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  #1  
Old 09-09-2007, 09:49 PM
 
Join Date: Sep 2007
Posts: 12
Default 626 Idle and Hesitation on Acceleration

This is on a 2000 626 with 2.0 4cyl. Strange conditions - When at normal steady idle around 700rpm, I do something like activate two electric windows simultaneously and the idle suddenly drops to 500rpm for about 10 seconds and then recovers. I'm thinking that the alternator is kicking in and for some reason the engine is not handling the sudden demand for a few more horsepower to offset the alternator.....maybe??
Second issue....the engine hesitates briefly when if I try to do a hard acceleration from a standing start.
I've checked for simple things like vacuum leaks, loose hoses, intake path leaks, etc.
Not sure what to really look for....perhaps its a fuel flow problem.
Any one had this type of thing go on?
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  #2  
Old 09-10-2007, 09:00 AM
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Default RE: 626 Idle and Hesitation on Acceleration

Any electrical load is sensed by the PCM and the idle is bumped up to compensate for the extra load on the altenator. You probably just need a good tuneup/throttlebody and injector flush. Could be you are using crappy gas too. I have fixed hesitation problems by simply having them switch brands. IMHO Exxon makes the worst gas on the planet. BMW spent 1 million bucks a few years ago to figure out why some of their cars hesitated and came up with Exxon as the culprut. Nowadays there are many different fuel blends,gasahol etc that just do not combust well. 14.7 to 1 is the perfect ratio of air/fuel and thats the standard for all gasoline engines. If you use crappy gas it can't maintain that so you get driveability issues.
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  #3  
Old 09-11-2007, 09:19 AM
 
Join Date: Sep 2007
Posts: 12
Default RE: 626 Idle and Hesitation on Acceleration

Hadn't considered crappy gas - I try to use the same station (Marathon). Here in Chicago all our gas comes from a congregation of refineries in N/W Indiana, plus being an urban area we get all the EPA required gas tweaks including summer & winter blends. Not sure if anyone around here sells any gas that does not have a % of ethanol.
I saw on another tech site some discussion about the mass air sensor being involved some way (like if it is also dirty and needs to be cleaned) - remarks?
Under all other driving conditions the car is Mazda zoom-zoom....it's just these idle idiosyncracies.....would dirty injectors do this only at idle? Any value to using some cleaners that are added to the gas tank?

Oh yeah....tune up. Not sure what extent that means, but about 15K miles ago I changed plugs and wires, which corrected a slight mis-fire. What else is there to tinker with that constitutes a tune up?
Less likely related - 4 months ago had engine light come on and code traced to the transmission position indicator sensor (I did have some erratic shifting) - changed that and erased code, problem fixed. 2 months ago battery died suddenly and I replaced it.
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  #4  
Old 09-11-2007, 09:58 AM
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Default RE: 626 Idle and Hesitation on Acceleration

Yes i consider cleaning the MAF hotwire part of a tuneup. I would run Techron or Seafoam in the tank to clean the injectors and decarbon the valves. Pretty cheap. Like 7 bucks and you just add it to the gas tank and drive.
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  #5  
Old 09-14-2007, 04:51 PM
 
Join Date: Sep 2007
Posts: 12
Default RE: 626 Idle and Hesitation on Acceleration

Update on my problem....today I cleaned the MAF, which really did not appear dirty at all, but did anyway. I pulled the throttle body and noticed some traces of air infiltration at the gasket area, cleaned it, reset the gasket seal.
Still have the hesitation when doing a hard acceleration.
Some thoughts....I have noticed after starting the car a sweet, sickly odor from the exhaust, which is the aroma of ethanol in gas. I also noticed a strong gas smell from the intake manifold - which was obvious when I was messing with the throttle body.
I'm now suspicious that the problem is not airflow, but too much gas injection initially during acceleration or startup. The conditions are very reminiscent of a carbureted engine where the carb is running too rich or dribbling out raw fuel from the jets, which creates the hesititation because of on over-rich mixture.
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  #6  
Old 09-15-2007, 01:17 PM
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Default RE: 626 Idle and Hesitation on Acceleration

