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1999 Beetle Turbo in Limp Mode Help Please

2572 Views 9 Replies 2 Participants Last post by  billymade
Hello everyone.
Can anyone figure out what's going on with my 1999 beetle 1.8t Turbo 5spd?
First of, the car has just shy of 150,000 miles on it. I bought it used for 2600 bucks and I run it like I paid 2600 buck for it. lol. As far as I can tell the car has no mods on it other then the boost gauge I installed.

The problem,
The car ran fine for the first 15000 miles I put on it. (Hard miles I might add.) The car built about 10 lbs of boost consistently. A few weeks ago (About 5 min into my drive to work) it went into limp mode and only builds about 3 to 5 lbs of boost. When I turn the car off it gets out of limp mode and builds full boost...until I punch the gas hard, then it drops back into limp mode. Sometimes when coming to a stop and downshifting the rpm's will drop and the car stalls. This cycle has been going on since. You get one good pull then it drops back into limp mode.

What I have tried so far.
The first thing I did was hook up the Code reader to read the codes. (Lots of codes..apparently someone before me figured out how to make the check engine lite never come up..kind of a good trick) So.. I erased all the codes and drove the car. That way when it went into limp mode I could see exactly what the code was.
Sure enough it dropped right back into limp mode. I did this two or three times and I keep getting the same codes.

P118/Manufacture Control Fuel Air Metering
P1198/Manufacture Control Fuel Air Metering
P0140/ 02 Sensor /No activity
P0139/ 02 Sensor /slow response
P0411 / secondary Air injection System Incorrect flow

From what I have read the P0411 should not effect the performance so I didn't do anything about that.
I did replace the hose to the boost gauge with a better on just to make sure it wasn't leaking pressure there. I checked the rest of the engine and intercooler tubing and nothing seamed dry rotted or leaking. (I could have of course missed something but everything looked and felt much better then I thought it would have)

I erased the codes and drove some more. Same problems and same codes.
Last night I changed out the o2 sensor (The one before the cat that's expensive and had to change lol) (What I have read said the o2 sensor before the cat is the one the computer uses and the one after the cat is the one the EPA cares about (and me not so much) Then I cleared the codes with the reader and took it for a spin. Same problems.
Now it only throws two codes
P118/Manufacture Control Fuel Air Metering
P1198/Manufacture Control Fuel Air Metering
The boost holds very steady at 5 lbs now.
Does anyone have an idea where I might look next?
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The links/codes below are for: 02 sensor bank1/sensor2: sensor AFTER the cat, so that needs to be tested or replaced. Based upon the codes; you posted and the links below, you replaced the wrong sensor bank1/senor1, 02 sensor before the cat: I am not seeing you post any trouble codes; related to that sensor.

17606 - Ross-Tech Wiki



This came up with P0118; not P118, don't know if its the same thing. If it is; it would indicate the temp sensor or wring is bad, they are cheap.... replace it. When my sensor has failed; it usually, causes a hard start, rough idle until warm and a rich fuel condition... black residue at the tail pipe.

P0118 - Engine Coolant Temperature Circuit High Input OBD-II Trouble Code Technical Description Engine Coolant Temperature Circuit High Input What does that mean? The engine coolant temperature (ECT) sensor is a thermistor screwed into a coolant passage in the cylinder head. Sensor resistance is high when coolant temperature is low and resistance drops when coolant temperature increases. The powertrain control module (PCM) provides a 5 volt reference and a ground to the sensor. The PCM monitors voltage drop to determine coolant temperature. If the ECT reads less than freezing temp. when engine has been running for more than a few minutes, the PCM determines a circuit fault and sets this code. Or if the PCM determines the sensor resistance is out of specs, this code is set. Potential Symptoms Symptoms of a P0118 could include: Very poor fuel economy A no start condition Vehicle may start, but run very poorly, blowing black smoke, running very rough and misfiring Illumination of MIL Causes A code P0118 may mean that one or more of the following has happened: A bad connection at the sensor An open in the ground circuit between the ECT sensor and the PCM A short in the voltage feed between the sensor and the PCM A bad PCM (less likely) A bad temperature sensor (shorted internally) Possible Solutions First, if you have access to a scan tool, check the reading of the coolant sensor. Does it read a logical number? If so, the problem is likely intermittent. Perform a "wiggle" test by wiggling the connector and harness to the sensor while watching the reading on the scan tool. Watch for any drop-outs. Drop-outs would indicate a bad connection. If the scan tool reads an illogical temperature, check the resistance of the temperature sensor. If it is out of specs, replace it. If it is in specifications, unplug the sensor and, using a fused jumper wire, jumper the two terminals of the connector together. The temperature reading should now be maxed out to above 250 degrees F. If not, there is likely a problem with the ground circuit or voltage supply. Check for 5 volts reference voltage at the connector. Also check for ground presence at the connector. If you do not have 5V ref. and/or ground continuity, check for these back at the PCM connector. If you have these at the PCM connector, then repair open or short between the PCM and the sensor. If you do not, remove the offending wire from the PCM and then check for proper voltage at the PCM pin. If it's present now, repair short on the circuit. If it isn't present after removing the wire and checking the pin, replace PCM NOTE: Usually, P0118 is indicative of a bad temperature sensor, but doesn't rule out these other possibilities. If you're unsure of how to diagnose a PCM, do not attempt.

