hello vovlo world. i have an 93 850 volvo.it heistate,when i start drving but when on highway it runs smooth.i changed the maf sensor,throttle body,fuel pump,fuel regulator still having problems.

OP- IF we're having the same problem (which I guessed we were..) Change your front O2 sensor. It solved my hesitation (short sample size though) and should take care of yours..
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If you're not driving it "like its stolen," are you really driving?

Since you cleaned the throttle body, are the spark plugs dirty? Sounds like you are running slightly rich, an indication of unmetered air entering the manifold through a vacuum line crack.

Check for any pending codes in A-2, like an O2 sensor responding slowly.

Klaus
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Always willing to listen, just not able to take direction.

Klaus, I'm undergoing a similar problem (perhaps exact, but OP didn't give enough information) where I can start the car and drive from the apt. parking lot to 40 (about 2 minutes, mile an a half) which gets the car just under operating temperature. Then as it crosses over (and I accelerate to the 50mph speed limit) I have some hesitation. If I floor it, tranny downshifts, and off I go with no problems. If I'm light on the gas (2500-300 rpm) it'll stay into second gear and act like it just hit a wall. It doesn't do it if I make a quick stop and restart, but if I were to stop for an hour or so and let the engine cool down some it will happen again as I cross that threshold.

Fuel pump appears to be good (correct pressure at idle at least.)
Plugs are fine, 10k miles on them with appropriate wear. Yesterday, I took the car for a "joyride" for about 130 miles on backroads where i drove it like it wants to be driven.
Wires are about 3 months old. Cap and Rotor appeared OK when I changed wires, but they're about 3 years old.
O2 sensors are two years (35k) old, shouldn't be them.
MAF was PnP'd about a year and a half ago, don't think its MAF.
Can't find a vacuum leak (and the car doesn't tell me there's one). Most elbows/hoses are less than 1 yr old.
Fuel filter changed 6 months ago.
Running Premium
Transmission was flushed 5k ago, no discoloration, no smells


I can think of only one cause the O2 sensor is just getting control and its not ready to go to work yet, so it starves the engine. I'm probably missing something, so any suggestions? With how it only acts up right as it gets to and crosses into operating temp leaves me guessing.

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If you're not driving it "like its stolen," are you really driving?

Boost control valve? Your LPT is still cold and might not be responding fast enough. Just a wild guess.

But now you have to tell me why my P0442 came back after 6 months of being off. I pulled down the charcoal cannister and the hoses all look good. Last September, I patched a 4 inch section of hose in the rear of the car and now I can't find it (meaning that the new hose isn't evident, I only looked at the right rear wheel well and everything looks original???) How do you smoke test the EVAP system? Grrrrrr. BTW, my AC charge is still holding since September. Amazing.

Klaus
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Always willing to listen, just not able to take direction.

Well, its an NA so there goes your theory..

I'm betting your P0442 is the hoses by the rollover valve have separated. Its on the bracket that holds your fuel filter in (read: not the easiest thing to access on your AWD).

You could hook up an air supply to the hose that goes rearward at 5-10 psi and listen for the hissing as to where the leak is.


Can you teach my A/C to hold a charge like yours has? I'm thinking of replacing the evaporator, but I'm also thinking of replacing the car..

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If you're not driving it "like its stolen," are you really driving?

OK so today I finally had a few minutes to do some diagnostics. I hooked up the OBDII to it and I found my short term fuel trim +25% shortly after starting it and lightly holding the gas (1800-3000rpms). IIRC + means the engine is running lean and its adding fuel. My next step will be to swap the O2 sensor in hopes that the one I have has gone bad. Hopefully I'll at least be able to gather some information from it while I have it out.

Fuel pressure was find a few days ago, and I don't see a reason for it to be low while warming, but OK while hot.. AFAIK my cat is working fine, so I don't think its too much back pressure. Could it be my SAS pump is cutting off early?
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If you're not driving it "like its stolen," are you really driving?

You are correct about the location of the vacuum line leading from the tank to the roll over valve. Last Fall I saw that the line had cracked, giving me a P0442 (small leak). I replaced the section of line with a silicone vacuum line.

Now that it is getting warm out, the silicone line cannot hold the tank pressure. I could smell trace amounts of gasoline vapors next to the fuel filter. I cut 5" of 1/4 fuel injector line and managed to get it fitted. Not the best location for size 15 hands! So now we wait... If I get the code again, I will get an OEM part and install that. Access through the rear hatch is fairly easy and beats laying under the car.

Klaus
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Always willing to listen, just not able to take direction.

Glad it seems to be an easy fix. Hopefully the injector line holds up, I think you have to buy the OEM part by the meter (I think its about $10/m). I snagged an extra hose when I replaced my purge valve a while back, its also the perfect hose to use for flushing the brakes!
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If you're not driving it "like its stolen," are you really driving?

I am going to try a 3oz bottle of stop leak, sold at NAPA, this summer when the R134a finally cooks out of the system. I know, bad stuff, but its worth a try considering the alternative. I suspect my system leaks when the gas expands in the heat.

So that's where I found the cracked vacuum line last year. Getting to the fuel filter is not hard, just replacing it is! I will look again. I hate that CEL, which was off only for less than a week. Perhaps a silicon vacuum line wasn't a good repair now that the outside temps are perfect!

Klaus
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Always willing to listen, just not able to take direction.