makes me think that maybe the cap may be cracked, new or not. Humidity/water entering the cap can make it crossfire all over the place. The cap should also have a vent in it to keep ionization at bay.
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Old 08-18-2012, 02:35 AM   #9
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Re: misses once warm

I'll double check the cap tomorrow as well and I'm not positive but I think it doesn't have the vent.
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Old 08-18-2012, 05:13 AM   #10
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Re: misses once warm

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I'll double check the cap tomorrow as well and I'm not positive but I think it doesn't have the vent.
You want the ones with the vent and brass contacts. Unvented and aluminum contacts just do not work as well.
Ionization occurs when the air inside the cap becomes electrically charged resulting in spark scatter or crossfire. It is more prevalent in smaller caps and in areas with higher humidity levels. A vented cap helps stir up the air to keep it from becoming charged.
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Old 08-18-2012, 08:24 AM   #11
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Re: misses once warm

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You want the ones with the vent and brass contacts. Unvented and aluminum contacts just do not work as well.
Ionization occurs when the air inside the cap becomes electrically charged resulting in spark scatter or crossfire. It is more prevalent in smaller caps and in areas with higher humidity levels. A vented cap helps stir up the air to keep it from becoming charged.
Ive acually seen a worn distributer do that too..It had alot of play in the shaft..at idle it would wobble and cause rough idle and erratic pickup signals ,,but once you rev it up it would straighten up..You could acually see it wobble with the cap off and spinning it over with the starter

---------- Post added at 07:24 AM ---------- Previous post was at 07:23 AM ----------

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Ive acually seen a worn distributer do that too..It had alot of play in the shaft..at idle it would wobble and cause rough idle and erratic pickup signals ,,but once you rev it up it would straighten up..You could acually see it wobble with the cap off and spinning it over with the starter
Wow probably havent seen a distributer in years..lol
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Old 08-18-2012, 12:21 PM   #12
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Re: misses once warm

Mine has some play too... But I replaced the coil cap and rotor dumped the codes and nothing changed... **** for fire and won't idle/run without me starting on the gas. I have a new hall effect sensor but haven't installed it. I can't run the koer test cause it won't run
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Old 08-18-2012, 01:45 PM   #13
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Re: misses once warm

So I changed the mad back to the stocker, and advanced the mess out of the timing...like 18 degrees or more... Did it by ear. Once I did that it idled fine but upon my test while it ran smooth but at wot it dumped some blue smoke and broke up a bit. Any ideas now?
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Old 08-18-2012, 02:54 PM   #14
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Becareful advancing the timing to far. I run 16* and may still have some left. But that's because I have aluminium heads. Most people can't run more than 14* and use 93 octane fuel.

Blue smoke usually means your burning oil. I would start by replacing the pcv valve and make sure it has the screen on it.
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Old 08-18-2012, 08:59 PM   #15
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Re: misses once warm

I changed the pcv already. Also I pulled the dizzy, cleaned everything and replaced the tfi. I also reset the timing 14btdc, and it's running better but still not perfect. Still throws the 66 (either maf) and 91... As well as a 212 on the koer code. I'm gonna replace the hall effect switch and see that that does for the 212.
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Old 08-20-2012, 01:15 PM   #16
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Re: misses once warm

Another update... Installed a new dizzy, and USC... And it helped but it still hiccups here and there and hunts around for idle. It's at least drivable now but the only things I haven't done is check replace the oxygen sensors and eliminate the egr. This weekend I'll be swapping on a 98 explorer intake manifold and throttle body and eliminating the egr. I'll keep checking for replies/ideas and see what happens after the manifold swap
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