Loss of power after a major backfire EA82

[Bababou]

A couple weeks ago I had a bad backfire on my 87 GL10, sever enough that it blew out the air filter and blew out the passenger side (USDM) exhaust gasket that was only a few weeks old. Corrected both of those issue but still had major power loss at that time, hard to even get it to 35 or 40MPH.  Checked and changed the plugs due to some build up, its been burning some oil since day 1 of me owning it.  Checked and replaced the ignition coil. Changed the oil.  Checked ECU codes and had a new one for the air flow meter and the ever present 34 EGR solenoid that I replaced with a brand new one 8 months ago.  Cleaned the connectors for the air flow meter code cleared.  Now it will eventually get to 70mph on a flat run but as soon as I have an incline to deal with it losses speed quickly all the way down to 58MPH.  I put some Lucas oil stabilizer in before I left from work, didn't have any when I changed the oil but I it slows up the leak I have not had an opportunity to find.  I only mention the stabilizer because on my way back to work tonight the power loss is not as dramatic on the "hills" not sure if the thicker oil plays into this.  Before the back fire the car ran fine it would go as fast as I was willing to deal with the death shakes from 80mph+, easily accelerated on the same inclines that now lower speed.  Its a 3spd auto front wheel drive only. Any suggestions as to what I should check next. 

[Steptoe]

Wonder if backfire blew out anything like a fuel pressure regulator diaphragm? HT plug leads?

Coincidence can also bite you

[scoobydube]

Most GL10's have a turbo, which you did not mention in your post.  You may have blown out a hole in the exhaust manifold, or caused a crack someplace that then reduces the velocity of the exhaust gases pushing on the turbo fan blades.  Which may then put the turbo mostly out of commission.  GL10 engines don't work well with a turbo that is not fully operational.  You might be able to look at the dash and read the indicator of when the turbo supposedly adds power, and notice that it does not indicate that it is adding power.

[Bababou]

Steptoe I had not though of the fuel pressure regulator, but a quick look at the symptoms and that does no match up.  I have no starting issues or long crank, my millage when down a tiny bit but considering heavy on the pedal that seems about normal.  The plug wires looked fine when I checked them and they are also fresh, less than a year old.

 

Scoobydube  No turbo on this one. Its the is the SPFI non turbo version.  I did look and listen for any leaks or cracks and nothing is obvious.

[DaveT]

The ECU 34 code for the EGR is for the solenoid,  not the EGR itself.

But this is not the cause of the power loss.

[88SubGL]

Really need to find what caused the backfire. Usually a timing issue. Maybe one of the timing belts jumped a tooth. Belts replaced recently?

[lrgvanman]

Check exhaust for flow as well. Sometimes backfires wreak havoc, clogging inside of the muffler as I found out with a Dodge. Vehicle also gets hotter with speed. Best of luck to ya!

 

[Subarule]

I had an enormous backfire once that blew the exhaust out. I had just come from picking the car up after detailing and engine steam cleaning. Something got wet under the hood that shouldn't have, I wish I could remember what. Had to have been something electrical tho'. I think it might have been the distributor. 

[FerGloyale]

Do a compression test.  Everything else is dependand on having 4 good cylinders.  Verify that first before chasing electrical or fuel issues.

You may have lost a valve seat or ring land.

FWIW, IMHO,  70~80 mph is torture to the engine and the 3AT in that car.  They were designed for 55-60 mph as 55 was the national speed limit at the time it was built.  Remnant of Oil Shortage policies from the late 70's OPEC crisis.

You WILL eventually wear out the governor gear in the 3at driving at those high speeds.  Heck it'll happen at some point driving 50, but will happen way sooner if driven at high speeds.  Plus again it forces the engine to rev waaay over 4K for long periods of time.

[Dee2]

You should also run a vacuum test.  It's dirt simple to do and can tell you a lot about the engine performance.

[Steptoe]

Fergloyale is on the money with suggesting a comp test for a new starting point. The simple task has often brought well respected technicians down who have been suggesting oil leaks onto cam position sensor can and does infiltrate wire looms causing problems, add a few codes to stray thinking further and then Steptoe suffers scoffing for suggesting comp test. 120,60,80,120 in a performance BMW - game over !

Meow? Cats and backfires might be bad news. Blowing out the exhaust port gasket also suggests true backfire in the exhaust rather than an intake backfire

80-85 mph on these 3 speed babies? An older mechanic once told me that was what tacho red line was for - sit there all day if you must! Maybe his Datsun but none of my car's thanks ya deaf bastard!

[Steptoe]

Blew out air filter too ...ok intake side as well!

