Cold engine issues

"Justino6969" (justino6969) 12/08/2016 at 17:24 • Filed to: None

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So I have a 2001 VW Jetta 1.8t 5spd, 200,000 miles. For the past couple months, I’ve been getting some serious cold engine issues. Starts fine, idles fine (at 1000rpm on a cold start like it should), back out of my garage is fine, turn around and go down my driveway is fine, but when I get to the road, the problems start. As soon as I give it some gas and try and accelerate, it bucks and jumps and I go nowhere fast. I can floor it and the boost builds, but there is no acceleration to be found. So I’ll be going down the road at like 10mph, turbo screaming, but holding the same speed, and there there is a loud pop (in the exhaust), and all of the sudden the full boost pedal to the floor kicks in and I go flying. Shift, have full power, but as soon as the clutch catches, back to no power until the exhaust pop and I go flying again. By the time I hit 5th gear, the engine has warmed up a little, all is good the rest of the way to work; no problems whatsoever.

So then when I leave work hours later, start the car, all is well. But then I get to the stop light before turning onto the main road, and the idle calms down, and it makes taking off a pain in the butt. I’ll get moving 20 or so feet, then turn on the road, and now I have no power and am just coasting along, again, turbo screaming, until it decides to pop and tires screeching and shooting off like a rocket.. until I shift again. Once I get to the highway and it’s warmed up for a couple minutes, all is well again for the rest of the drive.

What could it be? My MAF has acted funny in the past so it’s been unplugged for a good 15,000 miles, so that’s probably not it. Plugs replaced maybe 10,000 ago. The clutch slipped for the first time today on the highway, so now that needs replacing, which makes this issue even worse since I have to slip the hell out of it to get going properly with the issues it’s having. Any ideas? Forums are getting me nowhere.

RamblinRover Luxury-Yacht > Justino6969 12/08/2016 at 17:35

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I have nothing helpful to note here, other than to say that sometimes Bosch is German for Lucas.

V12 Jake- Hittin' Switches > Justino6969 12/08/2016 at 17:35

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Do you let it warm up at all before you drive?

Justino6969 > V12 Jake- Hittin' Switches 12/08/2016 at 17:37

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A couple minutes or so.

vicali > Justino6969 12/08/2016 at 17:38

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Tell me more about unplugging the MAF... wouldn’t that mean you are stuck in open loop? So if there was a situation like cold temps that needed different fuel levels your ecu is not ‘seeing’ it and not getting the right mix..?

I was smart once and swiss-cheesed the airbox on my 8v - it was great right up until -40c when the air froze the throttle open as I went down the freeway.. Once I got under the hood and got the throttle back it had the 200-3000k rpm hunt that was a dead givaway for a frozen MAF.

Justino6969 > RamblinRover Luxury-Yacht 12/08/2016 at 17:38

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Oh yes, electrical problems out the ass. I think I currently have 6 lights on on the dash. They have all been there for a while though, before this issue arose, and none are engine related (besides code for the MAF being unplugged).

Highlander-Datsuns are Forever > Justino6969 12/08/2016 at 17:43

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I would put money on your car having a plugged exhaust. I had similar symptoms on my old Isuzu and it was the exhaust. So I spent $500 getting a new exhaust system installed then proceeded to total the truck about 3 weeks later.

Justino6969 > vicali 12/08/2016 at 17:44

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A couple years ago, the car began to die when it reached idle. So stop and go traffic was a pain. I researched some and unplugged the MAF (along with new fuel filter, injector cleaner, stuff like that), and the problems went away. So I eventually bought a new MAF off ebay that turned out to be a dud. I would accelerate, boost would climb until around 2psi, keep accelerating, still 2psi, more gas, still 2psi, more, and then jump to 8psi. So since the MAF had been unplugged for quite a while before, I just left this new one unplugged too. It’s been through 2 winters (this is the 3rd) with the MAF unplugged, so I don’t think cold weather is the issue, also since this problem started when it was much warmer out (like 80 degrees plus sitting in the sun when I start the car). So maybe it’s been unplugged for more than 15,000, but it’s been a long time.

