I have a great daily driver. 1.8 L motor with L-jet injection, and it jerks like a son of a %^$%. It has all new vacume lines, none of wich are leaking (idles smooth at 900rpm) i have blocked off the deceleration valve. It was not letting the idle come back down fast enough for my taste. New jugs rings pistons etc. It has new plugs and wires. a new resistor pack and a newer duel relay. new alternator and new voltage regulator. Valves adjusted .006/ .008 perfectly with new valve cover gaskets. It has a new fuel pump and fuel filter, and many new wiring harness. Injectors were all cleaned and new screens put in. It runs up to 5K with no problems and runs strong to about 110mph on a flat.


Whe i accelerate easy it starts to jerk the whole way. If i try to run in 2nd or 3rd it jerks the whole time even at constant speed. sometimes i will seesaw the clutch just so i dont look to embarrising.

What is the list of things to check (i want to check everything) but i feel like i checked it all and then rechecked it


one other problem probably related, i cant keep constant power to the fuel pump through the relay, it chokes off sometimes and dosnt want to come back (PITA) so i jumped the fuel pump lead to the + coil for now. (dont be mad)

I've had really good results from putting in a rebuilt AFM from Fuel Injection Corp.

Pull the black cover off of the Air Flow Sensor. Look at the carbon resistor tract that the arm wipes across.

Does it look pitted? Are there areas where you can see the white or green PCB through the black carbon?

This may help:
Rejuvenating a Bosch Motronic Air Flow Meter

Make sure your rubber elbow isn't cracked.

Check the advance plates on the distributor and the little ground wire.

Capn Krusty had a few new ones on the shelf, and George at AA also has new ones on the shelf.

Also the vacuum advance canister on the distributor can contribute to the problem...pull it off of the advance plates, remove it from the distributor and cap the vacuum line...the car will run fine without it for testing purposes...


Those issues do create a jerky car.
First I would replace the gaskets on the oil filler cap, there are three...a o-ring in the lid, a gasket in the lid, and the gasket under the base of the filler assembly.

Rich

yep, either a sticking advance plate or vacuum leaks are the first things to look at.

I will have to pull the cover off the afm when the rain stops. I dont have a garage right now, it is full of boxes, since i sold my house. I will take a pic of what i see.

I am sure the huge elbow is not cracked, i took it off and cleaned it real good with armorall, it is perfect. and i thought i would have a real high idle if this was leaking. right?

as far as the distributor goes... i have never really taken one apart yet, not sure what theadvance plates look like, or how to tell if they were bad. same goes for the vacume advance. if i plug both lines going into it, how can i tell if this was the culprit?

thanks guys

Sticky flapper arm on AFC. At one point, mine was actually snagging on one of the contacts and was bucking badly until I found the problem.

so how did you resole it?

wd-40

I agree with the advance pate/advance springs/advance shaft. To test the vac can, a hand pump is the best way, available at HF pretty cheap and work well. You can also put a piece of hose on the nipple and suck on it, should move the advance/point plate, and it should hold vacuum. Also, on the top of the dizzy shaft, under the rotor, there is a small piece of felt inside the hole. Place a few drops of 3 n 1 oil or equiv. in there. WD40 is not a lubricant and should not be used in here. This will lube the mechanical advance. You should be able to grab the rotor with the dizzy in place and turn it about 15 degrees or so, and if you let it go it should snap back. If it does not snap back, the dizzy needs to come apart.

This is a good PM item to do even if something else is wrong.

Nope. WD-40 didn't fix it.

Read here.

thanks for the pic, tell me more about what i am looking at. It looks like an alien space ship control modulator
Click to view attachment

is this what it should look like. or what part is not right. and wich way did you bend it.

sorry

That L-jet hates vacuum leaks...

And you can set up a resonance/surging condition....

So you need to check everywhere that can leak a vacuum between the air flap and the heads such as...

Manifold boots, injector seals. phenolic spacers on the heads, the oil fill cap seals, the cork gasket under the oil fill area, etc.

thanks for the tips.

intake runner boots are brand new
injector seals are new big and small
spacers are new with a nice even bead of red silicon on both sides
cork gasket is new
all oil cap seals are new.

i replaced everything on this baby.

That's what's underneath the square black cover on the AFM. The way it look sin the photo is the way it's supposed to be. In my particular case, the contact with the dog-leg on the end was bent so that it occasionally got caught when the flapper opened up. Basically, this shut off the fuel to the injectors when fuel was needed most (e.g. more air coming thru the AFM). So under acceleration, it would bog down and go jerky.

