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After doing all my prep for the USA7s event at NJMP I now have a major engine issue. As you can see and hear from the video the engine is not idling well and my number 4 cylinder is cold. I suspect valve damage. I am double annoyed, I will likely have to pass on NJMP because I don't have time to straighten this out, and I may have been able to prevent it :banghead: 

 

The background: After working on the car, I went to start it up and the revs shot up so I turned off the car. I was not inside the car so I could not have been touching the gas pedal. I then operated the throttle at the engine and there were no anomalies noted. Based on it happening with no apparent actuation of the throttle I suspected some sort of sensor issue. I had done no work in the area of the throttle or the pedals - brake flush, oil change, check nuts and bolts for tightness, put on a Newton gas cap and some cleaning.

 

I then went on a drive and the revs shot up again. I only noted 5-6000 on the tach from a quick glance. I could not tell if the throttle was stuck but I shut the car down as fast as I could. Upon restart it was running as in the video and I drove the 1/2 mile home. I checked the throttle and it works fine at the engine but when I actuated the pedal about 1 in 10 times it stuck. Ugh.

 

I suspect I over revved the engine damaging a valve. I will need a compression test, any other areas I should be checking?

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Wow Jay, That's a bummer!

I think you're on the right track with a compression test. A leakdown test and borescope inspection could reveal a valve issue. 

 

Other ideas:

Could be a cam position sensor. That would make it put fuel in at the wrong time. I've had that happen on another car. It ran rough.

Check spark on #4 cylinder. Maybe a bad coil?

 

Good luck!

 

 

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In regards to the wild card on the throttle revving is an issue I had. It was two fold.

 

1) Cable would travel free until I parked. Then when I got into it the pedal was "frozen" in off position until I gave it a push and then it worked fine again until next cold stop. Issue was it was freezing up inside the cable housing right above the exhaust manifold. I think it's only a LHD Zetec issue, and wouldnt be a problem in the routing for a RHD Duratec.

 

2) Issue 2 was the cable end cap was actually coming out of the housing under acceleration at random times and upon relief of the throttle wouldn't go back into the housing but rather get stuck on the outside of the housing causing acceleration or revving regardless of throttle input. Not sure on your exact setup but certainly sounds familiar. It's a two man job to catch that happening and took me a long time to figure out. Somebody was in the car playing with throttle and I was under the hood looking at it. 

 

Cold cylinder doesn't sound good however.  

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Given this wasn't a mechanical overrev, I'm surprised a valvetrain issue would surface unless something was already weakened and simply looking for an excuse to go bang. Is it a high mileage engine?  You have stock cams and valve springs, correct?  

 

Although dead cylinder doesn't look good, check the cheap, simple things first.  Make sure you are getting spark as John suggests, and also check that the injector is delivering fuel.  Given you were cleaning things, is it possible you jostled the coil or injector connector for that cylinder?  Remove those and make sure the pins all look seated correctly.  

 

-John

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Sounds like she is running on 3 cylinders - no spark or combustion in the dead cylinder.  I don't hear valve issues.   Your quick reactions probably stopped that. 

 

There are two things going on:

1) The auto-rev issue

2) lack of spark/combustion in number 4

 

I would follow John's line of thinking from above:

1) Look at wires to/from the ECU to the ignition system and see if there is any fraying/arcing/grounding that should not be happening.  

2) Check the camshaft position sensor and throttle position sensor

3) Check the coil

 

My initial reaction is to suspect whatever went wrong on issue 1 ended up frying the coil on number 4.   Coil failures are reasonably common on Duratec so it would not surprise me if you have had one go bad.  

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Thank you all for the advice. Rosh Hashanah put a kink in my ability to work on the car. I plan to do troubleshooting tomorrow if work will cooperate. Hopefully none of my customers blow up one of their engines tonight making me busy tomorrow. 
 

I have not yet cancelled out of NJMP. Can I do that up to 48 hrs in advance without penalty (can’t seem to find the cancellation policy). On the other hand I saw there was a limit to the number who can register so I don’t want to block someone from registering if we are at the limit. 
 

I have never troubleshot a coil on plug ignition system. How do you verify if an individual coil is bad? For the TPS that woul just be a linear potentiometer in the 0-5 V range? For the CPS where is typically located on a 2.0 duratec and how is it tested?

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A simple test is to swap coils and see if the dead cylinder stays put or follows the coil.  You can do the same with the injectors if you then want to rule out that problem.

 

-John

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Last week I asked for a count as it’s not available on motorsportreg .com for some reason.  As of last week we were not at the cap and unless we have a last minute rush, I think we will be fine.  Croc may chime in when he wakes up.

Edited by yellowss7
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24 minutes ago, JohnCh said:

A simple test is to swap coils and see if the dead cylinder stays put or follows the coil.  You can do the same with the injectors if you then want to rule out that problem.

 

-John

Thanks. I realized that after I sent the post 😀. And easy to do. 

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Now awake again.  I would not worry about the cap.  Get your car sorted then sign up or cancel out 3 days before if you are not going to make it.  I don't think we will pop out the top of the cap.   

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Progress today that significantly ups my chances for NJMP. After moving coils around the car seemed to just run very poorly (and rich) at idle and ran slightly better with at higher RPM. I got new spark plugs because it was clear it was running rich but the results remained similar. A then while staring off into space I am looking at my car and voila - there is a hose under the inlet not going anywhere! Plug it in and the car now runs smoothly. Picture below shows the offending hose hooked back up from the PCV system. Just need to get a clamp to secure it (don't know if there was a clamp that popped off or if there was never one there)

 

I don't think anyone said look for a vacuum leak :classic_ohmy:

 

Now I just need to sort out the throttle. Today actuating it cannot make it stick open but I need to be confident on that before I track the car. Not sure why it stuck and why it is not sticking. Pretty simple system and the cable seems to actuate very smoothly. If anything, it is in the physical pedal. And I also need to ensure this was the cause of the rapid RPM increases that occured.

 

So the sequence of events:

RPM rises uncontrollably (the first time is when i started the car when I was not even in it)

I go for a drive and I have a second RPM rise that corrects itself after shutdown and a couple of restarts and the car runs fine

Drive the car 2 mi to breakfast - no issues, car runs great

Returning home RPM increases. Shut car down, restart the car and it runs very poorly. I assume the hose popped off at this time.

 

21-09-10_Caterham 7_13.jpg

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