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84 Volkswagen Jetta (1.8L engine) with 237,000 on it

The word performance should never leave your lips when you are talking about this car. With that kind of mileage, if you abuse this engine in any way you are going to end up with nothing but a big boat anchor with no engine. You may get a few more miles if you baby it and maintain it well but if you beat on it, it's going to die.

I think I know someone that has a compression checker, I will see if I can borrow it and check.

Also, a piece of metal is a piece of metal, in my opinion. I don't think that just because an engine has provided enough energy to travel 237k miles means that it is a baby. However if the cylinder walls are oval, then yea... Let's stick with the compression check and then go from there.

Also, I have a friend that own a junkyard with a few more of the same engine. If this engine goes boom, I've got another one :) although that doesn't sound like fun :(

I should mention that I am more interested in efficiency than performance.

All the bearings in that engine have 237K on them and there can't be much left. The oil pump has done more work than it's designed to and you can say that engine is on borrowed time from here on.

Whole car is 30 years old - every last moving anything. Plastics and rubber things all over go brittle, springs, seating hinges latches even wiring insulation and connections and so on. Point is it's not just a brick of metal, T

Fair enough. And now that you mention it, my friend did give me this car for free because it had broke down, the problem being that the ground for the ignition module had come off of the battery. But I can repair and replace wires as they go. Reliability isn't a big deal anyways, since I rarely go more than 5 miles from my house, and I'm not afraid to try to fix it on the side of the road.

Still trying to get access to a compression checker...

Compression tester:
/
In stock item almost anywhere! Probably rentable but only about $25 bucks.


Totally not adverse to older vehicles. Just know to go thru check and fix certain things pro-actively or declare one not practical any more for the time it would take or raw expense of parts to make one legally useful for public roads,


T

FINALLY GOT A COMPRESSION TESTER!
Like a month later I know :)
Someone I know owns a mechanic shop and he loaned me his. He warned me that it was damaged but usable. Without anything connected it 0'd at 25 psi. So I think the readings are at least 25 psi higher than real. It also didn't hold the pressure, so I had someone crank it while I recorded the peak value. The values I recorded are:
1. 177 psi +-3
2. 177 psi +-3
3. 177 psi +-3
4. 177 psi +-3
They were all darn close so I just rounded to the same number. They were all between 175 and 180 though.
Because the meter 0'd at 25 psi and because it is well used, I think subtracting 30 psi from each would get us a more accurate number.
I interpret the data as all cylinders with 147 psi +-8.

From what I have read that is a good psi and so I shouldn't have any compression-related issues, although I am open to other opinions. So, what can I do that is relatively easy and relatively cheap that would help the engine run better. I am already working on the fuel system. I know it is running lean, and I have ordered a new oxygen sensor/injector O rings/fuel filter and I will set the combustion ratio when they come. What else?

You really are looking for them all to be close to each other, 4th bounce up while cranking and it locks that pressure as cylinder would leak down. Then small squirt of oil to see the difference that makes especially if one is off from another and so on.


Accuracy of the actual PSI# I wouldn't be way too worried about. A real nice gauge would have a screw to set to zero.


You can also get a good clue from a vacuum gauge on crude mechanical engine wear - all this to know what you are dealing with.


You mentioned you seek "efficiency" and it's prior long run at a time use is naturally going to do better than short runs not even warmed up.


Think: World's largest cruise ship and most fuel efficient moped are both getting ZERO MPGs sitting still and it goes from there. Just make it to run as well as possible and you are there and there are no magic tricks short of pushing it or towing it to alter efficiency much.


It's sarcastic but just make all your trips downhill with a tailwind roundtrip helps


T

All of the PSI values I measured were very close. Also, the gauge I was using leakes and you have to be watching it while you crank.

Anyways, after I measured all of the PSI values on Monday, I put the spark plugs back on and parked it. The next day I noticed that something was wrong. When I rev the engine it sounded like 1 or 2 of the cylinders wasn't firing right or at all. And when you give it some fuel to accelerate, there seemed to be a 1-2 second delay before I got most of the acceleration force. For example, I shift into 3rd and give it some fuel. It slowly accelerates for 2 seconds, and then I can feel a small jerk as it starts to accelerate much more quickly. Let go of the fuel and shift to 4th, and this happens again. In addition, I have killed the engine several times lately because it doesn't have the power it used to have.

