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Fuel pressure - Mid-Range Hesitation and Stumble 1 Saabers Like This Post! Posted by Saabina [Email] (#33) [Profile/Gallery] (more from Saabina) on Mon, 5 Nov 2018 08:29:58 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Our '93 Turbo Hatchback (210k miles) has had a slowly worsening and irritating mid-range hesitation and stumble around 2800rpm under load (such as long uphill grades.) In normal relaxed driving, the car was running well. Over the last year, I replaced and repeatedly checked every component in the ignition and fuel system with new or known good components to address the stumble with sometimes moderate improvements but never a 100% cure. I added a fuel pressure gauge to the fuel rail several months ago which indicated around 30psi from a several year old Walbro in-tank replacement at idle. I mistakenly assumed the fuel pump was OK but further efforts absolutely eliminated everything else. The last straw was to swap out the fuel pump assembly from a '90 SPG. The result was dramatic. Smoothly pulling hard throughout the range and boosting into the red. Careful monitoring of the gauge showed the fuel pressure responding to throttle to around 42psi. A new fuel pump has completely revitalized the car and it has never run so well.
Lesson learned: Before spending many hours and dollars replacing parts and attempting to sort out even a small irregular running problem, make sure you have a proper fuel supply.
The good news is since everything even remotely connected to the fuel and ignition systems is either new or absolutely up to spec, the car is now a rocketship...
posted by 99.75.88...
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