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  #1  
Old 02-17-2002, 12:11 PM
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Still rough idle

Hello all,

Well, I just ran a large bottle of Techron through the engine. I mixed it with about 10 gallons of fresh fuel. I wanted to run another can of Diesel Purge through her, but can not seem to find locally.

The car runs good from just above idle through 3400 RPM (about 80 MPH). At idle it has a stumble. It seems like one injector is having trouble doing its job. It also smokes too much at idle, with a strong diesel smell. If I press the accelerator against the kickdown switch while cruising at say 45 MPH, I get some smoke in the rear view mirror, but I don't think an excessive amount.

I was thinking about cracking one injector line at a time to see if the idle gets worse at each cylinder, until I get to a cylinder where the idle doesn't change.

Well, I better get out there and get the oil changed out of the old girl while I have some ambition.

Any comments or advice would be appreciated.
Thank you,
Doug

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1980 Mercedes 300 SD, 215,000miles
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1993 Chevy Suburban, 185,000 miles
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  #2  
Old 02-17-2002, 04:14 PM
engatwork's Avatar
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go on ahead

it won't hurt anything.
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  #3  
Old 02-17-2002, 08:38 PM
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I guess my theory is that she has one bad injector that does not atomize the fuel adequately. Idle speed is the only speed at which it is very noticeable. Does this theory sound plausible?

Thanks again for the replies,
Doug
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1980 Mercedes 300 SD, 215,000miles
2001 F-350 Powerstroke turbodiesel, Crewcab, 4x4, 81,000 miles
1993 Chevy Suburban, 185,000 miles
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  #4  
Old 02-18-2002, 05:21 AM
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It is fairly easy to change injectors, you will need a deep socket though.

Good idea about finding which injector is missing, the one you loosen the line on and the engine doesn't change is the bad one.

But it sounds like it could be low compression on that one cylinder, sorry to say. But hopefully, you can try switching your injector with a junk yard one...

You can buy a cheap comp tester (under $60) and use the glow plug hole for access.
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  #5  
Old 02-18-2002, 08:51 AM
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had the same problem/symptoms - for me was stuck valve. got them all adjusted and had huge improvement/less smoke.
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  #6  
Old 02-18-2002, 08:10 PM
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Thanks for the replies.

I have adjusted the valves twice in the last six months so I think I should be good in that department. It would porbably be cheaper to do a compression test as the next step in diagnosis of the symptoms. That is unless I can by an injector cheaper than a gauge. I guess I could move the injectors that I have from one cylinder to another and see if the miss follows the injector.

I realize the compression test would be a very accurate way of narrowing things down. My seat of the pants diagnosis would not indicate low compression because she does not burn hardly any oil between changes. In the last 1000 miles the engine has only lost 2/3 of a quart and I think most of that is from leaks (oil cooler line fitting I think).

I know this may sound like wishful thinking on my part. "Just change the bad injector and it will be all better", LOL.

Thanks again all,
Doug
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1993 Chevy Suburban, 185,000 miles
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  #7  
Old 02-19-2002, 11:31 AM
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Get compression check!!

Hi Doug
My 87 300D had similar symptoms to yours. I monkeyed for a while with injectors and this and that but finally had a comp check done. The results were bad!! No2 down to 180psi. At Christmas I pulled the head off and saw a worn, kind of pitted cylinder (No 2). There was evidence of a leaking head gasket and also some evidence of a leaking inlet valve on no. 2 cyl and I am sorry now I didnt get it seen to before bolting it all back down!! Time pressures. Anyway the engine still runs on 5 cyls on startup and then the sixth decides to knock in when she heats up. At least I know what it is!!
Go for the comp check if possible.
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  #8  
Old 03-04-2002, 06:17 PM
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Hey Doug:

Have you gotten to the bottom of your smoking issue at idle yet? The reason I ask is that I have the identical problem.....sigh.....

