[jlillie]

I'm gonna try and explain this with the least amount of words i can but it probly will get a little wordy so sorry up front.
First - 1990 Turbo vert 5 speed, 277k miles on the clock and could be more since when i got her, the speedo was not working (it is now).
She's been my DD for nearly a year now. Back around last sept she started having this intermittent miss. Out of the blue she would just start chugging. No power although i could actually keep driving after few minutes it would go back to normal. This would happen every few days or so but when it wasn't missing, ran fine.
At that time, i decided to take the cap and rotor off, clean it up, put it back, also pulled all the plugs. they all pretty much looked normal. After i got her back together the miss never came back until this past week. I did the same thing this time(pulled the cap/rotor and all the plugs. Cleaned up where necessary but no luck this time). Btw, the cap/rotor, all plugs and plug wires replaced last spring. Now, she seem to be having this issue about 50% of the time.
I was thinking that maybe I had an injector going bad but not sure if they are prone to be intermittent bad/good. I have a set of injectors from an '87 that i cleaned up and swapped out but she would barely run with those in. I guess they are not interchangeable with the earlier injectors.
Oh, also, i just did a compression test - 1,3,4 cylinders are @123 and #2 is @110).
So i found something interesting, when she's running bad and missing, if i pull the plug on # 4 injector i dont hear much of a change. But if i pull any of the others she will choke and die.
So, i ordered a set of refurbs off ebay and will swap them out next week. But do you think an injector could act like this?
Thanks for any insight

 

[Jim Mesthene]

Squirt some window cleaner on the cap & wires at night when it's hot.
It costs nothing.

 

[jlillie]

Hi Jim,
I do trust your advice and will try this but i have to ask; what would the purpose of this be?

 

[Jim Mesthene]

It often reveals weaknesses in the Cap, Rotor, Wires, or Plug insulation.
The engine might stumble, you might see sparks jumping (better done without the cover on the plugs). Possible carbon tracks (created by earlier sparks) would conduct electricity better when hot.

 

[jvanabra]

Spray bottle test would be my first stop for sure... but those compression numbers are quite low. Was the engine hot? Did you try doing a wet test as well?

 

[jlillie]

It often reveals weaknesses in the Cap, Rotor, Wires, or Plug insulation.
The engine might stumble, you might see sparks jumping (better done without the cover on the plugs). Possible carbon tracks (created by earlier sparks) would conduct electricity better when hot.

ah, checking for arcs. i did this a little bit by just moving the plug wires around but i will try your way. Thanks!

 

[jlillie]

Spray bottle test would be my first stop for sure... but those compression numbers are quite low. Was the engine hot? Did you try doing a wet test as well?

Yes, the motor was warm when tested. Not sure what you mean by "wet test".....dropping some oil down the cylinders?
What would you consider a normal compression result?
Thanks,

 

[jvanabra]

Of course, there are no absolute numbers when it comes to compression testing, and all motors will lose compression over time so we're truly looking for variances that suggest problems rather than wear... but....

A healthy B202 would be in the 180psi range, and a nicely worn probably the 140-150psi range. 110psi is quite low, and suggests the motor is tired... not unexpected with 277k on it!

Dropping some oil in the cylinders and rerunning the test will help determine whether the problem is in the bottom end or not. If it's in the top end, you may have the same problem I had with a high-mileage head... a pile of money to the machine shop and I'm back at 180psi on a 250,000 mile old bottom end.

A leakdown test might pinpoint things further, but if the wet test brings up the numbers you know it's gonna be motor out, and if it doesn't you know it's gonna be head off so... maybe you don't care.

 

[jlillie]

well, she doesn't burn much oil so hopefully the bottom end can go a bit longer. I do happen to have a head from an '87 with only 55k miles on it;however, it did over heat and blow a head gasket.
I remember reading somewhere that you should not have the valves ground like other heads because they have a special coating or something. Can you expound on what should be done to the head and possible who i could have do head overhaul work?

 

[jvanabra]

Any competent machine shop should be able to take care of you... check flatness, valve seating, guide wear, etc. It's typical machine shop, nothing unusual. The exhaust valves are sodium filled so should not be ground... worn valves should be replaced.

 

[jlillie]

The spray bottle test on the cap and wires yielded no change.
I got a new compression tester which gave me quite a difference in readings but not much in difference between cylinders.
Engine hot, following general compression test procedures.
So here is the dry compression tests
cyl1 = 170, cyl 2 = 145, cyl 3 = 142, cyl 4 = 163
Wet
cyl1 = 200, cyl 2 = 175, cyl 3 = 179, cyl 4 = 185

opinions?