It's worth a quick look under this cover to see how things work while manually pushing the flapper. Other than that, tcheck he usual suspects: vacuum leaks, timing/dwell, dizzy advance. Lots of good advice above.

I also used this site for troubleshooting my L-jet: http://manuals.type4.org/ljet/

I've had the jerky acceleration in my L-Jet too.

First time was caused by a loose connector at the base of the dual relay. The wire that runs the fuel pump was not getting full contact.

Second time, the oil vapor hose that connects to the Boot had come loose at the point of contact. Air was getting sucked in and causing big jerks in acceleration

A vac gauge and fuel pressure gause mounted in the engine compartment helped diagnose both these gremlins fast.

First off.. readjust your valves. The Haynes manual has a typo for the valve adjustment specs for the 1.8. They should both be .006. The .008 setting is ONLY for the sodium filled valves that came in the 2.0 heads.



In the picture, the #1 is the fuel pump contact. If you open the AFM flap, that is what turns the pump on. #2 is the wiper contacts that send the air flow information to the computer.

DO NOT ADJUST THE AIR FLOW METER SPRING TENSION!! It is calibrated properly for the engine, and takes a special tool to readjust. Been there, done that. I even own the tool to readjust them. I suggest that you don't open the air flow meter at all.

Check to see if the boot between the air flow meter and the throttle body is cracked. It will cause bucking if it is. Also inspect the harness carefully for broken or cracked wiring.

I agree with the distributor advance plate issue. Try this... disconnect the vacuum advance and retard lines and see if it still bucks.

OK

i rechecked the valves, alls well. I pulled the air flow meter open, everything was perfect inside, as far as i could tell. I then squeezed the spade terminals a little bit snugger at the dual relay, and cleaned all the connections. Ran the same

THEN.....


All of a sudden the loudest banging you ever heard comming from the driverside valve area WTF happened. Car will not idle now and i dont even want to start it untill i have time to pull the valve cover and take a look.

Banging?
Like clatter clatter.

Or BANG BANG BANG?

Zach

more like clatter clatter

pull the rocker cover and look. you may have just had the nuts that hold the rocker on come loose. It will make a loud clatter, but won't harm anything.

put the two nuts back on and torque them down properly.

It happened to me once, and scared the dickens out of me.

Zach

Make sure to relieve the tension from an open valve(s) when you torque the rocker arm.

UPDATE...


pulled the driverside valve cover to find the intake rocker on #1 super floppy
i could fit my finger between the rocker and the push rod

sooooo, just for fun i backed off the nut and adjusted the screw all the way untill it was flush with the nut. I almost could get it to .006 but still a bit loose. I left it there for now.

So did i bend a push rod, is that possible, does that sound like the case? I rotated the wheel to see all the rockers including the F%^& up one moving in and out like normal. What is my next step? I guess i need to take a look at that push rod, figures it would be the one to but up against the suspension ear. When it rains it pours.

mabey its a cheap fix

pull the pushrod out of the bore and inspect it - if you can. you may need to lower the engine little at the engine bar to do so.

But you might be able to inspect it with a mirror and a flash light.

Zach

Did you happen to notice if the valve was the same height as the other ones? Maybe a dropped seat? Pushrods are aluminum stock, so yes you could have bent one.

When you turned the motor over, did it hang up on the faulty cylinder? Did it sound like anything was impacting (like the valve to the piston)

Underthetire beat me to it. I also suspect a dropped valve seat.

Zach

I thought the valve springs all looked similar at a glance. and i did not hear much more than the super loud clanking of the rocker hitting the pushrod that was about 1/8 of an inch too short. Not sure about all the different sounds. but when i turn the engine with the wheel i do not hear metal sounds, just compression sounds

If it was a dropped seat, that Cyl would not have compression any longer. It would just seem like a limp ,well you get it.

no compression checker with me, but if i stick my finger in the plug hole of #1 there is no compression

Okay, silly question, but did you have your finger over the hole during the compression stroke, or when it was pushing out the exhaust? One would have compression, the other would not. If it was compression stroke, you probably dropped a seat.

Zach

Have you sent your 2L heads to have them rehabbed yet? If not, I'd get on it.

Zach

Take a picture of the valves on the drivers side and post it here.
We can tell you if something is wrong if you post a very clear picture.

Rich

The intake valve spring on number one is not as tall as the other four, i got a better look at it today. I cannot take a good look at it, it is parked on a baltimore city street, and i want to get it home. All the valves are now moving as they should when i spin the wheel, and the shorter spring is holding now at .006 even though somthing is very wrong. I had a buddy from the local gas station do a leak down for me and he said 15 percent was acceptable and mine was 65 percent He also guessed somthing (carbon) was keeping that valve open. He also said it might have smacked the piston and bent the edge a little stopping it from seating now.