Justino6969 > Highlander-Datsuns are Forever 12/08/2016 at 17:45

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Is there any way to test this that I can do at home? Poor college student means no money, especially with new clutch coming up.

Highlander-Datsuns are Forever > Justino6969 12/08/2016 at 17:46

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Yes, just have some one rev it up and hold your hand over the end of the exhaust pipe. See if it’s flowing well. If you totally plug it the car should die.

Justino6969 > Highlander-Datsuns are Forever 12/08/2016 at 17:50

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It idles and revs fine, just accelerating in gear until it warms up makes it chug like crazy. I can see the exhaust gasses coming out now that it’s cold enough out, and they increase with application of the gas pedal, so I don’t think it’s plugged. I’ll have to double check, but thanks for the suggestion.

Kaputnik > Justino6969 12/08/2016 at 17:50

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Could need a carbon cleaning. The veeedubs are known for cold start misfires when enough carbon builds up around the valves though honestly I don’t have enough experience to say whether or not your other power related symptoms could be the cause. Also any DTCs would be helpful in diag

Justino6969 > Kaputnik 12/08/2016 at 17:52

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Only code thrown is for the MAF, since it’s unplugged.

V8Demon - Prefers Autos for drag racing. Fite me! > Justino6969 12/08/2016 at 18:06

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Well, there’s your problem. Once it’s warm it’s going to stored values in place of reading the MAF. It’s TRYING to go from open loop to closed loop, does wonky things and goes into a backup mode. You’re gonna notice it a bit more in colder weather. If it’s anything like most other MAF cars, it’s gonna wanna make the open to closed loop switch when it see’s a certain engine temp and/or a certain HEGO temp.

Why is the MAF unplugged????

TahoeSTi > Justino6969 12/08/2016 at 18:16

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Could you have a clogged Cat? It might flow enough when cold then heat up and clog up.

TahoeSTi > Justino6969 12/08/2016 at 18:17

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WHY is you MAF unplugged?

TheTurbochargedSquirrel > Justino6969 12/08/2016 at 18:30

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I would bet it’s that unplugged MAF. Without it the engine has no idea how much air it is getting in and has to make stuff up as it goes along, resulting in wonky behavior, especially as the intake temperature changes. You wouldn’t really notice it when it is warm as there will be failsafe procedures for the ECU to fall back on.

Phatboyphil > Justino6969 12/08/2016 at 18:33

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I’d think something emissions related. like a stuck EGR valve.

V8Demon - Prefers Autos for drag racing. Fite me! > Justino6969 12/08/2016 at 18:57

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Things you don’t buy from no name companies on ebay:

1. MAF

2. Turbo kits

Seriously, buy a factory MAF. Only go with a reputable aftermarket one if you’e for some reason modified the car to the point where it’s needed.

Justino6969 > TahoeSTi 12/08/2016 at 18:58

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The only thing is, as soon as I’ve been driving for a few minutes it’s fine. So it’s only an issue when I first start driving.

Justino6969 > V8Demon - Prefers Autos for drag racing. Fite me! 12/08/2016 at 19:01

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Car was dying at idle, forum research led me to bad MAF. Unplugging it resolved the issues. Replaced the MAF and the new one made the boost like an On/Off switch; either idle, press gas and get 2psi, more gas still 2psi, more gas still 2psi, more gas now 8psi. Go back to unplugged and it’s fine. It’s been unplugged through 2 winters so far, so cold temps are (probably) not an issue. Didn’t feel like spending another $150 for another MAF that may or may not resolve it.

Justino6969 > TahoeSTi 12/08/2016 at 19:01

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Car was dying at idle, forum research led me to bad MAF. Unplugging it resolved the issues. Replaced the MAF and the new one made the boost like an On/Off switch; either idle, press gas and get 2psi, more gas still 2psi, more gas still 2psi, more gas now 8psi. Go back to unplugged and it’s fine. It’s been unplugged through 2 winters so far, so cold temps are (probably) not an issue. Didn’t feel like spending another $150 for another MAF that may or may not resolve it.

