Mad Maddox

Idle issues, and other issue

13 posts in this topic

Hi, I recently bought a 1999 626 with the 2 LTR 4 cylinder automatic and I'm. Trying to figure out two issues that may be connected. The first is when the engine has warmed up and I am stopped at say a stop light my rpms dip like it is going to stall, and the longer I am stopped the worse it gets. It will even do this when in park but takes longer to manifest. I have been told this may be a fouled or faulty maf sensor, but I don't want to replace it and find out the issue is still there( I am on a tight budget). The other issue is with a rough shift from first to second. The odd thing is it only happens when the engine is warmed up. When the engine is cold or at least not up to temp it shifts smooth as silk even when I put the gas peddle to the floor. The computer is also throwing a bank 1 O2 sensor error. I am mechanically inclined but I have little experience with engines in general. Any help with this would be greatly appreciated. Thanks

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Maybe look into the Idle air control sensor for the idle dipping when stopped.  I had same problem and thats what it was.

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FWIW, you might want to invest in an inexpensive multimeter, like 10 or 15 bucks at WalMart. Get the kind with the needle-type probes on the end. There's lots of resources on how to quickly and easily check things like MAF sensor, TPS sensor, etc., before you buy replacements. Trust me, it'll save you gobs of cash in the long run.

Your condition definitely sounds like a closed-loop related issue. That's the mode it runs in after warming up - the engine control computer starts listening to more sensors and stuff so it can run leaner fuel/air on a fully warmed up engine.

One such sensor that comes into play, big-time, after warm-up is the oxygen sensor. If you haven't replaced them, or suspect they haven't been replaced in the past 60,000 miles or so, I would definitely suspect they are old and worn out.

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To me it sounds like a stuck IAC solenoid. What I think is happening is whilst the engine is cold and before reaching operating temperature the cold start air bypass is open, once engine is warm it should shut due to the hot water passing through the IAC on top of the throttle body. Once the cold start air bypass shuts the car relies on the IAC solenoid to bypass the throttle plate to maintain idle.

Simple test. Remove the air intake boot at the throttle body after reaching operating temperature. Start the engine (may take a couple of goes) put a finger over the small orifices (air bypass ducts) that are just before the throttle plate (sitting at about 1 and 11 o'clock. I think the one at 1 o'clock is the cold start bypass the other is for the IAC solenoid. If there is no suction (air flow) at either your IAC is stuck shut. There should only be air flow at the cold start air bypass when the engine is cold (it should shut when hot). Test resistance at IAC plug, if in spec will need to remove and give a clean.

Usual symptoms of bad MAF are difficult starting, rough idle, poor acceleration and no power when going up hill.

 

Let me know if this helps.

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Thanks for all the help folks, there were a lot of great ideas that I explored. I ended up cleaning the entire air intake system, and doing a tune up as well. Found some gunk in the throttle body, as well as a bad air filter. Just to be on the safe side I replaced the $.99 bin spark plugs,with some mid grade ones and changed out the old wires with a lifetime warranty set. Thank goodness for Rock Auto. Hole parts list cost less than $50 with shipping. Purring like a kitten at stop lights now. Thanks again!!!

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I'm experiencing same troubles, what are some tools/resources you suggest to have to clean air intake system. I have info from forum that listed what I should start with on the tune-up, so I'll do that as well! Thanks!

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I would suggest a small wire brush, brass preferably. Some air intake cleaner. And you will need a star security head driver to get the mass air flow sensor out of the housing. In mine there was a dot of plastic in one of the screw heads, digging out the plastic was the hardest part. I found that if you hear up your driver head with a torch after digging out as much plastic as you can worked for me. I got my driver set at harbor freight for $6. Also there are a lot of great videos on how to clean your entire air intake system on YouTube. They will give you a better idea of what to expect. Also don't forget the basics: air filter, spark plugs and wires, and fuel filter. Good luck

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Star security head driver? I'm a beginner DIY'er so I don't understand all tools/resources by alternate names, is there a technical name for this?

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Sorry, a star bit has a head shaped like an asterisk. The security version has a hole in the middle. Of you look at the top of your mass air sensor ( should be right behind the air filter housing) you will see a black plastic housing with 2 screws in it. That is your mass air flow sensor. You will also see an electrical connector plugged into the side. If you go to almost any auto parts store and describe what you need they will be able to find it for you. Let me know if you have any more questions. Also a good resource for diagrams. Open your browser and type your make model and year, then air intake diagram. Google has a tab for pictures of what you are looking for. Click on that and you will see several exploded diagrams of the are intake.

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I went on rock auto and found the NGK 7090 spark plugs but I was unsure if the wiring sets on their were a proper fit to the plugs as to the vehicle. I see you didn't have any issues with the wiring set you purchased, do you by any chance still have the part number to that wiring set. I would like to change both plugs & wiring set because I'm unsure whether or not the previous owner did appropriate maintenance like he said. He couldn't seem to find any service reports or receipts.

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I'm sorry I don't. But the best thing about rock auto is that as long as you have the correct make model year and size of your engine ( 4 or 6 cylinder) the site will only show you parts for your car. The only time I have had an issue is with the O2 sensor, due to the fact that there are sensors for California emissions as well as federal standards. I prefer to pick the part that is in the middle of the price range. Also resently they started marking parts that ship from the same place with a van icon, after you put the first part in your shopping basket to save on shipping. Last pay attention to heart icons. Those items are the most popular. I.E. best part for best price. Hope this helps

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