'98 V70 GLT Intermittent Surging/"Coughing"

Post by **bmdubya1198** » 09 Jan 2017, 13:46

I've had an issue for a while now where when I come to a stop (usually at an intersection) sometimes, after sitting a second the car has a little surge in the RPM for just a second or two, then goes back to normal. A while back I had attributed it to needing an ignition refresh, but I replaced the cap, rotor, wires, and plugs a while back now, and it's still happening. It never happens when the car is idling in park, though. It's only in drive and after I have come to a stop at an intersection and I'm on the brakes. I thought for a minute it could be my vacuum line to the brake booster, but I don't think there's a leak there. Funny enough, since I put in my boost controller and bypassed the TCV, that hasn't happened, but a new problem has come up now...
The past few days I've had a couple little "episodes" from what I thought was my transmission. While either approaching or leaving a stop, the car bucked a little bit, almost like a transmission slip, but more like it was upshifting then decided to downshift at the same time.
Well, as I was leaving my neighborhood earlier today, I momentarily lost all power while turning onto a main road. Luckily, no traffic was there, but it still scared me. It almost felt like the transmission went into neutral for a second, then back into drive, except the engine didn't rev up, the RPM actually dipped, which is why I think it's a problem with the engine rather than the transmission. This was definitely the most severe event so far with this issue. It felt almost like the fuel was cut very quickly, because it happened within a second or two.
I don't think I have any vacuum leaks, most of my vac hoses are new. Car pulls around 20 in-hg of vacuum at idle according to my boost controller, which I hear is normal. I have cleaned my MAF sensor a couple times before, so I know it's clean (but don't know for sure that it's good). The car has a new air filter, new fuel filter (both Mann), new cap, rotor, wires, plugs (Bosch cap & rotor, NGK wires & plugs). CEL is off, no codes present.
I also run fuel cleaner regularly, which in my experience has helped the surging at stops.

So, does anyone have any idea what this could be? I think the fuel pump relay is a possibility, but I wanted to see if anyone else had any suggestions before I go stock up on them at the junkyard.

Post by **bmdubya1198** » 10 Jan 2017, 13:21

Hasn't happened today so far, hopefully it'll stay that way. I pulled the fuel pump relay yesterday to check it out, and it looks to be fine. Maybe it just needed to be re-seated or something.
Any ideas?

Post by **abscate** » 10 Jan 2017, 13:36

If you get to the point where the hesitation is reproducible, or at least occurring weekly or more often, make your self up a fused fuel pump relay bypass wire and put it in, then see if it cures it.

Post by **bmdubya1198** » 11 Jan 2017, 18:26

I had one good day yesterday, and now it happened twice today. First time was coming out of an intersection about half way through first gear, then again probably 5 minutes later. The second time it happened today was the first time where I wasn't just taking off from an intersection. I was probably in third at the time.
I'm leaning towards a fuel pressure regulator. I might swap out the relay just to see what happens. It definitely feels fuel related, though. I don't think my boost controller has anything to do with it.

Post by **abscate** » 11 Jan 2017, 19:06

Pull the hose of the regulator and sniff for fuel. Positive smell means bad FPR

Post by **bmdubya1198** » 12 Jan 2017, 16:00

abscate wrote:Pull the hose of the regulator and sniff for fuel. Positive smell means bad FPR

Awesome. Where is that? From the looks of it, I have the fuel pressure damper on the rail. Is it near the charcoal canister and fuel filter?

Post by **abscate** » 12 Jan 2017, 19:14

The FPR lives either on the firewall or down low ...I don't have one on my Bastard

but follow the vacuum hoses to find it

Post by **bmdubya1198** » 12 Jan 2017, 20:59

Cool, I'll take a look tomorrow. I always though that little canister thing on the rail was a pressure regulator, but apparently not. According to FCP, it's a fuel pressure "damper."

Post by **bmdubya1198** » 13 Jan 2017, 10:27

Alright... so after cooling down for a little bit, I can speak without a million expletives. I took off a vacuum hose after cutting up my arms on the turbo heat shield, and it indeed smells like gas. Not too strong, but enough to notice. After fighting with a spring clamp for half an hour, I got this little "F" connector off, and after that wouldn't reach because of the hard line to the intake manifold, I tried to pull the vacuum hose to the back of the block. Well, when I pulled that it took the fitting with it. So now I need a new regulator, that "F" connector, and it couldn't hurt to replace the little hose between the connector and the regulator.
So now I'm down another car. My dad's E39 is down because of the upper radiator hose letting the bleed screw go, so he has our Sonata and I have two dead cars.
And the fun begins once again...

Post by **abscate** » 14 Jan 2017, 10:08

I borrowed some of those words when I had to do the E83 CCV....twice. Mainly because I broke it putting the hose on the first time.