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Discussion Starter #41
Did some tests out of the FSM for the code 47 and it looks like the logic module may be the cause for that code. Can anyone tell me which of the field terminals on the Chrysler 90 A alternator is F1 and which is F2? They aren't labeled on mine and I can't find any pictures in the FSM to show which is which. Thanks.
 

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Discussion Starter #42
Finally made some progress. It was actually the power module that went bad and was causing the code 47. After replacing it, the charging system appears to be working properly. As a bonus, the hesitations while accelerating are gone AND the engine is noticeably more responsive all the time. Before, it would be intermittently responsive and most of the time, acted like a dog. It still misses while idling.

Had a mechanic check it out (before I replaced the power module) and he couldn't figure it out, but he did mention that while monitoring the signals with his diagnostic tool, the o2 sensor seems lazy (stays towards the rich side) and the map sensor voltage was a little off...I don't remember which way. I'm pretty confident the o2 and map sensors are ok. He said he tried a new o2 sensor as well, but the laziness didn't change. I'm wondering if there may be an internal problem with the logic module. Unless I've missed something, all the wiring and grounds are good. He also noted that the fuel pressure at idle was 15.5-16, as I had noted earlier on in my diagnostics. Everything I have read, including the FSM, states that it should be 14.5 psi. I'm wondering if that has something to do with it as well. Can anyone confirm the correct fuel pressure?

PS - F2 is the lower field terminal on the Chrysler 90A alternator
 

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Discussion Starter #43
Bump for my questions above

Also, what might cause the car to run better when taking a hard right turn, but hesitate and feel like it's starved for gas when taking a hard left turn? Does it almost everytime
 

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EFI fuel pressure spec is 13.5-15.5 psi, so 15.5 would be on the high end but still acceptable. With higher fuel pressure and a slightly richer mixture, the fuel injector may shorten its pulsewidth 'on' time to reduce fuel spray time and compensate the mixture leaner.
The O2 concerns me. It should not be 'lazy' when fully warmed in closed loop. The voltage should swing high-low fairly rapidly with a good O2 sensor. I don't know what O2 sensor was substituted or if his fuel pressure gauge was accurate. I would replace the O2 sensor with an OEM NGK/NTK sensor and recheck its operation. Avoid Bosch or Universal sensors IMO.
Starving for fuel on hard turns can be verified by watching a fuel pressure gauge on a test drive. You can attach it and pin it under a wiper blade while you drive. Does it depend upon fuel level?
It may be an internal fuel pump pick-up inlet issue. Sometimes the sock falls off. There should be a reservoir inside the tank that the pump inlet gets its fuel from to prevent starvation issues when the fuel sloshes.
 

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If you are checking the 02 sensor at the the sensor wires disconnected from the harness the Logic module and anything else is immaterial of it's operation. As IC stated, that sensor should be moving voltage around pretty raipdly and would concern me before doing anything else in diagnostics.
 

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Discussion Starter #46
Thanks for the help!

I bought my own fuel pressure gauge and mine read 18.5 psi at idle. I changed the regulator and now it's reading about 15. Seems to run a little better, but not as good as I'd expect. I drove around with the gauge on the windshield and the pressure stayed constant no matter how hard or softly I drove, as well as constant while turning/sloshing the fuel around in the tank. This problem didn't seem to be dependent on fuel level in the tank. However, with the fuel supply line clamped at the throttle body (after the gauge), the pressure drops to zero within 15 minutes. That sounds like a possible pump check valve problem or maybe a leaky fuel line, right?

I checked the o2 (disconnected from the harness) and it sits at 0.98V. Doesn't move much at all...maybe a few hundredths of a volt. The engine idles perfectly with it disconnected and when it's reconnected, it starts missing shortly after. I didn't check the waveform this time with the o2 connected to the logic module. Is that normal behavior for the computer to richen the mixture when the o2 is disconnected?

Had a vacuum gauge hooked up as well and it reads about 19-20. If I rev the engine and snap the throttle shut, the gauge settles at 15 and then slowly creeps back up to 19-20. I can't remember if that's normal or not.
 

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Discussion Starter #47
Had a Chrysler mechanic look at it for the idle issue and he couldn't find anything wrong with it. Said all the sensors were reading normally, egr working properly, no codes, etc. He also mentioned that the misfire/shuttering I'm hearing in park and neutral is normal and apparently what happens when the car goes "full lean". He said it's supposed to go away and run smooth when in drive. I'm not sure that I buy that. If this is how these cars ran when new, I honestly don't think many people would buy them. The funny thing is that when I'm driving the car, it drives smooth. Just idles badly.

One thing I noticed tonight was that if I pinch off the return line (while the engine is idling and misfiring) the idle smooths right out and the engine sounds great. However, once I let go of the return line, the engine starts sputtering and coughing for 5-10 seconds before returning to its regular idle with the misfire. Could this point to a fuel delivery issue? Maybe the pump isn't putting out enough fuel? Kind of running out of ideas here and unfortunately, haven't had much luck with the local mechanics.
 

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The Chrysler mechanic is incorrect. These cars should idle as smoothly in park as in drive, if not more so. If they ran "full lean" all the time that they were in park, they'd overheat and burn a hole in a piston.

