Months and Months of Engine Issues



2003 VW GTI 1.8t 104,000 Miles

About 5 months ago, I get the engine light with really no other symptoms, bring it in to my mechanic and am told the engine is not warming up properly so temperature sensor is replaced.

Within a day of getting the car back, same thing… they replaced the sensor under warranty.

Within a week the same thing… this time they say there was a misfire code so they replace plugs and wires.

A couple of weeks go by and I get the CEL again but now when I’m at highway speeds and accelerate to pass the car hesitates… I take it in to 2 different places and they both tell me I need a catalytic converter.

A week later, it’s back on again… but this time every once in a while it’ll feel like I lose a cylinder and the CEL will flash for 30 seconds and then I get full power back.

It’s been in twice now for this, both under warranty repair. Once for coils (had engine coils replaced a few years ago) and the latest time, I didn’t speak to the mechanic, but the receipt says “converter”

Well it happened again the next day. So before I bring it in again… I thought I’d check here



bump… this is driving me nuts


I think they are using your “check engine light” to make their boat payments. Is this a dealership? I think you need to find a good, independent mechanic and let them find your “real” problem. This can go on for months and months if you don’t put a stop to it now.


It is an independent mechanic. And many of the times brought in they’ve done the work for free because they’re replacing a part they already put in.

When I had the catalytic converter issue, I brought it to both the dealer and the independent guy to check.


When an engine is not warming up it is ususally a stuck open thermostat!!! That has been the cars since the automobile thermostat was invented. No amount of fooling around with sensors is going to change that. The thermostat opens when the engine coolant temperature reaches the desired level (warm) and then the radiator starts cooling the fluid to keep the engine from overheating.

Your shop is either thoroughly incompetent or dishonest or both. A good independent mechanic who knows Volkswagens can sort out your problem in one visit.


I do not think that is the issue any more or wasn’t in the first place. My temp gauge has always been right on. Never noticed any fluctuations with the engine temp.


If the thermostat is stuck open there will be a problem with warming the engine up and it will not cause overheating.

Take the car by a local AutoZone, Checkers, Advance, or whomever and get it scanned for codes. They will do this for you free and it only takes a minute. Post the codes back for discussion.
Without knowing exactly what those misfire codes were it’s impossible to even guess.

I’m not convinced that you have a problematic car and this could be more a matter of guessing at the causes of the problems.


If by “not warming up” you mean no heat out of the heater or defrosters, that’s another problem altogether. No heat from the heater could be a cloggged ehater core or an air door stuck in the open position.


I’ll be posting the codes later today


But if the thermostat is stuck at say, halfway open, it will take longer than normal to warm the car up, but it will eventually overheat too. I had a thermostat do exactly this.



Plugs, 4 Coils on 8/21/08
Temp Sensor on 12/20/08
temp sensor in dec of '09
Plugs & 1 Ingnition coil on 1/19/10
plugs changed on 3/2/10
Cat Converter on 3/15/10 & 1/19/10


I’m not convined the engine is or was overheating. It it had been, the temp sensor would have been the wrong part to change, the T-stat would be the first on the list of suspects. I have to wonder if they checked the codes too. A bad temp sensor can store a failure code. It’d be in the P015? range.

You’ve had it to two (three?) different shops now that have told you you need a converter. Has any of them checked the oxygen sensor output signals? If they have, and the diagnosis was that you need a converter, than you probably need a converter. While the upstream sensor is the only one that affects the metering, converters can also fail internally in ways that can restrict exhaust flow, and and that can cause power loss as well as a CEL light.

If none of the shops has actually looked at the oxygen sensor signals, you may just need an upstream sensor.

I agree with OK4450 that your first step should be to have the codes read. Post them here.


Codes posted above.


P0301 - Misfire detected, Cylinder 1
P3081 - Engine Temp too Low
P2181 - Cooling system Performance

The questions I have are:

  1. Are these the latest codes, or the codes that they were working from since Dec, 2009?

  2. If these are the codes from Dec, which ones are current?

  3. When was the last coolant flush and fill, with new thermostat and radiator cap?

  4. What brand of plugs did they use on the last change?