V8Demon - Prefers Autos for drag racing. Fite me! > Justino6969 12/08/2016 at 19:02

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I think I currently have 6 lights on on the dash. They have all been there for a while though, before this issue arose, and none are engine related (besides code for the MAF being unplugged).

I think it’s time to step back and evaluate the situation.

What are all the other lights on for?

Perhaps it’s time to park the car for a bit and fix everything PROPERLY.

Justino6969 > TheTurbochargedSquirrel 12/08/2016 at 19:02

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Same behavior a few months ago when it was nearing 90 degrees out. MAF has been unplugged through 2 winters so far, this being the 3rd. This issue is new as of this summer/autumn.

Justino6969 > V8Demon - Prefers Autos for drag racing. Fite me! 12/08/2016 at 19:03

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It was a Bosch MAF.

V8Demon - Prefers Autos for drag racing. Fite me! > Justino6969 12/08/2016 at 19:05

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No MAF isn’t helping. Certain parts you spend the extra coin for at an actual store for this very reason. You may in fact have another issue that has just popped up. Gonna be a bitch to troubleshoot with OTHER known issues getting in the way and not rectifying THOSE first.

V8Demon - Prefers Autos for drag racing. Fite me! > Justino6969 12/08/2016 at 19:06

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...and?

I’ve had cars with 30 year old Bosch injectors that are perfect....

TahoeSTi > Justino6969 12/08/2016 at 19:06

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You could test the signal from the MAF with a Multimeter and see if it’s reading out side the correct range. The other thing to look at is the Ignition Coil. I’ve had them crack on a MkIII Jetta before and when it rained teh car would just die, and when it warmed up it would drive funking , but cold and dry it was fine.

Justino6969 > V8Demon - Prefers Autos for drag racing. Fite me! 12/08/2016 at 19:09

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They’re all for various sensors. Brake pad light for brake pads that don’t have a sensor, windshield washer fluid light for the fluid level sensor even though the tank is full, CEL for MAF, and ABS, Traction Control, and Brake lights because of an ABS sensor going wonky.

It’s a 200,000 mile MK4. It’s worth approximately nothing and there is no point in sinking money into it, especially for things that do not effect the usability of the vehicle.

Manwich - now Keto-Friendly > Justino6969 12/08/2016 at 19:09

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That tells me your car has/had at least TWO problems... the MAF and then something else... like maybe O2 sensors that need replacing.

I suggest hooking up the MAF, clearing the codes and then see what codes you get.

Justino6969 > V8Demon - Prefers Autos for drag racing. Fite me! 12/08/2016 at 19:10

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“...and?”

...and I didn’t buy it from a no name company on eBay. It is a factory MAF.

V8Demon - Prefers Autos for drag racing. Fite me! > Justino6969 12/08/2016 at 19:11

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Have you gone past the time frame where you can return it?

Justino6969 > TahoeSTi 12/08/2016 at 19:11

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No issues in the rain, no issues when warm. And I mean “warm” as in after I’ve been moving for about 60 seconds, all is well.

Justino6969 > V8Demon - Prefers Autos for drag racing. Fite me! 12/08/2016 at 19:12

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Yes, especially so now.

Justino6969 > Manwich - now Keto-Friendly 12/08/2016 at 19:15

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O2 sensors replaced relatively recently. I’ll have to try codes again; last time I just got random misfire codes stemming from the issue at hand.

V8Demon - Prefers Autos for drag racing. Fite me! > Justino6969 12/08/2016 at 19:20

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Know anyone else local with a VW that has the same MAF? Swap it in, see if it does in fact work. If so, sell it.

As far as all that other stuff, might be worth poking around a salvage yard.

gmporschenut also a fan of hondas > Justino6969 12/08/2016 at 19:32

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was it from bosch or nigerianprince123. There are loads of shitty knock offs on ebay.

