Compression doesn't seem to indicate anything amiss with the valves - good values, as spec is 170-225psi.

Your statement about the O2 sensors doesn't seem to make sense: you say nobody had an upstream but then tried a new one.. ??? The downstream would have no effect on fuel metering - it only measures catalytic efficiency.

Let us know what you find on the fuel pressure.

 

On the 4 cylinder, the crank should be almost a half tooth past the mark while the cam is dead on it's mark. If it's not, then it's off. It sucks that there's only one way to tell, unless you have a scan tool that can display the cam/crank difference.

 

Well I ended up buying a downstream one that I had to wire so I wired it to the upstream connector first and then the downstream. From what I've read, the sensors are the same but with different length wires. But I only base my knowledge off of what others have posted. I've also read that the downstream one is the one that sends signal for air/fuel ratio as well as compare temp with upstream to check cat efficiency.

I bet I am off on timing then because I'm pretty sure I just lined it up the crank with the mark. I guess I should have read my manual better.

And just to point out my terrible auto repair skills, I totally ignored the advise to change water pump when I changed the timing belt a couple years ago.

 

I've seen applications where the sensors are the same except for the wiring, so that's not impossible. ;-) But in almost all applications, the downstream (post-cat) sensor is only there to measure cat efficiency; the upstream is the first line in determining the FA mix from a combustion efficiency standpoint. There may be cases where the downstream readings are applied in conjunction with the upstream reading to change the mappings to prevent killing the cat - such as a super RunRICH state or several cylinders with misfires. Also bear in mind that there are many other sensor inputs that the PCM uses for setting fuel trims and timing: MAP, coolant temp and ambient temp, crank and cam position, feedback on the injector pulse efficiency.. the programming is not simplistic.

But it is sounding more like your crank/cam timing is off just enough to mess things up. Sorry that you have to go through all that hassle of disassembly to verify and fix.

 

Well I tore car apart this weekend and.... timing way off. I don't know exactly how it got off that far. When I put new water pump in, I didn't move anything and put belt right back on. Cams were off about a half inch from each other.

Haven't finished putting all back together yet. The tensioner pully has a spot to put an allen wrench in so you can get some slack. Well mine was stripped so I just took bolt out of middle. I went to buy another one and nobody had one on hand.

I did manage to use pliers to twist the old one to where you can put another allen wrench in a hole to hold it in place. Now just need to put it all back together.

 

Fixed! 6 hours to get them damn thing back together but runs great!!

Thanks again everyone.

 

what was the problem? Mine is cutting off when I put it in reverse it did it a month ago one time then started doing it 3 days ago & yesterday was fine but this morning kept stalling when put in reverse what was ur outcome of what was wrong ??

 

 

I recently installed a new ac system which created a giant cf on my 4 cylinder engine. It’s a 99 model and after the ac install the alternator went out then after replacing the alternator three fuel pumps went out and finally it clogged the converter and I’m assuming burned up the O2 sensors. Everything is brand new I removed the converter and straight pipes through it and now the truck runs terrible. How should I proceed?? I’m at a loss . I’m thinking upstream o2 censor?