On Tuesday I thought, "No big deal. I probably forgot to plug a spark plug wire in or messed up the gap." Well today I pulled my plugs, cleaned them, checked the gap, and re-tested the compression. The #2 plug was very black like it was running very rich. I didn't pay much attention to the plugs on Monday, but I don't think it was that black. As for the compression:
1. 150 PSI!!!!!!!!! This was 180 on Monday, what happened?!
2. 180 PSI
3. 180 PSI
4. 176 PSI
#1 cylinder with a cap of oil in it: 160 PSI
FYI firing order is 1-3-4-2
Ok, my car was running well on Monday, and now it sounds and runs like a trash can. What could have messed the #1 cylinder up so much? What should I check? What should I do?
The guy that loaned my the compression tester gave 2 suggestions. He said he thought it was running rich (I'm still planning on tuning the f/a ratio, but I thought it was running lean), and the valve springs. I believe he owns a mechanic shop, but I didn't give him as much description as I have given you.

Video of the issues my car is having:

Those steps you posted are almost exactly what I did. I feel fairly confident that the PSI values I got both times are fairly accurate. I had double checked #1 cylinder on Monday, and I triple checked it today, with consistent results. Right now I'm not so concerned about cylinder #2 because I am about to redo f/a ratio anyways. But what should I do about cylinder #1?

I plain don't know what you mean by adjusting air to fuel ratio on this or if so if you can target ONE cylinder.


If #1 is really off it will effect the overall show. At TDC on that one apply pressure and see where it leaks. Let's rule out plain wear on this thing.


If you can see if wires will fit another and the problem follows checking misfiring at a cylinder or cancel them one at a time to focus in better. RPM if just one will stay the same if one is dead and canceling that one doesn't change anything. A good one on a 4 cylinder with one bad cylinder would stall out no doubt.


* If cancelling a cylinder by taking off plug wire ground it as if just left hanging that spark might seek other routes confusing that test. This is crude basic testing. Any wires and plugs don't like being fussed with, dropped, pulled wrong or even good stuff will be harmed messing up diagnosing.


Keep trying and keep the investment low IMO. Rent, borrow and swap known good things within that car to a known bad and follow is cheaper than tossing all for a maybe on things.


For finding random or one cylinder not behaving without wild tools you can feel the pulse at tail pipe and usually tell just don't burn yourself please, use a rag if you do that.


I don't think converter is the issue on this for just this right now.


For whenever or soon if still not nailing it, a vacuum gauge test can be informative also. Takes stuff/tools even for the most basic things,


T


#1 compression funky and #2 with fuel fouling apparently

Someone please reply to this and say "random" because I got into my car to pick up the compression gauge again, and it was running great again! All I did was take the #2 fuel injector out and put it back in... Anyways, on further inspection, it seems than #2 is firing normally again. I was hoping that #1 also was up to 180 PSI, but it was not, still at 150 PSI. After that, I hooked up the 1-way valve-less adapter to the cylinder, and my compressor to the adapter. After establishing that anything over 40 PSI was enough to turn the engine until it hit an intake or exhaust stroke even when in 5th gear, I discovered that it seemed that the air was leaking into the cam-case. (I don't know if that is the technical term) When I took off the oil lid thing, which is directly above the cam and above #1, I can hear a rather strong hiss, and I think I can feel some air come out.

I could be wrong, but I think there is a leak on the top of the #1 combustion chamber. There are 2 reasons I think this: the above mentioned compressor test, and the fact that putting oil in the cylinder did not have a significant affect on the compression PSI. I also don't think it is the valves because I couldn't hear or feel air comping out of the intake or exhaust. What part of the engine would allow pressure to leak out of the top of the combustion chamber? What other things should I try?

Ok, I feel like I am on a wild goose chase. Checked the compression again:
1. 176
2. 177
3. 175
4. 178

Also, I put the compressor to all 4 of the cylinders, and they all made the same mild hissing sound coming out of the oil pour hole. So maybe the head gasket is a bit worn? I'm just guessing here, you guys are the pros. I have a spring break coming up and I wouldn't mind getting in over my head in an engine repair like a head gasket. But would it help? Or am I just crazy?