Lets all say it togeather

[size=7]ENGINE DROP

Sorry man. Not carbon, dropped seat i'll bet.

What he said. Thats going to be another top end rebuild.

Zach

If you get a set of the tow bar hookups, you are welcome to use my tow bar to get the car home. Get them from Rennmetal, I think.

Zach

Thanks for the offer Zach, not sure what i am going to do at this point. I am still in tears, the day is shot to hell already. I figure probably have a dropped seat like the world says, my car is in baltimore, 1 hour from my house, my house is in boxes, including most of my tools, since i am in the process of buying another house.

And then i walk to check my car out on my lunch break and find this
Click to view attachment

Click to view attachment

oh yeah,

to me

Everything can be fixed.
Get the tow bar eyes. You can borrow my tools to install them, and tow the car to your folk's house or something until you close next month. I'd lend you mine, but I think you need to have the car re-aligned after putting them on or taking them off, as you have to unbolt the front of the A-Arms.

I'd say you could park here, but I'm at my limit of vehicles outside.

When you get settled, we can pull the car back home and pull the motor out of it. This is incentive to get the 2056 done. Don't put any more time or money into the 1.8. Drive the Benz, and we will get the 2056 sorted.

As to the jack point... Don't use it as a jack point. Don't worry about it right now. Anyhting broken can be fixed. You can open the doors, and I have gotten into the car without it groaning. I gave it the big butt test when I welded on your battery tray. Whatever rust may be there, it is not terminal.

Zach

Hang in there.
You've made it this far!
Mike

I have done this so dont yell.
Assuming you have a broken valve spring, or a dropped seat.
You will need to replace the head and the piston.
If you do what I suggest, you will certainly need a piston.


You can pull the adjuster so the valve never gets compressed.
Pull the FI electrical.
Remove the spark plug wire.
Drive it home.

You can pull the motor and put a new head on it and put it back in place in a day or less. I may have a head, if not someone around here will.

This would be easier in a garage with jack stands, but it would also be possible (I know Dr Evil will smile here) on the side of the road without removing the engine.
Remove the HE, drop the motor down on one side and remove the head.
It can be done...those are the short instructions and you would need help getting it done right and quickly...

Start begging for help.

Rich

i am still a newb here. Thanks for the advise rich.

I actually adjusted the valve to .006 and fired it up and let it idle for about 15min. it still has enough compression that pulling the injector lead made the engine studder noticably. If i have lost a valve seat, why when i search do i see so much carnage, and my car is actually running the same as it was before this incident? since i adjusted the intake the sound is gone, and i even took it around the block 2 times with no problems.

am i playing with fire here. Mabey it is not the seat?

You have got crap compression on the cylinder at 65% leak. You can drive it on 3, as Rich says. if the valve seat is failing, it will fail faster if that part of the head gets hot, which it will if the cylinder is firing. If the seat falls into the motor, it will get unpleasant rather quick, and it would be best to avoid that.

I am free tomorrow (saturday) morning. I can follow you down to Fells with tools, and chase you back home. You can put the car in my garage for a short period of time - not longer then it takes to close on your house. But you can store it here short term. If this is somethign that you want to do, call me tomorrow earlyish and I will swing over and get you.

Let me know.
Zach

When a seat drops, it is no longer tight in its position in the head. It can drop and be crooked holding the valve open. It can also drop back into it's position and seal somewhat. This can repeat over and over. Sometimes it will seal and sometimes not. I had this on a 2.0 that must have gone on for quite a while. The spot for the seat was worn huge! this did not happen overnight.

Zach is a very generous guy.

I did not have time to get it home last night, I will be attempting tonight about 8pm. I will pull the injector lead and run nice and slow, and stop to check the valve a few times along the way. I will let you guys know ...


hell if i can drive it 60 miles with no clutch

this should be a cake walk

Well if anyone was interested, My car is now in PA, back in its nest. It took a really long time to get there, but i made it.

now i have to move, before i can drop the motor

Glad to hear you made it back. I was wondering how you made out this morning.

How did the car do on 3?

Zach

The car was not happy, Nor was I.

I cannot fix my car now, because my garage is in boxes and i am soon moving. Wife said engine drop is no longer allowed until i am in the new house

however i did get a pic today. if you look you will see the intake on #1 adjustment is now flush with the nut. but at TDC i still have .006 on both valves

now i get to wait.

I'd bet it is a dropped seat.

The seat came out of the head and moved in towards the case.

Ken