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Discussion Starter · #1 ·
Recently replaced plugs and coil packs on my daughter's 03 1.8t as she was getting misfire CEL's. Fixed a couple of vacuum leaks as well.

On the occasional am start it will crank fine begin to fire and sometime fire up/spin up slowly or sometime stall. Crank it up again an it is fine.

On the old plugs/packs it didn't do this and would sit at a higher idle for a few moments.

No CEL/stored codes, no loss in gas mileage. Actually runs better with the new plugs.

I'm not really concerned here, just wondering if anyone has seen this before.
 

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What brand coils and spark plugs, did you install? The oem vw is recommended for coils, stay away from typical auto parts store coils made in China; for the spark plugs, the oem NGK brand, work the best.

NGK online plug finder here:


For hard cold start issues; coolant temp sensor failures; can cause a hard start, rich mixture, rough idle and then, it will smooth out, once reach normal operating temps. Also, a worn out, weak fuel pump, low fuel pressure; can cause a hard start problem with a check valve failing, be a failure we see often. If the fuel pump is bad; stick with oem Bosch or VDO, they are the only brands we have seen that work correctly, aftermarket pumps, should be avoided, those always seem to have failure issues, right out of the box.


On 1.8T's, after 100k and 15+ years; it can take some time, to figure out, all the multiple issues to get them running at their best. Many parts, related to fuel delivery, turbo boost system and ignition, are worn, in soft failure mode and not performing at their top levels, which impacts engine performance. The basics, should not be overlooked; compression, fuel pressure, etc.
 

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Discussion Starter · #3 ·
Plugs were autolite irridium and whatever coil packs from O'Riley's. Note this is really minor and only takes 2-3 seconds before the idle recovers. Not like I'm having to crank, stall, crank, stall...

I do agree that with 140k, it's going to need more care and feeding. Just going to tell her to crank it longer. Also has a new battery and new starter a few weeks before the tune up.

Thanks
 

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i would assume, the coil packs from O'Reilly's are their "Import Direct" line of coils and sub standard made in China parts. I haven't used Autolite plugs in a 1.8T; NGK were factory install and that is recommended.

A fuel pressure test and new fuel filter; could be something to consider. Coolant temp sensors, that are not reading as they should; can cause a hard start issue, note the info in the above video. I also, noted; my gas cap rubber gasket, was cracked and when I replaced that, my 1.8T started easier, faster.


Overall, evaluation of the basics and checking things, like fuel trims ,can give you a sense of the current tune, how the engine fuel metering is working (confirm your vacuum leaks are ok now, fuel pump is good, maf is good, etc.).


As our 1.8Ts are getting up there in miles and age; every little thing, contributes, to a good or bad running engine. As I have gone through my 1.8T; I found it was a combination of many worn out parts, that was making it not run as it should.
 

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Discussion Starter · #6 ·
Well this if baffling, wonder if you've seen it before.

All the books say I should have a 4 bin but the sensor and harness is a black 2-pin. ??
 

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What sensor are you referring to?

I'm assuming you are referring to the coolant temp sensor; get the part # off the old one and match it up. There have been two and four pin versions, over the years.

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Discussion Starter · #8 ·
Well sir you and your brilliance ay be on to something. I just hooked up OBDeleven and the temp was bouncing between 177 and 55.


And just to confirm, this is the coolant temp sensor??

Automotive tire Automotive fuel system Automotive design Hood Motor vehicle
 

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That is the cooling fan switch; the coolant temp sensor, is on the cooling flange, that comes off the head.

Head Human body Rectangle Gesture Organism


Engine Coolant Temperature (ECT) Sensor -G62-, Checking


(click "next" to go to all the pages; for sensor testing info)

 

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Discussion Starter · #10 ·
Now that makes perfect sense, thanks. Put one on order.

Also had to order a fuse box, replaced the last one some 8 months ago and all has been well. It was cold by NC terms today and I'm wondering if she was using her heated seats. She said they felt funny, one leg was really hot.... Teenagers and diagnostic terms.

She came home and said the car is not "gassing right".. LOL Took it out and it felt like it was in limp mode and the battery light was on. Popped the hood and found this, it was fine yesterday when I checked the oil.
Bottle Glass bottle Beer bottle Alcoholic beverage Mass production
 

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Common issue; good video here and a long discussion about various issues here, possible fixes:


 

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Discussion Starter · #12 ·
Yep, I need to do some more digging and see what she was running this am. I did the 4ga alternator wire run about 6 months ago with a box replacement. Something new has raised its head...
 

