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240, high idle at light, smoke test leaked smoke at EGR

E

emem1160

New member
Joined
Dec 15, 2016
Location
Chicagoland
I did a plus T on my 240 with donor parts from a 940. It has turbo injectors and also a turbo ECU from a donor car. It holds boost well and generally is reliable. the problem I have is "high RPM Idle when at light, after driving." When I start car, all is well at 800-900 RPM. However, when car is driven and gets all hot and sporty, and I approach a light, the RPMS are at their lowest at 1200 and I even had it at 2500rpm before at a light in neutral. They idles do not "settle down" as I wait and this happens <most times> I drive. If I turn off the car and re start, it goes back to 800-900 RPM.

I had my local shop do a smoke test and they said there was a vacuum leak right at the CBV that is part of the turbo, I believe TD4 turbo. Smoke comes right out the top of the CBV during smoke test.

more info/randomness: No check engine light. the IAC was not touched. The car did not idle high before the plus t. When I did the +T, I put a shiny donor intake manifold from parts car, and with it came an aftermarket "adjustable fuel pressure regulator" with a fuel pressure guage, runs at about 4 bar. Not sure if this helps or not.

1) any ideas why the Idle would be so high? (Since no major leaks, should I be looking at the IAC valve?)

2)Would/Could a leaky CBV diaphragm be the culprit? My car turbo flutters quite a bit when I let off boost. It has a cone filter.

3) since idle is fine at first and then high after I drive, does this rule out Throttle position sensor?
 
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ZVOLV said:
I can't make sense of what exhaust side leak means. Ask to see it for yourself and take pics.
Click to expand...

I updated the post. The smoke was coming right out the top of the CBV. I am assuming that generally, during a smoke test or normal operating conditions , the CBV should hold pressure.
 
I'm fairly certain its related to VSS (Vehicle Speed Signal).

Mine does the same thing occasionally, my connector at speedo is not 100%.
 
I'm assuming this is running 2.4?

Did you connect up the speed signal wire from the back of the dash to the ecu? if not, then the idle air control valve won't close properly at idle after a spirited drive. As you've found, momentarily switching the car off and on again will fix the problem and it'll idle fine.

Find the correct pin from the ecu using volvowiringdiagrams.com, then run a wire to a spade connector to the back of the dash... damn, I can't quite remember where to. I'll check back later and if no-one has posted where to connect that wire to i'll take a pic of the back of my dash to illustrate.

Cheers
 
bugjam1999 said:
I'm assuming this is running 2.4?

Did you connect up the speed signal wire from the back of the dash to the ecu? if not, then the idle air control valve won't close properly at idle after a spirited drive. As you've found, momentarily switching the car off and on again will fix the problem and it'll idle fine.

Find the correct pin from the ecu using volvowiringdiagrams.com, then run a wire to a spade connector to the back of the dash... damn, I can't quite remember where to. I'll check back later and if no-one has posted where to connect that wire to i'll take a pic of the back of my dash to illustrate.

Cheers
Click to expand...


I dont have any speedometer related problems. The speedometer is accurate. Does this still apply to my issue? I am the original poster. Yes, 2.4 I believe, it is an 89 240
 
Wren said:
Does your diaphragm have a hole in it like many of them do?
Click to expand...


Yes, the diaphragm has a hole in it (replacement ordered from IPD, they started carrying them again, looks like nylon, I have found a scandix replacement on ebay but dont trust the rubber)

I am unsure how a leaky diaphragm would cause a high idle at a stop light, as it is part of the turbo system
 
emem1160 said:
I dont have any speedometer related problems. The speedometer is accurate. Does this still apply to my issue? I am the original poster. Yes, 2.4 I believe, it is an 89 240
Click to expand...

I had the same issue- it's not a speedometer problem, it's a 'ecu doesn't know that you've slowed down to idle' problem. The way to think of it is that the speedo produces the signal but it doesn't know whether it's read or not... and doesn't care either way.

Ok, I didn't take a pic of my car and now it's late- have a look at this link:

http://cleanflametrap.com/tempFaker.html

In the 5th pic there are two spade connectors under a piece of rubber hose up and left of the white part that says 268 on it. Connect either one of those two spades to the correct pin on the ecu. Look further down the page are pics 16 and 17 which show the piece of rubber hose closer up.

The correct pin is pin 34 on the engine ecu.

Run that wire and see how you get on...

Cheers.
 
I wouldn't do that if I were you. The blue/black wire from pin 34 on the ECU goes to terminal 6 of the round connector on the instrument cluster. The 2 spade connectors under the rubber hose are for the cruise control if equipped.


Edit:

A closer look at the wiring diagram reveals that they go to the same place.
 
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Cheers for checking the wiring diagram.

If you have that wire in place already (to pin 6 as hiperfauto says) perhaps start by checking the wire is intact. If for some reason it's not there or the wire is broken somewhere, you could run a new one.

Cheers
 
Thank you for all the information gents.

Is this the spade connection we are talking about?

space.png


I have not taken a look at the engine ECU yet. Is that the one by the passenger side right foot/floor?
 
That is the spade connector (there are actually two
Side by side, they go to the same place) that you want to connect to.

This is what the ecu looks like:

http://m.ebay.com/itm/1993-Volvo-24...%3A08b178a315e0a866da6fa73dffea9ebd%7Ciid%3A3

You could start by seeing if there's continuity between the spade connector and pin 34 by taking the plug off the ecu, finding pin 34 on the plug and checking between the two.

Cheers
 
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bugjam1999 said:
That is the spade connector (there are actually two
Side by side, they go to the same place) that you want to connect to.

This is what the ecu looks like:

http://m.ebay.com/itm/1993-Volvo-24...%3A08b178a315e0a866da6fa73dffea9ebd%7Ciid%3A3

You could start by seeing if there's continuity between the spade connector and pin 34 by taking the plug off the ecu, finding pin 34 on the plug and checking between the two.

Cheers
Click to expand...

thank you for detailed info. If I am forced to manually run a wire from spade to the ECU...how would I go upon connecting it to the ECU pin 34? would I splice into the corresponding wire on the ECU harness that corresponds with pin 34?
 
Hmmm, if you check between the back of the panel and the plug and don't find continuity I'd take a length of wire and add a spade connector to one end, then plug that onto the back of the panel.

At the plug end, peel back the rubber bootie and undo the one screw on the plug- this will allow the top of the plug to be slid off. Don't worry, all the individual pin connectors inside are fixed in place it's not going to fall apart in front of you. The individual pin connectors are numbered, find 34 and trace it back to the other side of the rubber bootie- i.e. Where you can get to it after putting the plug back together. The easiest way to connect to that wire would be to use one of these:

https://www.edwardes.co.uk/en/produ...MIr4jtvP7x1QIV1TLTCh3NiwOGEAQYAyABEgJPePD_BwE


Obviously route the wire using at least 20 zipties, since this is turbobricks.

Hope that helps.

Cheers
 
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