Backfire and stalling at idle when hot, followed by no start conditions *video included*

[CarlB]

I know checking cam timing correctly is time consuming. With stock cams you can pull the cam cover and put the engine on top dead center. You can get close with a screwdriver in the number one spark plug hole and intake and exhaust valves closed. The back of the cams have slots in them. The slots should be in line and parallel to the surface the cam cover bolts to.  I know it sounds different to adjust cam timing with a compression gauge, but it works. Generally it is the spot the cam will give the best low end power. This assumes you are close to the correct cam timing, but the engine ran at NJMP. 

[Vovchandr]

I should have a chance to dig into it this week. 

 

Still no luck with tuners at this moment.

 

I'm leaning towards this being a primary timing/cam issue at this moment.

 

I'll do compression test/leak down/ and exhaust gasses in coolant tests to establish a baseline. 

 

Cat is likely clogged or close to clogged so I'm planning to take it out. I have an OEM backup with a virgin Cat in place just in case I need to go back to that configuration.

 

 

 

Primary question to all experts. This blacktop (Non SVT) Zetec is non interference. I should have no risk trying to use my adjustable cam to dial in the timing a little bit right? 

 

I know for a fact that the car pre head gasket change and post head gasket change has cams in different positions. They were not at 0 position before change and are 0'ed out now. I have a hunch maybe the non 0 configuration was on purpose and will be better. 

 

 

 

Car is misfiring/backfiring at cold and warm throughout the RPMs.

 

I also don't think I go into the idle table due to me removing the IAC and having the ITB's stop on idle screw. I'll consider putting the IAC lines back on. I know it's unusual to have IAC on ITB's but thats how it came and I can't find any parameters in the tuning software to adjust the idle table or IAC at all. 

 

Here it is prior to taking it apart. Wasn't sure if it was intentional or accidental slip. (still honestly not sure)

 

 

I'll go back through and use the suggestions one by one given here so far. 

[Vovchandr]

So I've done a quick dry/cold compression test and got (front to back ) 150/150/180/180. Peculiar.

 

Still have yet to do wet/warm test and leakdown test.

 

Also question for the experts. Am I crazy to try to rotate the cams to match what they looked like before I changed the headgasket as seen in the picture above?

 

Due to the backfiring I can assume the exhaust might be fine so I'll set that as a 0 and rotate the intake alone? Maybe rotate  both towards each other slightly? I know nothing about messing with timing but still no luck finding anybody who's willing to take this on. I should be non interference so thinking of trying a wild card in meantime. Any advice? 

 

I'm essentially trying to dial in physical cam positions to whatever the ECU would be mapped to right (if the engine is out of sync with ecu right now?)

[MV8]

The compression is not great but should be good enough and even enough to run properly. The cams may not rest without the belt installed properly timed due to the spring pressure and lobe angles. Did you ever check the cts resistance/temp chart or is that not available?

[Vovchandr]

18 minutes ago, MV8 said:

The compression is not great but should be good enough and even enough to run properly. The cams may not rest without the belt installed properly timed due to the spring pressure and lobe angles. Did you ever check the cts resistance/temp chart or is that not available?

 

Compression used to be much better before the head gasket change, but I'm pretty sure it was at least done on warm engine last time. 

 

I'm not sure what you mean about cams "resting"?

 

As far as Coolant Temps Sensors and temp charts I'm not sure how to proceed with that. I don't believe my ecu provides any temp charts. 

[MV8]

An ecu typically relies heavily on the cts to determine the engine operating temperature. The cts resistance is calibrated to be around a certain value depending on coolant temp. Sometimes they fail by being out of tolerance or if the connection shorts or opens. If the engine is at 200f but the cts says 300f, it will be too lean and more likely to stall at idle.

If you know the oem application or part number for the sensor, the chart should be available like this one for GM.

Resting means nothing preventing the cam from rotating. Free to rotate to a resting or balanced pressure position on the base circle/least overlap position once the belt is removed. When on tdc for #1, some of the valves will still be open but the spring pressure is trying to close them, so the cam will rotate. It is not unusual to have to force one of the cams to rotate a few degrees to align with the marks when installing a belt.

[Vovchandr]

10 minutes ago, MV8 said:

Resting means nothing preventing the cam from rotating. Free to rotate to a resting or balanced pressure position on the base circle/least overlap position once the belt is removed. When on tdc for #1, some of the valves will still be open but the spring pressure is trying to close them, so the cam will rotate. It is not unusual to have to force one of the cams to rotate a few degrees to align with the marks when installing a belt.

 

Thank you for the info about the temp sensor. I'll look into that. 

 

I'm not planning on taking a belt back off but I understand what you're saying. That's what happened when I took it off the first time and haven't measured the "current operating position" before they snapped out of that position once the cam was removed.

 

I'm thinking of using the picture above to try to replicate the last operating position that is different from the "0" position that I have put everything back together on, to hopefully make it run better. Just reluctant to mess with timing. The thought is, if it's non interference I have little to risk and I might as well put the adjustable cam gears to use and maybe even learn something. 

[CarlB]

I wouldn't say anything definitive about the correct position of the cams because we have no idea what they are. A good cam grinder would have used the stock cam positioning reference and ground the cams so the slots in the back of the cams were parallel to the head. If the cam isn't a whole cam belt tooth off you can get close by setting the intake cam to the highest cranking compression. If you think you are way out of the ball park put a degree wheel on the crank and measure the opening and closing points of both cams. Look at a custom cam catalog and find similar cams. That should get you close enough to run correctly.

D