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Old 06-02-2003, 04:40 PM
Tod Labrie
Posts: n/a
rough running 300TDT solved, but the answer is mysterious

My friend has a 1987 300TDT. For the past few weeks it has idled poorly, even after the engine was warm. It also billowed/belched smoke out the tailpipe as it surged (at idle only). Everyone thought it was either the air filter/fuel filters etc. The repair shop fixed in 2 hours. The problem was 5 out of the six glow plugs were shot, only one plug was working. MY QUESTION: how does 5 non-functioning glow plugs affect the idle of a diesel? I always thought they only contributed to a hard start/no-start when burned out (that was never the case with this car though). After a diesel is running, isn't the job of the glow plugs finished?

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Old 06-02-2003, 05:27 PM
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Join Date: Jul 2001
Location: SoCal
Posts: 1,303
How were the glow plugs 'shot'? were they electrically malfunctioning, or were they mechanically damaged?

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Old 06-02-2003, 08:14 PM
Posts: n/a
Question glow plugs

Where in Boston are you located and what is the name of said shop?

Not to be NEGATIVE, however, did your friend NOTICE if the car has NEW FILTERS in it now?

An UNETHECICAL type shop could do such a thing and then do the glow plugs for the added PROFIT.

I am a born skeptic (however that is spelled)

Rough idle could be anything from AIR in the fuel lines to poor fuel injection to erratic compression (not likely) as the car runs well now to dirty filters and poor fuel.

I am on the north shore and that is the reason for the question.

Thanx, and keep those diesels humming!~

Spo out
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Old 06-02-2003, 09:14 PM
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Join Date: Dec 2000
Location: Battle Ground, WA
Posts: 576
I'm with SPO123 on this one...

Hi there,
The short and sweet of it is that bad glow plugs don't affect the idle once the engine is firing on all cylinders. My brother has a Kubota 3 cyl tractor with one glow plug that's been absent low these many years, (broken off in head, hole plugged with weld for several years), and once it starts and fires on all three it's just fine. However, last year during mowing season the air filter plugged with chaff, and it started running terribly rich! Wouldn't idle worth a darn, either. If they fixed your engine in two hours it was something simple - possibly valve lash or dirty filter. Could have even been a partly plugged injector. I don't think it was the glow plugs, although they might have tested them and found them to be in need of replacement. The thing to do is ask for your old ones back, then you'll know.

Richard Wooldridge
'82 300D/4.3L V6
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Old 06-03-2003, 09:09 AM
Tod Labrie
Posts: n/a
rough running 3ooTDT (w/126K on it)

Thanks for all the responses. The shop is actually in Maryland. They simply said that five out of six glow plugs were not "working", that accounted for a rough idle. It had been idling poorly for about a month. The shop thinks that the lack of all six plugs working upon start-up subjected the engine to higher-than-normal compression and may have bent the rods (?). I was in mD last week and checked the air filter myself. I was expecting the filter and the box to be "jammed" with debris for it to be running that poorly. The air filter (surprisingly) was dirty but FAR FROM completely plugged. They said they also changed both fuel filters, the in-line fuel filter looked a little dirty. Hmmmm. As of today, the car runs much better at idle (never was a problem on the highway-still isn't) but it still puts out a lot of smoke at idle, more than it ever did. The engine only has 126K on it.
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Old 06-03-2003, 09:31 AM
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Join Date: Jan 2002
Location: Colorado Springs, CO
Posts: 1,006
The glow plugs turn OFF once the starter fires. IF was cold outside and it ran rough for a few seconds at idle after starting that's one thing but to run rough at idle continuous is NOT the glow plugs. Most shops remove the intake manifold to change the glow plugs on that engine. While it may be possible to do that & the filters in 2 hrs I'd think most shops would charge more. Might could be a mistunderstanding to whom he paid and who did the work as well, worth checking on.
Brian Toscano
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Old 06-03-2003, 10:22 AM
rdanz's Avatar
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Join Date: Sep 2002
Posts: 1,158
Sounds like a very possible rip off.

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