1972 145 D-jet very rough cold idle

Gary,

The catch with driving a 25 year old and older car is you need to find a mechanic that has been mechanicing longer than that!! ;o) It is better if you do your own maintenance,

OK. The best thing I can recommend is you buy a book or two about bosch fuel injection and basic automotive wiring. The D Jet really isn't that complicated, but the under the hood parts have been abused due to the environment they are in. (A fuel hose split on me recently) The CPU is essentially bullet proof.

You need to do several things, since somebody has obviously screwed up the system. The timing should bve set first, so you know that variable is not affected things. If you are thinking about passing up this step, then forget the rest. Don't be scared off by needing the special "tool" for the air intake. You can make your own from a peanut butter jar lid or anything else similar.

Check the wires/connectors going to the temperature sensor. (One disintigrated in my hand last year) Look at the wores carefully all the way to the fire wall.

Check the wires going to the cold start valve.

Check the resistance on the temperature sensor. Hot and cold. can't remember the spec off hand. You can probably get it from the brickboard or ask at the 1800 list.

The butterfly should be closed when the gas pedal is released. There could be an issue with the cable.

The throttle position sensor needs occasional cleaning. A pencil eraser does the trick. Just be cautious.

I hope the last mechanic did not jack up the fuel pressure. Checking the pressure at the fuel rail is a little more detatiled than most folks are prepared for, but is an outside chance.

good luck

chuck petterson

I found on my old D-Jet cars, many years ago the best thing to do is eliminate the idle circuit. Among other problems it gets rid of that lurch that occurs when the computer switches from the idle to the running circuitry. If you unplug the throttle switch, you can see what happens. This eliminates the acceleration enrichment as well though, so the "real" fix involves disconnecting one of the wires for the idle part of the switch.

P.S. I sold my last D-Jet Volvo in 1985!

Gary,

Don't be too overwhelmed by mysteries of D-Jet. Many problems are mechanical and/or loose wiring/poor grounding.

The hints you give relate to temp change. If you have not replaced the injector seals in last 3 years, it's time. Each injector has 3 seals, which may be hard, brittle, cracked. When cold, these don't seal. When warmed, these may expand and cause a little tighter (but not great) seal.

Another temp related part is the aux. air regulator. You may have mentioned this already among the $495 in parts. Don't overlook the hoses to this part. If old, dry, cracked, or if you don't know how old, it's time to replace these, as these also can behave differently with temp change.

The short sections of rubber fuel line hose along the fuel rail to each injector may be another source of problem. If old, dry, cracked, of if you don't know how old, you know the rest.

The hose between the intake and the air pressure sensor - is it old - you know the rest.

Check the joined ground wires between the injectors and the ground terminal on the intake manifold. Be sure this is a good, solid, clean connection.

Double check all the connections from the injectors wiring harness to the each injector.

After you've completed the above, it's time to check your ignition timing, and set it correct. Peanut butter jar lid has become the D-Jet Expert's correct tool of choice for controlling the idle RPM.

That's most of the very simple, very cheap, and correct sequence of troubleshooting that I can think of. I'm no expert, so I must concentrate on mastering the simple things. Usually, D-Jet is well maintained by just focusing on the simple things: seals, hoses, and ground connections.

Pat Q

I'll dig out the owners manual and see if I can track down that wire. I do have a replacement TPS--new old stock; still in the original box.

I'm not sure I'm worried about acceleration enrichment; it's already running too rich.

I probably should have sold this one last year instead of putting tires on it; since I didn't want to waste the $550 in new tires, I decided to go ahead and have the front end redone ($2100 at the shop plus about $600 in parts I provided), then the fuel system... I'd have been better off in may ways to just buy a newer Volvo.

However, nobody pulls out in front of me... :-)

Thanks,

Gary

The shop I took it to was owned by a guy who had worked on 140 series in the past, and still had the factory manuals for them.

Which books?

I'll see if I can get under the hood this weekend and take a look at it; wasn't aware of any special tool being needed.

Ok.

I'd have thought if that wasn't working, it'd run lean. Will look at it as well.

Probably in my Haynes book; I think I have a spare one.

There's slack in the cable. The idle stop is definantly cranked all the way down.

I have a NOS TPS, I may just go ahead and swap it. I think I have a link to a web site that includes TPS adjustment instructions.

I don't have a gauge suitable for that; the regulator was replaced, though.

Thanks

Gary