Troubleshooting Advice

[jeffs]

 

So moving to Florida has made the winter drives much more enjoyable, but one of the unfortunate downsides has been not finding a local mechanic that really understands the car.  I've been rather fortunate that I haven't had any problems with the car outside of Caterham's recall on the rear diff bracket...  well until now.  It seems that I have some sort of electrical gremlin and I thought maybe instead of taking the car to yet another mechanic that doesn't quite get it, I might try to troubleshoot it myself....  I figure if I can nail down the problem I should at least be able to find someone to fix it if I can't do it.  

 

So here is what's going on.  Problem is intermittent but has been going on a while.  Started at happening about once/year and has made its way to about once per drive.  The car will drop into not a limp mode, but lets call it 'bad kitty' mode.  At idle, bad kitty will drop the rpms by 500-1000.  As you can imagine this will sometimes cause the car to stall.  When bad kitty stalls she is REALLY hard to get started again.  Usually take 4-5 attempts to start and runs really rough when she does start (20% throttle to get 500 RPM kinda rough).  After 15s-60s it doesn't want to be a bad kitty anymore and is right back to normal.  

 

After poking around on a number of forums and looking at people that have had similar issues I've narrowed it down to a few likely causes:

 

1)  Bad Sensor

2)  Bad Ground

3)  Less likely but possible:  Shorting wire or bad coil pack.

 

Where I need the help is, how do I start to rule some of these things out?  I think I get the sensor thing...  I can get one of those fancy cables and use Easymap to pull the engine and sensor data.  At least I can once SBD gets the cables back in stock, so I think I've got that down.  How do I identify if have a bad ground somewhere?  Is this something I can do with a multimeter?  Would I see a bad coil pack through the easymap data, or is there another/better way to do it?  

 

Any advice would be greatly appreciated.  Oh, its a Caterham r500 with a 2.0L Duratec

 

[JohnCh]

I hate intermittent electrical issues. I had something similar on my car a few years ago. After proactively replacing a lot of stuff, the eventual fix was a new engine loom.  Not as drastic as it sounds given I hacked together the original out of the Ford loom that came with my engine and the replacement was professionally made.

 

Easy things to check:

• First, any commonality to when this occurs?  Engine hot? Engine cold? After engine fan kicks on? etc.
• When the engine is running normally, start shaking parts of the engine loom to see if that triggers the condition.  You're trying to expose a broken wire or connector for a sensor, fuel injector, or ignition.  
• Disconnect the sensors, ignition coil, and injector plugs then check the pins for corrosion or if one pin is further down the connector than the others, indicating it is not fully seating with its mating pin on the other connector. (note: if shaking the various wires results in bad kitty mode, check the pin seating depth as that could be the cause.)
• Clean all your engine grounding points with some very fine sandpaper.  
• Murphy's Law fully applies to intermittent electrical issues.  It might not be one thing that is egregiously bad, but rather several little things that in aggregate create the problem.  Hence the reason I needed to replace my loom.

If all that checks out, then I'd move on to the bad sensor/coil pack theory.  I'm sure other (and better) advice is incoming.

 

-John

 

[jeffs]

Cool, thanks for the advice!  Got some cables to shake this weekend

 

I know it is not related to the engine fan.  Problem does not kick in when its cold, only when the engine is warm, and will appear at temps below when the fan kicks on.  I don't think I've seen it kick in within the first 5 minutes of the first drive of the day.  However if I drive the car and stop for gas or something, after starting it when its warm it can certainly show up quickly.

 

[lg2k]

Welcome to Florida. I had a similar problem before and it was the IACV (idle air control valve).  I would also check vacuum lines, PCV, and related hoses.

Edited February 19, 2022 by JohnCh
Fixed unintended self-quote

[Anker]

Look up Sevens and Elans, owned by Chris Tchorznicki in St Augustine. He has built, serviced and supported Caterhams for many, many year. He built my Supersprint in 1987.

[IamScotticus]

I found a Formula Ford race prep garage in Tx through Ken at Dave Bean I would have never found on my own. 

He should know the shops in the area.  Possibly Pegasus too.

[jeffs]

3 hours ago, Anker said:

Look up Sevens and Elans, owned by Chris Tchorznicki in St Augustine. He has built, serviced and supported Caterhams for many, many year. He built my Supersprint in 1987.

 

I spoke to him, and unfortunately he said he couldn't help.  

[Croc]

Calling @Anaximander to the discussion.  Hi Bob - you are not that far away from Jeff, do you know of a specialist style of mechanic suitable for a Caterham or even just a good auto electrician please?

[Anaximander]

Croc and Jeff, I do not live that far from you Jeff but I do not know of a good auto electrician in the area. If your Caterham has an OBDII port, I would first head over to a local AutoZone and have them put their OBD reader on your OBD2 port to see if it is throwing any fault codes that are remaining in the system? That may let you know if you have a bad sensor like an O2 going bad. I would also just pull the cover off the fuse box(s) and check that all of your fuses are in securely and there are no blown fuses. That at least would eliminate two issues without first finding a good automotive electrical tech. I have put in a call to a neighbor that has his more exotic cars worked on by a local mechanic. I will get the fellow's name and forward it to you Jeff when I get it. My neighbor is not the quickest to respond but I will let you know when I know.

