Re: 1992 Volvo 740 turbo 4-cyl in line.... I know you are familiar with these 740 cars. I rechecked the codes being set, and the code for a bad speed sensor is being set. I found bad wiring at a speed sensor on an '89 740 sedan a few years ago, and this fixed something like the current problem...won't idle at all. But I can't remember where the speed sensor was mounted now. I am thinking it was an inductive type pickup, probably sensing the flywheel rotation?
Do you access this sensor possibly by removing the center console?
Engine speed is picked off the ignition system. Older cars use a hall sensor in the distributor, newer ones use a flywheel sensor. What do you mean by it won't idle at all? Does it die if you let off the gas? Does this have the LH-Jettronic fuel system with an air mass meter? If so try unplugging that and see if it runs better, if so that's your problem.
The engine speed sensor is found @ the rear of the engine just in front of the transmission that being said the engine speed sensor is just used for starting only nothing to do with the engine running. it sounds like you have another problem the Volvo code is 214 for the speed sensor if you could post back with all the codes then we can see if we can resolve your problem Glenn
Yea it is the LH Jettronic system. Yea, it dies as soon as you let off the gas. You have to really punch it hard, and then it is revving up to 3000+ to keep it from dying. All this trouble started after fixing a leak in the turbo...three bolts were left out. But the car was driven around town for a while after the repair, running better than ever with the exhaust leak gone...before it overheated and developed to idle problem. The fuel system code being set is 3-1-1, which is "speed sensor", not crankshaft sensor. Come to think of it I do think the sensor that I found with shorted out wiring on the sedan
740 I use to have was on the top of the bell housing. Perhaps once the distributor is removed at rear of valve cover, then it can be accessed? When I unplugged the AMM on the 740 sedan which had same control system, the engine could be started but wouldn't run, it would stall. And it is not setting a code for a bad air mass meter....but we saved the one from the defunct sedan, still have it, so we could try tht also.
The only code being set now is 311. This is when jumpered for fuel system. Shows only 111/no problem under ignition. Well, I have a print out from an article off the internet showing all the codes for 92 740, and it listed 311 as speed sensor.
Yea, now I remember... I got to the speed sensor by removing the distributor at the rear of the valve cover, and it was then accessible at top rear of engine. It was not the sensor itself that had gone bad, but the two wires right at the connector that were shorted together. Combination of a lot of heat and something acting as a solvent over many years had turned the plastic wire insulation into goo, allowing the conductors to come together. So it was a fix that cost nothing. The sedan could be started, but would not keep running....until I fixed the wiring to the sensor. So I am hoping that the same thing happened with the sensor on this 92 turbo wagon. This no-idle symptom occurred at the same time as the engine overheated. And the overheat has been something of a periodic ongoing problem, but an internittent one. It had been running fine without any overheating for quite a few days, with perfect idle, then the brother fixed the exhaust leak on the turbo...and then after driving around town a little right after the turbo fix, it overheated. I asked him if he could have disconnected a sensor perhaps while working on turbo, he said no. Now I find it setting this 311 code, when it was not setting it before the turbo fix/overheat incident. Thought at first the timing had jumped, but I have the timing at least close...and varying the cam sprocket just slightly either way is not fixing the no-idle problem at all. Am I on the right track possibly, or no? Are you sure it is 214 for the speed sensor? I wish I had the factory manual, but all I have is this info from a Volvo site on the internet.
The AMM changed from time to time, make sure the number matches before you try swapping them or you can burn out a good AMM and damage the ECU in the process.
How badly was it overheated? You might want to do a compression check, the cylinder head may have warped. Normally if the flywheel pickup sensor fails, the engine won't start at all.
Figure out why the timing marks are wrong before you proceed any further. It's amazing how critical that is, off by a single tooth is enough to make the engine run horrible and a few teeth will keep it from starting at all. You'll never figure out the other problems you have until that one is nailed down, wouldn't surprise me if that's your whole problem.
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