OK: Oil test remains unproven. Guess to be verified is that #1 needs better leak-down test but might be intermittent which is troublesome by itself but a gasket could allow it's compression into no useful place in cylinder #2 throwing off proper firing and complicating even that one getting correct useable spark, fouled plug from fuel or if metal shaving ground out plug that ends that. Consider cylinder wash and more.


High miles for this engine let alone age. May need to pull head to get a good look to see it this engine is even worth your time!


T

Ok what I am thinking is I can pull off the head and do a partial overhaul. Clean the cylinders, replace head gasket and header gaskets, valve gasket, replace the valve springs if then need it, clean up valves and camshaft, ultrasonic clean anything that fits in my little ultrasonic cleaner, and put it all back together. Would that be worth my time? Is that way over my skill level? Can I get a time estimate, cost estimate, steps and some advice?

As a side note, I decided it was time to patch some exhaust leaks, and it quickly escalated to my exhaust getting cut right behind the cat. I'm planning on bypassing the cat, cleaning the exhaust pipe, and patching the holes, but it sure is fun to drive without a muffler. I knew it was going to be loud, but it is louder than I expected. There is a kid at my school that probably has $50K into his truck, probably several thousand just in his exhaust, loves blowing black smoke clouds. Anyways, I was passing him opposite direction and I pushed the clutch in and revved it, and his jaw dropped. It was awesome. Especially the fact that I have put less than $150 into my car, $110 of that was the stereo, and the car itself was free.

I know I am going to have to put the muffler back on if i don't want to get tickets, but it is sure fun to drive without it.

Anyways I would like several opinions on if the partial overhaul I proposed would be practical.

I'm planning on bypassing the cat,

You do realize that is against Federal law and carries a fine up to $25,000?

I meant remove the cat. Yea I know it's illegal, but my dad has been running his car without the cat for over 10 years. In addition, vehicles over 25 years are exempt from emission testing, and where I live doesn't do emission testing anyways. In more addition, this cat is over 30 years old, has been through rich and lean. Do you think there is anything left?

I would be surprised if the cat is still functional at all. Just in the time I have had it, I had 1 cylinder that wasn't firing, sending a ton of unburned fuel to the cat. If it is not doing anything, and if I am not going to get caught for it, then I see no reason to leave it on. Do you?

None of that changes the fact that it is illegal to remove it without replacing it with a new one. I doubt you will find a shop willing to do that.

:) you don't know me. Half of my friends are in automated manufacturing. Plasma lasers, lasers, welders, grinders, metal benders, cnc machines, all manned by a bunch of teenagers. I know a shop that will do it for me. How do you think I took my muffler off anyways?

Also, I would really appreciate if we can get away from the morality of removing my cat and get back onto how feasible it is for me to pull the head off. Thanks.

I think you pulling off the head is feasible. I think you having a running engine when you are done is not.

You shouldn't be pulling anything apart until you have absolutely isolated your problem, unless your into that sort of thing. Compression numbers look fine. You can also do a dynamic compression test on that cylinder you believe it having an issue to see if you have an engine breathing problem. A static compression test won't tell you if the exhaust valve isn't opening.

Haven't played around with any K jet fuel systems that one has, but it does have an O2 sensor. You could scew a back pressure gauge in place of the O2 sensor and measure that amount of back pressure in the exhaust before the cat to see if you have an excessive amount of restriction going on. That would save you the time and expense of removing the exhaust system.

Is this vehicle going to be your daily driver or are you wanting to turn it into a race car?

Daily driver race car that gets great mpg, of course!

But really, if you haven't got the contest clues, I'm 17 in high school. My high school is acrossed the street, so if my car dies it really isn't a big deal. I am currently very interested in working on my car. Spring break is next week, which would be a great time to take the head off. From what I understand, what that would entail is the following:
1. Take timing chain cover off (I think it is a chain)
2. Take timing chain off, take note of timing positions so it can be put back on properly.
3. Take valve cover off.
4. Probably some bolts and bearings holding the cam. Remove them.
5. Remove the cam.
6. Remove exhaust and intake manifolds.
7. Find head bolts and remove them.
8. Remove the head?
9. Clean all parts thoroughly.
10. Reassemble in opposite order, putting gaskets where necessary.
11. Fresh oil?
How close am I? Obviously each step is fairly large, but taking them 1 at a time can't be too hard, right?

