89 300TE Idle Problem

All- The dealer says I need a new engine, but I believe other wise. The wagon has a very VERy low idle speed, and continually stalls out. It is hard to start and keep running. It behaves better when it is hot
out and the engine is warm. I have replaced the fuel filter, and found a blockage in one of the fuel lines, and am now convinced that the fuel part is ok. I have replaced the air filter, and verified that it has a clean path to the manifold. I have replaced and re-gapped the sparks. I haven't looked at the distributor, as it looks like a bear to remove. A friend believes that there is an idle motor that may be bad, although I don't see anything that looks like it could be described as that.
Without a computer, is there anything else I should test before taking it to another dealer for evaluation? How does the 300 maintain it's idle, and what adjusts it?
Thanks for any suggestions.
Chris.
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How many miles has this motor done? Any reason for it to be doing this?
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The reason that you found fuel blockage... have you tried to blow your fuel lines clean to eliminate that possibility throughout your injection system?
Distributor cap... if it is real old.... like 10 years old, replace it. There is date stamp on it. There is only two screws to remove it... spring loaded... press down and turn 90 degree to release it... watch how it moves.
How about some fuel injection cleaner?
There is not adjustment in idle... it does it via an air valve... called idle control valve... if you pull the electrical plug off while running, idle will speed up sky high... meaning it works... here is a pic...
http://www.mr-auto-parts.com/epcksoap.epc?action=Search&cookieID=1PC0LWZRJ1RO1408K3&drillid=7&subcatid 1758@@Idle+Control+Valve&clientid=mr-auto-parts
If you need a new one... go to ebay and look for new one there for like $50... instead of $250.
Another possibility of the problem is the idle control unit... computer... which is fairly cheap rebuilt... $150... but your must be absolutely sure before you spend for any parts...
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Ok all -
That all sounds good. A couple of questions: 1) The destributor cap has 5 allen head nuts on it, and it looks like I may need to remove a pully to get at two of them. Is there an easier way, or just musle through? 2) I have run a "Gallon" of injector cleaner through, and some other junk I found, which I think was just another detergent. 3) The engine has 110k on it, and the compression is well within reason, and fairly balanced.
So here's the plan for the weekend: a) I'm going to check the distributor cap again and be brave about removing it. Although I don't think that's the bigger problem, it's definitely been 10-15k since it was last changed. b) The air flow idle control valve sounds like a good idea, and that might explain why it runs just fine outside of idle. c) It sounds like from the description that I should be able to fiddle with the idle motor, and determine if it is sticky or not prior to removing it. I have seen this in the engine, but the way it was described to me, I was looking for an actual electric motor that turned the belt.
It really runs fine once out of the idle zone, so I'm holding back on the temp and other sensors.
I'll post what I come up with.
Thanks
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Wonderdog wrote:

Don't fret over the distributor, so long as you just take off the cap. Also, the temp switches are probably fine. But that idle solenoid is 95% probable. I may have mistated its operation slightly--can't remember if the plunger maintains a position or rapidly fluctuates. Its a no-brainer to clean, just scary as hell to go tearing into your SEL. Some chance that the idle control box is bad, but the fact that it does better warm sounds like the gunk in there is a little less viscous when warm. If you open it up, you'll see exactly why its doing this.
Just take out that big Aluminum Air Cleaner, admire that gorgeous engine, find that Tee-shaped solenoid, unplug its connector, undo a simple clamp and pull it out. Nick the metal band with a hacksaw, remove band w/ pliers. Twist off top; clean. Tape it shut and replace. Its just like losing virginity: scary at first, but glad ya did it after ! --:)
I'm reading some posts around here, and these folks are smart. You are in good hands.
Regards Will
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M100 wrote:

PLEASE NOTE: The Idle air valve I have described is the VDO-brand. These are used with Bosch systems in Mercedes often. I have not disassembled BOSCH IAVs, but ALL IAVs are *very* similar in operation. I have disassembled several others. You should be able to figure-out disassembly from inspecting the part. Alternatively, remove the IAV and spray a cleaning solvent through it, without disassembly. Run 15-20 sprays through. If you can reach a moving part through one of its ports, manipulate it with a screwdriver to make sure it is free. I have also used cotton swabs to aid cleaning. Ether starting fluid is excellent, as is carburetor cleaner. Do not, however, use a solvent which will dissolve "solid plastics". btw: I referred to your car as an SEL. It is, of course, a TE, not an SEL.
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Howdy -
Turns out it is a Bosch model. There doesn't seem to be a way to dissasemble it. After spraying cleaner fluid through it, how freely should it spin? Also, when I removed it, the outside of it was coated in fresh-ish engine oil. Is this oil flowing through it? It is dry around the mounting bracket, and there is engine oil in the ICV. Any thoughts?
Chris.
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Wonderdog wrote:

The idle motor is usually a "Tee"-shaped aluminum cylinder, about the size of your hand. It will be near the cold-start valve.*** Remove the air filter entirely, for a better view. Remove the part. A metal sealing band must be severed (use a hacksaw and pliers). Note that this band is like 3-5mm wide, not the clamp which holds the part to the engine. Remove the piece formerly held by that band. Clean everything with a solvent such as ether starting fluid. Be very careful with ether! (flammability-work in a damp area to prevent static sparks, or use a ground-strap like for electronics) Never use it to start a non-diesel, unless you know what you're getting into. Inside this Idle air valve will be a piston which, when clean, will operate freely. The engine electronics provide a duty-cycle which fluctuates this piston rapidly. The time (ms) on/off ratio (duty cycle) is how the electronics modulate the idle air. These electronics, usually a single box devoted to idle-control, also fail, but can be re-furbished more easily than you think. Heavily wrap the metal band area with tape. The parts fit close, so no worry about it coming loose (the band is a trick to prevent you from servicing the part) Replace the idle air valve and test the car.
*** cold-start valve is usually blue, held by two screws, has a square electrical connector at an angle, and a small metal fuel *pipe*, just like the six coming from the fuel distributor to each injector.
The temperature switches which report status of warm-up, could be the trouble. Also, the warm-up/full-load compensator. Does the car have normal wide-open performance? Does wide-open differ cold/warm? But first, you should take the 90 minutes to clean that idle solenoid (it goes by many names) When clean and disassembled, the plunger or piston should give way freely. Have a helper turn on ignition (not all way to start) , and the plunger should retract easily. When key switched off, should spring back.

Inputs of temp switches, rpm, gear-selection and engine load feed a small box, usually on the center firewall, which, in turn, sends pulses to that solenoid valve which excludes, or admits, air. The wider the pulse-width or faster frequency, the more idle air bypasses the air-flow plate via that solenoid valve. The valve's normal operation is to fluctuate very rapidly between open/closed , and not usually remain in one place.

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