 

[jvanabra]

You won't see a change from the spray bottle - you're looking for sparks & arcing in the air where the water mist is. Definitely best done at night, although sometimes you can hear the popping & cracking.

There's nothing painful in those compression test results. That variance between 1/4 & 2/3 is borderline but not insane. The big jumps from wet would be consistent with a worn bottom end. IMO that 200# in #1 wet might be the result of carbon buildup in the cylinder. Overall, kinda just feels like a really old motor to me, which, you know, it is.

Tough call on how to proceed... what's the maintenance history here? When was the ignition system replaced? Fuel system? Have you checked fuel pressure & oil pressure?

 

[Jim Mesthene]

Wiggle the distributor plug and the NTC resistor plug, check for codes.

 

[jlillie]

Tough call on how to proceed... what's the maintenance history here? When was the ignition system replaced? Fuel system? Have you checked fuel pressure & oil pressure?

Maintenance history is unknown. When I adopted the car, it had been neglected for at least several years and probably abused as well. The guy i bought it from was a real character but one thing i remember him saying was that he/wife could not have put 10k miles on the car. He also said the previous owner kept it in a garage and only drove it in the summer (came from Michigan). I did pull a carfax on it but it didn't tell me much accept that there were 3 previous owners and it had been hit right rear quarter.
It actually ran (barely) when I took it home and was able to drive it up on the tow dolly.
I spent months fixing just about everything you could imagine but the motor seemed fairly solid and ran well once i was done with all the neglected areas.
Couple months ago i set out to roll in a new timing chain and found that the current chain was well within spec - 8mm on the tensioner so I left it alone. With at least 277k on the clock someone had to have put a new chain in at some point. I think someone installed a new steering rack as well.
I would also guess a new clutch had been done. Who knows what else had been done to the engine. I would guess the bottom end is untouched.
After being all over every inch of this car for one reason or another i surmised that someone cared for the car very well with proper maintenance and fixes by knowledgeable mechs. except for the person who beat the firewall in in an attempt to pull the alternater pivot bolt out
She got all new plugs/wires/cap/rotor few months ago. New fuel filter and the fuel pump seemed strong when i check it but never did a pressure test. No idea on oil pressure either. I can check the fuel pressure though soon as i can figure out how to hook my test fuel gage up to it.

anyway,
I pulled my spare '87 head out of the shed and i think i'm gonna take to a shop and have it gone over.
I'm also considering going ahead andrebuilding the block i have and swapping them out with the current motor.

I dunno, i'm gonna think on it for awhile. Let me know what you think.
Thanks,

 

[jlillie]

Wiggle the distributor plug and the NTC resistor plug, check for codes.

Just tried that Jim - no Joy. I did have to look up what a NTC resistor plug was though.
While i was doing that, it seemed like the motor was running as its normal happy self so i i took her out for a drive with the top down in a nice warm Florida night and she was running well for about 5 mins then she started to miss.
Missed all the way back home
I left her running and tried the plugs above again but no change.

 

[jlillie]

I have verified I have 30psi fuel pressure at the rail. Fuel pressure rises slightly on acceleration then drops back to 30 +- 2.
Still missing both at idle and acceleration.
When i pull Cyl #3 spark plug wire or Cyl #3 injector electrical plug i get no change. Pull same on any other cylinder she stumbles and wants to die.
Spark looks good on #3
I also just installed 4 refurbished injectors I bought from ebay.
I think i'm gonna swap injector 3 and 4 see if problem follows.
Let me know if anyone has anything i should try.
Thanks,

 

[jvanabra]

That seems like not enough. The factory FPR is 2.5 bar which means you should have 37psi over intake manifold pressure at all times. At idle, under vacuum, you will probably see around 30-32psi but under acceleration as boost builds you should hit 37psi quickly and then onwards to about 50psi at peak boost. If you're using a tester and not a cabin gauge, you can simulate this with a vacuum pump adding and removing pressure from the vacuum line that goes to the FPR.

 

[Jim Mesthene]

Without stored codes, I'd still be looking at spark. Remember that the injectors fire in pairs.

 

[jvanabra]

All four, actually. LH 2.x has only one injector channel so the whole bank of cylinders is fired at once... generally referred to as "batch fired."

I'd agree that spark seems the likely culprit but poor pressure and/or poor atomization could be at fault as well. As could cylinder conditions like carbon build up or blow by.

Engines are fun.

 

[jvanabra]

One thing I notice is that in the OP it's #4 that seems to be having an issue, but just above you say the problem is with #3. Am I misreading?