When you pinch off the return line, what happens to the fuel pressure? And I don't want to go back over the entire thread, but is the gas filter new? If not, replace it. They are specified for 52,500 miles between changes.
 

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Discussion Starter #49
I figured that, but thought I'd mention his findings anyway in case I was wrong. Filter was the first thing I replaced and there was no change in the symptom. The pressure rises when the return line is pinched, but only if I really clamp down on it to completely block off the flow back to the tank. Regulator was recently replaced as well.
 

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I was reading diagnostics in my FSM last night. They say to measure the pressure both at the fuel rail (which you did) and between the fuel tank and filter. If more than 5 psi difference, replace the pump. There is a check valve that acts as a pressure regulator built into the pump (at least in my 92), and perhaps that has failed.
 

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Discussion Starter #52
Ok thanks, I will do that and see what the gauge reads. Speaking of the check valve, if it's supposed to hold the fuel pressure close to 14.5 psi for more than 30 minutes, then I don't think that's working. Pressure drops to zero after about 30 mins. Thought that maybe the lower injector oring was leaking, so I connected a 12V battery directly to the fuel pump and let it run for a while and watched the injector. I didn't see any signs of leakage at all. However, the pump sounded a little noisy (like worn brushes in a drill or perhaps like it was sucking in some air), but I didn't want to condemn it solely based on that.
 

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Check the number of wires going to your 02 sensor. If it only has 2 wires, then it relies on the exhaust gases to heat it up and the computer won't start using the info for several minutes. 3 and 4 wire 02 sensors have internal heaters and only require a couple of minutes to begin outputting a usable signal. The 02 sensor may be the issue here, at least for the 2nd phase of your missing problem (after several minutes).
 

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Discussion Starter #54
It's got a single wire o2 and it's been replaced 3 times with out any noticeable change. It's also started missing all the time now and yesterday it actually stalled out a few times.

I took the tank out today and found that the return line hose (from the sender to the fuel reservoir in the tank) can be swivelled around at the reservoir and if I blow air through the return line, I can feel air escaping at that connection. The hose clamps are tight. Is that connector on the outside of the reservoir supposed to swivel around like that or is it supposed to be fixed? It looks like the return hose gets clamped to some kind of connector that's pressed into the plastic body of the reservoir. Maybe there are some orings between this connector and the reservoir body that are leaking? Does the reservoir come with a new tank?
 

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Discussion Starter #55
Got one problem fixed.

The noise turned out to be coming from too much friction between the timing belt and the cam pulley. I was able to replicate it by pushing the belt in/out of the pulley grooves. The noise went away when I squirted the belt with water, but returned shortly after. The dealer thought the cause was a bad bearing in the tensioner (which was very believable as the noise did sound like a bad bearing), but it was really from the belt being too tight. Once I got that adjusted properly, the noise disappeared. That was a weird problem - especially because it would only become audible when the engine was hot.

Question about the idle issue and the AIS motor - when I turn the A/C on, does that cause the AIS to open (induce more air) to bump up the idle a bit? Or does the AIS close a bit to richen the idle mixture when the A/C is turned on? Does anything happen with the injector and the amount of fuel injected when the A/C is turned on?

Reason I ask is that with the A/C on, the idle smooths right out. But as soon as I shut the A/C off, the idle starts hunting for about 10 seconds (sometimes longer) before it eventually settles out to an occasional miss here and there. I know the AIS pintle passage is clean and I'm not sure why it takes that long to adjust itself. It seems like when the A/C is switched on, it's either getting the needed air or fuel it's lacking when at a regular curb idle...just not sure which.
 

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I believe that since it bumps the idle up, the AIS pintle moves in and reduces the amount of air, enriching the mixture and making it idle a little faster. So one might suspect that the pintle does not retract promptly when the A/C is shut off. But that assumes that everything else is in good working order.
 

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Discussion Starter #57
I rebuilt the head and upgraded to a roller cam and that fixed the idle problem. Now it runs smooth with no more misfire/hunting and the timing mark is now steady when I shine my light at it. The old slider cam had worn lobes/followers and some of the valves were leaking, probably from pitting. Thanks all.
 

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I rebuilt the head and upgraded to a roller cam and that fixed the idle problem. Now it runs smooth with no more misfire/hunting and the timing mark is now steady when I shine my light at it. The old slider cam had worn lobes/followers and some of the valves were leaking, probably from pitting. Thanks all.
Nice job sticking with it and thanks for your report. I hope your vehicle continues to run smooth in the years to come. :)
 

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I was going to suggest pulling the head and checking the valaves as I've had many "coke" up the back of intake valves to the point of the engine with a dead skip on some. Poor gas was to blame for some back then and the old cams when worn didn't help either.
 

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Discussion Starter #60
Thanks, I hope so too! I definitely learned a lot. And yes, there was quite a bit of build-up on some of the valves. By the way, I used a Felpro headgasket. Seems like it is pretty well made and is reinforced in the corners at the water jackets where the older style would tend to get crushed or eaten away. One thing I recommend if anyone ever has to pull the valve cover or the head is to use the one piece Felpro blue valve cover gasket that gets installed DRY. Unless the mating surface on the head isn't flat, forget the sealer and the two rubber pieces. It will save a TON of time removing/replacing sealer if you ever have to pull the valve cover in the future.
 
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