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General Forums => The Mess Hall => Topic started by: TexWalther on July 16, 2012, 11:47:22 AM
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Hey guys, having a little issue out of the old jeep. For some reason it has recently started stalling out and/or backfiring during acceleration. At first it seemed this problem just happened when the vehicle first started. i would floor the gas and it would act right for the rest of the time it ran. This problem has since gotten progressively worse. I have taken apart and cleaned the throttle body, and IAC. The TPS and Crank sensor are relatively new, past 2 years.. Last thing i tried was disconnecting the O2 sensor before the cat to see if it would clear up the problem. As of now I am out of ideas, any help would be appreciated.
Thanks in advance
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Should also mention that it is throwing no codes...
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coil maybe?
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Replaced it about 2 months ago.. honestly think i may have to give in and take it to a mechanic this time..
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what about loose connection to the coil, or maybe ASD relay going in and out. other than that fuel pressure, anything else should throw a code i think.
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Mine was having the same symptoms, and it turned out to be a loose connection on the coil. The female connectors on the wire harness were not tight on the male plugs on the coil. I found the problem by shaking wires while the Jeep was idling. As far as the ASD relay, you can swap with your horn relay (assuming your horn works well). The fuel pressure is best checked with a gauge of course. Good luck!
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Does it do this when cold or warm. As in does it run good for a while then start or does it do this right off.
Why did you change out the coil the 1st time.
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It doesn't seem to change with temperature. I changed the coil last time because it was cracked and i was losing spark when it was moist out. since my post this morning i have checked the injectors, and checked my plugs for spark. the oddity of the day was when i would slowly disconnect my MAP sensor from my throttle body the idle would smooth out and the vehicle would be more responsive to steady throttle. However i changed that sensor and it is still acting the same way. It is almost like a timing issue on an older vehicle, am starting to suspect the PCM is going bad
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If all the ignition components are in good shape and as you say disconnecting the vacuum hose to the map sensor makes it a lot happier , I would check fuel pressure. Pretty good change the fuel pump is on the way out.
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Timing chain could be worn and loose and jumped a tooth. That would be about the last thing I'd look at though.
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replaced the fuel pump about 2 months ago. It's when i disconnect the MAP sensor itself that it acts better, not the hose...
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replaced the fuel pump about 2 months ago. It's when i disconnect the MAP sensor itself that it acts better, not the hose...
hmm,
1. did you try to measure the map output voltage at all?
2. did you test the tps voltage?
3. did you measure the fuel pressure?
4. did you check the ignition timing? is the distributor rotor positioned properly (did you take the distributor out and maybe missed the mark and it is off by a tooth? that might make sense if by disconnecting the map your ignition timing advance goes to zero although i never tried it to be sure it would explain why it starts to run better if you have the wrong position on the rotor).
check those and report back, a cheap timing light is about $15, you'll have to use it in the shade but it's good enough to get an idea what happens when you disconnect the map sensor - don't want to do it on mine so i don't store a code.
also check the rotor position when cyl 1 is in compression at TDC to make sure it's lined up with the plug wire (i think it's marked on the distributor body anyway). And the least likely make sure you got the right firing order (i'm sure you do but who knows)
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replaced the fuel pump about 2 months ago. It's when i disconnect the MAP sensor itself that it acts better, not the hose...
Either one makes it run rich
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Either one makes it run rich
he should at least check the fuel pressure when it does that so it can be ruled out or determine if that's the cause
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Guess I will pick up a timing light and voltmeter on my way to work today... Have a jeep I bought solely for parts that I am probably going to take the TPS off of see if that is the problem.. I haven't taken the distributor off since I replaced the coil so i hadn't really thought to mess with it. I didn't think I could adjust the timing from there though so it is definitely worth a look too.
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Guess I will pick up a timing light and voltmeter on my way to work today... Have a jeep I bought solely for parts that I am probably going to take the TPS off of see if that is the problem.. I haven't taken the distributor off since I replaced the coil so i hadn't really thought to mess with it. I didn't think I could adjust the timing from there though so it is definitely worth a look too.
you can't adjust timing from the distributor, but you can be a tooth off which would make the rotor and the cap prongs to be not aligned, if you didn't touch it i would not mess with it. The reason i mentioned the timing was to check what the hell is going on with the map sensor disconnected - but you could start with the voltages and the fuel pressure and go from there, if you need the voltage levels i can dig them out of the FSM.