[Steptoe]

3AT has vacuum line from inlet manifold possibly centrally close to below throttle body on Spfi as it is just rear of turbo throttle body. It goes to a vacuum unit on the LHD passenger side just above the tranny pan line. Is it all still ok after backfires?

I really only discovered mine on converting to manual, was a sloppy fit on vacuum hose and finger tight screwed in and the bastard used to hold onto each gear until I backed off. Did not affect power, just driveability

[Bababou]

I checked the vacuum lines all are in place and no obvious signs of splits, I replaced every vacuum line under the hood less than a year ago.

No muffler but I would not be surprised if its not the original cat with 255k miles on the car. It could has disintegrated. Need to check that. 

I did a timing kit on it when I did the water pump and oil pump less than a year ago. I'll double check timing today.

The back fired happened taking off at a light. Hit the gas faster than normal.

Typically 70 is the max I run puts it at 4100 - 4100rpm well below redline. The car and motor are very smooth at that point. Well was anyways.

I need to get a kit for a compression test. But its on my list 

Edited May 12, 2019 by Bababou

[scoobydube]

I had a backfire of sorts once and the timing belt slipped a tooth.  And the engine then did not run well.

[FerGloyale]

On 5/12/2019 at 7:23 AM, Bababou said:

I

Typically 70 is the max I run puts it at 4100 - 4100rpm well below redline. The car and motor are very smooth at that point. Well was anyways.

 

 

Right, was.  I'm telling you, it say's in the owners manual for that car not to run constantly above 4K rpms.

As it sits now, you are on here with a broken down car.  So it seems that driving that car that fast hasn't seemed to work out so well?

I advise those with 3AT equipped cars to not exceed 65 on a regular basis.

[Bababou]

Did a leak down test today about 30% loss in each cylinder.  They didnt have a compression test kit on site.

Did discover there is zero intake vacuum at this point. 

[Steptoe]

Zero intake vac test done with leak down gear? Regardless with this gear, what steps did you do to get zero vacuum result? Plain old vacuum gauge has been a long time diagnostic tool. Backfires on carby engines have better outcomes than fuelies with sensors, sadly

[Bababou]

No two separate things the leak down test gave the 30% loss across the board. Then while running if you disconnect any of the vacuum lines there is no or next to no vacuum.  Before I could hear the vacuum with a line disconnected.  Right now if you disconnect the line from the throttle plate to the regulator nothing changes.  The line by the EGR that goes up to the pump on the strut tower disconnect that, no vacuum.  We pulled and did a visual check on the injector it is flowing as to how well we didn't have a way to test it, the gasket that seals the injector in place had a rip in it we put a thin layer of silicon to help seal that better. At the suggestion of the shop I ran some compressed air and a pipe cleaner through the vacuum ports, still not generating manifold vacuum but the car ran much better tonight.  Got up to 65 no issues but still lost some speed on the hills. 

I really just need this thing to last another week or so until my bugeye wagon is done.  Then this one can go back to being my parts runner / back up car.  Or really probably sell it pre move.

[idosubaru]

Check the timing belt alignment marks. 

[Bababou]

27 minutes ago, idosubaru said:

Check the timing belt alignment marks. 

The one  thing I forgot to check while spinning it around for the leak down test.

[idosubaru]

33 minutes ago, Bababou said:

The one  thing I forgot to check while spinning it around for the leak down test.

do it.  that's the first thing i'd check.  EA/ER belt systems aren't the most robust in stock form, aftermarket parts can fail, and an event like you're describing can easily jump time.

both side covers have 3 10mm bolts and come off in just a couple minutes very easily.  takes very little time to pull those and check timing. 

Edited May 14, 2019 by idosubaru

[Bababou]

The timing marks still match up as they should. 

[Steptoe]

It still sounds from your first to latest report, like a load condition that gives you problems. But also need to take note of what you report on the vacuum suck it lacks with your testing. So many ( not really ) variables for us to suggest but I would still like to see down the cat . No obvious rattles from it? I think the only "load" sensor is the air flow metre. A simple vacuum gauge hook up could be valuable.

[Bababou]

Haven't had a chance to get back on here to update but the cats were both junk, 256K miles on what looks like the factory installed cats, not a bad run.  Not having a minimum of $500 to throw at the car its now a rather loud straight pipe car.  Runs great but still makes no intake vacuum and the mileage seems to be up higher than ever, filling up for the first time since the "fix" after work this morning and I'll know for sure.  Short of the meteor that is due to take me out any day now should be good to go until the shop finishes my 02 wagon.