Justino6969 > gmporschenut also a fan of hondas 12/08/2016 at 19:38

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I don’t remember who it was from; but they were a VW/Audi part re-seller. It came in an official (looking) Bosch box.

gmporschenut also a fan of hondas > Justino6969 12/08/2016 at 19:49

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Loud pop and then flying is most likely unburned fuel entering the exhaust.

With the MAF unplugged your fuel air mix will be all kinds of messed up. I had mine go in the middle of running errands and had to limp home. The default of the engine may be for when the engine is relatively cold (intentionally running rich), thus as it warms up starts acting erratic (too much fuel) as the computer doesn’t know how much fuel to spray thus acting erratic until rpms increase to a point they all burn off.

A second alternative would be a head temp sensor. It could be thinking its cold and then staying in cold mode even after it is warm (spraying extra fuel) until finally another sensor overrides the first. Or the head temp thinking it is hot when it isn’t

“The Engine Coolant Temperature (ECT) sensor is mounted in the water outlet on the back side of the head. If you vehicle still has a original VW part it will be black in color with a four terminal connector. This device signals the engine management system with the current coolant temperature, the ECU takes this information and uses it to control other such circuits as the idle speed, knock control system, oxygen sensor circuit, exhaust gas recalculation, and fuel tank venting. It is also important to note that if at any time ECU does not receive a signal from the ECT it will substitute a value of 176°F (80°C).”

http://www.autozone.com/repairguides/Volkswagen-Golf-Jetta-Cabriole-1990-1999/Electronic-Engine-Controls/Coolant-Temperature-Sensor/_/P-0900c15280267c3a

Two things I would check.

1. plug MFA back in

2. check condition of head temp sensor with an ohm-meter

2. replace MFA or head temp sensor if needed.

Manwich - now Keto-Friendly > Justino6969 12/08/2016 at 19:52

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“Poor college student means no money, especially with new clutch coming up.”

An old VW Jetta with the 1.8T engine is the WRONG car to have as a poor student.

I suggest you stop spending money on that Jetta and instead (before your Jetta dies or the clutch goes completely), look at getting something that has a proven track record of being cheap/basic/reliable... like an old Toyota Tercel/Echo/Yaris/Corolla. You can get ones that are decent enough for under $2000.

A 3 cyl Pontiac/Chevy/Geo/Suzuki Firefly/Metro/Forsa/Swift with the manual transmission would do the job as well... only they’re harder to find in decent condition.

Manwich - now Keto-Friendly > Justino6969 12/08/2016 at 19:59

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Now that you mentioned all that, I’m now 100% sure what the solution is to your problem is:

Of course this solution is what you do after you get a car to replace the Jetta...

Justino6969 > gmporschenut also a fan of hondas 12/08/2016 at 20:00

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Thanks for the reply. That guide is for a Mk3 Jetta, but I’m sure it’s similar for a MK4. I’ll have to take a multimeter to it.

Justino6969 > Manwich - now Keto-Friendly 12/08/2016 at 20:02

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I mean, I did recently get a Jeep.. I always planned on keeping the Jetta till I get a new car, and then putting a manual boost controller on it and increasing it 1psi a day until something blows.

gmporschenut also a fan of hondas > Justino6969 12/08/2016 at 20:26

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principle should be the same. I’ve had similar issues on multiple cars over the years.

Manwich - now Keto-Friendly > Justino6969 12/08/2016 at 23:03

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Well since you have another vehicle, it sounds to me like you can start increasing the boost every day starting today.

Then once it blows, donate it to the hydraulic press channel!

Justino6969 > Manwich - now Keto-Friendly 12/09/2016 at 23:13

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I also have a 1996 Cherokee, so no worries if I ever have to park it for something serious. The Jetta has seen me through over 100,000 miles since I bought it, and has never had an issue until now, and after a minute or so driving it’s perfectly fine again. Not undriveable, just a slight annoyance that I don’t know the resolution to, so I thought I would ask Oppo. MK4s get a bad rap, but this one has been amazing.