Read more at: OBD-II Trouble Code: P0118 Engine Coolant Temperature Circuit High Input
Copyright © OBD-Codes.com

Both the 02 sensor and temp sensor; are definitely used by the ecm to adjust the car to run right, so I would fix those first and see how things are improved. From what i understand; "limp mode", to protect the engine from getting damaged, so maybe with your 02 sensors failed and the temp sensor failed, it didn't have enough info to adjust things correctly and went into the limp mode, to protect the car? Just theorizing and talking out loud... test/fix/replace/repair the above two issues and get back with us, on how things are going.

When replacing the 02 sensor; be SURE to get high quality oem parts, not junk from your typical auto parts store. I went with BOSCH; as that was what came in the Volkswagen's from the factory; you can look up your correct 02 sensor here (get the "oem" version not the "universal" one and it will be identical, to the one you remove). Cheap parts; can cause more problems and make your troubleshooting even more of a challenge.

BOSCH AUTO PARTS FINDER: (be sure to get the right parts: based on VIN# and correct engine code)


Lastly, info about the SAI issues: (typically, hose leaks, sai pump failure or combi valve stuck/failed)


PS: when i replaced my bank1/sensor2 02 sensor; I had to do a "hard reset", for the trouble code, to finally go away.
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Thanks for the information Billymade. I did replace the 02 sensor with Bosh factory OEM. (Don't tell my wife, it was pricey). I will change the other (cheeper) 02 sensor, check the coolant temp sensor then get back to you guys. When you say "Hard reset" you mean taking the terminals off the batter and grounding then to each other...correct? Thanks again for the info.
Yes, for 30 seconds or so and then install them back on the battery.

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So, car is still in limp mode and still throws the two codes it did before. (P1118/Manufacture Control Fuel Air Metering
P1198/Manufacture Control Fuel Air Metering).
When I first start out it spools a solid 10 psi..then after about 10 min (or one good hard WOT) it kicks back into limp mode. If I turn the key off for a sec while I am driving then turn it back on I get full boost for a bit till I hit it hard again, then back into lips mode. I can do this cycle as many times as I want but it's just a work around and very annoying.
Someone suggested I change the 02 sensor down from the catalytic converter. (Does this sensor have anything to do with the turbo?) I thought it just tested the efficiency of the converter.
I did the battery terminal trick to hard reset the computer....no help, car still acted the same.
Anyone know what those codes mean, or have any advice what my next move should be? Any help would be most appreciated.

So based on the codes you have; there are two problems: 1. the coolant temperature sensor 2. O2 sensor bank1/sensor2: 02 sensor after the cat.

Have you tested or diagnosed either of these sensors?

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Update. So I fixed both 02 sensors. (Changed them out). Erased all the codes, then did a hard reboot on the computer. The car still goes into limp mode just like it did before. The only difference is now the car isn't throwing any codes at all. When I hook up the scanner I get a big "all systems passed".
Anyone have an idea why I am still in limp mode?
What brand and model of scanner are you using does it have any live data capability?

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Big orange scanner (scantron or something like that.) I got from auto zone a long time ago. It will give you the real time readings though. You have an idea of something I should look for?
A thought that accrued to me, is it possible that the diverter valve is going out and causing the issue? Car does have 150,000 on it and as far as i know that valve is original.
I was wondering what your fuel trim reading are: (maf or vacuum leaks)

Fuel Trim Info - Ross-Tech Wiki

Read these links for info about my DV issues and testing procedures, what worked for me:


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