Misfire :: 2003 - Engine Stumbles After A/C Pump Is Engaged
Apr 5, 2015
I own a 2003 Ford Ranger 4x4 Automatic with the 4.0l V6. I bought the truck a little over two years ago with 150k miles. The Engine had alway had a slightly rough idle and I never really noticed until a friend pointed it out at around 170k. Every time the pump engages after a short warm up period there is a distinct stumble in the engine, although it never stalls or trips a check engine light. I have replaced the spark plugs with four prong pre gapped Bosch platinum plugs and new plug wires as well. I have installed an Optima red top battery that tests at 1100cca and have tested the voltage draw when the AC engages and it only drops .2 volts from 14.48v to 14.24v. I thoroughly cleaned the MAF sensor and before changing plugs I ran a can of non chlorinated brake cleaner through the throttle body to clean out carbon deposits and dirty throttle body. The engine still stumbles. Yesterday at 182k I disconnected the low pressure switch on the AC pump and boom, smooth low idle with no stumble. What could be wrong with the AC pump that could cause this stumble in the engine?
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My 02 F150 4.6 has 84K miles on it, and started stumbling/hesitating during accellartion about three weeks ago. Before this problem started (about 2,000 miles ago), I installed a new fuel filter and air filter. Since I noticed the problem, I installed new plugs. The problem didn't go away, so today I checked the fuel pressure. At idle the pressure is 32psi with the vacuum line left on the fuel pressure regulator (30-45 is normal as per Chilton's), and 42 with the vacuum line off (40-50 is normal as per Chilton's). I also had someone else rev the engine so I could observe, and found that the fuel pressure went as low as 28 when the engine speed was quickly increased. The standing fuel line pressure is 30 (30 is normal as per Chilton's) Does this sound like a fuel pump problem, or is there something else that I'm missing.
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I have a 2000 Explorer 4.0 SOHC that I'm having a persistent problem of cylinder 3 misfire. I've changed plugs with Motorcraft plugs set to the proper gap, put on new wires and have checked the resistance across the ignition module, both primary and secondary without change. I doubt that the problem could be the ignition control module as only cylinder 3 is affected. I have Auto Enginuity that I use to read the codes, attempt a repair and then clear the codes only to have P0303 appear again. Obviously the engine stumbles and has poor acceleration.
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Okay so I have a 2003 Nissan Maxima 150k and the problem that I'm experiencing is that when the vehicle is in drive my foot on the brake for example at a red light and I have the AC on the engine will begin to stumble similar to a misfire however no check engine light will be displayed if I were to turn the AC off and sit at a red light in here with my foot on the brake the car idles fine and smooth the car currentl drives fine accelerates fine idles fine it's only when I'm stopped with my foot on the brake and the car and in drive with the AC on that the engine stumbles accelerating or cruising any speed above idle with a/c the runs smooth its only at idle and the simple is not predictable it happens often but at random intervals
What I've done so far 1.5 years ago I put in iridium spark plugs Recently cleaned the throttle body its a electronic throttle body Fuel pump and filter were replace in March 2016I tested the alternator put a load on it to see if the engine would stumble but it didn't
My a/C blows cold air and everything in the car works.
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After almost an entire year of trouble-free running (with the exception of replacing a ground strap), my 2009 accent decided to start bucking and shuddering again. It only does this when warmed up, runs perfect cold. In the last 16 months, I've replaced the plugs, coils, battery, PCV valve, and ground strap. Car starts with zero hesitation.
Strong battery and starter, consistent output from alternator. After @5 miles, the car stumbles on acceleration, and idles sporadically. While looking at it tonight, I noticed a few exhaust brackets under the car had broken, and the flex section of the intermediate pipe had torn open. Could this presumed exhaust leak be causing the crap running performance?
My "exhausted" brain thought it could cause the O2 sensor to misinform the ECM, resulting in the P0300 code I pulled...
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We have a 1999 Audi A6 Avant (wagon) with about 190,000 miles. Best car we've ever owned, and want to keep her running until the wheels fall off (so to speak). We split our time between sea level and a ski town at 7000' (yes, that may be relevant).
Last spring our Trusty (sea-level) Mechanic repaired the exhaust system; both tailpipes were shot (car sounded like a tank). Rather than replace with Audi parts (was going to be a full exhaust system replacement - $000s) they spliced in some new tailpipe. Car ran quietly after that.
