Major hesitation

Arfsnarfy · Post by **Arfsnarfy** » 14 Oct 2005, 16:37

My 87 760 turbo has me stumped. The car will idle and perform perfect at low RPM, but as soon as I hit about 1/3 throttle, it just dies. I had my local mechanic look at it, they aren't that great, but I had no time myself, and the only thing he surmised was that the spark plugs were all sooted, an indication that I'm burning rich.

I'm going to rty and dig into this on the weekend and was hoping to get pointed in the right direction.

Thanks

Guest · Post by **Guest** » 15 Oct 2005, 10:10

Check the fuel pressure. If the pressure is too high the car will run very rich.

Guest · Post by **Guest** » 30 Oct 2005, 23:22

I have a '90 760 Turbo with 274k miles on her. About 100k miles ago, she did a similar stunt. After taking her to my trusty Volvo expert, I found that it was the air mass meter. That did the trick for me. Careful though, because even a refurbished one might run you about $275.00USD. Hope this helps.

Guest · Post by **Guest** » 31 Oct 2005, 20:51

if you do need a air mass sensor you can buy a used one at

www.car-part.com plug your make model year they call it an air flow sensor go to the bottom of the page. the page with the asterisk has the least expensive part. I bought two working 007 air mass sensors for my 240 for $20 each plus $15 shipping

Guest · Post by **Guest** » 01 Nov 2005, 17:30

I recently had the same problem and my fuel pressure regulator was at fault. Its only around 50 bucks (which is around the cost of a mechanic diagnosis), so its a good shot especially if your car gets better after it gets warmed up.

Richard L · Post by **Richard L** » 10 Nov 2005, 08:21

Did you check the fuel filters? They may be resricting an increased flow of fuel when you increase the enging speed. I am not familiar with your model and whether it has one or more filters, but this is a common problem worth eliminating.

Volvord · Post by **Volvord** » 11 Nov 2005, 12:06

Another common problem is the low pressure fuel pump in the gas tank, if it is not working the main high pressure fuel pump will not supply enough fuel for acceleration causing a bog or hesitation.

Guest · Post by **Guest** » 14 Nov 2005, 15:42

if the throttle postiion sensor has a bad spot it will die when you get to that point. You can check it with an analog(needle not digital) volmeter.. It should smoothly go up as you turn the throttle with no dips.

Volvord · Post by **Volvord** » 14 Nov 2005, 17:23

Anonymous wrote:if the throttle postiion sensor has a bad spot it will die when you get to that point. You can check it with an analog(needle not digital) volmeter.. It should smoothly go up as you turn the throttle with no dips.

The TPS on an 87-760T is a single pole switch, it may be worth checking it but it will only indicate open/closed

wojeepster · Post by **wojeepster** » 15 Nov 2005, 18:00

all the volvo throttle postion sensors have a single pole switch that is made when the throttle is closed to tell the ecu to use the idle air control to regulate the idle. They also have a potentiometer to let the ecu "know" what position the throttle is in. At least that is the way it works on my LH Jetronic 240 and 740.