Edited February 21, 2022 by Anaximander

[Pokey]

Is it possible it is misfiring or firing on only three cylinders?  If so, you could try disconnecting each spark plug coil one at at time while the issue is occurring.  If you unplug a coil and the problem doesn't worsen then you've possibly isolated it to the coil or a connection upstream in the harness. 

[ashyers]

jeffs,

If you have an infrared thermometer you can check the header tubes to see if it's dropped a cylinder. A somewhat cruder method is to flick a bit of water on the tubes and try and determine if you have a cold one. In addition check the harness connection at the coolant temp sensor. If it's sending wonky values occasionally that will seriously mess up the fueling.

 

What MBE/easymap system are you running?

 

Andy

Edited February 22, 2022 by ashyers
fixed name

[jeffs]

 

Thanks everyone for the advice...

 

lg2k... the symptoms of a bad IACV are just about spot on to what I'm seeing.  Haven't been able to check it yet, but sounds like a really good lead.

 

Anaximander...  I have had a mechanic connect to the ODBII port and he did not pull anything meaningful.  

 

Pokey...  I don't think its running on 3 cylinders.  Plugs seem pretty evenly worn, and the difficulty starting has the feel of a bonkers air/fuel ratio.  That said I'm not going to rule it out, and if I can get it to behave badly without stalling I will give that a try.

 

ashyers...  I don't remember the model number of the ECU, but it is Caterham stock and locked.  I can't connect to the car with Easymap yet b/c it requires a proprietary cable which is currently backordered.  The oil temp and coolant temp sensors I believe are working correctly (as I can monitor them and they are returning reasonable values).  I've disconnected the lambda sensor to see if that stopped the problem (it did not).  

[BlakeJ]

I had an intermittent no-start/stall issue when I first completed my 2017 build. It turned out to have been loose wiring from the factory under the dash to the fuel pump fuse/relay. Full disclosure; an auto electrician friend of mine diagnosed the problem, not me, so I don't recall the specifics of it.  Could be worth taking a look, though it sounds like perhaps you have, already.

[Vovchandr]

Are you running ITBs?

[jeffs]

15 hours ago, Vovchandr said:

Are you running ITBs?

 

Stock RBTBs

[ashyers]

jeffs,

The TPS could be going downhill. That would cause the mixture to go bonkers. You could check the signal with a meter and see if you get a clean sweep from idle to WOT.

 

Andy

[yellowss7]

Hi, Jeff. It’s simple. Your car needs to be driven like it was meant to.  Bring it back up to NJMP and get it back on track where it belongs. I’ll drive at half throttle so your R500 can keep up..   either that or the smoke has come out of your wiring. And you need to replace it.         
 

Electrical issues suck.  Hope you are doing well otherwise. We miss you.  Tom
 

 

[jeffs]

21 hours ago, yellowss7 said:

Hi, Jeff. It’s simple. Your car needs to be driven like it was meant to.  Bring it back up to NJMP and get it back on track where it belongs. I’ll drive at half throttle so your R500 can keep up..   either that or the smoke has come out of your wiring. And you need to replace it.         
 

Electrical issues suck.  Hope you are doing well otherwise. We miss you.  Tom
 

 

 

You might keep up with me if you put those double-wide slicks on the orange car... and then painted it yellow to make it faster    Yeah, I miss going to the track with you guys, and I'm sure the car does too.  There are days when I think that if I'm not going to track it I should sell it and get something a little (and only a little) more practical for the street and for Florida weather.  

[jeffs]

 

Data makes life so much easier....  Sent my datalogger out to be fixed and just got it back.

 

In the first run I noticed that the engine ran well for a while and then started to surge.  Started at 140F which is when the lambda sensor kicks in and both rpm and lambda started a slow sin curve (or cos if you prefer).  

 

Disconnected the lambda and reset the ECU.  Runs 2 and 3 just idling in the driveway, no surging and no stalling.  Will add new lambda sensor to the shopping list.  

 

Kept the datalogger in for a run to the store.  Things ran fine for a while and then the idle RPM dropped.  Data shows the coolant temp dropped down to 20F (high was 170F).  The stack dash did not show this so I'm assuming just a bad sensor.  I also noticed some noise in the TPS at idle (equates to about 0.2% of full throttle).   Temp sensor gave a reasonable reading for the first 5 minutes of the run and towards the end, but in the middle read as low as -5F and as high as 212F (fractions of a sec apart).  

 

Does anyone know if the standard Caterham map has a dependency on coolant temp?  Just trying to determine if this is the culprit or if the whacky readings are the fault of something else.   

[ashyers]

jeffs,

If that coolant sensor is the one the ECU is using I'm surprised the car didn't flood when it read -5F! You may want to check your harness if you have a couple of senders doing goofy stuff in sync.

 

I assume you've picked up an MBE download cable. What can you look at in the stock restricted Caterham units?

 

Andy