However, immediately thereafter (like, on my drive home from Trusty Mechanic's shop) and ever since the car will occasionally stumble (misfire) and throw a check-engine light. Typical scenario is after having been off the throttle while going downhill and then tipping into the throttle at the bottom of the hill, the car will stumble and on comes the CEL. Stumbling lasts 5-10 seconds then gradually subsides. Light stays on, though. Not 100% reproduceable under those circumstances (but doesn't really happen under other scenarios), but happens often enough to be disconcerting.
We recently decamped from sea level to spend the summer up in the mountains (great bicycling), and while the car misbehaved a couple of times on the way out of town, by the time we got to 5000 ft or so, the CEL was no longer illuminated. The car has not misfired once while at altitude despite plenty of situations that would presumably have triggered the issue, were we at sea level.
Trusty Mechanic has replaced some injectors, some coil packs, and the spark plug cables. No behavior change.
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2001-F150 5.4 Eng. bucking/stumble. I think my problem is slightly different than what I am reading about. Here is what I get (125k miles):
* Engine only bucks/stumbles intermittently and not at idle or at harder acceleration (this bucking is really harsh and makes the truck feel like a learner trying to drive a manual transmission and it is jumping down the street). The engine stumble is not a regular timing such as a cylinder going out and staying out for a period of time. It is quite a random pattern to the jumping
* Originally thought it was humidity related, but now I realize it happens in any climate
* No stumble in neutral at any rpm... only at a stop if I put it in a power brake load.
* When the stumble shows up, it seems like the throttle is around 10-25% (my best guess)
* Sometimes goes days without issue, but sometimes every ride and virtually every acceleration.
* Normally no stumbling at highway speeds, unless going up a hill.
* Every time it stumbles, it can be eliminated by either backing off on the accelerator some, or hitting the accelerator harder.
* No engine codes or CEL has ever come on
* Fuel mileage appears to be the same before and after the trouble started
Here is what I have done to try to correct it:
-> Fuel related (bad gas)... tried to run the tank as close to empty and fill it with fuel from different stations... when this didn't work, I have added HEET to it to dry up any water in tank.
-> Fuel delivery... replaced the fuel filter... seemed to work for one day, but then the gremlins came back.
-> Fuel delivery... ran multiple injector cleaners through tanks of gas.
-> Intake... replaced the filter.
-> Electrical... I don't believe this is related, but my battery died... parts store tested the system and stated the alternator was bad... replaced it, and took the old one to the parts store for bench testing and it was 100% OK... even thought the old showed OK, I left in the new one as a precaution. Only other item was a set of plug changes around 30k miles ago... I think I put in the super duper Bosch plugs with a lifetime warranty.
Current thinking and items I don't understand:
A) The bucking is so severe, it appears to be a random harsh loss of either fuel or ignition. A component that has failed electrically should give me a fault code with this level of severity. No trouble codes or indicators to electrically sense this disturbance...
B) For the fuel path, the most likely item is bad gas and I emptied my tank by running it as close to empty as possible and then used different gas and HEET to eliminate water. THIS MIGHT STILL BE THE CAUSE???
C) Another one for the fuel path is an intermittent fuel pump electrical connection or a weak pump from a pressure point. But if this is the cause, then why does it dissappear upon harder acceleration?
D) One last fuel thought is injectors... perhaps one or more have a range of delivery that they don't work properly... but this doesn't make much sense as at idle and harder accels are fine
E) From an ignition standpoint, perhaps I have failing COP's. I have not just gone out an replaced them due to my limited budget and the difficulty I read about changing them. Again, if one of these is failing in an either open or short condition, the computer should set a code for a misfire for the related cylinders. I get nothing. Hence my hesitation in making this change so far.
One thing i don't understand from the various posts is that the cops can fail under loading. what makes this happen as electrically, i don't think they can detect a load or not? it is hard for me to also understand why my truck would allow me to back off on the throttle or hit it harder and the issue disappears.
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'03 Excusion 6.0psd....new batteries a year ago, new starter a month ago, head gaskets etc a year ago....
Today I go out and start it up, no problem. Gather up the kids and head out to load up. When I climb in, I hit the unlock button to make sure the kid's doors are open and the engine stumbles.
I thought maybe I was imagining things so I hit it again and the same thing happened but it died but fired right back up. Drove the kids to school and it ran fine, no problems.
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I've got a misfire problem with my Focus. It started about a month ago and did not trip a code until last week. It stumbles on acceleration between 2,000 and 4,000 rpms. It is only a slight stumble and although noticeable, it does not impede driveability much. Last week I was able to get it to finally trip an OBD code. P302 - Cylinder 2 misfire. I changed the plugs and wires with no effect. I thought I had it narrowed down to the coil or injector until my wife noticed a new wrinkle.