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Guess I will pick up a timing light and voltmeter on my way to work today... Have a jeep I bought solely for parts that I am probably going to take the TPS off of see if that is the problem.. I haven't taken the distributor off since I replaced the coil so i hadn't really thought to mess with it. I didn't think I could adjust the timing from there though so it is definitely worth a look too.
The distributor is either in on 180* out. That's all you get. Everything else is PCM controlled through the CPS.
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The distributor is either in on 180* out. That's all you get. Everything else is PCM controlled through the CPS.
you can go 1 tooth or more off, the oil pump moves freely so you can rotate that whichever way you want (should lineup with the distributor gear but won't keep you from missing the mark). Anyway, since he didn't touch it it's not an issue.
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you can go 1 tooth or more off, the oil pump moves freely so you can rotate that whichever way you want (should lineup with the distributor gear but won't keep you from missing the mark). Anyway, since he didn't touch it it's not an issue.
The PCM is able to adjust for those minor differences though.
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The PCM is able to adjust for those minor differences though.
timing is the same, there's nothing to adjust by the PCM when you're out a tooth at the distributor gear since the spark is based on the crank sensor signal and not the cam signal in the distributor (this one is used for injector opening sequence). the problem is when the spark occurs the rotor is not in line with the prong inside the cap, so to try and explain a little better - think when the crank rotates and the spark fires for cyl 1 at (for the sake of argument) 20 deg before tdc and the rotor is in line with the prong for cyl 1 - now, if the dist gear is off 1 tooth the spark will still occur at the same rotational position of the crank (20 deg since it's all based on the crank sensor) but the metal at the end of the rotor will be away from the cyl 1 prong by some distance and not lined up, you lose spark there, might still run but the spark would be weak or missing.
that's what i was trying to say in my initial post abou this.
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i remember now seeing a post where it would start and stop immediately due to the cam and crank sensor being out a tooth and the PCM was throwing an error, so the whole thing premise i started with might not even work in real life scenario, anyway i'm going off-topic here.
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Due to lack of tools for checking fuel pressure, voltages, timing, or compression I gave in and took it to a shop.. turns out the fuel pump I installed a few months ago was garbage. Autozone replaced it and all I got stuck with was the labor so didnt end up being to bad.. Thanks for all the help and input though
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Autozone sells garbage, i would check rockauto or amazon for brand parts next time.
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Autozone sells garbage, i would check rockauto or amazon for brand parts next time.
Most auto parts chains get their parts from the same third-party mfg. that Mopar gets theirs from. Also, not having to ship parts back and forth compared to in-stock local parts store is a huge advantage.
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my thinking is you buy a Bendix rather than a store brand fuel pump for example, 20 or 30 bucks more but better quality, it less likely to have a DOA pump. With Amazon you get free shipping back and forth if the part is faulty or wrong to get a replacement.
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usually at the autoparts store there are 2 or 3 options. so you can buy the garbage that dies in a year or the quality stuff that will last. I've only been to an auto-zone a handful of times so can't speak for them but o'rielly is good if you can find an employee that knows what they are doing or when to get out of the way.
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my thinking is you buy a Bendix rather than a store brand fuel pump for example, 20 or 30 bucks more but better quality, it less likely to have a DOA pump. With Amazon you get free shipping back and forth if the part is faulty or wrong to get a replacement.
That's still a week wasted unless you but two and get credited back. I've bought a bunch of parts from Amazon and with Prime it's nice since I can get one-day shipping for a few bucks more. Because of their weird pricing, you can sometimes find really good deals as well. Like Chardrc said, you typically get a few options at the LPS. If the price difference is small, then it's a no brainer. I used to shop O'rielly's but I go to Napa now as there is one in town. They can get parts my 11am if they don't have it in stock and I call in early. Not to mention the old guy there recognizes me and the store has been in that location for what seems forever.
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i got platinum plugs for $2.50 at amazon that were quoted $8 at Napa (same brand), same for plug wires $25 at Amazon and $63 at Napa, I can go on. Where you actually get the same deal or better at Napa or other stores like that is on private labels or things that don't get sold as much, at least where i'm at not sure in California. There is the odd time when i need it "now" and go to the LPS, nothing you can do about that. Thing is that if you replace the pump or anything else that is not easily accessible it sucks to do the work (or pay for it) twice, if it's something easily accessible no brainer. I got stuck on the hwy once with an ignition coil that failed after 2 months, bought an MSD oem replacement next and it's been running fine ever since. My prime membership has paid itself over a few times if not more, can't beat 2 day free shipping