Hesitation issues uphill

I have a 1998 Legacy Post Wagon (2.2l) that just recently, in the last 2 weeks, has developed a hesitation, but only uphills (steep or gradual), and only when I back off on the throttle and then try to start off...she will stumble, knock a little, and sometimes stalls.

 

Hooked up a fuel pressure gauge, and when my car was idling 22-25 PSI, under load, it was between 28-32...when it hesitated, the pressure didnt drop. Took the vacuum hose of the FPR, and PSI went to 35. Car off, key on, was not getting a pressure reading, so I did end up changing the pump to a Walboro.

 

With the new pump, key on, car off, pressure is holding at 30... start car, pressure holds at 27 when idling, 26 when going down hill....max PSI I saw was 35, and that was on a straight with the throttle matted. Better power now with the new pump, but still didnt change the hesitation issue.

 

Installed new NGK plugs, NGK wires, NGK coil, transmission filter, fuel filter, air filter, oil and filter, OEM thermostat, OEM radiator cap...still the problem exist...had my battery and alternator checked, and they came back perfect. No codes....nothing....so at a loss right now. Any help would greatly be appreciated.

 

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You were definitely low on fuel pressure before the pump swap.

 

Hard to say what is going on with it. Do you have a way to read out the sensor data? If we knew what the computer thinks is going on vs. what is really going on we could pin it down better.

 

One of the common things that cause poor running is if the timing belt is jumped. You can get a pretty good idea of this just taking off the end covers, but to really be sure you would have to take off the A/C belt, alternator belt, the pulley for them and the center cover. Let's keep kicking it around here for a while before you do that.

You were definitely low on fuel pressure before the pump swap.

 

Hard to say what is going on with it. Do you have a way to read out the sensor data? If we knew what the computer thinks is going on vs. what is really going on we could pin it down better.

 

One of the common things that cause poor running is if the timing belt is jumped. You can get a pretty good idea of this just taking off the end covers, but to really be sure you would have to take off the A/C belt, alternator belt, the pulley for them and the center cover. Let's keep kicking it around here for a while before you do that.

I ran my scan tool and have not had any codes, other than a P0400 (been on forever.) My mechanic is going to check the timing belt and pulleys Monday...probably just going to have him change them anyways.

 

It did do something weird today....only hesitated twice and stalled once, and when it did, the temp gauge was a little above the middle line. After the first hesitation, I ran with my heat on, and went up a steep hill....didnt stall...didnt hesitate...nothing. ran perfect. Turned the heat off and the next long hill I came to, I stopped at the mailbox at the top, and it stuttered and died. Started right back up, completed the next 60 miles of my mail route with the heat on full blast, and it was perfect.

 

I'm so confused....I wish it would just pop a code on and tell me what it is lol...

 

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Hm. It would be worth checking the electrical grounds around the engine bay. I'm in AZ so corrosion isn't much of a thing, but corroded grounds is a big problem on cars this old in most of the rest of the country. It can cause the weirdest things. The ECU can get all sorts of incorrect sensor readings and that leads to it making terrible decisions.

 

If it is around or past the 60k official life of a timing belt it sure would be a good idea to go through that stuff.

Hm. It would be worth checking the electrical grounds around the engine bay. I'm in AZ so corrosion isn't much of a thing, but corroded grounds is a big problem on cars this old in most of the rest of the country. It can cause the weirdest things. The ECU can get all sorts of incorrect sensor readings and that leads to it making terrible decisions.

 

If it is around or past the 60k official life of a timing belt it sure would be a good idea to go through that stuff.

I installed 2 ga. wire from battery to alternator, 2 ga. from battery to starter and I also upgraded the grounds all with 2 ga (from battery to engine, from battery to frame, and from frame to engine.) I was having electrical problems with another one of my subarus and was told this would solve it....so, I did it to both of mine just in case.

 

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Cool. The only one not in your list is about a 10 ga. from the intake to somewhere else grounded (I went to the ground points on the strut towers). The gaskets between the head and intake can isolate it and there are sensors and solenoids on the intake. Probably not your problem, but it's good to have that wire there.

Manual or Auto trans?

 

Is this with the A/C compressor running? I know you said heat on, is this with the AC button pushed?

 

Have you checked your new plugs since installing them? If so what did they look like?

Manual or Auto trans?

 

Is this with the A/C compressor running? I know you said heat on, is this with the AC button pushed?

 

Have you checked your new plugs since installing them? If so what did they look like?

Automatic. Car does it with or without AC on. Just did (3 days ago) the timing belt kit, front/rear differential fluid changes and head gasket (exhaust getting into the overflow.) Plugs looked good when we took them out. Also drained and put in new transmission fluid (was just done with filter 4000 miles ago...came out red in color.) Has brand new coil and wires, but I swapped them out with my other Subaru, and that didnt change anything soni swapped them back.

 

All of this done, and still a slight hesitation (not as bad, but still there.) I'm at a total loss. I have legit tried everything....some twice. About to take it to Subaru and have them figure it out.

 

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Edited August 27, 2019 by tobykinkle

How long have you had the car? You said it recently developed this problem so I'm guessing a while.

 

You said you have another subaru - assuming the same generation of 2.2

 

Have you considered swapping the knock sensor and/or pressure sensor to just see if they make a difference? Both of those CAN cause hesitation/timing retard without a CEL.

Your problem happens under heavier load of getting on throttle up a hill and its as if the ECU cannot react to the immediate throttle adjustment/load.

 

I hope you continue with this one and we find out where it goes. Have you had any CEL's recently?

I have a 1999 Legacy RHD, my 1998 Legacy RHD and a 1996 Legacy (project car). I replaced the knock sensor on both of my RHD cars (cheap and easy insurance.) I have had the 1998 for about 7 months, put about 500 miles a week on it for work. My 1999 runs better, but the right rear strut housing is almost gone (big hole from outside to inside) so I havent been driving it, and havent had a chance to get it fixed.

 

One of my friends told me to check the convertor with a temp gun, so I tested both front and rear cats.

 

Car was warmed up and just came from doing 100 miles, and measured at 2000-2200 RPM.

 

First converter temp going in was 160F-170F, going out was 260-280 (100 degree difference, which is good.)

 

Rear converter going in was 108-120, and the exact same going out....so my rear one is bad according to that test. The rear cat isnt monitored by an oxygen sensor, so that could be why it didnt throw a code. I ordered a new one (what's more money spent lol) and hopefully this solves my problem.....if I didnt need a RHD for my job, I would be bringing it to a dealer.

 

 

 

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