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Yep, I need to do some more digging and see what she was running this am. I did the 4ga alternator wire run about 6 months ago with a box replacement. Something new has raised its head...
Did you cut or take out the factory alternator wire? Also, if you did 4g for the alternator, you should really run some new grounds in 4g. Just upgrading the charging wire, to me and my 2015 beetle. I have 1/0 run for my radio system and also the grounds. Idk how the NB ground's are from the factory. But the one coming off the battery to the body is thick and heavy. But I still ran new one's to different spots other than the factory location. You alternator is the best place for your ground to the body. You will have to take a bolt out of it, if you can. I had to take mine totally lose. But it was a pain. No room. Do you know what type of voltage you were getting before you put the 4g on?. This is how you check the ground location you are wanting to use. The lower the number, the better the ground. You will be surprised in the difference in a higher number, like .05+ and a .01 ground. You can just grind some paint and just put it anywhere, but if you want the best location and performance out of your grounds. That's what's best. Resistance in the wire. Voltage drop off. Say you upgrade your wire's. Both p/g. Now you would expect a gain in voltage to the battery. But if it's cheap wire and not true 4g. Ofc wire is the best. But CCA is still available. Don't use welding leads. Get wire that is for a vehicle. There's a big deference. Also I didn't see anyone mention to check your voltage at the sensor in question. Also, I learned the hard way about part store parts and online store parts. They're cheaper than OEM, but when you figure in the time to change it. And if it doesn't work out, you will have to go OEM. It may work for ever or a week. Then you will have to take it back apart again. IDK if the more knowledge people think about this. I did A Lot of research before I touched mine. It's too corkie to just jump in and wing it. Now I do have a nice radio system. That's how I learned about the "big three" upgrade. I never had 14.1 voltage at the battery. It was always in the high 13's. My lights outside and inside are brighter now. I'll put two links for you.
Grounding
Big three upgrade. Most people do this for car audio. But it does more than car audio. You use it in car audio to get more power out of your factory system.


It may be a long shot but I would rule it out. Also on the sensor. You can check the omhs on it to see if it's with in factory specs. I would test the original one first to see if it's bad. Checking all the basics take a little time, but you can diagnose it better before you go and buy parts that you may not need to. I would check the connections at the coils also. I had a ground break right at the coil. The eyelet At the end of the little wire that goes under the coil hold down bolt broke right where the wire goes into the eyelet. Was just barely hanging on. This is all mainly for your charging system. But with the car being old and 140k miles. It's worth a check.

Checking ground location
I can't find the video I wanted, but just search for " how to check ground location on a car"..
Most of them are going to be related to car audio, but it applies to the whole system.
 

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One more thing to think about. You have a 4g wire for power supply to the car, but you have the factory grounds. You are basically choking the flow within the loop. Think of it like this.
Take a large straw. Run water through it. Now add a small straw into the flow. It chokes, the flow slows down and you don't have a proper, efficient water system. Same concept with electricity. If someone tells you that welding leads or something like that. Please don't do it. The strains in the wire are big and not many individual strains of wire. Most people use car audio wire. The stains of wire are very thin and conduct electricity much better and with less resistant. Which equals more current flow within the system. It is important that if you buy 4g that it really is 4g and not mainly insulation around the wire to look like the correct size. Easy check. When you buy your wire, look at the end of it to see if it is wire or just insulation and hardly any wire. If you order online. Make sure that it's a reputable company. The cheap wire is just that. Cheap. Here where I live, I pay about $4-6 per foot. Plus all the copper connectors and heat shrink. There's two types of wire.
Ofc - oxygen free copper
CCA- copper clad aluminum
Ofc is the best, but CCA works also.
But ofc doesn't turn green and corrode light CCA. Plus it conducts electricity much better.
 

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i would assume, the coil packs from O'Reilly's are their "Import Direct" line of coils and sub standard made in China parts. I haven't used Autolite plugs in a 1.8T; NGK were factory install and that is recommended.

A fuel pressure test and new fuel filter; could be something to consider. Coolant temp sensors, that are not reading as they should; can cause a hard start issue, note the info in the above video. I also, noted; my gas cap rubber gasket, was cracked and when I replaced that, my 1.8T started easier, faster.


Overall, evaluation of the basics and checking things, like fuel trims ,can give you a sense of the current tune, how the engine fuel metering is working (confirm your vacuum leaks are ok now, fuel pump is good, maf is good, etc.).


As our 1.8Ts are getting up there in miles and age; every little thing, contributes, to a good or bad running engine. As I have gone through my 1.8T; I found it was a combination of many worn out parts, that was making it not run as it should.
I had to go to the rip-offship to get one for my 2015 beetle 1.8t. no part's store carried one. Yep. I got ripped for $32 for a gas cap.
 

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Start checking out fcpeuro; oem and genuine vw parts with a lifetime warranty!

For your 2.0T: APR and others are making performance coils; which might help, your tuned engine.

Sent from my iPhone using Tapatalk
 

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Discussion Starter · #17 ·
Replaced the coolant sensor and the temp readings are stable now. Starting a new thread as it has a burned up fuse box, suspecting bad radiator fan....
 

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Did you see, any improvement on the start and running issues? A new and correctly working cts; will typically, in crease fuel milage, quicker starting and your fuel trims, will correct, fuel mixture will stop being so rich.

Keep working through things here; lots of good responses, history of what work you have done and you can keep everything in context, thanks.


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Discussion Starter · #19 ·
I'll do a cold start in the AM but I had another related post going with the title now changed to RESOLVED.

The fan switch was bad too, battery voltage was down from her driving it home with the burnt fuse box.

So now with a charged battery, clean wires, new grounds, new fuse box, new temp sensor and new fan switch, yes it is running much better :) Thanks as always for the help.
 

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Discussion Starter · #20 ·
Looks like it was a bad coolant temp sensor. Started it up this am, 54f and she fired right away and went into high idle. It warmed up a bit and came back down as expected.

Cooling fans cycling as required too with the new switch.

Thanks for all the help!
 
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