Anyways Discretesignals , I have already used a recip saw right behind the cat, and it would take about as much time to measure back pressure as it would to simply remove the cat.

Also, this isn't the first engineering I have done. As a one man team, I went to nationals for robotics, and ranked in the upper half. I know how to build and maintain efficient mechanical things.

As for a dynamic compression test, I don't think I have any of the tools that would require. I don't know where I would find the tester, and I don't plan on buying one.

What do you guys think I should do?

Quote"How close am I? Obviously each step is fairly large, but taking them 1 at a time can't be too hard, right?"


You don't even own a compression tester or able to borrow one that I believe yet and going to take on this? Trust me, it will be a learning experience but will never run again, even poorly.

You have to do your diagnosing before tearing into it. At best if you did a perfect job, sent head out and all fine the lower end could give up fast.

This could have cracked magor parts you can't see at all without some tests.

Soooooo, you've got essentially no investment in the thing and unless somehow this car is in exceptional shape in all other aspects just part it out before you lose your shirt. It's worth something as just metal by weight,

T

You have a point. I don't plan on parting out my car. As far as metal weight, this thing is one of the lighter cars on the road. I think it is under 2K lbs.

Besides that the head, what other fun mods could I do to it? I was reading about water injection, which sounded interesting.

Water injection now! Did someone lace something you ate?


You lost about $100 for a junk converter already as even dead ones are good for the metals they use. Rest of car call local salvage for what they would pay for whole vehicle delivered or if they pick it up.


A couple ways you could make some bucks would be to find a good party for St. Patrick's Day, paint some shamrocks all over it and get a baseball bat and charge $5 buck a whack at it for the fun of it.


Do what you want but you clearly are NOT in any position to make this a decent running car from the read of this thread.


It's your $$ but I'd start off the learning thing with something that at least runs well right away and work on details not something that is quite this hopeless - your call,


T

The car is running pretty well right now. I just would like to make it run better.

General rule of thumb is don't modify your daily driver. If your daily driver was running bad and had problems, you would have to diagnose and repair those problems. If this is something you drive to school or work everyday, you don't want to play around with modifying and racing it because you depend on it.

Majority of people that own race cars also have daily drivers that are bone stock and reliable. You really can't have both in one, unless you have lots of money laying around and not too concerned about breaking down or breaking things.

Being young and wanting to go fast is a normal thing for a teenager to dream about, especially with all the Fast and Furious related movies around. The reality is as you get older you start to realize things aren't cheap and your constantly paying bills, trying saving money, and working you hind off to make things meet.

I'm not trying to be a parental figure, but giving you the realities of life.

Although it is my daily driver, I can easily do without it, and that is why I am not afraid of taking a chance with it. My high school is acrossed the street, and the tech center (part of school) is like 1/4 mile away. I do have a bike.

I also try to be very conservative with my limited funds, and have never watch Fast and Furious movies. I just like building things.

So what are some fun mods I could do to the engine? Preferable low cost and low risk ones.

I just took a flash light to my cat, and it is COMPLETELY HOLLOW. No honeycomb structure AT ALL. It is simple a large hollow black area. I was hoping to get performance improvements... Do you still think removing it will help?

First thing you should do is run a compression check on it. Make sure the battery is fully charged, the ignition and fuel systems are disabled, and the throttle is wide open when you perform your compression test. Write down the numbers for all cylinders. Post them in here, so we can see what your dealing with.

If the engine is tired, messing around with the other things is a waste of time.

I won't be able to follow this up with you but at a minimum find out what the heck it is. Uncertain of model year, engine size of perhaps four possible, whether it's fuel injected or not and a distributor pulled out and who knows why for now. Distributor type will matter whether it's an automatic or standard.

It cranks when key released or you seem to think so. Spark testing and how you determined no spark questionable.

For the moment at least see if rotor turns in distributor with cranking. The initial problem and still now could be ignition switch itself. 30 year old or so with some miles up there despite low per year is still up there IMO.