Under normal driving conditions the misfire is annoying, but my wife found that if she turns on the A/C, it is undriveable and will not accelerate past 30 mph without some patience and a neck brace for the bucking. My first thought was the A/C compressor was freezing up. I turned off the A/C and left the blower on and it would not stop missing. I turn off the blower and it smooths right out to the annoyance I described first.
Right now I drive the car without A/C and blower whenever I accelerate. If I'm going a steady speed, all is well and I can run the blower and A/C.
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2002 F-150 4.2L. About a year ago, it threw the P0171 and 0174 codes up. After replacing all the simple stuff, I bit the bullet and replaced the lower intake gasket as well as the upper intake gaskets. Buttoned it all up, reset the codes and we were back in business. No issues, truck ran good. About 6-8 months later, the check engine light came back on, I check it and it was that pesky set of codes again, 0171 and 0174.
It still ran fine, but the codes were there, so I just drove it for a while (it's a company truck that doesn't get driven that much).
A couple of weeks ago while driving it, it acted very sluggish. You could mash the accelerator and it would just very slowly run up the speed. It never hesitated or missed, it just got very very sluggish. Checked the codes, no additional codes.
Then it began to stumble when you mashed the gas.
I put new plugs (old one's looked great, other than a huge gap), new wires, new coil pack and started it. Pushed the gas pedal, it just dies.
I look for obvious vacuum leaks and replace a couple of elbows for the PCV and it seems to run a little better. Enough so that I can drive it, but still not running right.
I ordered all the intake gaskets and new isolator bolts and spend Saturday pulling that apart. I didn't do the lower intake because the upper intake gaskets looked so good, I just don't believe this is a intake gasket problem. None the less, I installed the new gaskets on the plenum and upper intake, new isolator bolts, replaced a couple pieces of vacuum hose that looked cracked, started it back up, it ran as smooth as silk.
Convinced I had it fixed, I went for a test drive. Idling, it is as smooth as you could ask for. Pull up to a stop sign, wait, step on the gas and it chokes. Just stumbles and you can hear it almost backfiring and pushing air back through the system.
I've put new PCV, new EGR, new vacuum lines in several places, new upper intake gaskets, new plenum gaskets, new isolator bolts, and even new o-rings on the injectors, and I'm still getting the 0171 and 0174 codes.
With the diagnostics on, I can see voltage varying on all O2 sensors, so I assume they are working (none of them are reading 0 volts). It doesn't throw any other code up, other than the 0171 and 0174.
At this point I feel like I'm replaced every single thing ever mentioned in any 0171 and 0174 thread on the internet. Where to go next? 1 more point, if you very slowly push the gas, it runs fine, but any pressure on it, it bogs down and just stumbles.
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I have 57K miles on my 1.8t. It runs great except for the first start of the day. About half of the time, first thing in the morning it runs rough for the first 30 seconds. Like it is running on 2-3 cylinders. Then it sorts out and runs great the rest of the day. I took it to my dealer where they charged me $200 to replace the spark plugs. I would prefer to fix this myself if I can.
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I come over from the old school forum (48-60) with a question about a new to me 1999 F150 XLT 5.4L, 4x4, Auto. Truck has ran awesome for a couple of days. Truck has in excess of 410,000 miles but don't let that mislead. I believe the engine has been replaced sometime along the way. Yesterday I was driving and it just stumbled and stopped. After sitting for 5 minutes it started again, stumbled and stopped.
Today I checked the following:
- Fuel pump/relay - both work
- Dropped gas tank and replaced fuel pump strainer and fuel filter
- Fuel pressure at rail remains steady
- No codes present and no SES/CEL on.
Could this be a plugged EGR valve or IAC valve? I have had similar issues on Tauruses but it always threw a code when it did. Could this indicate a cat issue?
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95 explorer 4.0l ohv. I go to take off and then come to a stop after about 10-15 feet, i just give it a little gas then lightly press the brake, rpm's drop to around 400-500 then back to normal. I have replaced:
IAC
MAF
Plugs & wires
Coil pack
intake manifold gaskets
fuel system cleaner
fuel filter
air filter
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I am 2nd owner of 98 Ford Explorer Eddie Bauer V6SOHC. Vehicle is almost showroom condition w/ 70,000 miles and properly maintained.
Problem: engine seems to stumble quite frequently and is most noticeable when ambient temp is above 60*. Highway speeds , 40MPH doesn't matter. RPMS drop but it has completely shut down only twice in the last 9 months.
