740 Turbo issues

>
> How do I know if it is a wideband O2 sensor? Or how do I find one?
>
> Mine has an M46 w/electric OD.
>
> My symptoms came and went. Mine ran perfect in cool weather (it was
> during summer), but as soon as it got hot out, the problem came back. I do
> remember coorelating it to a particularly hot day.
>
> I didn't see any smoke in the mirror, but also did not have anyone
> behind me
> to check for smoke, so maybe it did puff, but I didn't see it.
>
> thanks, /glenn
>
>
>
>
>



If you're not sure, then you don't have a wideband O2 sensor. They were
not OEM equipment until the mid 2000's or so, and even today many cars
still use narrowband sensors. Aftermarket wideband systems are available
and useful for diagnostics & tuning, but rarely really needed.

I couldn't see any smoke in the mirror either, it was only when I had
someone behind me that I found out. At any rate I swapped the air mass
meter tonight and it seems to be running noticeably more smoothly and
with a bit more power. I noticed when I got back that the main fuel pump
(which I replaced a couple years ago) was noisy and I can't hear the
in-tank pump running so I ordered a replacement for that. Fingers
crossed that this fixes any remaining issues.

The idle air control does wear out but often needs a good clean out only.
"/g" <(E-Mail Removed)> wrote in message
news:hQU_n.616$(E-Mail Removed). ..
>
> "James Sweet" <(E-Mail Removed)> wrote in message
> news:i1ggvn$3am$(E-Mail Removed)...
>> Glenn K wrote:
>>> On 7/12/2010 3:49 AM, /g wrote:
>>>> "Jon Robertson"<(E-Mail Removed)> wrote in message
>>>> news:4c3ab408$0$3033$(E-Mail Removed) ...
>>>>> Accumulation of oil in the intercooler is normal so a hot day up hills
>>>>> a
>>>>> blow out is ok .I drain mine once a years and get a couple of
>>>>> teaspoons of
>>>>> oil out of it .
>>>>> "James Sweet"<(E-Mail Removed)> wrote in message
>>>>> news:i1de69$jso$(E-Mail Removed)...
>>>>>> Got a couple of issues that I've noticed recently on my '87 740
>>>>>> Turbo.
>>>>>> Not sure if they're related but both are intermittent. Firstly, it
>>>>>> has
>>>>>> started to idle occasionally at 1200-1400 RPM. I thought it was the
>>>>>> idle
>>>>>> air valve sticking but I've tried tapping on that and it doesn't seem
>>>>>> to
>>>>>> make any difference. Next step is to remove, clean, and bench test
>>>>>> that.
>>>>>>
>>>>>> The other issue is that once the engine is all nice and hot, it
>>>>>> starts to
>>>>>> stumble when the boost is up near the top. A friend who was following
>>>>>> me
>>>>>> commented that there was some smoke from the exhaust when this
>>>>>> occurred.
>>>>>> My first thought was a split in some of the plumbing to the
>>>>>> intercooler,
>>>>>> it behaves exactly like that except that it doesn't happen when the
>>>>>> engine is cold, in fact it may have been going on for some time but I
>>>>>> didn't notice it until I was going up a mountain pass on a hot day
>>>>>> with
>>>>>> the A/C on.
>>>>>>
>>>>>> Anyone run into either of these issues? Intermittent problems are
>>>>>> tough
>>>>>> because they never seem to happen when I'm in any position to
>>>>>> diagnose
>>>>>> them. Overall the car has been running really well and I got 25-28
>>>>>> mpg on
>>>>>> various legs of the recent trip.
>>>>>
>>>>>
>>>>
>>>> Hi James. I have an '86 740 turbo intercooler. When I first got
>>>> mine
>>>> on the
>>>> road a few years ago, it was during summer, and it ran great except at
>>>> higher rpms.
>>>> It would stumble and break up, kind of like a rev limiter when I wound
>>>> it
>>>> out. I
>>>> tried everything I could think of. Finally, I can't remember which,
>>>> but I
>>>> either ohmed
>>>> out the mass air sensor, or swapped in another that I had, and that
>>>> cured
>>>> it. It was
>>>> only doing it when the car was fully hot, or during hot weather. Has
>>>> been
>>>> fine since,
>>>> although at max rpm, it does break down like it has a rev limiter, but
>>>> I
>>>> figure that will
>>>> keep me from blowing it up.
>>>>
>>>> Your mileage! I can only get 22-23 max. I do have the mixture a
>>>> bit
>>>> rich, because
>>>> I'm afraid to lean it too much. How do you set your mixture? Do you
>>>> follow
>>>> the
>>>> procedure found in brickboard using the LED?
>>>>
>>>> good luck, /glenn
>>>>
>>>>
>>> Use a ohm meter between pins 2 & 6 on the maf sensor adjust the screw
>>> very carefully to 700 ohms
>>
>>
>> A better solution is to install a wideband O2 sensor to read the actual
>> mixture, but those can be a bit spendy.
>>
>> The automatic versions get 18-22 mpg but this has a manual gearbox and
>> consistently gets 22-26 on average, on one occasion I got 29.8 mpg with a
>> light foot on a long fairly flat highway trip.
>>
>> I'll try a different air mass meter and see if that makes a difference.
>> I'm suspecting something electrical since the problem comes and goes,
>> experience tells me that most other problems come and then just keep
>> getting worse.
>
> How do I know if it is a wideband O2 sensor? Or how do I find one?
>
> Mine has an M46 w/electric OD.
>
> My symptoms came and went. Mine ran perfect in cool weather (it was
> during summer), but as soon as it got hot out, the problem came back. I
> do
> remember coorelating it to a particularly hot day.
>
> I didn't see any smoke in the mirror, but also did not have anyone
> behind me
> to check for smoke, so maybe it did puff, but I didn't see it.
>
> thanks, /glenn
>
>
>
>
>

Jon Robertson wrote:
> The idle air control does wear out but often needs a good clean out only.



That's the next step, I've got a cleaned up spare that I'll pop in and
see if it fixes the fast idle. I swapped the air mass meter and it has
been running noticeably better, feels more powerful and smoother
although I haven't had the combination of a hot day and mountain pass to
really test it.

The pre-pump is shot as well, I can hear the main pump (which I replaced
last year) cavitating and no nose from the tank, replacement is on order
and will be installed shortly.

Changed some vacuum lines too that were getting ratty, they hadn't split
yet but can't hurt to have nice new ones in there.