Find out exactly what this is at least,

T

Should be a 1.7L. I agree with Tom that you should make sure the rotor rotates when you crank the engine. If it doesn't, you won't have any spark.

Another thing is that when you test a coil using that type of test, it might not produce enough spark because your cut off time isn't fast enough. Your cut off time has to be under 30 microseconds. You need to do a bypass test at the igniter and the spark has to at least be able to jump a 3/4 inch gap. If you have a scope and know how to use it, you have an ace in the hole.

More info incoming.
Its an 84
I think its a 1.8L (The cylinder head is 026 103 373h)
I'm almost certain it is fuel injected.

The distributor has been removed and is going to need re-timed or whatever you call it when it is put back in. I'm fairly sure the rotor would rotate if the distributor was in the engine.

My coil testing showed that the coil DID produce a spark. The spark didn't jump very far at all, but that is probebly because I had a high cut off time? However, the coil isn't getting a signal. When the ignition is turned on, the coil gets 12V
The distributor is getting battery voltage on on 3 of the wires. I think this is an issue. (It's supposed to have + , ground, and signal, right?)

I got another ICU, it isn't identical but it has the same plug. It also isn't know good, it could be bad. It has the same voltage on the distributor wires as the original one. If the ICU is bad, I saw a really good deal on one that I would like to order ASAP if a new one is needed.

I tested the distributor by connecting 12V and ground to the respective pins, and monitoring voltage on the signal wire. As i turned the distributor I got a signal ranging from 0V to 1.5V. I THINK it is ok.

I have also manually grounded the signal wire for the distributor when the distributor was off, and the voltage on the coil stayed at battery.

A wiring diagram for the ignitinon would be very helpful in diagnosing it. Would any of you happen to have an ignition wiring diagram for an 84 volkswagen jetta 1.8L?

Check your messages.

Thank you for that. It seems incomplete though, where do the wires go to on the fuse/relay section? Anyways, it should help quite a bit. I don't think the fuses have been checked on it since it broke, I think it would be worthwhile to do that...

I will let you know any more info next time I work on it (tomorrow evening). If you have any comments/suggestions before then I would love to know. Also, do you think the ICU is bad?

The Euro track schematics are pain to read. Especially when they use alphanumeric codes to name components. Usually the top is power and the bottom is ground. The numbers and letters at the left hand corner are indicators for how the circuit is powered. The track is huge and to provide every single path would be like 40 attachments. What makes the track difficult to read unless you have practice is that every symbol, number, and letter refers to something. Almost like a legend on a map.

Does your hall sensor have power, ground, and produces a signal when you rotate the distributor. I honestly don't know which wire is what for the hall, but checking each wire should tell you what they are.

By looking at the schematic the wires going to the ICM is going to be:

Black is ignition or starting supply voltage for the coil and the ICM
Green is the ground side of the ignition coil. The ICM's transistor will ground that wire to charge the coil and remove the ground to cause the coil to fire.
Brown/white, Green/white, Red/black are going to be power, ground, and signal for the hall effect sensor that the ICM uses for position input.
Brown is going to be ground and should have less than 0.3V with the ignition turned on.
Red/black at the coil ground side splice is going to the engine controller and fuel pump controller to be used for the engine speed signal or tach.

All these checks need to be made by back probing the connector with the circuits loaded.

Sorry for delay.

Engine wasn't running well because the timings were off. Timings got off because since the vacuum advance thing wasn't in, the timing sensor was free to rotate by itself.

Anyways, got the vacuum advance back on, and it's running fairly well. Thanks a ton for the advice, and those diagrams are amazing! If I have any more questions or problems, and I probably will, I will start a new thread.

Again, thank you.

Your welcome! Glad to read that you got it figured out. Thanks for the follow up.

Thread is locked as solved. Can be reopened upon request by the OP.

Maybe this one will be easier

Reminds me of the old Chrysler wiring schematics...LOL. Those are a big PITA.

Most of the old ones look like that. My Vette has everything on one diagram. I have Mitchell Vintage and they all look like that.

I love Mitchell diagrams...especially when you can highlight each circuit. If AllData had Mitchell's style of wiring diagrams, they would be #1.