There are no codes. Plugs and wires changed several months ago, fuel pressure checked by Ford and it's ok, injectors cleaned at dealer, MAF seems ok so I am at a loss. Since there are no codes diagnostics don't work. Except for the issue above, this is a very nice reliable vehicle.
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I have a 1997 forkd F150 with a 4.6L Romeo engine. I have recently rebuilt the engine and now since it is put back together I am having a issues that i cannot pin point. When the truck is running and in gear my RPM drop to around 500 or below and my oil pressure drops and comes back up when the rpm's come back up this an intermittent problem and I have replaced the IAC valve and every once in a while i get a P0401 code for the exhaust recirculation. I think I am loosing some kind of vacuum. It was not doing this when I tore into the truck. It seems to be running okay not hesitation.
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recently I've been having this problem with my '90 C1500 305. The engine stumbles after holding down the throttle slightly for any time longer than 5s and then releasing, like if I apply the gas lightly to slowly roll up to a light. When i let off the pedal, it will stumble then recover after a second. Sometimes its so bad it almost stalls.
There is no stumbling after heavy throttle inputs. Not sure what causes this.
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This 97 F150 4.2 is new to me, originally a very base 2wd white fleet vehicle, with 189,000 miles, runs smoothly and quietly, idles well, transmission shifts smoothly. Gets reasonable gas mileage.
Problem statement: the truck has an intermittent starting problem. The failure to start happens about 5-10% of the time. The motor will turn over fine, but but immediately stumbles while trying to start. Turn key off and then re-start attempt will be again followed by a bucking stumble. Some times the motor might try and run for 2-3 seconds bucking and stumbling. It is possible the problem happens more often when the truck is warm and has been shut off for 15 minutes or so. Once the problem happens it is very repeatable. It won't start again unless I wait about 30 minutes to an hour. Once it starts it seems to run very nicely. I have noticed some times when I go to successfully start the truck it might run roughly for the first 3-4 seconds bucking and sputtering a bit and then smooth out and not have an issue until the next re-start attempt.
The truck runs so nicely when it is running I doubt it is an issue with the plugs, air filter general tune up. Could it be an intermittent fuel pump issue? The next time it occurs I will check fuel pressure. Could it be fuel pressure regulator? Also tested by fuel pressure. ECU? The truck runs very nicely most of time that seems like a long shot. Crank sensor? Bad fuel? I did add some dry gas.
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I have 97 150 it has a misfire on cylinder 4 and 6. I put new coil packs on and new plug wires. Spark plugs are only a year old. what else it could be?
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I've got 120,000 on my 08 manual Accent. Recently I've been getting white smoke after running it hard. It happens like this. I slow down from 70mph or so with the clutch engaged to about 40mph, then upon acceleration the engine stumbles and white smoke pours from the tailpipe. My guess is a leaky head gasket.
I had the dealer go through it. They pressure tested the cylinders and put a scope in them. They claim nothing is wrong with the engine.
I mentioned since they can vouch for the engine now, I'd like to get an estimate on trade in value. I don't think I want to keep it much longer.
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My engine started shuddering rather considerably a few days ago, seems to be misfiring. Happens both while idling and accelerating. Thought it could be a bad spark plug, and was prepared to replace them. Which is doable, but not easy, considering they're not very accessible with this particular engine. But when I lifted the plastic cover off the engine to take a look, I noticed this tube (circled in picture) had been worn away considerably in one spot. In fact, it's barely attached.
Now I'm no expert, but I've read that a leaking or disconnected vacuum hose can cause exactly the type of issue I'm experiencing. I'm wondering if the object pictured is in fact a vacuum tube. Might that be the issue? If so, how easy would it be to repair it myself? I'm not very experienced with making my own repairs, but I'm good with a set of tools, as long as I have instructions.
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2000 ML430 230,000 mi. The engine starts and all is fine until I hit a spot of rough pavement or a minor bump and the engine "stumbles," feels like it has cut out or starving for fuel. I have been unable to tell whether it is left front or rear right tire or corner of the car that hits the bump and starts the engine running on limp home.Once it happens and I stop at a light then hit the gas, I can count to 4 before the engine responds, making left turns dangerous. MB factory service since new. The dealer has replaced spark plug wires, spark plugs, crankcase sensor, gas pedal sensor and still the same problem. I think it is a loose wire or ground since it only happens after I go over a bump(even a seam on concrete any jiggle does it).
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