desertsubaru

Let the car run for 20-30 minutes. Then use your temp gun, the back should be at least 75 degrees hotter than the front. If the front is hotter than the back, then the cat is restricted. As far as a range (once car is warmed up) something like 275 front and 375-400 back would be acceptable. If its under 250, the car isn't warmed up enough and if it temps something stupid like 550 front and 650 rear, then there is a problem.

Is that a freer flowing exhaust? Even a reduction of back pressure might cause it. I got that code after removing the rear cat.

I have read even an old clogged air filter can cause it.

You maybe right and I may be wrong or I may be right and you wrong because we cant visibly inspect his engine but pouring cold water into any steaming hot engine even an all cast iron engine can warp/crack the head or blow the HG. I had it happen to an EA82 and an Ej2.2 and on a bulletproof dodge slant six. I know he said he does not want to replace his HGs so that leaves him with 5 choices. 1 ,Replace with either a known good used engine, 2 Replace with rebuilt engine, 3 Pay someone to do the HGs 4 sell the car or 5 junk the car.

When you Cleaned the iacv did you also clean where it goes into the throttle body. It can carbon up causing the IACV not to work correctly.

You have most likely blown a head gasket and now maybe cracked/warped a head. No snake oil in a can you pour into it will fix it. Either do a HG replacement having the heads pressure checked and if not cracked have them shaved. Or if it is an engine with close to 200k on it just get a jy engine and drop it in.

How low was the radiator when you poured it in? How much water? Was the engine running?

Pouring cold water into a hot engine will crack/warp a head real fast.

The fuel does not detonate properly leaving unburnt gas fouling the plugs. This will also kill your catalytic converter which can get real expensive.

That is just the A/C belt only needed if you want your A/C to work. Check out videos on You tube for the timing belt job. Probably one the easiest cars in the world to do timing belts on.

I picked up another free Subaru because of rust issues, it is a 2000 impreza with a 2.2 150 k on engine. It will be strictly an off road beater because of the rust. I had the rear cat cut out because it had rust holes in it and had a straight pipe welded in but now I get a p0420 code. I understand that the code has to do with catalyst but was wondering if it will do any damage to the front cat or engine if I drive it like that. I would also like to know if there is a fix like the spark plug fouler trick that would turn that code off?

I bought a upull junk yard 2.2 one time that had 89k on it. It should low compression, Turned out the belt slipped 2 teeth and it was enough to show low compression. Changed the belt, put the engine in and it ran great with 175 psi in all cylinders.

Which engine? How many miles on it? Search youtube for How to change your head gasket on a Subaru. There are a few good videos.

The 2003 Forester had this code before engine swap from 2.5 to 2.2 and still has it. p0030. I cleared it once and it came back so now for the track down to see if it is the O2 sensor or if it is the relay/ bad ground in ecu. So first question is where is the O2 sensor relay? 2. Which wires do I check with my ohm meter to test the heater circuit. 3 What is a good replacement if it is the O2 sensor? I know the connectors are good and tight + clean.

It just might have been a blessing in disguise.

As gary said sometimes it is cheaper to get a used engine and do the Tbelt kit then to have the heads checked/resurfaced. In my area the only shop that does heads is 60 miles away and they get $375 plus tax to do the heads. Ad in gaskets and such it comes to well above $600 bucks. I got a used 99 2.2 for $500 bucks with 126 k on it and a six month warranty. I also got lucky to find a sticker under the Tbelt cover from a Subaru dealer that noted the Tbelt kit was done at 100k. I still replaced the belt that had Subaru on it and all idlers and other tbelt related stuff looked brand new including the water pump, It even had the Subaru label on it so I know it is oem.

Try what istevens said first and if that does not help read this thread. http://www.ultimatesubaru.org/forum/topic/96703-p0304-issue-solved/page-2 Also even if the plugs look good put new ones in to eliminate that part of the problem.

Notorious for bad HGs.

Yes that looks like what you think it is. 99 2.5?

My rule of thumb when I want to buy a used car is to take it for a long hard test drive on the highway and through town. Drive it a minimum of 20 miles round trip and don't be afraid to really test the car. Then if you do buy it put a few hundred miles on it locally before a long trip driving it hard to really test it.

Even air cooled cars like the Corvair were prone to overheating and blowing head gaskets.

Yes I would definitely keep an eye on that cylinder. Compression check is easy. Buy a compression gauge, then take all 4 plugs out and disconnect the coil power wire. Screw gauge into spark plug hole then crank it over three times with starter and look at reading on gauge dial. Repeat for each cylinder. Should be up near 150psi at the least and at 170 to be in manufacturers specifications.

Were all the plugs like that or just one? That is not good. Either buy or rent a compression checker to check compression,Should be up around 170 psi.

So what should the minimum crank amps be?

2003 Forester I am pretty sure there is not a difference but when I looked at batteries on line at Auto zone some say in the description for Manual trans. Anybody have some input on this?