'96 850 GLT Surging

bensr20det · Post by **bensr20det** » 15 Aug 2012, 19:00

I have a 1996 850 GLT. The problem I am experiencing is random surging. The problem is not constant and may only happen once a week or so. When the surging begins it is normally right when I start the car, it will rev between 200 an 1500 RPM and begins to smoke. Once I begin to drive I feel slight hesitations. Once I stop again the high and low revving starts again. I have traced and replaced most vacuum lines. I can almost guarantee that once I get around a 1/4 tank of fuel this problem will start but it is even starting to happen with 3/4 tank and anywhere in between. And almost every time if I fill the fuel tank up the surging will stop. Or if I leave the car sitting over night it may temporarily remedy the issue as well. The problem has been going on for maybe 8 months and as far as I can remember it has only actually died on me once but it started right back up. Any help would be great and thank you in advance.

Also there is no check engine light on.

Post by **jblackburn** » 15 Aug 2012, 22:09

Unplug the mass airflow sensor and start the car and see if it still behaves that way.

One other test:

Unplug that hose and duct tape off both ends (the tape is important to avoid a vacuum leak). See how it behaves then.

That hose goes to the purge valve that vents the contents of the EVAP canister into the engine. Your purge valve may be stuck.

bensr20det · Post by **bensr20det** » 15 Aug 2012, 23:29

I have tried unplugging the mass airflow sensor while the problem was going on and there was no change except it turned on the check engine light. I have done the same thing with the idle air control valve also with no change. As far as the purge valve, when the problem first started I replaced the crank case vent box ( I believe that's what its called, located on the front of the engine under the intake manifold) when I replaced it I was looking around and found the purge valve. When I pulled it out and looked at it it was clogged so I bought a brand new one from the dealer for a pretty penny. Before that I did have an evap code but that has not returned since I replaced it.

bensr20det · Post by **bensr20det** » 16 Aug 2012, 11:49

A little more info, this morning when I got in my car there was a very strong smell of gasoline maybe that has something to do with the problem.

Post by **j_cd** » 16 Aug 2012, 14:14

Check the fuel system then. Fuel filter, pump, pressure regulator, pulse dampener, etc... seems like it could be any of those. It's probably more than just a clogged filter though. Bad injector?

Post by **j_cd** » 16 Aug 2012, 18:01

On second thought, I don't think a bad injector would cause surging. If you're smelling fuel, the obvious thing to do is check for a leak. The fuel rail itself can leak, usually at the end where the fuel line attaches. I don't think a leak there would cause surging either though. Sounds like the pump or regulator to me.

bensr20det · Post by **bensr20det** » 16 Aug 2012, 20:08

I decided to pull out the pump just to look at it and see if I noticed anything. It almost looked brand new, the hose looked great, all the connections looked great, all the rubber seals looked brand new, and the sock on the bottom was very clean. Obviously this is only a visual inspection but I dont really know how to test it. I was able to drive all over town today with no problems she ran like a champ, until I was leaving auto zone with the fuel line removal tool. The car had ran fine getting there and I only turned it off for 5 minutes max. When I started it back up it died immediately. I started it back, up and it was doing the very ruff idle and struggling to stay running. I drove only about 50 yards and stopped at a stop light. I turned it completely off for the entire duration of the red light. When the light turned green I started her back up and she ran great once again. I maybe drove another 15 miles with no problems at all. This is getting super frustrating and I have no idea how I will track this down.

Post by **j_cd** » 16 Aug 2012, 23:22

Could the ECU be freaking out and messing up the air/fuel ratio? Wish I knew more about the fuel system. You'll have to call in the big guns for this one. Where's jimmy57?

Post by **jblackburn** » 16 Aug 2012, 23:30

I wonder If the ECT sensor is acting up. Check the plug to the coolant temp sensor (under the thermostat housing) for corrosion and check for proper resistance levels.

Searching "ECT or coolant temp resistance" should turn you up the chart I and others have posted around the site several times. I'm on my phone or I would look it up for you.

Good luck! It sounds like SOME kind of sensor rather than the ecu.

Post by **j_cd** » 16 Aug 2012, 23:51

I was thinking a temp sensor too, but didn't think the ECT would cause this kind of problem. I could be wrong.

I wonder if the fuel pressure regulator could be physically disrupted by the steering rack if it got out of position?