A sticking fuel pressure regulator could do that. Or a bad temp sensor telling the PCM the engine is cold and the PCM is keeping the regulator at high pressure. Remove the vacuum hose while its running and see if the idle changes during warmup and normal temp.If you smell gas in the engine compartment you may have a leaky injector. They leak through the connector so you either pull the connector to see or look at them cold. There are a lot of possibilities such as a poor connection somewhere. Check all connections like the main wire on the altenator. Autozone will check the output and codes free so maybe do that first. Might be a pending code at least. Bang on the bottom of your converter. if it rattles it has come apart usually.
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  #7  
Old 10-26-2007, 05:59 PM
 
Join Date: Sep 2007
Posts: 12
Default RE: 626 Idle and Hesitation on Acceleration

I'm back into this problem. I tried pulling the vacuum off and on from the fuel prressure regulator during warm-up - no changes observed....then after warmed up, tried the same - there was very momentary shift in rpm, maybe 50 up from idle, but it immediately recovered and resolved to normal.

I've tried varied acceleration techniques when test driving - if I floor it from a standing stop, there is no apparent hesitation. If I stop momentarily, but reaccelerate before the idle drops completely down, there is typically no hesitation. If I am completely stopped and go for a very slow and gradual acceleration, the engine then sputters and gags forseveral seconds before a normal acceleration occurs.

I see there is a sensor on the throttle body that has slotted holes (indicating it has some adjustments?) - what's that for?
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  #8  
Old 10-26-2007, 07:07 PM
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Default RE: 626 Idle and Hesitation on Acceleration

That would be the TPS. They very rarely go bad and unless it has been tampred with require no adjustment that i have ever witnessed though it is always possible. Have you taken it to Autozone to see if there are any pending codes? The hesitation sounds like an ignition problem. Maybe the coil pack. You should effect a repair soon even if it is just plugs/wires etc as a bad running engine damages converters and they are expensive.
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  #9  
Old 11-01-2007, 02:45 PM
 
Join Date: Nov 2007
Posts: 4
Default RE: 626 Idle and Hesitation on Acceleration

Well, I told myself I'd do something new on the 1st day of each month...so today I got into messing with the wife's 02 626 which is having a similar problem. Basically when warmed up at a standing idle...the idle will drop way down (kinda like the ac ingaged but it is off). It has stalled on her once or twice while doing this. The car does have the acceleraton issue as well.

So I'm all ears on this one...and will keep you posted if I have any luck.

Things I've tried so far.
-New plugs
-fuel filter
-airfilter
-pcv valve
basically ur usual tune up stuff.

Any thoughts on pulling the fuel rail and cleaning the injectors by hand with carb cleaner vs. using a gas addative? Looks like the rail is pretty easy to get off on this engine.
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  #10  
Old 11-13-2007, 08:40 AM
 
Join Date: Sep 2007
Posts: 12
Default RE: 626 Idle and Hesitation on Acceleration

I feel like a dope. I've worked on my cars since the late 60's, but have only had a few 4 cyl. cars (before this in 1977) - forgot how more obvious ignition issues are to the smooth running of them.
I had changed plugs not all that long ago, using factory spec. NGK's. Guess what, I decide to pull the plugs after looking at everything else and find them not only pretty eroded, but gaps like more than twice out of spec.....no wonder the idle and acceleration start was stumbling.....which brings me to a question on plugs --- seeing how the standard plugs deteriorate, I'm thinking I should consider something else, like Bosch +4 or split-fire or ???? that would give a fat, consistent spark. Suggestions?
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Old 11-13-2007, 08:40 AM
 
 
 
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acceleration, briefly, car, drops, during, gas, hesitates, hesitating, idle, mazda, mx3, running, rx7, smells, tribute, warmup


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