Just wondered

Don
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'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)

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  #9  
Old 03-04-2002, 10:56 PM
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Smooth cold idle, rough warm idle

Diesel Don,

I have noticed that the car idles very smooth while it is cool. After a drive that brings it to operating temperature, it starts doing the - mmmmm buh mmmmm buh mmmmm - thing.

This past Saturday I started it to back it out of the garage so I had some room to tinker with the truck. After getting over its normal ice cold bogginess (just a couple of moments), it settled into a real nice smooth idle. I decided to just leave it running to see what happened to the idle. I let it idle for, I would guess, about 20 minutes. It did not quite reach operating temperature I don't think.

Later that same day I did that same routine and it still idled nicely. This time I took it for a drive where the speed limit is 45 MPH. I can't remember how long I ran her, but she was as warm as she was going to get in the winter. When I got home, put the trans in park and, you guessed it, - mmmmm buh mmmmm buh mmmmm - all over again.

Any hoo, that is where I am at this point. I am open to any comments from the group. What do you think, maybe try to adjust the valves one more time (maybe would explain the cold versus warm idle differences)?

Doug
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1993 Chevy Suburban, 185,000 miles
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  #10  
Old 03-05-2002, 07:58 AM
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My hunch is that your car and mine are suffering from a very similar problem. Mine functions that way at idle as well but the more disturbing problem for me is the excessive (and I mean excessive) smoke at idle. When I come to a stop light, it acts like a totally different car. Cruising down the road, you'll only catch a faint wisp of smoke from time to time. Yet the minute you stop, watch out.

My hope was that you would swoop in for the rescue by fixing yours first and letting me benefit from your wisdom

My current plan is to pursue injectors first, valve stem seals second.

What is your fuel mileage? Are you burning excessive fuel?

Don
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DAILY DRIVERS:
'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)

SOLD:
'82 240D 229k (Matt's - Converted-300DT w/ 4 speed
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  #11  
Old 03-05-2002, 09:49 AM
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Do you guys still have the egr valve hooked up? Sometimes the diesel doesn't like the hot gasses going into the intake. It will make it smoke at slow engine speeds after engine warms up. From what you have discribed sounds like thats what is happening.
Bill
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  #12  
Old 03-05-2002, 07:58 PM
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Diesel Don,

We are getting in the low to mid twenties. Most of the miles are around town. I try to get her out on the open road at least once a week for a few miles if not an extended trip.

I tried to isolate the cylinder that is missing by cracking each injector line, one at a time. I could not notice any discernable difference between the cylinders. I do not know what that means. Would anybody like to comment on this?

I realize that a compression test would probably be the most cost effective next step for me. I don't have the equipment for this though, and would have to take to a shop. I HATE doing that for some reason.

Bill,

The EGR is plugged on my car.

Thanks for the interest,
Doug
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1980 Mercedes 300 SD, 215,000miles
2001 F-350 Powerstroke turbodiesel, Crewcab, 4x4, 81,000 miles
1993 Chevy Suburban, 185,000 miles
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  #13  
Old 03-05-2002, 09:22 PM
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Thanks for the update. I sense that our mileage supports the idea of injector problems as we drink too much fuel. Or perhaps its the injection pump. Thanks for the update and lets keep each other posted. My next step is injectors I think.

Don
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DAILY DRIVERS:
'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)

SOLD:
'82 240D 229k (Matt's - Converted-300DT w/ 4 speed
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  #14  
Old 03-06-2002, 08:51 PM
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Diesel Don,

Are you planning to change injectors soon? Let me know if it makes any difference.

Doug
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1980 Mercedes 300 SD, 215,000miles
2001 F-350 Powerstroke turbodiesel, Crewcab, 4x4, 81,000 miles
1993 Chevy Suburban, 185,000 miles
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  #15  
Old 03-06-2002, 09:19 PM
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Lightbulb Compression Test?

Checking out this thread I have no knowledge or opinion, but I just bought a compression tester that is cheap and nice if you decide to go that way. Here's the thread with the info although the auctions might no longer be current, you can just call these guys and buy what you need directly.

http://www.peachparts.com/shopforum/showthread.php?threadid=32136

Good luck!

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