1989 740 Turbo Questions (Gages, Rough Idle, Clearing Codes)

johnboy740 · Post by **johnboy740** » 29 Dec 2007, 07:59

Hi everyone, new guy here with an 89 740 Turbo Wagon. I just bought it a week ago and am having some issues. I've been searching the forum and have seen some great advise, but still haven't found the answers to my questions. First, my speedometer, gas gage and temp gage don't work. I've checked the ground behind the kick panel on the drivers side, but that din't help. The gas gage twitches when the key is turned on, but doesn't move at all from there. The "anti-lock" light is on as well. I've read that the speedo and abs light could be related. What are the steps to follow to check this. Second, when the engine is cold, it's very hard to keep it running at idle. I start it, it runs for a second or two, and then dies. Once it's warm, it seems to run fine. Could this be an idle air valve? Would the seafoam treatment I just read about help that? Which brings me to the third issue. After I use the seafoam treatment, if I get a code, how do i clear the code?

Post by **sseir39** » 29 Dec 2007, 09:06

The idle problem could be a dirty throttle body. They get dirty and do require servicing. Could also be the idle speed motor, again they get messed up. I have cleaned ISM's with WD-40. Check the throttle body first. Also check the hose to the fuel pressure regulator as well as the tap into the manifold to see if it is clean.

The speed sensor etc: Look on the differential housing first. The wires can short out or break. Have had to repair a couple of mine in the past.

If you get codes, just DC the battery for 30 min. or so and they self clear.

Speedo: sometimes they go out and my need to get a good used unit. At least that is what happened to wifes 940 SE.

Gas gauge: check all wiring first. Worst case is could be the sender in the tank.

Old cars give problems. Go the Brickboard FAQ for an excellent reviewd of RWD Volvo problems and solutions.

Dick

johnboy740 · Post by **johnboy740** » 29 Dec 2007, 10:19

Thanks Dick

johnboy740 · Post by **johnboy740** » 13 Jan 2008, 08:17

Just a quick update. I pulled the cluster out this weekend and discovered a seven pin connector that wasn't seated correctly. I plugged it back in and all of my gages except the speedo started working. I then climbed under the car and found the speed sensor in the differential. The wires had broken off right at the connector. I pried open the connector and did a little surgery to the rubber boots to expose a lttle of the wire inside. I reattached the main wires to the connector and plugged it back in. The ABS light went off and the speedo works now too. So on to the idle issue. I pulled the IAC motor and cleaned it. It really wasn't that dirty. I cleaned the Mass Air Flow sensor while I was at it. I tried to clean the throttle body, but it's kinda hard when you can't look directly into it. It still idles rough, so next weekend I think I'll pull the entire TB as outlined in the brickboard FAQ section and make sure all the lines are clear and set screws adjusted correctly. Thanks for any info you gave me. John

Post by **sseir39** » 13 Jan 2008, 10:09

Happy to hear thiings are going well. You will never run out of little things needing your help, but you can do it.

Dick